dextran _1_

ti cng ngh sn xut dextran

MC LCI. GII THIU CHUNG Trang 1. Gii thiu chung v dextran ........................................................... 2 2. ng dng dextran ........................................................................... 6 II. NGUYN LIU 1. Ma................................................................................................... 7 2. Vi sinh vt ....................................................................................... 9 III. QUY TRNH CNG NGH SN XUT DEXTRAN A. S khi ....................................................................................... 10 B. Gii thch quy trnh cng ngh: .................................................... 12 IV. SN PHM 1. Tnh cht dextran:. ......................................................................... 42 2. Ch tiu cht lng sn phm: ....................................................... 42 V. BI BO KHOA HC V THNH TU CNG NGH 1. Cc nghin cu khoa hc: .............................................................. 44 2. Ln men dextran t dch chit carob v ng lactose: ............... 45 3. phng php sn xut dextran mi: ............................................. 48 VI. TI LIU THAM KHO: ................................................................ 50

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ti cng ngh sn xut dextran I. GII THIU CHUNG: 1. Gii thiu chung v dextran: a. nh ngha dextran: Dextran l mt polymer sinh hc, phn ln c tng hp t cc vi khun Lactic, c cc monomer l cc gc glucose lin kt vi nhau nh lin kt 1,6-glucoside. Nhng vi sinh vt khc nhau thng to nn nhng dextran khc nhau v trng lng phn t, v s phn b nhnh trong cu trc phn t. Cu trc ny cn ph thuc vo iu kin nui cy nhng vi sinh vt sn sinh ra dextran. Cc polysaccharide kiu dextran khng bt mu vi iod, phn t lng ca chng rt ln v khng c nh, dao ng trong mt phm vi rng, t 1000 2.000.000 Da. Dextran ch c tng hp t saccharose, khng th tng hp t glucose hay bt k cc loi ng no khc. Cc loi ng khc trong mi trng ln men ch ng vai tr nh ngun cung cp cacbon cho vi khun pht trin. b. Cng thc cu to: Dextran l mt loi polysaccharide tng t nh amylopectin, nhng mch chnh c hnh thnh bi lin kt -1,6 glucoside v cc nhnh bn c gn vi nhau bi lin kt -1,3 hoc -1,4 glucoside .

Hnh 1: Cng thc cu to Dextran c. C ch hnh thnh: a s cc polysaccharide ngoi bo t vi sinh vt u l sn phm ca s chuyn ha ni bo c cht thnh cc sn phm trung gian, v cui cng thnh polymer. Dextran khc cc polysaccharide ny, c cht khng thm nhp vo t bo vi sinh vt m n c-Trang 2-

ti cng ngh sn xut dextran chuyn ha bn ngoi t bo thnh -D-glucan phn nhnh, tc l dextran. Ch c saccharose c dng lm c cht cho phn ng ny. Nh vy, polysaccharide c th c sn xut bi cc t bo nguyn vn trong mi trng nui hoc c th c to ra t cc ch phm phi t bo cha phc h enzyme dextransaccharase ( -1,6-glucan : D-fructose 2-glucosyltransferase). Enzyme ny gii phng fructose v chuyn gc glucose ln mt phn t cht nhn cng c lin kt vi enzyme : (1,6- -D-glucosyl)n + saccharose (1,6- -D-glucosyl)n+1 + fructose

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Hnh 2: C ch hot ng ca enzym dextransaccharase. X1,X2,X l k hiu thay th cho enzym hot ng. Enzym gii phng fructose ra khi saccharose v kt hp to phc vi gc glucose. Sau nhm C-6 OH ca mt gc phc khc kt hp vi C-1 v gii phng X, kt qu l hai gc glocose lin kt li vi nhau bi lin kt -1,6-glucoside. Trong qu trnh polymer ha chui dextran ang di ra vn lin kt cht ch vi enzyme, mc polymer ho tng cho n khi phn t cht nhn (trong trng hp n gin nht l mt phn t c cht) gii phng chui polymer khi enzyme. Nng lng t do ca ln kt glucoside trong phn t disaccharide nm vo khong 23 kJ trong khi nng lng t do ca lin kt glucoside bn trong dextran thp hn mt cht (12-17 kJ). Do vy phn ng din ra theo chiu t tri sang phi i km vi mt s gim nng lng t do. Fructose c th chuyn thnh acid lactic, acid acetic, ethanol. ng lu l trong chui phn ng cn c s xut hin ca mt cht cho H+ trong phn ng gii phng fructose v nhn H+ trong phn ng lin kt hai gc glucoside li vi nhau. l hai nhm imidazolium(C3H4N2) ca histidine rt cn thit cho qu trnh tng hp dextran.

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Cc loi ng khc ngoi saccharose (nh l maltose) tham gia phn ng to thnh cc oligosaccharide thay v cc dextran cao phn t. Cc gc glucosyl cn st li trong qu trnh tng hp dextran c chuyn thnh cc gc t do ng vai tr nh l cht nhn c nh hng ln n phn ng. Trong tt c cc cht nhn th maltose v isomaltose c xem l c nh hng ln nht n phn ng. Cc cht nhn ny tng tc cng ho tr vi phc enzym-glucosyl hoc enzym-dextranosyl gii phng glucose hay mch dextran ra khi enzym hot ng, ng thi to lin kt vi glucose hay dextran ngay ti v tr ca enzym.

Hnh 3: C ch ngng phn ng tng hp dextran ca cht nhn Cc thnh vin thp nht ca cc oligosaccharide khng phi l cc phn t cht nhn c hiu qu, i lc i vi enzyme tng dn theo di chui. Tuy nhin, s hn ch v khuch tn cng tng theo trng lng phn t. Da vo c ch ny ngi ta c th khng ch c di mch dextran trong qu trnh sn xut bng cch iu khin s thu phn dextran to cc cht nhn.

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ti cng ngh sn xut dextran Khi cht nhn l dextran cao phn t, C-3 ca dextran lm cht nhn kt hp vi C-1 ca phc glucosyl-enzyme hoc dextranosyl-enzyme gii phng glucose hay dextran v hnh thnh mt lin kt nhnh gia dextran cht nhn v glucose hay dextran gii phng ti v tr ca enzyme.

Hnh 4: C ch ngng phn ng tng hp dextran ca cht nhn Phn ng ny to thnh lin kt nhnh cho mch dextran, dng (1,3)-glucosyl. Ngoi ra vn c lin kt nhnh dng (1,2)-glucosyl nhng rt t gp trong cu trc dextran. 2. ng dng: Dextran c bit n t th k mi chn, n c tm thy trong khi cu c trong sut qu trnh sn xut ng ma v ng c ci. Dextran c nhiu ng dng trong cng ngh thc phm, y dc, ha cng nghip chng hn nh t dc, cht nh ha, cht mang, cht n nh. Lin kt ngang trong dextran chng hn nh sephadex c s dng rng ri trong phn ring, sc k lc gel v tinh sch rt nhiu sn phm khc nhau nh protein trong nghin cu v cng nghip. Trong cng ngh thc phm: Dextran c s dng nhiu tuy nhin phm vi ng dng ca n rt hp. Dextran c s dng trong sn xut sa bt, yoghurt, nc xt c, mayonnaise, cht lm c mc ng v kem. N c s dng ngn chn qu trnh kt tinh ng, ci thin kh nng ht m, duy tr hng v hnh dng ca thc phm.-Trang 6-

ti cng ngh sn xut dextran Ngoi ra dextran cn c dng ch thnh thc n king i vi mt s bnh nh i tho ng, lm cht ng ha, cht n nh, cht to mng trong bo qun v ch bin thc phm. Trong y hc v th y: dextran c phn t lng khong 80000 c dng lm cht thay th huyt tng. Dextran c gn vi Fe thnh phc dextran Fe lm thuc tr bnh thiu mu v mt s triu chng c lin quan dn suy dinh dng, ri lon tiu ho. Dextran cn c dng ch to ch sinh hc, bng dnh sinh hc dng trong phu thut.

II. NGUYN LIU 1. Ma: Cy ma thng trng khu vc nhit i, ch yu l cc nc ang pht trin. Thi im thu hoch: Thu hoch tt nht khi cy ma t chn cng nghip, c hm lng ng o c phn gc v phn ngn l gn tng ng v phi m bo cc ch tiu: Brix >20%, Pol >19%, Rs87%, ECS (ch ng)>11. Nn thu hoch cc rung ma cn trng mi li trc cc rung ma lu gc. Khng thu hoch ma trong cc ngy rt m, tri ma to, t cn m t. Thu ma theo c tnh ging: ging chn sm phi thu hoch trc, ging chn mun thu sau bng cch cht th cng hoc thu bng my. Thu n u chuyn nhanh v nh my trong ngy. Bng 1: Thnh phn cc cht dinh dng trong ma Thnh phn Tnh theo trng lng ma(%) Saccharose ng kh Protein Acid t do Acid kt hp Cht keo Cht tro Nc 11.88 1.35 0.42 0.13 0.14 0.39 0.39 59.12 Tnh theo nc ma hn hp(%) 12.63 1.44 0.48 0.14 0.15 0.41 0.6 78.15 Tnh theo phn trm cht kh(%) 70-90 4-8 0.5-0.6 3-7 0.3-0.6 3-5

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ti cng ngh sn xut dextran Bng 2: Thnh phn khong trong nc ma: Thnh phn SiO2 K2 O Na2O CaO MgO Fe2O3 P2O5 SO3 Cl Hm lng (%) 0.25 0.12 0.01 0.02 0.01 Vt 0.07 0.02 Vt

Trong thnh phn quan trng l Saccharose. Saccharose l mt disaccharide do glucose v fructose lin kt vi nhau theo lin kt 1,2-glucoside v c gc quay cc l +66.5o6 CH 2OH 5

H4

O H OH3

H1

HOHC 2 O

1

O H3

H C56

H2

2C

OH4

OH

CH 2OH

H

OH

OH

H

SACCAROSE Hnh 5: Cng thc cu to saccharose

Saccharose d b thu phn nh enzym invertase hoc acid to glucose v fructose theo t l 1:1 c gi l ng nghch o. thc phm c pH acid cng thun li cho s nghch o. S nghch o ng lm tng cht kh ln 5,26%, tng nh v ngt v nht l tng ho tan ca ng trong dung dch. S tng tnh ho tan ca ng trong dung dch l do tnh ho tan cao ca fructose v tnh kh kt tinh ca glucose so vi saccharose.-Trang 8-

ti cng ngh sn xut dextran 2. Vi sinh vt a. Ging vi sinh vt: Vi sinh vt dng ln men dextran l cc chng thuc Streptobacterium destranicum, Streptococcus mutans, Leuconostoc dextranicus, Leuconostoc

mesenteroides, L.citrovorus Trong mi trng cha saccharose vi khun tit ra enzym dextran-saccharase (-1,6-glucan: D-fructose 2-glucosyltransferase, khi lng phn t 170kDa) phn gii saccharose ngoi bo thnh glucose v fructose ng thi tng hp glucose thnh dextran. Sn phm ph thuc c vo chng ln vo cc iu kin s dng cho sinh trng v tng hp polymer. mt s chng, dextransaccharase nm dng ha tan trong khi cc chng khc, n lin kt mt phn hay hu nh hon ton vi t bo. Sn xut dextran cng nghip dng Leuconostoc mesenteroides to ra mt polymer cha khong 95% lin kt -1,6 (phn cn li l lin kt -1,3) v mt trng lng phn t l 4-5 x 107 dalton.

Hnh 6: Vi khun Leuconostoc mesenteroides Leuconostoc mesenteroides l cu khun gram m, kch thc 1-1.5m khng c kh nng sn sinh catalase, ky kh hoc vi hiu kh, c kh nng ln men ng, khng tng hp acid lactic t D- v L-arabinose, D- v L-xylose, D- v L-ribose. Trong qu trnh nui cy chng c xp thanh chui. Trn mi trng rn c cha saccharose chng mc ln thnh cc khun lc v c ph mt lp mng nhy.-Trang 9-

ti cng ngh sn xut dextran C ging tng hp c acid lactic t ng lactose v c ging khng tng c acid lactic. Nhit sng ti u l 30oC, pH ti u l 7.0. Ging Leuconostoc mensenteroides c th c phn lp t cc loi rau ln men nh ci bp, sp l, b ng, c rt, v khoai ty. Ging sau khi c phn lp s c duy tr trong mi trng dinh dng cha saccharose 40C. b. Yu cu chn ging: Kh nng sinh c t : khng c . Kh nng sinh tng hp sn phm chnh: sn lng dextran to thnh l ln nht. Kh nng thch nghi v tc sinh trng: d nui cy, thch nghi tt vi mi trng, tc sinh sn nhanh. iu kin nui cy: mi trng nui cy d kim, r tin. Yu cu khc : Dextran to thnh bi ging vi sinh vt phi d dng lc v kt lng tt . III. QUY TRNH SN XUT DEXTRAN: A. S khi

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Ma

Ging Leuconostoc mesenteroides

Tch nc ma

B ma

Lc Nhn ging Chun b mi trng Ra Thanh trng

B ma

Ln men Ethanol Kt ta ln mt

Mm dextran

Ly tm

Chng ct

VSV v than hat tnh

Lc

Thu hi ethanol

Ti kt ta Ethanol Ha tan trong nc

Sy phun

Dextran

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ti cng ngh sn xut dextran B. Gii thch quy trnh cng ngh : 1. Tch nc ma : Mc ch: Khai thc. Tch nc ma ra khi ma . Bin i: +Vt l: Gim kch thc ma. +Sinh hc: s lng vi sinh vt tng. Phng php thc hin: X l ma trc khi p:

Mc ch: To iu kin p d dng hn, nng cao nng sut v hiu sut ca cng on p. Cy ma thng khng thng, xung bng ln xn, ma c v cng, c sc khng ln, ngoi v c nhiu phn trn trt kh p. Bi vy nn san bng v bm nh ma ma c d ko vo my, mt ma trn bng ng u ma trn bng y ti v my p ma lm vic n nh. Cc thit b x l ma thng dng l my san bng, my nh ti. My san bng: My gm mt trc quay gm 24 n 32 cnh cong c lp trn mt mt bng, quay ngc chiu vi chiu bng ma i. Chiu cao t mt bng n cnh tay my ty theo yu cu dy ca lp ma. My c dng san u lp ma va xung bng. Tc quay khong 40-50 vng/ pht. My bm: My bm ma thnh nhng mnh nh, ph v cc t bo ma, san ma thnh lp dy n nh trn bng, nng cao mt ma trn bng t 125-150 kg/m3 ln n 250-350 kg/m3. Cng dng my bm: - Nng cao nng sut p, do san ma thnh lp dy ng u, ma d c ko vo my p, khng d b trt, tc nghn. - Nng cao hiu sut p do v ma c x nh, t bo ma c ph v, lc p phn b u mi im nn my p lun y ti v nc ma chuyn ra d dng. Khi lp mt my bm nng sut my p tng ln 12-20%, hiu sut p tng 0.2%.

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ti cng ngh sn xut dextran My bm gm mt trc ln lng c nh vo cc tm a c khe lp cc li dao c trn hai u bng bi. Trn mi da li dao c lp i nhau v cn bng trng lng.

Hnh 7: My bm ma

Khong cch ca cc li dao k nhau thng l 50mm v c nhiu kiu li dao bm nh: li dao rc giy, kiu rng ca, kiu li vung.

r

h

Hnh 8: C li lp dao bm-Trang 13-

ti cng ngh sn xut dextran My nh ti: Sau khi qua my bm th cn nhiu cy ma cha c bm nh, cn c x v nh ti ra ma vo my p d dng hn, hiu sut p cao hn. Do ngi ta x dng thm my nh ti d gii quyt vn v lm cho hiu sut tng ln khong 1%. My nh ti kiu ba: l mt dng my dp bng cc ba xoay lp thnh hng song song xung quanh trc quay bng thp, t trong v my hnh tr, mt ct ngang hnh mng. Bn sn trong ca v c gn nhiu ming st dc thn my v c coi l cc tm k ca ba p. Ba p vi tc khong 1200v/ph theo chiu chuyn ng ca ma. Khi lp mt my nh ti kiu ba, t l t bo b x tng ln 95%.Ma vo1 3

2

4

Ma ra

Hnh 9: My nh ti kiu ba. 1. Thn v my 2. Ba dp 3. Trc da quay 4. Tm k My nh ti kiu da: Kiu ny gm hai trc p li bi nhiu da rng ca hnh nn lp tng i mt p vo nhau, hai trc quay tc khc nhau, do ma c x ti. Trc trn khong 150v/ph, trc di nhanh hn khong 460v/ph.

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Mia

Hnh 10: My nh ti kiu da My p dp: Mc ch: nhm tch nc ma ra khi cy ma v lm cho ma dp vn hn, thu nh th tch lp ma cho h thng p ma lm vic n nh hn, tng hiu sut p v lm gim bt cng hao ph. Cu to: My p dp c nhng rnh trn thn trc hnh ch V, gc m 60o, chiu su ca rnh khong3 / 2 ca khong cch gia cc rnh vi nhau.

Hnh 11: Trc p dp kiu Krajewski.

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ti cng ngh sn xut dextran My p dp hai trc: Gi my c nghing t 60-75o sao cho my vo ma lm vi ng ni gia hai tm trc mt gc 75od ma vo my v nc tho ra d dng.

Mia

Hnh 12: My p ma 2 trc My p dp ba trc: My gm ba trc, lp trn mt gi my, thc hin hai ln p. Cu to ging nh my p hai trc.

Hnh 13: V tr lp tm dn ma-Trang 16-


Thng s : + Tc my p dp bao gi cng nhanh hn cc my p sau khong 25% nh vy mi cung cp ma cho my p v ma vo my cn ln xn, cha u . + Lc nn trn trc nh: - i vi my p dp hai trc: lc nn bng 50-75% lc nn trn my p sau . - i my p dp ba trc: lc nn bng 65-75% lc nn my p sau . + Nng sut my p : - My p dp hai trc: 45-55% nc ma trong cy ma. - My p dp ba trc: 65-75% nc ma trong cy ma. p ma :

Mc ch: ly kit lng nc ma c trong ma ti mc ti a cho php . Cu to my p: Gm cc b phn chnh : - Gi my: l b khung chu lc rt ln t 3500-7000F, c bng thp, trn lp tt c chi tit ca my . - Cc trc p: trc nh, trc trc, trc sau. Trc p thng c li trc bng thp, mt u gn mt bnh xe rng cao chn truyn chuyn ng lng cht trong o trc bng gang c bit. Khi c ngi ta phi to ra mng kt tinh ln mt gang nhm ko ma d. Mt v trc c x nhiu rnh quanh trc ko ma tt hn to thun li cho b p sau. Thng dng ph bin nht l loi rng c tit din hnh tam gic. cc trc trc v trc sau thot nc ma nhanh ta tin thm nhng rnh su 25 mm v rng khong 5 mm, khong 4 rng tin mt rnh i vi trc trc v 6 rng i trc sau. - B gi trc v b iu chnh v tr lp trc. Hu ht khng s dng trc bng bi m dng cc gi c ng dn nc lm ngui v c lt bng vng lt kim loi mm (Cu), c rnh dn du bi trn thng xuyn. - B phn nn trc nh: c gi l bnh t sc to ra lc nn trn trc nh, tng kh nng ly nc ma. Thng dng thit b nn bng kh, din tch t thit b nh, tc dung tng d dng, iu chnh lc kh nn nhanh, c th lp tc x van kh nn khi ma vo trc p kh khn gim lc nn, ma i qua trc d dng.

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Hnh 14: Thit b nn bng kh - Tm dn ma (lc y) v cc lc khc. c lp trn gi my nm gia hai trc di. Ma p t ming trc c chuyn sang ming sau nh tn dn ma. Tm dn ma phi dy, v n phi chu mt lc nn nht nh v c cong mt lc thch hp dn ma d dng. Khi lm vic, tm dn ma chu tc dng ca hai lc: mt lc y ca ma vo v mt lc nn t trn trc nh xung. Bi vy khi xc nh hnh dng mt lc ngi ta phi xc nh phng ca tng hp ca hai lc trn. Thng s : Lc nn ca my p :

Trc y v ngay c hin nay cc x nghip ln ng bn c gii, cc trc p khi lm vic khng t thay i c v tr. Trong qu trnh lm vic, lp ma vo lc dy lc mng. Lc dy ma c p kit, cng sut ng c ko my tng cao; nhng lc mng ma khng c p kit, cng sut ng c ko my li gim thp. Do , hiu sut p khng cao, cc ng c lm vic khng n nh cng sut, gy lng ph vn u t v d c s c trong sn xut. khc phc nhc im trn, hin nay trong cc my p hai hoc ba trc, trc nh u c thit k c th t nng ln h xung c tu thuc lp ma. Nhng lp ma c p vi mt lc nht nh, trn trc nh ngi ta lp cc b phn tng lc nn. Khi lm vic di tc dng ca b phn tng lc nn, trc nh tc dng ln lp b ma mt lc. Lc c biu th bng quan h sau : P = k.L.D Trong : P: tng lc nn (N). k: h s.-Trang 18-

ti cng ngh sn xut dextran L: chiu di trc nn (m). D: ng knh trc p (m). Vi cch biu th trn, cng thc ny khng th hin c ngha thc t. Khi lm vic lp b chu mt p sut rt ln do tng lc nn P ch phn b trn mt b mt c chiu di L v chiu rng bng D/10. V vy, lc nn trn n v din tch ca my p c xc nh theo quan h : p=P 0.1.D.L

Trong : p: p sut (N/m2). P: Tng lc nn trn nh trc (N). L: chiu di trc p (m). D: ng knh trc p (m). Quan h gia lc nn v hiu sut p: khi tng lc nn, hiu sut p tng. Theo thc nghim lc nn tng t 0 n 148.105 N/m2 hiu sut p tng nhanh, khi tng n trn 148.105 N/m2 hiu sut p tng nhng chm. Chn v phn phi lc nn ca dn p: chn lc nn ca dn p thng phi cn c vo nhng im sau: - S lng my p trong dn p, s my p nhiu c th h thp lc nn. - Cng sut ko ca motor hoc my hi nc, cng sut cao cho php s dng lc nn cao. - S bn vng ca cc b phn trong my p. - c im ca nguyn liu: ma nhiu x cn dng lc nn cao mi t c hiu sut cao . Nu thit b tt, my p dp c th dng ti 148.105 N/m2 v cc my p kit c th dng ti 296.105 N/m2. Hin nay c nhiu quan im khc nhau v vic phn phi lc nn trn cc my p: - Dng lc nn tng dn t b u n b cui, hiu sut p t cao. - Dng lc nn gim dn, khc phc c nhc im trn. - Dng lc nn nh nhau. Nhng ni chung hin nay hu ht cc nh my u dng lc nn tng dn . S phn phi lc nn mt s nh my (105 N/m2)

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Nh my Philipin(h my p 15 trc) Qung ng Ha Oai Tc ca my p :

My dp 212.87 151.07 112.81

My I 230.535 245.25 241.32

My II 235.27 247.21 243.38

My III 269.77 254.09 255.06

My IV 272.71 261.97

Tc my p trong cng nghip biu th di hai loi: - Tc thng, k hiu V, n v m/ph. - Tc vng quay, k hiu , on v vng/ph . Hai loi cng thc ny c th chuyn i theo cng thc : V = D. . Trong : D: ng knh trc p. Hin nay cng c nhng vn sau : - Tc nhanh p lp ma mng. Lc nn xung u, tr lc nh, nc ma t b b ht tr li, nc thm thu phun vo c thm u. - Tc chm, lp ma dy. Tc chm, thit b lu mn, cng sut tiu hao t. Nhng v mt cng ngh hc c nhc im l s phn b lc nn khng u, b ma d ht nc ma tr li do nh hng n hiu sut p. Vi hai quan im trn c mt s nh my dng tc my p tng dn t my u n my cui, mt s nh my khc dng tc chm dn t my u n my cui. 2. Lc: Mc ch: chun b cho qu trnh ln men. Tch cn cn li trong nc ma sau khi p. Thit b: thit b lc khung bn .

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3. Chun b mi trng : Mc ch: chun b cho qu trnh ln men. Bin i: + Ha hc: Thay hm lng cc cht dinh dng, pH tng. + Cc ch tiu cn li bin i khng ng k. Phng php thc hin: Mi trng ln men l mi trng nc ma c b sung dng cht, khong v cc yu t cn thit cho vi khun sng. Pha long: nc ma sau khi c loi b tp cht c em pha long vi hm lng ng ban u khong 17%. Chnh pH: pH ca mi trng ln men ban u l 7, l pH ti kch cho L.mesenteroides tng sinh trong giai on u ca qu trnh ln men. B sung ngun khong: Mi trng cn c b sung mui phosphat, mui amon v ion Mg2+, cc loi khong ny c nh hng trc tip n cu trc ca dextran. K2HPO4 0.2%-Trang 21-

ti cng ngh sn xut dextran MgSO4 MnSO4 FeSO4 NaCl CaCl2 0.02% 0.001% 0.001% 0.001% 0.005%

B sung cc cht dinh dng khc: Dch chit nm men 0.5% Peptone 0.5%

V mt s cc cht vi lng khc: Histidin, Thiamin, Biotin, acid panthothenic, acid nicotinic, amino acid valine, glutamic acid . nh hng ca mi trng n sn phm dextran to thnh: Mi trng: Vic la chn mi trng hp l v duy tr nhng thnh phn dinh dng trong qu trnh ln men, chng hn nh amino axit, vitamin, v cc nguyn t khong l ht sc quan trng. Bi v n s nh hng tc pht trin ca vi khun v sn lng dextran to thnh. Vic trung ha nh k mi tng ln men s lm tng sn lng dextran c phn t lng ln v kh nng sinh tng hp enzym ca vi khun t gi tr ln nht l 6.5-7.2. S gim nht ca dextran trong mi trng nui cy l do s xut hin ca cc enzym ni bo khng bn nhit. Cc enzym ny xut hin khi t bo Leuconostoc b cht v phn hy . Nhit thch hp ca mi trng nui cy cho s hnh thnh cc enzym ni bo l t 200C n 300C. CaCl2 khng nh hng ti sinh khi ca vi khun nhng nh hng n lng dextransaccharase to thnh v hot tnh ca enzym trong qu trnh ln men. Sau y l s cho thy nh hng ca CaCl2 vi lng dng l 0.05% ln s to thnh dextransaccharase.

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Biu 1: nh hng ca CaCl2 n s to thnh enzym dextransaccharase K2HPO4 ng vai tr nh ngun dinh dng, tuy nhin nu cho nhiu K2HPO4 qu s lm gim lng Ca++ c trong mi trng. Nng c cht : Nng c cht nh hng n sn lng v trng thi dextran to thnh. Rt t dextran c to thnh khi nng c cht nh hn 2%. Vic tng nng saccharose t nh hng n sn lng dextran to thnh, nhng nh hng n khi lng phn t dextran to thnh. Trong khi vic tng nng glucose v NaCl s lm tng sn lng v t nh hng n lng dextran to thnh. Nng saccharose cng cao th khi lng phn t dextran to thnh cng thp, hay s lng dextran cao phn t to thnh cng thp, dextran vi khi lng phn t thp cng tng, nht cng gim. Khi nng ng 30%, t l gia lin kt 1,6 v cc lin kt nhnh khng phi 1,6 l 29 trong khi ti nng ng 5% th t l l 8.5. Bng 3: nh hng ca nng ng saccharose ln sn lng dextran ca ging L.mesenteroides NRRL B-512F Nng Succharose (g/100ml) Sn lng dextran (g/100 ml)-Trang 23-

nht (cp)

ti cng ngh sn xut dextran 5 10 20 30 40 50 1.7 4.08 5.46 5.45 4.46 3.12 4.73 22.03 31.89 27.59 24 18.59

Nu cc dextran trng lng phn t thp c a vo lm mi th enzyme s c nhiu im khi u v cc polymer tng i ng nht s c to thnh. iu quan trng l cc t bo vi khun khng c cha cc vt ca cc dextran c trng lng phn t cao. V vy nguyn liu cy phi c ra vi ln bng dung dch mui loi cc dextran bm vo. Khi nng ng >20-25% th s to thnh dextran xy ra yu do vi khun khng th pht trin tt trong mi trng c p sut thm thu cao. 4. Thanh trng: Mc ch: chun b. Thanh trng l tiu dit cc vi sinh vt khc b nhim vo trong mi trng ln men. Ta khng th tit trng v qu trnh tit trng lm phn hu cc cht dinh dng c trong mi trng ln men. Ta cng khng th tit trng nc ma trc ri mi b sung dng cht vo mi trng ln men v mt s dng cht c sn trong nc ma d b phn hy nhit cao v nguy c ti nhim vi sinh vt l rt cao trong qu trnh b sung dng cht. Bin i: + Vi sinh: Vi sinh vt b tiu dit hoc c ch. + Vt l: Nhit tng. + Ha hc: Mt s cht dinh dng b mt. + Ha l: ha tan tng. + Ha sinh: Mt s enzym b c ch. Thit b: thanh trng mi trng nc ma ta dng h thng my thanh trng v lm ngui dng bn mng. C ch: Lu cht mi trng i vo thit b bn trong bn mng theo mt ng ng, hi nc i vo thit b theo mt ng ng khc. Hi nc v dch mi trng qua-Trang 24-

ti cng ngh sn xut dextran cc bn mng khc nhau v thc hin trao i nhit vi nhau. Cc bn mng c vch ngn c bit ch cho mt loi lu cht i qua bn. Bn mng c b mt gn sng lm tng din tch b mt truyn nhit v to ch chy ri tng tc truyn nhit.

Hnh 15: S cu to thit b truyn nhit bn mng

Hnh 16: Nguyn l lm vic ca thit b bn mng

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Thng s: Mi trng ln men sau khi c chnh pH v pha trn cc cht dinh dng, khong theo t l thch hp cho qu trnh ln men c em thanh trng 70-75oC, sau c lm ngui v 30oC l nhit ti u nht vi khun pht trin tng sinh trong giai on u ca qu trnh ln men. Sau khi thanh trng mi trng c lm ngui n 30oC v c a thng vo bn ln men. 5. Nhn ging: Mc ch: Chun b ging cho qu trnh ln men. Phng php thc hin: Chun b cy chuyn: Canh trng vi khun c chun b bng cch cy 1 ng ging vi khun vo mi trng tit trng. Canh trng c lc c hc trong 24 gi 250C. Sau thc hin cc bc nhn ging (mi trng c o trn 100 v/ph). Mi cp nhn ging c thc hin trong 14-16 gi (vn ti nhit 250). n khi s lng ging cn thit, cho vo bnh ln men. Khi s dng thi gian cy chuyn l 24 gi, mi trng ln men c gi tr nht cc i cao (dextran A trong bng sau). Nu s dng thi gian cy truyn l 36 ti 48 gi (nh i vi dextran D v B) th gi tr nht cc i s thp hn Bng 4: D liu v cc loi dextran thu c t cc mi trng nghin cu Dextran nht Tnh cht ca dextran tinh khit P (%) nht tng []

tuyt i Hm lng N (%)-Trang 26-

ti cng ngh sn xut dextran ca mi (%) i ti 250,

trng (cp) A B C D E F G 446 73 5 203 10 14 847 25.3 24.7 22.2 23.7 21.6

dextran _1_

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