physical and chemical control of microbes

8/11/2019 Physical and Chemical Control of Microbes

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Physical and Chemical

Control of Microbes

Engr. Vera Marie L. Lanaria

ChE Department

CIT University



Why is microbial control necessary?

It is mainly to inhibit the growth of

pathogens.



Sterilization

• it refers to the removal or destruction of all

microbes, including viruses and bacterial

endospores, in or on an object

• is an absolute term that implies the

complete and total removal of all living

things



Aseptic

• it describes an environment or procedure

that is free of contamination by pathogens

• Ex. vegetables & fruit juices are available

in aseptic packaging; surgeons & lab

technicians use aseptic techniques to

avoid contamination while doing their job



Antisepsis

• refers to a process of

using chemical or

antimicrobial agent on

skin or other tissue• the chemical agent is

called antiseptic



Degerming

• is the removal of microbes from a surface

by scrubbing



Sanitizing

• is the process of disinfecting places and

utensils used by the public to reduce the

number of pathogenic microbes to meet

accepted public health standards



Pasteurization

• is the use of heat to kill pathogens and

reduce the number of spoilage

microorganisms in food and beverages



What is microbial death?

Death – is a phenomenon that involves the

permanent termination of an

organism’s vital processes



Factors that affect Death Rate

1) Number of microorganisms.

2) Nature of microorganisms.

3) Temperature & pH of the environment.4) Concentration of the agent .

5) Mode of action of the agent .

6) Presence of solvents, interfering organicmatter, and inhibitors.



How Antimicrobial Agents Work?

The cellular targets of physical & chemical

agents fall into 4 general categories:

1. the cell wall

2. the cell membrane

3. cellular synthetic processes (DNA, RNA)

4. proteins



Methods of Physical Control

Heat

Radiation

Filtration

Ultrasonic waves

Cold



Wh t i th ff t



What is the effect on

microorganisms when moist heat is

used as compared to dry heat?

Moist heat generally coagulates and causes

denaturation in microbes. In denaturation,

proteins separate as an insoluble mass as

they revert from their 3-dimensional

structure to a 2-dimensional structure.

In dry heat, the primary effect is due to

oxidation of large molecules; is a less

efficient process which requires a longer

period of process time



COLD

“Cold merely retards the activities of most

microbes.”

Lyophilization –

a combination of freezing anddrying; a common method of preserving

microorganisms and other cells



Radiation

Types of radiation that can be used as anti-microbial control agents:

1) Ionizing radiation – include x-rays and

gamma rays, which form free radicals incytoplasm and the free radicals destroymicrobial proteins and DNA

2) Ultraviolet radiation –

will effect nucleic acidsby binding together adjacent thymine bases;microbes will die because DNA cannotfunction or replicate itself



Ultrasonic waves

These high-frequency sound waves causes

vibrations that coagulate cellular proteins

and disintegrate cellular components.

Ultrasonic vibrations are commonly used as

cleaning agent for lab materials and as a

cell disrupters.



Filtration

Modern microbial filters: cellulose acetate;

polycarbonate; plastic materials (teflon &

nylon) where pores size can vary from

coarse (8 microns) to ultrafine (0.02 micron)



Applications of Filtration

use to prepare liquids that cannot withstand

heat, including serum & other blood products,

vaccines, drugs, IV fluids, enzymes, and

media

use for decontaminating milk & beer without

altering their flavor

used in water purification

used in removing airborne contaminants that

are common source of infection & spoilage



Chemical Agents

Gases that can perform sterilization:

• ethylene oxide (ETO) is used to sterile

plastics (such as petri dishes)

• beta propiolactone (BPL) is used to sterile

liquids

•

formaldehyde can be used for variousmaterials



Qualities in choosing antimicrobial

chemical agents:

rapid action even in low concentration

solubility in water or alcohol and long-term stability

broad-spectrum microbicidal action without being

toxic to human and animal tissues penetration of inanimate surfaces to sustain a

cumulative or persistent action

resistance to becoming inactivated by organic

matter noncorrosive or nonstaining properties

sanitizing and deodorizing properties

affordability and ready availability



Thank

you

physical and chemical control of microbes

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