13 Applied and Industrial Microbiology

APPLIED AND INDUSTRIAL
MICROBIOLOGY

Food Microbiology

 The earliest methods of preserving foods were:
 Drying.
 Addition of salt and sugars.
 Fermentation.

Foods and Disease

 Food products might be a source of widespread disease
outbreaks.

 To minimize the potential for disease outbreaks, communities
have established local agencies whose role is to inspect dairies
and restaurants.

 Food safety is monitored by:

 FDA (United States Food and Drug Administration).
 USDA (Department of Agriculture).
 HACCP (Hazard Analysis and Critical Control Point).

Industrial Food Canning

 Commercial sterilization of food is accomplished by steam
under pressure in a retort (operate similar as autoclave).

 Commercial sterilization heats canned foods to the minimum
temperature to destroy C. botulinum endospores while
minimizing alteration of food.

 The process uses sufficient heat to reduce a population of
C. botulinum by 12 logarithmic cycles (12D treatment).

 Canned food stored above 45oC can be spoiled by
thermophilic anaerobes.

 Thermophilic anaerobic spoilage is sometimes accompanied
by gas production.

 If no gas is formed, the spoilage is called as flat sour spoilage.

Industrial Food Canning

 Mesophilic bacteria can spoil canned foods if the food is
underprocessed (improper heating procedure) or if the can
leaks.

 Acidic foods such as tomatoes or preserved fruits can be
preserved by heat of 100oC because microorganisms (molds,
yeasts, vegetative bacteria) that survive are not capable of
growth in a low pH.

 Byssochlamys,Aspergillus and Bacillus coagulans are acid-tolerant
and heat-resistant microbes that can spoil acidic foods.

The commercial sterilization process in industrial canning.

Blanch in hot water
or steam softens
the product to
easily fill the can.

Washing, Steam box
sorting,
blanching Cans are Steam is used to The cans are Cans are Cans are then Cans are labeled,
filled to exhaust, or drive sealed. sterilized by cooled by stored, and
This treatment capacity, out, dissolved air. pressurized submersion in a delivered for sale.
lowers the microbial leaving steam in a water bath or by
population and minimal dead retort, similar to spraying them with
destroys enzymes space. an autoclave. water.
that might alter
color, flavor, or
texture.

Commercial canning retorts.

The construction of a metal can. Sealing
Formation of a side seam compound

Formation of a double seam for
top or bottom

Common Types of Spoilage in Low-Acid and Medium-Acid Canned Foods (pH above 4.5)

Aseptic Packaging

 The use of aseptic packaging to preserve food has been
increasing.

 Presterilized materials are assembled into packages and
aseptically filled with heat-sterilized liquid foods.

 Packages are usually made of some material that cannot
tolerate conventional heat treatment, such as laminated paper
or plastic.

 Metal container can be sterilized with superheated steam or
other high-temperature methods.

Radiation and Industrial Food Preservation

 Gamma and X-ray radiations can be used to:

 Sterilize food.
 Kill insects and parasitic worms.
 Prevent the sprouting of fruits and vegetables.

 Radiation is measured in Grays.
 Levels of irradiation doses:

 Low doses of irradiation (less than 1kGy).

 Used for killing insects and inhibit sprouting as in potatoes.
 Delay ripening of fruits during storage.

 Pasteurizing doses (1 to 10 kGy).

 Used on meats and poultry to eliminate/ reduce the number of
specific pathogen.

 High doses (more than 10kGy).

 Used to sterilize/lower the bacterial in spices.

Irradiation logo. This logo, the international radura symbol, indicates that a food has received irradiation treatment.

Approximate Doses Of Radiation Needed To Kill Various Organisms (Prions Are Not Affected)

High-Pressure Food Preservation

 A recent development in food preservation is the use of a high-
pressure processing technique.

 Pressurized water (87,000 psi) is used to kill bacteria
(Salmonella, Listeria and E. coli) in fruit and meat.

 It also killed non-pathogenic microorganisms that tend to
shorten the shelf life of products.

 Advantages:

 Preserve colors and taste of foods.
 Does not provoke the concern of irradiation.

The Role of Microorganisms in Food Production

Cheese.
 All types of cheeses require formation of curd.
 Curd is made up of a protein, casein and is usually formed by

action of enzyme rennin, which is aided by acidic conditions
provided by certain lactic acid-producing bacteria.
 Curd can be separated from the main liquid fraction called
whey.
 Hard cheeses are produced by lactic acid bacteria.
 Semisoft cheeses are ripened by Penicillium on surface.

Making cheddar cheese.

The milk has been coagulated by the action The curd is chopped into small cubes to
of rennin (forming curd) and is inoculated facilitate efficient draining of whey.
with ripening bacteria for flavor and acidity.
Here the workers are cutting the curd into
slabs.

The curd is milled to allow even more drainage
of whey and is compressed into blocks for extended
ripening.The longer the ripening, the more acidic
(sharper) the cheese.

The Role of Microorganisms in Food Production

Other Dairy Products.
 Butter is made by churning cream until the fatty globules of

butter separate from liquid buttermilk.
 The flavor and aroma of butter are from diacetyls (metabolic

end-product of fermentation by some lactic acid bacteria).

 Yogurt is made from milk and is inoculated with a mixed
cultures of Streptococcus thermophilus (acid production) and
Lactobacillus delbrueckii bulgaricus (flavor and aroma).

Nondairy Fermentations.
 Sugars in bread dough are fermented by yeast to ethanol and

CO2.The CO2 causes the bread to rise.

The Role of Microorganisms in Food Production

Alcoholic Beverages andVinegar.

 Microorganisms are involved in the production of almost all alcoholic
beverages.

 Beer and ale are products of fermented starch by yeasts.

 Beer is fermented slowly with yeasts strain remains on the bottom.
 Ale is fermented rapidly at high temperature with yeasts strain that form

clumps.

 Yeasts unable to use starch directly.
 Malting: germinating barley converts starch to maltose and glucose.
 For sake, rice starch is converted to sugar by Aspergillus.
 Wines are made from fruits (grapes) that contain sugar where yeast can

use directly for fermentation.
 Yeast ferment sugars to ethanol and CO2.

 Grape wine requires bacterial malolactic fermentation.

 Acetobacter and Gluconobacter convert ethanol to acetic acid (vinegar).

The basic steps in making red wine.

Grapes are tested and Sulfite is added to kill undesirable
picked. yeasts and bacteria.

Yeast inoculum is Result is pressed to separate
added. solids from wine.

Wine is clarified in
settling vats.

Fermentation
occurs.

Grapes are
crushed and
destemmed.

Wine is filtered. Wine is aged. Wine is bottled.

Microbial Metabolism

Sugar Saccharomyces cerevisiae Ethanol + CO2
Lactic acid
MALOLACTIC FERMENTATION
Lactic acid bacteria
Malic acid

Ethanol Acetobacter or Gluconobacter Acetic acid

Industrial Microbiology

 Microorganisms produce alcohols and acetone that are
used in industrial processes.

 Industrial microbiology has been revolutionized by the
ability of genetically modified cells to make many new
products.

 Biotechnology is a way of making commercial products
by using living organisms, cells or cell components.

 Recombinant DNA.

Fermentation Technology

 The industrial production of microbial products usually
involves fermentation.

 Industrial fermentation is the large-scale cultivation of
microbes or other single cells to produce a commercially
valuable substance.

 Animal cells are used to make monoclonal antibodies.
 Production of insulin and growth hormone from genetically

modified organisms.

 Industrial fermentation is carried on in biorector, which
control aeration, pH and temperature.

 Widely used is the continuously stirred type.

Bioreactors for industrial fermentations. Motor

Acid/base
for pH control

Steam for
sterilization

Foam breaker
Liquid level

Flat-bladed
impeller
Culture broth

Cooling Baffle
jacket Diffuser

Sterile air

Harvesting
drain

Section of a continuously stirred bioreactor

Bioreactors for industrial fermentations.

Bioreactor tank, at left

Fermentation Technology

 The microbes in industrial fermentation produce primary or
secondary metabolites.

 Primary metabolites such as ethanol are formed as the cells grow
(during the trophophase).

 Secondary metabolites such as penicillin are produced during the
stationary phase (idiophase).

 In many ways, microbes are packages of enzymes.
 Industries are increasing their use of free enzymes isolated from

microbes to manufacture many products such as paper, textiles and
high-fructose syrups.
 Enzymes or whole cells can be bound to solid spheres or fibers.
When substrate passes over the surface, enzymatic reactions change
the substrate to the desired product.

Primary and secondary fermentation.

Cells
Ethanol
produced

Cell weight or numbers

Time

(a) A primary metabolite, such as ethanol from yeast,
has a production curve that lags only slightly behind
the line showing cell growth.

Primary and secondary fermentation. Idiophase

Tropophase

Cell weight or numbers Cells
Penicillin
produced

Time

(b) A secondary metabolite, such as penicillin from
mold, begins to be produced only after the logarithmic
growth phase of the cell (tropophase) is completed.
The main production of the secondary metabolite
occurs during the stationary phase of cell growth
(idiophase).

Industrial Products

 Amino acids.

 Most amino acids used in foods and medicine are produced by bacteria.
 Microbial production of amino acids can be used to produce L-isomers.
 Chemical production results in both D- and L-isomers.

 Citric acid.

 Used in foods and is produced by Aspergillus niger.

 Enzymes.

 Enzymes are used in manufacturing foods, medicines and other goods
are produced by microbes.

 Vitamins.

 Some vitamins used as food supplements are made by microorganisms.
 Vitamin B12 – produced by Pseudomonas and Propionibacterium.

 Steroids, vaccine and antibiotics are products of microbial growth.

Alternative Energy Sources Using Microbes

 Organic waste, biomass, can be converted by microorganisms
into alternative fuel methane, a process called bioconversion.

 Bioconversion :

 Process of converting biomass into alternative energy
sources.

 Decrease the amount of waste materials requiring disposal.

Biomass Bioconversion Methane
Ethanol

Hydrogen

 Biofuels (renewable replacement fules) includes alcohol and
hydrogen (from microbial fermentation) and oils (from algae).

Methane production from solid wastes in landfills.

Gas flaring stacks

Microturbines produce
electricity from methane

End of Lecture
All the Best for Final