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1/12

/

E L S E V I E R

0 9 6 0 - 8 5 2 4 9 4 ) 0 0 I 0 1 - 4

ioresource Technology 5 1 ( 1 9 9 5 ) 1 - 1 2

1 9 9 5 E l s e v i e r S c i e n c e L i m i t e d

P r i n t e d i n G r e a t B r i t ai n . A l l r i g h ts r e s e r v e d

0 9 6 0 - 8 5 2 4 / 9 5 / 9 . 5 0

B I O S U R F A C T A N T S P R O D U C T I O N A N D P O SS IB L E U S E S IN

M I C R O B I A L E N H A N C E D O IL R E C O V E R Y A N D O IL

P O L L U T I O N R E M E D I A T IO N A R E V I E W

I M B a n a t

Department o f Biology, United Ara b Em irates Universi ty, PO B ox 17551, Al-A in, A bu-D habi, U AE

(Acce p ted 4 Octobe r 1994)

bs trac t

S u r f a c t a n t s a r e w i d e l y u s e d f o r v a r i o u s p u r p o s e s i n

i n du s tr y , b u t f o r m a n y y e a r s w e r e m a i n l y c h e m i c a l ly s y n -

t h e s iz e d . I t h a s o n l y b e e n i n t h e p a s t f e w d e c a d e s t h a t

b i o l o g i c a l s u r f a c e -a c t i v e c o m p o u n d s (b i o su r f a c ta n t s )

h a v e b e e n d e s c r i b e d . B i o s u r f a c t a n t s a r e g a i n i n g p r o m i n -

e n c e a n d h a v e a l re a d y ta k e n o v e r f o r a n u m b e r o f

i mp o r t a n t i n d u s t r i a l u s es , d u e t o t h e i r a d v a n t a g e s o f

b i o d e g r a d a b i l i t y , p r o d u c t i o n o n r e n e w a b l e r e s o u r c e s

a n d f u n c t i o n a l i t y u n d e r e x t r e m e c o n d i ti o n s ; p a r ti c u la r l y

t h o s e p e r t a i n i n g d u r i n g t e r t i a ry c r u d e -o i l r e co v er y. C o n -

f l i c t i n g r e p o r t s e x i s t c o n c e r n i n g t h e i r e f f i c a c y a n d t h e

e c o n o m i c s o f b o t h t h e i r p r o d u c t i o n a n d a p p l i c a ti o n . A t

p r e s en t , t h e i r us e s a re m a i n l y i n t h e o i l a n d p e t r o l e u m

i n d u s tr i e s , w h e r e t h e y a r e e m p l o y e d p r i ma r i l y f o r t h e i r

e m u l s i f i c a t io n c a p a c i t y i n b o t h t e r ti a r y r e c o v e r y a n d p o l -

l u t e d - si t e s re me d i a t i o n . Ho w e v e r , c a u t i o n i s f r e q u e n t l y

e x e r c i s e d w i t h r e s p e c t t o t h e i r u s e b e c a u s e o f p o s s i b l e

s u b s e q u e n t m i c r o b i a l c o n t a m i n a t i o n o f e i t he r u n d e r-

g r o u n d o i l r e se r v o ir s o r p r o d u c t s . T h e l i m i t e d s u c c e s se s

a n d a p p l i c a t io n s f o r b i o s u r f a c t a n t s p r o d u c t i o n ,

recovery, use in o i l po l lu t ion con tro l , o i l s torage tank

c l e a n - u p a n d e n h a n c e d o i l- r ec o v e ry a r e re v i e w e d f r o m

t h e t e c h n o l o g i c a l p o i n t o f v i ew .

K e y w o r d s :

B i o s u r f a c t a n t s , e m u l s i f i c a t i o n , b i o d e g r a d a -

t i o n , b i o r e m e d i a t i o n , m i c r o b i a l l y - e n h a n c e d o i l

r e co v e ry , M E O R .

I N T R OD U C T I O N

B i o s u r f a c t a n t s a r e a h e t e r o g e n e o u s g r o u p o f su r f a c e -

a c ti ve m o l e c u le s p r o d u c e d b y m i c r o or g a n is m s . T h e s e

m o l e c u l e s r e d u c e s u r f a c e t e n s i o n , c r i t i c a l m i c e l l e c o n -

c e n t r a t i o n ( C M C ) a n d i n t e r ra c i a l te n s i o n i n b o t h a q u e -

o u s s o l u t i o n s a n d h y d r o c a r b o n m i x t u r e s . T h e s e

p r o p e r t i e s c r e a t e m i c r o - e m u l s i o n s i n w h i c h m i c e l l e

f o r m a t i o n o c c u r s w h e r e h y d r o c a r b o n s c a n s o lu b i li z e i n

w a t e r , o r w a t e r i n h y d r o c a r b o n s . T h e p r o p e r t i e s o f t h e

v a r i o u s b i o s u r f a c ta n t s h a v e b e e n e x t e n si v e ly r e v i e w e d

( C o o p e r , 1 9 8 6 ; R o s e n b e r g , 1 9 8 6 ; H a f e r b u r g e t a l . ,

1 9 9 0 ; F i e c h t e r , 1 9 9 2 a ; G e o r g i o u et al . , 1 9 9 2 ; K o s a r i c ,

1 9 9 3 ) . G e n e r a l l y t h e s t r u c t u r e o f b i o s u r f a c t a n t s

i n c l u d e s a h y d r o p h i l i c m o i e t y c o m p o s e d o f a m i n o a c i d s

o r p e p t i d e s , a n i o n s o r c a t i o n s , o r m o n o - , d i - , o r p o l y -

s a c c h a r i d e s . T h e h y d r o p h o b i c p o r t i o n i s o f t e n m a d e

u p o f s a t u ra t e d , u n s a t u r a t e d o r h y d r o x y l a t e d f a tt y a c id s

( G e o r g i o u et al . , 1 9 92 ) , o r c o m p o s e d o f a m o p h o p h i l i c

o r h y d r o p h o b i c p e p t i d e s . W o r l d - w i d e i n t e r e s t i n b i o -

s u r f a c t a n t s h a s i n c r e a s e d i m m e n s e l y d u e t o t h e i r a b i li t y

t o m e e t m o s t s y n t h e t i c s u r f a c t a n t s ' r e q u i r e m e n t s

( M o r k e s , 1 9 9 3 ) .

B i o s u r f a c t a n t ( s ) s p o n t a n e o u s r e l e a s e a n d f u n c t i o n

a r e o f t e n r e l a t e d t o h y d r o c a r b o n u p t a k e ; t h e r e f o r e ,

t h e y a r e p r e d o m i n a n t l y s y n t h e s i z e d b y h y d r o c a r b o n -

d e g r a d i n g m i c r o o r g a n i s m s . S o m e b i o s u rf a c t a n ts , h o w -

e v er , h a v e b e e n r e p o r t e d t o b e p r o d u c e d o n

w a t e r - s o l u b l e c o m p o u n d s , s u c h a s g l u c o s e , s u c r o s e ,

g l y c e ro l o r e t h a n o l ( G u e r r a - S a n t o s , 1 9 8 6 ; C o o p e r

G o l d e n b e r g , 1 9 8 7 ; P a l e j w a l a D e s a i , 1 9 8 9 ; P a s s e r i e t

al., 1 9 9 2 ; H o m m e l H u s e , 1 9 9 3 ). I n s o m e i n s ta n c e s ,

t h e s e c o m p o u n d s h a v e a n t i bi o ti c p r o p e r t i e s w h i c h m a y

s e rv e t o d i s r u p t m e m b r a n e s o f m i c r o o rg a n i s m s c o m -

p e t i n g f o r f o o d . E x a m p l e s o f t h e s e i n c l u d e t h e l i p o -

p e p t i d e s o f t h e i t u r i n f a m i l y p r o d u c e d b y B a c i l l u s

sub t i l i s , w h i c h h a v e p o w e r f u l a n t i - f u n g a l p r o p e r t i e s

( S a n d r i n et al . , 1 9 9 0 ; T h i m o n et al . , 1 9 9 2 ) , C a n d i d a

an tarc t ica , w h i c h h a v e a n t i m i c r o b ia l a c t i v it y ( K i t a m o t o

et al . , 1 9 9 3 ) , a n d B a c i l l u s l i c h e n i f o r mi s , w h i c h i n h i b i t

b a c t e r i a , y e a s t a n d f i l a m e n t o u s f u n g i ( F i e c h t e r , 1 9 9 2 a ) .

C h e m i c a l ly - s y n t h e s iz e d s u r fa c t a n ts h a v e b e e n u s e d

i n t h e o i l i n d u s t r y t o a i d t h e c l e a n u p o f o i l s p i l l s , a s

w e l l a s t o e n h a n c e o i l r e c o v e r y f r o m o i l r e s e r v o i r s .

T h e s e c o m p o u n d s a re n o t b i o d eg r a d a b le a n d c a n be

t o x i c t o t h e e n v i r o n m e n t . B i o s u r f a c t a n t s , h o w e v e r ,

h a v e b e e n s h o w n i n m a n y c a s e s t o h a v e e q u i v a l e n t

e m u l s i f ic a t i o n p r o p e r t i e s a n d a r e b i o d e g r a d a b l e . T h u s ,

t h e r e i s a n i n c r e a s i n g i n t e r e s t i n t h e p o s s i b l e u s e o f b i o -

s u r f a c t a n t s i n m o b i l i z i n g h e a v y c r u d e o i l , t r a n s p o r t i n g

p e t r o l e u m i n p i p e l i n e s , m a n a g i n g o i l s p i l l s , o i l - p o l l u -

t i o n c o n t r o l , c l e a n i n g o i l s l u d g e f r o m o i l s t o r a g e f a c i -

l i t i e s , s o i l / s a n d b i o r e m e d i a t i o n a n d m i c r o b i a l l y -

e n h a n c e d o i l r e c o v e ry ( M E O R ) . M E O R o f fe r s m a j o r

a d v a n t a g e s o v e r c o n v e n t i o n a l E O R i n t h a t l o w e r c a p i-

t al a n d c h e m i c a l / e n e r g y c o s ts a r e r e q u i r e d ( S a r k a r e t

al . , 1 9 8 9 ) .

7/26/2019 banat1995 MEOR

2/12

2 I . M . B a n a t

B I O S U R F A C T A N T - P R O D U C I N G

M I C R O O R G A N I S M S

A l a r g e v a r i e ty o f b i o s u r f a c t a n t s i s k n o w n ; t h e i r ty p e ,

q u a n t i t y a n d q u a l i t y a r e i n f l u e n c e d b y t h e n a t u r e o f th e

c a r b o n s u b s t r a t e ( G e o r g i o u

e t a l . ,

1 9 9 2 ) , t h e c o n -

c e n t r a t io n o f N , P , M g , F e a n d M n i o n s i n th e m e d i u m

( A t l a s , 1 9 8 1 ; C o o p e r

e t a l . ,

1 9 8 1 a, b ; G u e r r a - S a n t o s

e t

a l . ,

1 9 8 4 & 1 9 8 6 ; H a f e r b u r g

e t a l . ,

1 9 8 6 ; A b u -

R u w a i d a

e t a L ,

1 9 9 l b ) a n d c u l t u r e c o n d i t io n s , i n c lu d -

i n g p H , t e m p e r a t u r e , a g i t a t i o n a n d d i l u t i o n r a t e

( G u e r r a - S a n t o s

e t a l . ,

1 9 8 4 & 1 9 8 6 ; A b u - R u w a i d a

e t

a l . ,

1 9 9 1 a ; F i e c h te r , 1 9 9 2 a ; D r o u i n & C o o p e r , 1 9 9 2 ;

L i n

e t a l . ,

1 9 9 4 ) .

W h e n c o n s i d e r i n g w h i c h m i c r o o r g a n i s m s t o u s e f o r

M E O R , t h e v a r y i n g c o n d i t i o n s i n w h i c h t h e y w i l l b e

u s e d , s u c h a s t e m p e r a t u r e , p r e s s u r e , p H a n d s a l i n i t y ,

m u s t b e g i v e n p r i o r it y ( K h i re & K h a n , 1 9 9 4 b ) . T y p i c -

a l l y , m i c r o o r g a n i s m s i n j e c t e d i n t o a n o i l w e l l s h o u l d

e n d u r e h i g h t e m p e r a t u r e s , p r e s s u r e s a n d s al in it y, a n d

b e c a p a b l e o f g r o w t h u n d e r a n a e r o b i c o r m i c r o a e r o -

p h i li c c o n d i t io n s . I t h a s b e e n e s t im a t e d th a t 5 0 - 7 0 o f

o i l w e l l s i n t h e U S A c o u l d s u p p o r t m i c r o b i a l g r o w t h

w i t h p H v a l u es f r o m 4 t o 8 , t e m p e r a t u r e s < 7 5 C a n d

s a l i n it y < 1 0 (C l a rk

e t a l . ,

198 1 ) .

S o u r c e s o f c u l t u r e s

S e v e r a l t y p e s o f b i o s u r f a c t a n t h a v e b e e n i s o l a t e d a n d

c h a r a c t e r i z e d , i n c l u d i n g g l y c o l i p i d s , p h o s p h o l i p i d s ,

n e u t r a l l i p i d s , f a t t y a c i d s , p e p t i d o l i p i d s , l i p o p o l y -

s a c c h a r i d e s a n d o t h e r s n o t fu l ly c h a r a c t e r i z e d . M i c r o -

o r g a n i s m s w h i c h p r o d u c e b i o s u r f a c t a n t s , a n d t h e i r

s t r u c t u r e s , a r e l i s t e d i n T a b l e 1 . C e r t a i n m i c r o -

o r g a n i s m s a r e l i k el y t o b e f o u n d t o b e b e t t e r a d a p t e d t o

p a r t i c u l a r e n v i r o n m e n t s , s u c h a s o i l r e s e r v o i r s , s o i l o r

t h e o c e a n . A s t r a i n o f

P s e u d o m o n a s a e r u g i n o s a

i s o -

l a t e d f r o m c r u d e o i l - a s s o c i a t e d i n j e c t i o n w a t e r i n

V e n e z u e l a n o i l f i e l d s w a s f o u n d t o b e a d a p t e d t o t h e

c o n d i t i o n s p r e v a l e n t i n t h i s o i l r e s e r v o i r ( R o c h a

e t a l . ,

1 9 9 2 ) . F u r t h e r , th e b i o s u r f a c t a n t s ( r h a m n o l i p i d s ) p r o -

d u c e d b y t h i s s t r a i n w e r e n o t i n a c t i v a t e d b y p H , t e m -

p e r a t u r e , s a l i n i t y , c a l c i u m o r m a g n e s i u m a t

c o n c e n t r a t i o n s i n e x c e s s o f t h o s e f o u n d i n m a n y oi l

r e s e r v o i r s i n V e n e z u e l a ( R o c h a

e t a l . ,

1 9 9 2 ) . A h a l o -

t o l e r a n t

B a c i l l u s l i c h e n i f o r m i s

s t r a i n J F -2 , wa s a l s o i s o -

l a t e d f r o m o i l f i e l d i n j e c t i o n w a t e r , a n d w a s f o u n d t o

p r o d u c e b i o s u r f a c t a n t u n d e r b o t h a e r o b i c a n d a n a e r o -

b i c c o n d i t i o n s ( J e n n e m a n

e t a l . ,

1 9 8 3 ; J a v a h e r i

e t a l . ,

1 9 8 5 ) .

B a c i l l u s

s t r a i n S P 0 1 8 w a s f o u n d t o t o l e r a t e

a n a e r o b i c c o n d i t io n s a t 5 0 C a n d < 1 0 N a C l w h i l e

p r o d u c i n g b i o s u r f a c t a n t s ( P f i f f n e r

e t a l . ,

1 9 8 6 ) . T w o

Table 1 Various biosurfactants produced by microorganisms

M icroorgan ism Biosuffac tan t Referen ce

A r th r o b a c t er R A G - 1

A r th r o b a c te r

MIS 38

A r t h r o b a c t e r s p .

Ba c i l lu s l i c h e n i fo r mis J F- 2

Ba c i l lu s l i c h e n i fo r mis

86

Ba c i l lu s s u b t i l i s

B a c i l l u s p u m i l u s

A 1

Ba c i l lu s s p .

A B - 2

Ba c i l lu s s p . C - 1 4

Ca n d id a a n ta r c t i c a

C a n d i d a b o m b i c o la

Ca n d id a t r o p ic a l i s

Ca n d id a l ip o ly t i c a

Y-917

C l o s t r i d i u m p a s t e u r ia n u m

Co r y n e b a c te r iu m h y d r o c a r b o la s tu s

C o r y n e b a c t e r i u m i n s i d i o s u m

C o r y n e b a c t e r i u m l e p u s

Stra in MM1

No c a r d ia e r y th r o p o l i s

O c h r o b a c t r u m a n t h r o p i i

P e n i c i l l i u m s p i c u l i s p o r u m

P s e u d o m o n a s a e r u g i n o s a

P s e u d o m o n a s f l u o r e s c e n s

P h a f f t a r h o d o z y m a

R h o d o c o c c u s e r y t h r o p o l i s

R h o d o c o c c u s s p .

ST-5

R h o d o c o c c u s s p .

H 1 3 - A

R h o d o c o c c u s s p .

33

T o r u l o p si s b o m b i c o l a

het ropo lysacchar ides

l ipopep t ide

t reha lose , sucrose and

fruc tose l ip ids

l ipopep t ides

l ipopep t ides

surfact in

surfact in

rhamnol ip ids

h y d ro c a rb o n - l i p i d p ro t e i n

ma nnosy ler th r i to l l ip id

sopho rose l ip ids

m a rm a n - fa t t y a c i d

s o p h o ro s

l ipid

neu t ra l l ip ids

p ro t e i n - l i p i d -c a rb o h y .

p h o s p h o l i p i d s

fat ty acids

glucose, l ip id and

hydroxyd ecano ic ac ids

neu tral l ip ids

p ro t e i n

sp icu lospor ic ac id

rh a m n o l i p i d

l ipopep t ide

carbohydrates-lipid

t reha lose d ico rynomyco la te

glycolipid

glycolipid

po lysacchar ide

sopho rose l ip ids

R o s e n b e rg

e t a l .

(1979)

M o r i k a wa

e t a l . 1 9 9 3 )

Suzuk i

e t a l .

(1974)

I t o h

e t a l . 1 9 7 4 )

M c l n e rn e y

e t a l . 1 9 9 0 )

Ho ro wi t z

e t a l . 1 9 9 0 )

A r i m a

e t a l .

(1968)

M o r i k a wa

e t a l . 1 9 9 2 )

Banat (1993)

Eliseev

e t a l .

(1991)

Ki t a m o t o

e t a l . 1 9 9 2 )

Go b b e r t

et al.

(1984)

Ka p p e l l a n d F i e c h t e r

(1976)

Les ik

e ta l .

(1989)

C o o p e r

et al.

(1980)

Zaj ic

e t a l .

(1977)

Ak i t

e t a l .

(1981)

C o o p e r

e t a l .

(1979)

Passeri (1992)

M a c D o n a l d

e t a l .

(1981)

Wasko and B ra t t (1990)

Ban and S ato (1993)

R o b e r t

e t a l .

(1989)

N e u

e t a l .

(1990)

L e s i k

e t a l .

(1991)

Shu lga

e t a l .

(1990)

A b u - R u w a i d a

e t a l .

( 1991 a)

Singer and F inner ty (1990)

N e u

et al.

(1992)

In o u e a n d I t o (1 9 8 2 )

7/26/2019 banat1995 MEOR

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B i o s u r f a c t a n ts p r o d u c t i o n a n d a p p l i c a ti o n s 3

b i o s u r f a c t a n t - p r o d u c i n g B a c i l l u s s t r a in s , A B-2 and

Y 12 -B , w ere a l s o i s o la ted f rom o i l s ludge-m ixed s and

a n d h a d t h e a b il it y t o g r o w o n h y d r o c a r b o n - c o n t a i n i n g

m ed ium a t -

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4 L M . B a n a t

1 0 0 1 0 0

8 0 8 0

6 0 - 6 0

.~

40 - ~ 4o

2 0 - 2 0

0 - 0

0

x B i o m a s s

0 C M D - l

C M D - 2 x~ ~ . . - x - - - - - - - .~ . x

- - C M D 3

E 2 4

/ x

S u r f a c e t e n s i o n

[

I I - . ~ ~ I I I I

8 1 6

4

3 2 4 0 4 8

T i m e h )

1 0 0 1 5

6 0 3 ~

- 4 o . - - ~

2 0 1 1

0 0

Fig . 1 . Th e result s of a typica l ba tch fe rm enta t ion of n-para f f in m inera l m ediu m by

R h o d o c o c c u s

sp . ST-5 cul ture a t 37C , pH

6-8 a nd d i s s o l ve d oxyge n 30 - 5 0% s a t u ra t ion ( A bu- R uw a i da

e t a l .

1991 b). Symbols : x = biom ass (g/l ) ; o --cri t ical mieel le di lu-

t i on (C M D - 1 ) ( m N / m ) a t 1 : 10 c u l t u r e b r o t h t o c on t r o l m e d i um ; = C M D - 2 ( m N / m ) a t 1 : 10 0 c u l t u r e b r o t h t o c on t r o l

m e d i um ; = C M D - 3 ( m N / m ) a t 1 : 100 0 c u l t u r e b r o t h t o m e d i um ; = E 24 ( em u l si fi ca ti on i nde x % ); = s u rf a ce t e n s i on

( m N / m ) .

l a t e d p r o t e i n s . A n a q u e o u s t w o - p h a s e f e r m e n t a t i o n

s y s t e m h a s b e e n d e v e l o p e d w h i c h s e p a r a t e s s u f f a c ta n t s

o n t h e b a s is o f t h e i r c h a r g e ( D r o u i n & C o o p e r , 1 9 9 2 ) .

T h i s t w o - p h a s e s y s te m , e m p l o y i n g p o l y e t h y l e n e g l y c o l

a n d d e x t r a n , w a s f o u n d t o p a r t i t io n c a t i o n i c s u r f a c ta n t s

t o t h e b o t t o m p h a s e a n d a n i o n i c s u r f a c t a n t s t o t h e t o p

p h a s e . B a c i l l u s s u b t i l i s c e ll s p a r t i t i o n e d i n t o t h e b o t t o m

p h a s e , w h i l e t h e b i o s u r f a c t a n t ( s u r f a c t i n ) p a r t i t i o n e d

i n t o th e t o p p h a s e .

S y n t h e s i s a n d m o d i f i c a t i o n

L a b o r a t o r y s y n t h e s is a n d m o d i f i c a ti o n s o f b i o s u r -

f a c ta n t s h a v e a l s o b e e n c a r r i e d o u t . C h e m i c a l c o n v e r -

s i o n o f t h e c a r b o x y l i c m o i e t y o f r h a m n o l i p i d t o a

n o n - i o n i c m e t h y l e s te r r e s u l t e d i n e n h a n c e d i n te r f a ci a l

l o w e r i n g a n d w e t t i n g a c t i o n ( I s h i g a m i

e t a l .

1 9 9 3 ) . I t

w a s a ls o n o t e d t h a t t h e m o d i f i e d r h a m n o l i p i d C M C

v a l u e h a d i n c r e a s e d s ig n i fi ca n tl y . P h o s p h o l i p i d s w e r e

s u c c e s s f u l l y m o d i f i e d b y l i p a s e - c a t a l y z e d t r a n s e s t e r i f i -

c a t i o n t o i n c o r p o r a t e n - 3 p o l y u n s a t u r a t e d f a t t y a c i d s

( M u t u a & A k o h , 1 9 9 3 a ) . T r a n s e s t e r i f i c a t i o n s w e r e

a l s o u s e d t o p r e p a r e p o l y u n s a t u r a t e d p h o s p h o l i p i d s

( T o t a n i & H a r a , 1 9 9 1 ) .

C a n d i d a c y l i n d r a c e a

a n d

R h i z o p u s d e l e m a r

l i p a s e s w e r e u t i l i z e d t o p r e p a r e

p o l y u n s a t u r a t e d p h o s p h o l i p i d s f r o m s o y p h o s p h o l i p i d

a n d s a r d i n e o i l. A l k y l g l y c o s i d e f a t ty a c i d e s t e r s w e r e

a l s o s y n t h e s i z e d b y l i p a s e - c a t a l y z e d t r a n s e s t e r i f i c a t i o n

o f m e t h y l g l u c o s i d e , m e t h y l g a l a c t o s i d e a n d o c t y l

g l u c o si d e w it h m e t h y l o l e a te ( M u t u a & A k o h , 1 9 9 3 b ) .

A f i x e d - b e d r e a c t o r h a s b e e n u t i li z e d f o r c o n t i n u o u s

e n z y m a t i c t r a n s e st e r if i c a t io n o f r a p e s e e d o i l a n d l a u ri c

a c i d ( F o r s e l l e t a l . 1 9 9 3 ). T h e s e t e c h n i q u e s m a y p r o v e

u s e f u l i n d e s i g n i n g b i o s u r f a c t a n ts o r i n p r o d u c i n g

l a r g e r q u a n t i t i e s o f r e l a t iv e l y p u r e p r o d u c t s .

B I O S U R F A C T A N T S I N P O L L U T I O N C O N T R O L

O i l p o l l u t i o n a c c i d e n t s h a v e b e c o m e n u m e r o u s a n d

h a v e c a u s e d e c o l o g i c a l a n d s o c ia l c a t a s tr o p h e s ( B u r g e r,

1 9 9 3 ; S h a w , 1 9 9 2 ; B u r n s

e t a l .

1 9 9 3 ) . T h e a b i l i t y o f

b i o s u r f a c t a n ts to e m u l s i fy h y d r o c a r b o n - w a t e r m i x -

t u r e s h a s b e e n w i d e l y r e p o r t e d ( B r o d e r i c k & C o o n e y ,

1 9 8 2 ; H a r v e y e t a l . 1 9 9 0 ; O b e r b r e m e r e t a l . 1 9 9 0 ;

W a s k o & B r a t t , 1 9 9 0 ; F r a n c y e t a l . 1 9 9 1 ; Z h a n g &

M i l le r , 1 9 9 2 ) . T h e s e e m u l s i f i c a ti o n p r o p e r t i e s h a v e

a l s o b e e n d e m o n s t r a t e d t o e n h a n c e h y d r o c a r b o n s

d e g r a d a t i o n i n t h e e n v i r o n m e n t , h e n c e m a k i n g t h e m

p o t e n t i a l l y u s e f u l t o o l s f o r o i l s p i l l p o l l u t i o n - c o n t r o l

( A t la s & B a r t h a , 1 9 9 2 ; A t l as , 1 9 9 3 ; B e r t r a n d e t a l .

1 9 9 4 ) .

B i o r e m e d i a t i o n ( la b o r a to r y e x p e r i m e n t s )

E x p e r i m e n t s w i t h

P . a e r u g i n o s a

i s o l a t e 8 , i s o l a t e d

f r o m o i l - p o l l u t e d s e a w a t e r , s h o w e d i t s a b i l i t y t o

d e g r a d e h e x a d e c a n e , h e p t a d e c a n e , o c t a d e c a n e a n d

n o n a d e c a n e i n s ea w a t e r by u p t o 4 7 , 5 8 , 7 3 a n d 6 0 % ,

r e s p e c t i v e l y , a f t e r a 2 8 d a y i n c u b a t i o n p e r i o d ( S h a f e e q

e t a l . 1 9 8 9 ) . T e n s i o m e t r i c s t u d i e s i n d i c a t e d t h e p r e -

s e n c e o f b i o s u r f a c t a n ts i n t h e c u l t u r e m e d i u m . O i l- p o l -

l u te d s e a w a te r , w h e n s u p p l e m e n t e d w i th n i t ro g e n a n d

p h o s p h a t e , w a s a b l e t o r e d u c e t h e q u a n t i ti e s o f n - p a r a -

f f i n s p r e s e n t i n t h e c r u d e o i l s ( V r d o l j a k e t a l . 1 9 9 2 ) .

T h e a d d i t i o n o f

P s e u d o m o n a s a e r u g i n o s a

U G 2 b i o -

s u r f a c t a n t t o s o i l c o n t a m i n a t e d w i t h a h y d r o c a r b o n

m i x t u r e o f te t r a d e c a n e , h e x a d e c a n e , p r i s t a n e a n d

2 - m e t h y l n a p h t h a l e n e , f o l lo w e d b y a 2 m o n t h i n c u b a -

t i o n p e r io d , a l s o s h o w e d e n h a n c e d d e g r a d a t i o n o f a ll

h y d r o c a r b o n s e x c e p t 2 - m e t h y l n a p h t h a l e n e (J ai n e t a l .

1 9 9 2 ) .

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5/12

B i o s u r f a c ta n t s p r o d u c t i o n a n d a p p l i c a ti o n s 5

I n a n o t h e r e x p e r i m e n t , c o n t a m i n a t e d s o i l , p a c k e d

i n t o 8 m l s o l i d -p h a s e e x t r a c t i o n c o l u m n s , w a s i n o -

c u l a t e d w i th 108 c e l l s /m l o f

P s e u d o m o n a s

M L 2 o r

A c i n e t o b a c t e r h a e m o l y t i c u s .

O t h e r t r e a t m e n t s w i t h

M L 2 b i o s u r f a c ta n t p r o d u c t ( at 4 1 o r 8 2 / ~ g / m l ) w e r e

u s e d i n a d d i t i o n t o t h e b u f f e r c o n tr o l s . A f t e r 2 m o n t h s ,

3 9 - 7 1 % r e d u c t io n in h y d r o c a r b o n s w a s a c h ie v e d b y

A . h a e m o l y t i c u s ,

w h i l e t h e

P s e u d o m o n a s

M L 2 s h o w e d

1 1 - 7 2 % r e d u c t i o n ( a v e r y w i d e r an g e ) . T h e t r e a t m e n t

w i t h t h e M L 2 - b i o s u r f a c t a n t p r o d u c t g a v e t h e b e s t

r e su l ts , y ie l d in g 4 4 - 4 6 % r e d u c t i o n s ( w h e n u s e d a t 4 1

/~ g/m l) a n d 3 2 - 3 4 % r e d u c t i o n s (w h e n u s e d a t 8 2 / t g /

m l). H y d r o c a r b o n r e d u c t i o n w a s b e l i e v e d to b e d u e t o

de gr a da t ion . T he se r e su l t s sugge s t e d tha t us ing c e l l -

f r e e b i o s u r f a c t a n t s t i m u l a t e d d e g r a d a t i o n b y i n d i g e -

nous m ic r oor ga n i sm s in t he so i l , g iv ing c lose ly

c o n s i s t e n t re s u l ts a s c o m p a r e d t o u s i n g a c t u a l m i c r o -

b i al c e ll s. T h i s m i g h t h a v e b e e n d u e t o p o o r a d a p t a t i o n

a nd l im i t e d su r v iva l a b i l i t i e s o f non- ind ige nous ba c -

t e r i a i n t he c on ta m ina t e d so il .

B i o s u r f a c ta n t s h a v e a l s o b e e n d e m o n s t r a t e d t o s u c -

c e s sf u l ly s o lu b i li z e a n d r e m o v e h y d r o c a r b o n p o l l u t a n ts

f r o m c o n t a m i n a t e d s u b s tr a te . S t u d i e s e m p l o y i n g b i o -

s u r f a c t a n t - c o n t a i n i n g c u l t u r e b r o t h s f r o m R h o d o -

c o c c u s S T - 5 ( A b u - R u w a i d a et a l . , 1 9 9 1 a , b ) a n d t h e

t h e r m o p h i l i c B a c i l l u s A B - 2 ( B a n a t , 1 9 9 3 ) w e r e c a rr i e d

ou t t o a sc e r t a in t he i r e f f e c t i ve ne ss i n r e m ov ing r e s idua l

o il f r o m s a n d - p a c k e d c o l u m n s . S a n d p a c k s c o m p o s e d

o f 4 5 - m e s h a c i d - c l e a n e d s a n d w e r e s a t u r a t e d w i t h o il

a n d t h e n f l o o d e d w i t h t h r e e p o r e v o l u m e s o f w a t e r t o

r e l e a s e u n b o u n d o il. B i o s u r f a c t a n t - c o n t a i n i n g c u lt u r e

m e d i a ( ST -5 , A B - 2 a n d P e t 1 0 0 6 ) w e r e t h e n c o m p a r e d

t o 0 . 1 % S D S , 1 % s p o l e n e a n d 1 % p e t r o l e u m s u l f o n a t e

f o r t he i r a b i l i t y t o r e m ove the r e s idua l o i l . Bo th Pe t

1 0 0 6 a n d A B - 2 c u l t u r e s b r o t h s w e r e f o u n d t o r e le a s e

9 5 % o f t h e r e s id u a l o i l ( T a b le 2 ), c o m p a r e d t o 6 3 a n d

5 8 % f o r t h e s u r f a c t a n t s s p o l e n e a n d p e t r o l e u m s u l -

f ona t e , r e spe c t ive ly ( Ba na t , 1993) . E l i se e v et a l . 1991 )

a l s o r e p o r t e d t h e a b i l i t y o f a b i o s u r f a c t a n t p r o d u c e d

f r o m B a c i l l u s sp. C- 1 4 to r e l e a se o i l f r om o i ly sa nd a t a

c o n c e n t r a t i o n o f 0 0 4 m g / m l . T h e s e e x p e r i m e n t s

d e m o n s t r a t e d t h e e f f e c t i v e n e s s o f b i o s u r f a c t a n t s i n

r e m o v i n g r e s i d u a l o i l f r o m s a n d a n d a r e s u g g e s ti v e o f

p o s s i b le a p p l i c a ti o n s i n E O R a n d i n o il re m o v a l f r o m

oi l - po l lu t e d sa nd .

N u m e r o u s b i o s u r fa c t a n t- p r o d u c in g m i c r o o r g an i s m s

we r e sc r e e ne d f o r t he i r a b i l i t y t o so lub i l iz e C 14 l a be l l e d

3 ,3 ', 4 ,4 ', 5 ,5 ' - he xa c h lor ob ip he ny l i n he xa n e (Va n

D y k e et a l . , 1993 b ). T h e i r f i l t e r e d b iosur f a c t a n t - c on-

t a in ing c u l tu r e b r o ths we r e use d to so lub i l i z e t he

h y d r o c a r b o n m i x e d w i t h so i l i n c e n t ri f u g e t u b e s w h i c h

we r e i nc ub a te d w i th sha k ing f o r 2 h a t 22C, c e n t r i -

f u g e d a n d t e s t e d f o r s o l u b i l i z e d h e x a c h l o r o b i p h e n y l .

O f t h e o r g a n i s m s t e s t e d , A c i n e t o b a c t e r c a l c o a c e t i c u s

R A G - 1 a n d P s e u d o m o n a s a e r u g i n o s a U G 2 d e m o n -

st ra ted th e best solubi l iza t ion, a t 41-9 an d 48 0%,

r e spe c t ive ly , c om pa r e d to c on t r o l s .

R h a n m o l i p i d b i o s u r f a c t a n t s f r o m

P s e u d o m o n a s

a e r u g i n o s a we r e c ha r a c t e r i z e d f o r t he i r a b i l i t y t o

r e m o v e h y d r o c a r b o n s f r o m s a n d y - l o a m s o i l a n d s i l t -

l o a m s o i l ( V a n D y k e et a l . , 1993a ) . So i l c on ta in ing

h y d r o c a r b o n m i x t u r e s (n a p h t h a l e n e , a n t h r a c e n e , p h e n -

a n th r e ne , f l uor e ne , 2 ,2 ' , 5 ,5 ' - t e t r a c h lo r ob iphe ny l ,

3 ,3 ' , 4 ,4 ' , 5 ,5 ' - he xa c h ior ob iphe ny l ) p lus pa r t i a l l y - pur i -

f i e d b iosur f a c t a n t so lu t ions we r e i nc ub a te d be f o r e te s t -

i n g h y d r o c a r b o n r e m o v a l . D i s ti ll e d w a t e r w a s f o u n d , i n

m o s t c a s e s, to r e m o v e < 1 0 % o f t h e h y d r o c a r b o n s

f r o m t h e s o il. T h e r h a m n o l i p i d s a t a c o n c e n t r a t i o n o f

5 g /1 w e r e f o u n d t o i n c r e a s e r e c o v e r y o f t h e h y d r o -

c a r b o n s t o 2 5 - 7 0 % i n s i l t - l o a m s o i l a n d 4 0 - 8 0 % i n

sa nd y- loa m so il . Ho we v e r , subs t a n t i a l a dsor p t io n o f

t h e r h a m n o l i p i d t o t h e s o i l w a s o b s e r v e d a n d s u c h a

h igh c onc e n t r a t i on o f b iosur f a c t a n t ( 5 g / l ) wa s use d a s

to be h igh ly im pr a c t i c a l .

S im i l a r e xpe r im e nt s w i th a m ix tu r e o f a l i pha t i c a nd

a r o m a t i c h y d r o c a r b o n s , m i x e d w i t h s a n d y - l o a m s o i l

y i e lde d s im i l a r r e su l t s ( Sc he ibe nboge n et a l . , 1994) . I n

t h is s t u d y , a 0 0 8 % m i x t u r e o f r h a m n o l i p i d s r e m o v e d

3 6 a n d 4 0 % o f t h e a li p h a ti c a n d a r o m a t i c h y d r o -

c a r b o n s , r e s p ec t iv e l y , c o m p a r e d t o 8 . 9 a n d 7 . 2 % f o r

w a t e r. T h e a d d i t i o n o f 0 1 % p y r o p h o s p h a t e t o t h e

r h a m n o l i p i d m i x t u r e w a s f o u n d t o e n h a n c e a l i p h a t i c

a n d a r o m a t i c h y d r o c a r b o n r e m o v a l to 5 6 a n d 7 3 % ,

r e sp e c ti v e ly . T h e s e r e s u lt s c o m p a r e d f a v o u r a b l y w i t h

2 % T r i t o n X - 1 0 0 ( 4 3 a n d 7 1 % ) a n d 2 % T w e e n 6 0 (7 . 9

a n d 3 2 % ) , w h e r e th e T w e e n 6 0 h a d t h e d i s a d v a n t a g e o f

c lo g g i ng t h e c o l u m n a f te r s e v e r a l t o ta l p o r e - v o l u m e

passages .

B i o r e m e d i a t io n f ie ld e x p e r i m e n t )

O i l - c o n t a m i n a t e d s o i l i s a c o m m o n p r o b l e m a n d i t s

t r e a tm e nt t e c hn ique s , i nc lud ing e xc a va t ion , i nc ine r a -

t i on , l a ndf a r m ing a n d l a ndfi ll i ng , c a n be d i f f ic u l t o r

e c o n o m i c a l l y p r o h ib i ti v e . T h e o t h e r m o s t e c o n o m i c a l

Ta ble 2 . Ef fec t iveness of var ious surfactant s o lut io ns in re leas ing res idual l ight crud e o i l f rom sand Abu-Ru waida e t aL 1 9 9 1 ;

Ba na t e ta L 1 9 9 1 ; B a n a t , 1 9 9 3 )

Surfactant ST (mN/m) RO (%) RR O (%)

0 1% SDS

1% Spolene

1% Petroleum sulfonate

ST-5 (from Abu -Ruw aida et aL, 1991a)

Pet 1006 (from Banat eta l . , 1991)

AB -2 (from Banat, 1993)

27 1 35 0 0

28 0 33 63 0

27 5 33 58 0

27-6 35 80 0

29 0 35 95 0

29 0 35 95 0

ST = surface tension; RO = residual oil; RR O = reco vere d residual oil.

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6 I . M . B a n a t

m e t h o d s i n c l u d e

i n s i t u

b i o r e m e d i a t i o n . M a c h i n e - o i l-

c o n t a m i n a t e d s o il h a s b e e n s h o w n t o b e r e m e d i a t e d b y

m i c r o b i a l i n o c u l a t i o n a n d b y b i o s u r f a c t a n t t r e a t m e n t

( F r y

e t a l .

1 9 9 3 b ) . F u r t h e r m o r e , F r y

e t a l .

( 1 9 9 3 a )

d e m o n s t r a t e d t h e s u c c e s sf u l b i o r e m e d i a t i o n o f o i l -c o n -

t a m i n a t e d s oi l a n d g r o u n d w a t e r f r o m a U S A r m y e n g i -

n e e r i n g p l a n t u s i n g n a t u r a l s u r f a c t a n t s p r o d u c e d b y

i n d i g e n o u s m i c r o o r g a n i s m s . T h e a d d i t i o n o f b i o -

sur f a c t a n t c a n inc r e a se t he b ioa va i l a b i l i t y o f hydr o-

p h o b i c c o m p o u n d s t o r e c e p t i v e b a c t er i a.

B i o s u r f a ct a n t s f r o m

P s e u d o m o n a s a e r u g i n o s a

S B 3 0

we r e t e s t e d f o r t he i r a b i l i t i e s t o r e m ove o i l f r om the

E x x o n V a l d e z A l a s k a n c o n t a m i n a t e d g r a v e l i n t h e

l a b o r a t o r y ( H a r v e y

e t a l .

1990) . A 1% b iosur f a c t a n t

so lu t ion wa s f ound to c ons i s t e n t ly y i e ld t h r e e - t im e s

h i g h e r oi l r e m o v a l at t e m p e r a t u r e s > 4 0 C a n d 1 m i n

c o n t a c t t i m e c o m p a r e d t o w a t e r c o n t r o l s. T h e s e r e s u l ts

d e m o n s t r a t e t h e c a p a c i t y o f b io s u r f a c ta n t s t o r e m o v e

e nv i r onm e nta l po l lu t a n t s , suc h a s o i l , f r om na tu r a l l y -

oc c u r r ing subs t r a t e s . I n a r e c e n t l a r ge - sc a l e i nve st i ga-

t i on , Br a gg

e t a t

( 1 9 9 4 ) r e p o r t e d t h e e f fe c t iv e n e s s o f

b io r e m e dia t i on a c t iv i t ie s on the E xx on Va lde z o i l spi ll

i n s i t u .

T h i s w a s c a r r i e d o u t t h r o u g h t r e a t m e n t o f t h e

c on ta m ina t e d shor e l ine s w i th a n o l e oph i l i c li qu id fe r t i -

l iz e r c o n ta i n i n g N a n d P t o a c c e l e r a t e t h e g r o w t h o f th e

n a t u r a l ~ h y d r o c a r b o n - d e g r a d i n g m i c r o o r g a n i s m s ;

c h e m i c a l s u r f ac t a n t a g e n ts , i n c o m p a r i s o n , w e r e f o u n d

t o b e i n e f fe c t iv e i n r e m o v i n g o i l f r o m s e d i m e n t s . O t h e r

e x t e ns ive b io r e m e dia t i on s tud i e s we r e suc c e ss f id ly

c a r r ie d o u t o n o i l - c o n t a m i n a t e d d e s e r t s a n d i n K u w a i t ,

b o t h

i n s i t u

a nd on- s i t e ( AI - Awa dhi

e t a l .

1994) . Al l

t he se t e c hn ique s d i r e c t l y i nvo lve d u t i l i z ing ind ige nous

m i c r o b i a l p o p u l a t i o n s , t h r o u g h t h e i n t r o d u c t i o n o f

s p e c if ic n u t r ie n t s a n d o x y g e n t o e n c o u r a g e b i o -

s u r f a c t a n t p r o d u c t i o n a n d h y d r o c a r b o n u t i l i z a t i o n

(Mii l le r -Hur t ig

e t a l .

1993) .

B I O S U R F A C T A N T S I N O I L S T O R A G E T A N K

C L E A N - U P

Fie ld t e s t s , u t i l i z ing b iosur f a c t a n t s p r oduc e d f r om a

pr op r i e t a r y ba c t e r i a l s t r a in ( Pe t 1006) , we r e pe r f o r m e d

to t e s t t he i r a b i l i t y t o c l e a n o i l s t o r a ge t a nks a nd to

r e c o v e r h y d r o c a r b o n s f r o m t h e e m u l s i f i e d s l u d g e

( Ba na t

e t a l .

1991) . P i lo t -p l a n t - sc a l e p r o du c t ion o f t he

b i o s u r f a c t a n t u si n g a 1 5 0 0 1 u p - li ft f e r m e n t e r p r o d u c e d

2 t o n n e s o f c u l t u re b r o t h . T h e b i o s u r f a c ta n t - c o n t a in i n g

br o th wa s use d a s a subs t i t u t e f o r c he m ic a l su r f a c t a n t s

i n a t e s t c a r r ie d o u t o n a n o il s t o r a g e t a n k b e l o n g i n g to

K u w a i t O i l C o m p a n y , K u w a i t . B a s a l s al t m e d i u m c o n -

t a in ing 2% w/v g luc ose a s a r e a d i ly a va i l a b l e c a r bon

s o u r c e w a s u s e d a n d o l e ic ac i d, a h y d r o c a r b o n s o u r c e

( 2 % v / v ) , w a s a d d e d a f t e r g l u c o s e c o n s u m p t i o n . B i o -

s u r f a ct a n t p r o d u c t i o n r e a c h e d a m a x i m u m a f te r

18 -19 h , a s m e a s u r e d b y r e d u c t i o n s i n t h e s u r f a c e a n d

in t e r r a c i a l t e ns ion in t he b r o th ( Ba na t

e t a l .

1991) . A t

t h e e n d o f t h e p r o d u c t i o n r u n , t h e c u l t u r e b r o t h w a s

s t e r il i z e d in t he f e r m e n te r a nd s to r e d in 20 0 1 s t e r il e

d r u m s .

S u r v e y s c o n d u c t e d o f t h e 4 4 m d i a m e t e r f l o a t i n g -

r o o f t a n k s h o w e d t h e p r e s e n c e o f a p p r o x i m a t e l y

750 m 3 o f s ludge . A f t e r i ns t a l la t i on o f c i r c u l a t i on

p u m p s , h o s e s , c i rc u l a ti o n b o x e s a n d c o n n e c t i o n s t o

m a n h o l e s , 1 5 t o n n e s b i o s u r f a c ta n t w e r e a d d e d t o t h e

t a nk , i n a dd i t i o n to a 1 : 1 c r ude o i l t o s ludge r a t i o a nd a

1 . 2 5 :1 b r a c k i s h w a t e r t o t o t al h y d r o c a r b o n

( s ludge + f re sh c r ude ) r a ti o . C i r c u l a t i on o f t he m ix tu r e

w a s c a r r i e d o u t f o r 5 d a y s , a t a m b i e n t t e m p e r a t u r e s o f

b e t w e e n 4 0 a n d 5 0 C , af t e r w h i c h m o s t s l u d g e h a d

b e e n r e s u s p e n d e d . A n e m u l s io n b r e a k e r w as a d d e d t o

s e p a r a t e t h e w a t e r f r o m t h e c r u d e o i l a n d t h e t w o

l a y e rs w e r e e a si ly e x t r a c t e d f r o m t h e t a n k . A f t e r c l e a n -

ing , t he t o t a l s l udge wa s de t e r m ine d to b e 85 0 m 3, a nd

ne a r ly 91% ( 774 m 3) wa s r e c o ve r e d a s c r ud e o il ,

w h e r e a s 7 6 m 3 r e m a i n e d a s i m p u r i ti e s a t t h e t a n k

b o t t o m a n d c o n s i s t e d m a i n l y o f n o n - h y d r o c a r b o n

m a t e ri a ls . T h e c h a r a c te r i st i c s o f t h e r e c o v e r e d c r u d e -

o i l s a m ple s a r e shown in T a b le 3 . T he c r ude o i l

e x t r a c t e d a f te r c l e an i n g w a s f o u n d t o h a v e A P I v a l u e s

r a n g i n g b e t w e e n 2 7 . 6 a n d 2 9 . 8 , s i m i l a r t o t h e A P I

r a n g e f o r t h e s t a n d a r d K u w a i t i c r u d e , a n d a t o t a l

h y d r o c a r b o n c o n t e n t o f 1 0 0 % . A p p r o x i m a t e l y 5 5 5 0

b a r r e l s o f s a l e a b l e c r u d e o i l w e r e p r o d u c e d . T h i s o i l

m a y b e s o l d t o c o v e r c o s t s o f th e c l e a n i n g at a p p r o x i -

m a t e l y S 1 0 0 0 0 0 - 1 5 0 0 0 0 ( U S ) p e r s t o r a g e t a n k . S u c h

a c l e a n- up p r oc e ss i s h igh ly de s i r a b l e a s i t i s e c on om i -

c a l ly re wa r d ing , e nv i r onm e nta l ly sou nd a nd i s l e ss

h a z a r d o u s f o r t h e p e r s o n s i n v o l v e d t h a n t h e c o n v e n -

t i ona l p r oc e ss ( L i l l ie nbe r g e t a l . 1992) . In a ddi t ion i t is

a l im i t e d a pp l i c a t i on f o r b iosur f a c t a n t s t ha t c a n be

e a s i l y c on t r o l l e d a nd , t he r e f o r e , would be a su i t a b l e

w a y f o r p r o g r e s s i n g t o w a r d s i n v o l v i n g t h e o i l c o m -

p a n i e s w h o a r e u s u a l l y r e l u c t a n t t o a d o p t t h i s t e c h -

no logy .

M I C R O B I A L L Y - E N H A N C E D O I L R E C O V ER Y

MEOR)

M E O R is a n i m p o r t an t t e r ti a ry r e c o v e r y t e c h n o l o g y

u t i l i z i n g m i c r o o r g a n i s m s a n d / o r t h e i r m e t a b o l i c e n d -

pr od uc t s f o r r e c o ve r y o f r e s idua l o il . I t is ge ne r a l l y

a c c e p t e d t h a t a p p r o x i m a t e l y 3 0 % o f t h e o i l p r e s e n t i n a

r e s e r v o i r c a n b e r e c o v e r e d u s i n g c u r r e n t E O R t e c h -

no log y ( S inge r & F inne r ty , 1984) . Poor o i l r e c ove r y in

e x i s ti ng p r od uc in g we l l s m a y be du e to se ve r a l fa c to r s .

T h e m a i n f a c t o r i s th e l o w p e r m e a b i l i ty o f s o m e r e s e r -

vo i r s o r t he h igh v i sc os i ty o f t he o i l whic h r e su l t s i n

p o o r m o b i l i t y . H i g h i n t e r f a d a l t e n s i o n s b e t w e e n t h e

wa te r a nd o i l m a y a l so r e su l t i n h igh c a p i l l a r y f o r c e s

r e t a in ing the o i l i n t he r e se r vo i r r oc k ( Bube la , 1987) .

S inc e m os t o f t he o i l r e m a in s i n t he r e se r vo i r fo l l owing

p r i m a r y a n d s e c o n d a r y r e c o v e r y t e c h n i q u e s , i n t e r es t

h a s e v o l v e d i n t e r t ia r y r e c o v e r y t e c h n i q u e s ( M o r k e s ,

1 9 9 3 ) . T e c h n i q u e s i n v o l v i n g t h e u s e o f c h e m i c a l o r

phys i c a l p r oc e sse s suc h a s p r e s sur i z a t i on , wa te r f lood-

i n g o r s t e am i n g , h o w e v e r , a r e g e n e r a l l y u n a p p l i c a b l e t o

m o s t o i l r e se r vo i r s . T h e us e o f c he m ic a l su r f a c ta n t s f o r

c l e a n ing- up o i l r e se r vo i r s i s a n unf a vour a b le p r a c t i c e

7/26/2019 banat1995 MEOR

7/12

B i o s u r f a c t a n t s p r o d u c t i o n a n d a p p l i c a t i o n s 7

T a b l e 3 . C h a r a c t e r i s t ic s o f b io s u r f a e t a n t - r e c o v e r e d c r u d e o i l s a m p l e s b e f o r e a n d a f te r b l en d i n g w i t h f r e sh c r u d e a n d a f t e r l o n g

s t o r a g e ( B a n a t e t a t 1 9 9 1 )

Property Test method Uni t Sample

1 2 3

Specific gravity IP 16 0/D 12 98 g/ml 0-883 0 877 0 888

AP I gravity IP 200 /D1 250 AP I 28.6 29.8 27 6

Viscosity kinematic at 20C IP 71 /D 44 5 cSt 166.6 54.1 196.6

Water con ten t (A) IP 74 /D95 % vo l ND ND ND

Sediment (B) IP 53 % vol ND ND ND

Water & sediment

( BS&W ) ( A + B) - - % v ol N D N D N D

Asphaltic material IP 143 % wt 2.09 2-14 1 05

Oil content

100

- ( A + B ) - -

vol 100 100 100

ND = N one detected.

Sample 1; biosurfactant-extracted crud e oil bef ore blending.

Sample 2; biosurfactant-extracted crud e oil after blending.

Sample 3; biosurfactant-extracted crud e oil after blending and 2 m onths storage.

t h a t i s h a z a r d o u s , c o s t l y a n d w i l l l e a v e u n d e s i r a b l e

r e s i d u e s w h i c h a r e d i f f i c u lt t o d i s p o s e o f w i t h o u t

a d v e r s e l y a f fe c t i n g t h e e n v i r o n m e n t .

S t r a t e g ie s a n d f a c t o r s a ff e c ti n g M E O R

T h e a p p r o p r i a t e r e m e d y f o r a n y g i ve n o il r e s e rv o i r w i ll

v a r y a n d b e b a s e d o n t h e c o n d i t io n s p r e s e n t. T e m p e r a -

t u r e , p r e s s u r e , p H , p o r o s i t y , s al in i ty , g e o l o g ic ma k e - u p

o f t h e r e s e r v o i r , a v a i la b l e n u tr i e n t s a n d t h e p r e s e n c e o f

i n d i g e n o u s f l o r a m u s t a l l b e t a k e n i n t o c o n s i d e r a t i o n . I t

i s e s t i m a t e d , b a s e d o n c r i t e r i a d e v e l o p e d b y t h e

N a t i o n a l I n s t i t u t e f o r P e t r o l e u m & E n e r g y R e s e a r c h ,

t h a t 2 7 % o f th e o i l r e s e r v o i r s i n t h e ma j o r o i l - p r o d u c -

i ng s ta t e s in th e U S A m a y b e s u i t a bl e fo r M E O R

( Br y a n t , 1 9 9 1 ). I t h a s a l s o b e e n e s t i m a t e d t h a t 4 0 % o f

t h e o i l- p r o d u c i n g c a r b o n a t e r e s e r v o ir s in th e U S A m a y

a l s o b e s u it a b le f o r M E O R ( T a n n e r

e t a l . ,

199 1 ) .

T h e m e c h a n is m s o f M E O R ' s a c t io n

in s i tu

a r e m o s t

p r o b a b l y d u e t o m u l t i p le e f f ec t s o f t h e m i c r o o r g a n is m s

o n t h e e n v i r o n m e n t a n d o i l. T h e s e m e c h a n i s m s

i n c l u d e : g a s f o r ma t i o n a n d p r e s s u r e i n c r e a s e s ; a c i d

p r o d u c t i o n a n d d e g r a d a t i o n o f l im e s t o n e m a t ri c e s;

r e d u c t i o n i n o i l v i s c o s i t y a n d i n t e r fa c i a l t e n s i o n b y b i o -

s u r f a c t a n t; s o l v e n t p r o d u c t i o n ; p l u g g i n g b y b i o ma s s

a c c u m u l a t i o n o r p o l y m e r fo r m a t i o n ; a n d d e g r a d a t i o n

o f l a r g e o r g a n i c m o l e c u l e s i n o i l, r e s u lt i n g i n d e c r e a s e s

i n v i s c o s i t y ( J a c k , 1 9 8 8 ; K h i r e & K h a n , 1 9 9 4 a ) .

T h e p r e s e n c e o f d if f e r e nt t y p e s o f m i c r o o r g a n i s m s

w i t h v a r y in g g r o w t h p r o p e r t i e s a n d m e t a b o l i te p r o d u c -

t i o n w i ll h a v e d i f f e r e n t e f f e c t s o n t h e r e s e r v o i r e n v i r o n -

me n t . T h u s , i t i s i mp o r t a n t t o c o n s i d e r a l l a s p e c t s o f

M E O R w h e n t r y in g t o i n fl u en c e o il p r o d u c t io n b y o n e

m e c h a n i s m , s u c h a s t h e u s e o f b io s u r f a c ta n t s . T h e r e

a r e s e v e r a l s t r a t e g ie s i n v o l v i n g t h e u s e o f b i o s u r f a c t a n t s

i n M E O R ( S h e n n a n & L e v i, 19 8 7) :

1 . T h e f i r s t i n v o l v e s i n j e c t i o n o f b i o s u r f a c t a n t - p r o -

d u c i n g m i c r o o r g a n i s m s i n to a r e s e r v o i r t h r o u g h t h e

w e l l , w i t h s u b s e q u e n t p r o p a g a t i o n

in s i tu

t h r o u g h

t h e r e s e r v o i r r o c k ( Bu b e l a , 1 9 8 5 ) .

2 . T h e s e c o n d i n v o l v e s t h e i n j e c t i o n o f s e l e c t e d

nu t r i en t s in to a reservo i r , t hus s t imula t ing the

g r o w t h o f i n d ig e n o u s b i o s u r f a c t a n t - p r o d u c i n g

mi c r o o r g a n i s ms .

3 . T h e t h i r d m e c h a n i s m i n v o lv e s t h e p r o d u c t i o n o f

b i o s u r f a c t a n ts i n b i o r e a c t o r s

ex s i tu

a n d s u b s e q u e n t

in j ec t ion in to the reservo i r .

L a b o r a to r y st u d ie s o n M E O R

L a b o r a t o r y s t ud i e s o n M E O R h a v e t y p ic a l ly u t il iz e d

c o r e s a m p l e s a n d c o l u m n s c o n t ai n in g t h e d e s i r e d s u b -

s t r a t e . T h e s e s u b s t r a t e s h a v e b e e n u t i l i z e d t o d e mo n -

s t r a t e t h e u s e f u l n e s s o f b i o s u r f a c t a n t s i n o i l r e c o v e r y

f r o m s a n d a n d l i me s t o n e . S i mi l a r l y , c o r e s a mp l e s h a v e

b e e n u s e d t o m o d e l t h e m o v e m e n t o f m i c r o o rg a n is m s

a n d n u t r i e n t s t h r o u g h s u b s t r a t e s t o a s c e r t a i n t h e i r u s e -

fu lness a f t e r i n j ec t ion in to o i l reservo i rs .

I n a n i n v e s t i g a t i o n i n w h i c h

B. sub t i l i s

w a s i n j e c t e d

t h r o u g h s a n d - p a c k e d c o l u m n s ( 2- 5 c m d i a m e t e r x 2 8

c m l e n g t h ) w i t h a p e r me a b i l i ty o f 4 0 0 0 md , a r e l e a s e o f

3 5 % r e s id u a l o i l, c o m p a r e d t o 2 1 % u s i n g t h e n u tr i e n t

s o l u t i o n c o n t r o l , w a s o b s e r v e d . S i mi l a r e x p e r i me n t s

w i t h

C . a c e t o b u t y l i c u m

u s i n g mo l a s s e s ( 4 % ) a n d 0 5 %

a m m o n i u m d i p h o s p h a te n u t ri e n t m e d i u m y i e l d e d 6 6

a n d 5 0 % o il r e c o v e r y i n t h e p r e s e n c e a n d a b s e n c e o f

p y r o p h o s p h a t e , r e s p e c t i v e l y . I t w a s s u g g e s t e d t h a t C .

a c e t o b u t y l i c u m

h a s a n a d v a nt a g e in M E O R b e c a u s e o f

i t s a n a e r o b i c g r o w t h a n d g a s - p r o d u c i n g c a p a b i l i t i e s

( Ch a n g , 1 9 8 7 ) . T h e a d d e d o i l w a s n o t s t e ri le , h o w e v e r ,

a n d t h e r o l e o f i n d i g e n o u s b a c t e r i a i n t h e o i l r e c o v e r y

w a s n o t m o n i t o r e d .

Vibr io aspar t igen icus

s t r a i n G SP- 1 a n d

B a c i l l u s

l i c h e n i f o r mi s

J F - 2 w e r e a l s o t e s t e d f o r t h e i r a b i l i t y t o

r e c o v e r r e s i d u a l o il f r o m c r u s h e d u n c o n s o l i d a t e d V i o l a

l i m e s t o n e ( 2 0 - 5 0 m e s h ) c o r e s ( A d k i n s

et al . ,

1992) .

Vi tr io aspar t igen icu s an

a c i d - p r o d u c i n g , h a l o p h i l i c ,

a n a e r o b i c , m o t i l e b a c t e r i u m ) w a s o b s e r v e d t o r e c o v e r

3 2 - 3 6 % m o r e o i l f r o m s a t u r a t e d c o r e s t h a n th e c o n t r o l

c o l u m n s a f t e r t h r e e t r e a t me n t s ( i n j e c t io n o f n u t r ie n t s ,

7/26/2019 banat1995 MEOR

8/12

8 I . M . B a n a t

i nc uba t ion , f l ood ing w i th b r ine ) . I n t h i s e xpe r im e nt a

2 7 - 3 8 % i n c r e a se in d i s so l v e d c a lc i u m c o n c e n t r a t i o n

w a s o b s e r v e d , d u e t o a c i d p r o d u c t i o n w h i c h c a n

d e g r a d e t h e l i m e s t o n e m a t ri x a n d c a u s e r e l e a s e o f t h e

r e s idua l o il . I n c om p a r i son , B . l i c h e n i f o r m i s i n c r e a s e d

o i l r e c ov e r y by 27%, w i th a 13% inc r e a se i n d i s so lve d

c a l c ium whic h wa s a l so a t t r i bu t e d t o b iosur f a c t a n t

p r o d u c t i o n ( A d k i n s et a l . 1992) .

P l u g g i n g a n d c l o g g in g i n v e s t i g a t i o n s

O n e o f th e m e t h o d s o f M E O R i n vo lv e s u s in g m i c ro -

or ga n i sm s in in s i tu se l e c t i ve p lugg ing t h r ough the

i n t r o d u c t i o n o f v i ab l e b a c t e r ia i n t h e a q u e o u s d i s p la c -

ing- f l u id i n j e c t e d i n to t he o i l we l l wa t e r - swe pt z one s .

I nve s t i ga t i ons i nvo lv ing h igh- pr e s sur e c onso l ida t e d

s y s t em s w e r e e m p l o y e d u s i n g 1 : 1 m i x t u r e s o f a

c e m e n t - s a n d m i x t u r e w i t h p o w d e r e d a l u m i n u m a n d

s h a p e d i n t o c o r e s . T h e s e o i l - s a t u r a t e d c o r e s w e r e

m o u n t e d i n a H e s s l e r c e l l a n d s u b j e c t e d to h i g h p r e s -

s u r e s w e e p s ( 2 5 0 - 3 5 0 k P a ) . W a t e r r e s u l t e d i n a 1 5 %

r e c o v e r y o f O I P , w h e r e a s i n j e c ti o n s o f m i c r o o r g a n i s m s

r e su l t e d i n p lugg ing o f t he c or e s . E xpe r im e nt s us ing

b r i n e - s a t u r a t e d B e r e a s a n d s t o n e c o r e s s h o w e d t h a t

i n j e c ti ng nu t r i e n t s a nd v i a b l e ba c t e r i a l c e ll s r e su l t e d i n

p e r m e a b i l i ty r e d u c t i o n s ( c lo g g in g ) o f 6 0 - 8 0 % ( J e n n e -

m a n e t a l .

1984) .

T o f a c i li ta t e m i c ro b i a l m o v e m e n t s a n d f o r m a t i o n o f

p lugs de e p w i th in t he r e se r vo i r , s t r a t a s t ud i e s e xa m in-

ing t he i n j e c t i on o f nu t r i e n t - s t a r ve d u l t r a m ic r o ba c t e r i a

( U M B ) i n t o t h r e e - d i m e n s i o n a l s a n d p a c k - r e s e r v o i r

s i m u l at io n s h a v e b e e n c a r r i e d o u t ( C u s a c k e t a l . 1992) .

S t a r ve d P s e u d o m o n a s sp . FC3 c e l l s we r e f ound to

p e n e t r a t e a s a n d p a c k 4 5 c m i n d i a m e t e r a n d 3 8 c m i n

l e ng t h . T h e U M B w e r e t h e n r e s u s c i ta t e d w it h n u t r ie n t s

t o g r o w in s i tu a nd f o r m a c onf lue n t ba c t e r i a l p lug .

S c a n n i n g e le c t r o n m i c r o s c o p y a n d c a r b o h y d r a t e a s s ay s

r e ve a l e d g lyc oc a lyx f o r m a t ions i n a l l s e c t i ons

e x a m i n e d . U M B a r e e f f e c ti v e f o r d e e p e r p e n e t r a t i o n

into oi l r eservoi r s as they a re smal l in s ize , have high

she a r - s t r e s s t o l e r a nc e a nd a r e use f u l f o r m ic r ob i a l

p lugg ing i n r e se r vo i r s w i th a pe r m e a b i l i t y r a nge o f 200

m D - 5 . 9 D ( C u s a c k e t a l . 1992) whic h c a n f a c i l i t a t e

s e c o n d a r y o i l - r e c o v e r y t e c h n i q u e s i n v o l v i n g w a t e r

sweeps .

S t u d ie s t o d e t e r m i n e t h e f a c t o r s i n f lu e n c i n g m i c r o -

b i a l m o v e m e n t t h r o u g h a n a e r o b i c , n u t r i e n t - s a t u r a t e d ,

u n c o n s o l i d a t e d O t t a w a s a n d - p a c k e d c o r e s w e r e c a r -

r i ed o u t u n d e r s t a ti c c o n d i t io n s ( R e y n o l d s e t a l . 1989) .

G a s - p r o d u c i n g m o t i l e E s c h e r i c h i a c o l i w e r e f o u n d t o

p e n e t r a t e c o r e s s a t u r a t e d w i th g a l a c t o s e - p e p t o n e u p t o

s ix t i m e s f a s te r t h a n n o n - g a s - p r o d u c i n g m o t i l e o r n o n -

m ot i l e m uta n t s . S im i l a rl y , m ot i l e s t r a ins o f E . c o l i w e r e

f o u n d t o p e n e t r a t e t h e c o r e f o u r t i m e s f a s t e r t h a n

m u ta n t s t r a ins de f e c t i ve i n f l age l l a r f o r m a t ion . Fur the r -

m or e , m ot i l e s t r a ins w i th f a s t e r g r owth- r a t e s pe ne -

t r a t e d t h e c o r e s a t a m o r e r a p i d r a t e. C h e m o t a x i s w a s

n o t f o u n d t o i n f l u e n c e th e p e n e t r a t i o n r a t e o f th e s e

ba c t e r i a . Suc h f a c to r s a r e im por t a n t t o c ons ide r i n t he

c h o i c e o f b a c t e r i u m t o e m p l o y in i n s i t u M E O R .

F i e ld s t u d ie s o f M O R

O n e o f t h e e a r ly f ie l d s t u d i es o n M E O R i n v o l v ed a n

u n c o n s o l i d a t e d w a t e r f l o o d e d s a n d s t o n e r e s e r v o i r i n

U n i o n C o u n t y , A r k a n s a s , U S A ( Y a r b r o u g h & C o t y ,

1983 ; H i t z m a n , 1988) . M ola sse s wa s i n j e c t e d a long

w i t h a n i n o c u l u m o f C l o s t r i d i u m a c e t o b u t y l i c u m i n to

t h e r e s e rv o i r. A f t e r t r e a t m e n t , c a r b o n d i o x i d e p r o d u c -

t i o n i n c r e a s e d a n d t h e p r o d u c t i o n o f o i l i n c r e a s e d b y

2 5 0 % ( T a n n e r e t a l . 1 9 9 1 ) . M e t a b o l i t e p r o d u c t i o n ,

h o w e v e r , w a s f o u n d t o m a t c h t h a t o f a n i n d i g e n o u s

m ic r oor ga n i sm , C . k l u y v e r i d e t e c t e d i n t h e r e s e r v o i r

w a t e r . T h e m e c h a n i s m s b y w h i c h t h e s e m i c r o -

o r g a n i s m s a c t e d w e r e b e l i e v e d t o r e s u l t f r o m a c i d

p r o d u c t i o n .

R e p o r t s o f s u c c es s fu l M E O R u s e i n c a r b o n a c e o u s

r e s e r v o i r s h a v e b e e n r e v i e w e d ( T a n n e r e t a l . 1991) .

I n j e c t i o n o f m o l a s s e s a n d a n a e r o b i c a c i d - a n d g a s -

p r o d u c i n g m i c r o o r g a n i s m s r e s u l t e d i n i n c r e a s e d o i l

r e c o v e r y . A d e c r e a s e i n w a t e r p H a n d a n i n c r e a s e in

c a r b o n d i o x i d e p r o d u c t i o n i n d i c a t e d a c t i v e g r o w t h o f

m i c r o o r g a n i s m s i n t h e r e s e rv o i r . A c i d a n d g a s p r o d u c -

t i o n w e r e b e l i e v e d t o b e i m p o r t a n t e l e m e n t s i n t h e o i l

r e c o v e r y ( L a z a r e t a l . 1 9 8 8 ; T a n n e r e t a l . 1991) .

O t h e r M E O R i n v e s t i g a t i o n s i n c a r b o n a t e r e s e r v o i r s

s h o w e d a n i n c r e a s e o f 6 0 - 1 2 6 % i n oi l p r o d u c t i o n i n

H u n g a r y ( H i tz m a n , 1 9 8 3 ) a n d a 2 0 0 % i n c r e a s e i n

G e r m a n y ( W a g n e r , 1 9 9 1 ) . I n j e c t i o n o f n u t r i e n t s a n d

D e s u l f o v i b r i o d e s u l f u r i c a n s

( H i t z m a n , 1 9 8 8 ) o b t a i n e d

f r o m s e w a g e s l u d g e , f o l l o w e d b y a s h u t - d o w n o f o i l

p r o d u c t i o n f o r a p p r o x i m a t e l y 6 m o n t h s , r e s u l t e d i n a

6 0 - 2 0 0 % i n c r e a s e i n oi l r e c o v e r y . A f t e r p r o d u c t i o n

r e s u m e d , a r e d u c t i o n i n p H , a n i n c r e a s e i n c a r b o n

d iox ide a nd a de c r e a se i n o i l v i sc os i t y we r e obse r ve d .

I n c r e a s e d n u m b e r s o f D . d e s u l f u r i c a n s i n t h e w a t e r

p r o d u c e d f r o m t h e r e s e r v o i r w e r e a l s o d e t e c t e d . I t i s

t he a u thor ' s be l i e f , howe ve r , t ha t t he use o f su lpha t e -

r e d u c i n g b a c t e r i a s u c h a s

D . d e s u l f u r i c a n s

w o u l d n o t b e

f a v o u r e d i n , o r r e c o m m e n d e d t o, t h e o i l in d u s t ri e s, d u e

t o t h e a d v e r s e e f f ec t s a n i n c r e a s e i n s u l p h u r c o n t e n t

c ou ld h a ve on t he o i l qua li ty .

T h r e e w e ll s o n t h e B u r n e t t J l e a s e ( U S A ) w e r e u s e d

i n a p i l o t i n v e s t i g a t i o n o f M E O R w h i c h i n v o l v e d t h e

in j e c t i on o f 80 1 o f ke r ose n e , f o l lowe d by 15 I o f a c om -

m e r c i a l b i o s u r f a c t a n t p r o d u c t ( R A M B i o c h e m i c a l s '

W e l P r e p 5 ). T h e w e ll s w e r e t h e n f l u s h e d w i t h s a l tw a t e r

a n d s h u t d o w n f o r 4 8 - 9 6 h . O i l p r o d u c t i o n i n cr e a se d

f iv e - fo l d f r o m 0 .3 b a r r e l / d a y b e f o r e t r e a t m e n t , t o 1 6

b a r r e l / d a y a f t e r t r e a t m e n t ( N e l s o n & L a u n t , 1 9 9 1 ). I n

a n o t h e r s e t o f e x p e r i m e n t s i n v o l v i n g t h e i n j e c t i o n o f

m ic r oor ga n i sm s a nd nu t r i e n t s i n to t he we l l s , f o l l owe d

b y a 3 d a y s h u t - d o w n p e r i o d ; a n 1 1 - 2 5 % i n c r e a s e i n

w e e k l y o il p r o d u c t i o n w a s d e t e c t e d ( N e l s o n & L a u n t ,

1 9 9 1 ; B r y a n t

e t a L

1993) .

Simi la r ly , injec t ions of P . a e ru g in o sa X a n t h o m o n a s

c a m p e s t r i s a n d B . l i c h e n i fo r m i s t h r ou gh th e we l l c a sing ,

f o l l o w e d b y l o n g e r s h u t - d o w n p e r i o d s o f 4 0 a n d 6 4

da ys f o r two we l l s a t t he Da q ing o i l f i e ld i n China ,

r e s u l te d i n a n i n c r e a s e in t h e n u m b e r s o f i n j ec t e d b a c -

t e r i a , o r ga n i c a c ids a nd c a r bon d iox ide a nd a s l i gh t

7/26/2019 banat1995 MEOR

9/12

B io su r fa c ta n ts p ro d u c t io n a n d a p p f i c a t i o n s 9

d e c r e a s e i n t h e i n t e r f a c i a l t e n s i o n i n t h e o i l - w a t e r

m i x t u r e s . T h e t w o w e l l s t e s t e d s h o w e d a n i n c r e a s e

f r o m 3 5 t o 5 5 t / d a y i n t h e f ir s t a n d f r o m 7 6 t o 1 0 - 1 1

t / d a y i n t h e s e c o n d ( Z h a n g & Z h a n g , 1 9 9 3 ).

I n a l l t h e p r e v i o u s l y - me n t i o n e d s t u d i e s , h o w e v e r , i t

is n o t k n o w n w h a t e f f e c t t h e s h u t - d o w n o f th e o il p r o -

d u c t i o n w e l l i t s e l f ma y h a v e h a d o n t h e i n c r e a s e i n o i l

p r o d u c t i o n , w h i c h i s a s e r i o u s d r a w b a c k i n t h e

m e t h o d o l o g y . F u r t h e r m o r e , a f ie l d e x p e r im e n t c a r r ie d

o u t a t t h e Ro ma s h k i n o o i l f i e l d i n Ru s s i a , w h e r e w e l l s

w e r e i n j e c t e d w i t h p h o s p h a t e a n d n i t r o g e n t o s t i mu l a t e

t h e g r o w t h o f n a t i v e mi c r o f l o r a ( I v a n o v

et al . ,

1 9 9 3 )

r e s u l t e d i n a n i n c r e a s e o f 3 2 9 % i n o i l p r o d u c t i o n , t h e

m e c h a n i s m s o f w h i c h a r e n o t y e t c le a r.

N e v e r t h e l e s s , c a r e f u l l y c o n t r o l l e d f i e l d s t u d i e s o f

M E O R a t t h e A l t o n F i e l d in Q u e e n s l a n d , A u s t r a li a

w e r e c a r r i e d o u t ( S h e eh y , 1 9 9 0 ). T h e M E O R s t ra t e g y

u s e d w a s t o i n t r o d u c e m i c r o o r g a n i s m s t h a t w e r e p r e -

s c r e e n e d i n s a n d p a c k s d e s i g n e d t o s i m u l a t e t h e

p h y s ic a l p a r a m e t e r s f o u n d i n t h e r e s e rv o i r. L a b o r a t o r y

a n a l y se s o f n u t ri e n t r e q u i r e m e n t s , m e t a b o l i t e p r o d u c -

t i o n a n d i n t e r a c t i o n s w i t h t h e i n d i g e n o u s mi c r o b i o t a

w e r e c a r r i e d o u t. A m i x t u r e o f m i c r o o r g a n i s m s a n d

n u t r i e n t s w a s f i l te r e d t h r o u g h 1 0 a n d 2 8 ~ m f i lt e r s a n d

i n j e c t e d i n t o t h e w e l l f o l l o w e d b y a s h u t - d o w n o f 2 0

d a y s . Co n t r o l e x p e r i me n t s w e r e i n i t i a t e d i n w h i c h t h e

n a t u ra l b a s e l in e p r o d u c t i o n w a s d e t e r m i n e d b e f o r e a n d

a f t e r t h e t r i a l s h u t - d o w n p e r i o d , a s w e l l a s a f t e r a c o n -

t r o l i n je c t io n o f w a t er . A n a p p r o x i m a t e l y 4 0 % i n o e a s e

i n o i l p r o d u c t i o n w a s o b s e r v e d , c o m p a r e d t o t h e c o n -

t r o l b a s e l i n e ( Sh e e h y , 1 9 9 0 ) . A d d i t i o n a l l y , a d e c r e a s e

i n t h e l e v e l o f t h e b a s e s e d i me n t a n d w a t e r , w i t h a n

i n c r e a s e d p e r c e n t a g e o f o i l c o n t e n t w a s o b s e r v e d .

I n c r e a s e d g a s p r o d u c e d i n t h e r e s e r v o i r w a s f o u n d t o

b e t h e r e s u lt o f i n c r e a se d c a r b o n d i o x i d e a n d m e t h a n e .

M i c r o b i a l n u m b e r s w e r e f o u n d t o r i s e f r o m = 1 0 3 / m l

i n p r e - i n j e c t io n w a t e r t o > 1 0 5 / ml a f t e r m i c r o b i a l

i n j e c t i o n . Su l p h a t e - r e d u c i n g b a c t e r i a w e r e n o t

o b s e r v e d t o b e s t i m u l a t e d a n d H 2 S p r o d u c t i o n w a s n o t

d e t e c t e d .

I n a l l t h e p r e v i o u s r e p o r t s i n v o l v i n g mi c r o -

o r g a n i s ms , n o c h a n g e s i n a n y p h y s i c a l c h a r a c t e r i s t ic s o f

t h e o il w e r e r e p o r t e d o r o b s e r v e d , h o w e v e r , o c c a s io n -

a l l y t h e i n t e r f a c i a l t e n s i o n o f t h e w a t e r - o i l i n t e r f a c e

d e c r e a s e d c o m p a r e d t o t h e c o n t r o l v a l u e s . T h e s e

r e su l ts a r e i n d ic a t iv e o f t h e e f f e c t i ve n e s s o f M E O R i n

o b t a i n i n g o i l w i t h t h e s a me d e s i r e d c h a r a c t e r i s t i c s a s

b e f o r e t h e t r e a t m e n t .

C O N C L U S I O N A N D F U T U R E O U T L O O K

T h e u s e f u l n e s s o f b i o s u r f a c t a n t s i n t h e e mu l s i f i c a t i o n

o f a q u e o u s h y d r o c a r b o n m i x t u r e s h a s b e e n c l e a r l y

d e m o n s t r a t e d . B i o s u r f a c t a n t s i n m a n y c a s e s h a v e

p r o v e d t o b e m o r e e f f e c ti v e t h a n c h e m i c a l s u r f a c ta n t s

a n d h a v e t h e a d d e d b e n e f i t o f b e in g b i o d e g r a d a b l e .

S t u d ie s o f o il - o r h y d r o c a r b o n - c o n t a m i n a t e d s a n d o r

s o i l h a v e a l s o i n d i c a t e d t h a t m i c r o o r g a n i s ms w h i c h

p r o d u c e b i o s u r fa c t a n t s, w h e n s t i m u l a t e d p r o p e r l y , c a n

a i d b i o r e m e d i a t i o n . L a b o r a t o r y s t u d i e s h a v e s h o w n

t h a t th e a d d i t i o n o f b i o s u r f a c t a n t m i x t u r e s a l o n e ma y

b e u s e f u l f o r s t imu l a t i n g b i o d e g r a d a t i o n o f th e s e c o n -

t a mi n a n t s i n t h e e n v i r o n me n t . B i o s u r f a c t a n t s h a v e a l s o

d e mo n s t r a t e d t h e i r u s e f u l n e s s i n t h e s o l u b i l i z a t i o n a n d

r e mo v a l o f o i l f r o m s a n d a n d s l u d g e i n o i l s t o r a g e

t a n k s . T h e r e f o r e , i n e c o l o g i c a l t e r ms , t h e u s e o f b i o -

s u r f a c t a n t s i s o b v i o u s f o r c l o s e d s y s t e ms b u t r e ma i n s

s p e c u l a t i v e i n t h e o p e n e n v i r o n m e n t .

T h e u t i li ty o f M E O R h a s n o t b e e n c o n c l u si v e ly

d o c u m e n t e d i n t h e fi e l d a t t h is s t a g e. P r e l i m i n a r y f i n d -

i n gs f r o m t h e f e w i n v e s t ig a t i o n s c a r r i e d o u t t o d a t e ,

h o w e v e r , s e e m p ro m i s in g . T h e p r e c i s e m e c h a n i s m o f

e n h a n c e d o il r e c o v e r y

in s i tu

i s u n c l e a r d u e t o t h e l a c k

o f c o n t r o l s i n s o me c a s e s , w i t h th e u n f o r s e e n d i f -

f i c u l t i e s u s u a l l y e n c o u n t e r e d

in s i tu

and insu f f i c i en t

a n a l y s e s i n o t h e r c a s e s . I t w o u l d a p p e a r t h a t i n c e r t a i n

c i r c u m s t a n c e s M E O R c o u l d b e a v i a b le a lt e rn a t iv e ,

w h i c h , i f c a r e f u l l y a p p l i e d , c o u l d p r o v e t o b e a n e c o n o -

mi c a l l y - f e a s i b le me t h o d o f e n h a n c i n g o i l r e c o v e r y .

H o w e v e r , t h e t e c h n o l o g i e s i n v o l v e d r e q u i r e a n i n t e r -

d i s c i p li n a r y e f f o r t a mo n g m i c r o b i o l o g i s ts , b i o c h e m i s t s ,

g e o l o g i s t s a n d p e t r o l e u m e n g i n e e r s . A n e v a l u a t i o n o f

t h e d i f f e r e n t c r i t e r ia f o r t h e a p p l i c a t i o n o f t h e v a r i o u s

mi c r o b i a l me t h o d s n e e d s t o b e e x t e n s i v e l y i n v e s ti g a te d .

F u t u r e e f f o r ts in s tr a in i m p r o v e m e n t a n d d e v e l o p m e n t

w i t h t h e a i d o f g e n e t i c e n g i n e e r i n g a r e e x p e c t e d t o h e l p

p r o g r e s s i n th i s e me r g i n g t e c h n o l o g y .

R E F E R E N E S

AI-Awadhi, N., Williamson, K. J. & Isok, J. D. (1994).

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