Physical and Chemical Control of Microbes
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Transcript of Physical and Chemical Control of Microbes
8/11/2019 Physical and Chemical Control of Microbes
http://slidepdf.com/reader/full/physical-and-chemical-control-of-microbes 1/23
Physical and Chemical
Control of Microbes
Engr. Vera Marie L. Lanaria
ChE Department
CIT University
8/11/2019 Physical and Chemical Control of Microbes
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Why is microbial control necessary?
It is mainly to inhibit the growth of
pathogens.
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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
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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
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Antisepsis
• refers to a process of
using chemical or
antimicrobial agent on
skin or other tissue• the chemical agent is
called antiseptic
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Degerming
• is the removal of microbes from a surface
by scrubbing
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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
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Pasteurization
• is the use of heat to kill pathogens and
reduce the number of spoilage
microorganisms in food and beverages
8/11/2019 Physical and Chemical Control of Microbes
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What is microbial death?
Death – is a phenomenon that involves the
permanent termination of an
organism’s vital processes
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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.
8/11/2019 Physical and Chemical Control of Microbes
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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
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Methods of Physical Control
Heat
Radiation
Filtration
Ultrasonic waves
Cold
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Wh t i th ff t
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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
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COLD
“Cold merely retards the activities of most
microbes.”
Lyophilization –
a combination of freezing anddrying; a common method of preserving
microorganisms and other cells
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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
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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.
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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)
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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
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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
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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
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Thank
you