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Chapter 28
Applied and Industrial
Microbiology
Food Microbiology
• Food preservation essential for modern civilization
– Many methods discovered by accident
• Foods prepared centrally and widely distributed
• FDA and USDA
– Hazard Analysis & Critical Control Point
• “Farm to the Fork”
• Home canning
• Commercial sterilization
– Uses retort
– Thermophilic bacteria may be resistant
• Thermophilic anaerobic spoilage
– low-acid foods
– Can swells, lowered pH and sour smell
• Flat sour spoilage
– Can not swollen as no gas is produced
• Mesophilic spoilage
– under processed or contaminated foods
• Lower temps used with acidic foods
• Some microbes both heat and acid resistant
• Aseptic packaging
– Plastics or paper
– Hydrogen peroxide, UV light,
electron beams
• High pressure
• Radiation
– completely sterilizes food
– Doesn’t change taste or
appearance
– gamma rays or electron
accelerators
– Electronic pasteurization
Microbes in Food Production
• Cheese
– Curd (casein protein) separated
from liquid whey
– Aided by action of Lactococcus
and rennin enzyme
– Ripened or un-ripened
– Physical and microbial ripening
– Classified by degree of hardness
– Hard cheeses
• Ripened by lactic acid bacteria in interior
• The longer the incubation the higher the acidity and
sharper the flavor
• Propionibacterium – swiss cheese
– Softer cheeses are ripened by aerobic bacterium
and molds on surface
• Penicillium – blue cheese
• Other fermented dairy products:
– Buttermilk, sour cream, yogurt and fermented
milk beverages
– Lactococcus lactis, Streptococcus
thermophilus and Lactobacillus bulgaricus
• Non-Dairy fermentations
– Sauerkraut, coffee, pickles, soy sauce,
chocolate, coffee, olives, meats and fish
– Lactococcus, Streptococcus, Lactobacillus
and Aspergillus
• Bread fermentations:
– Saccharomyces cervisiae
– Aerobic conditions favor CO2 production
• Kneading
– Lactic acid bacteria produce tart flavor
• sourdough and rye breads
• Alcoholic fermentations
– Yeasts, molds and bacteria
ferment grains, rice or fruits
– Saccharomyces cervisiae,
Aspergillus, Leuconostoc
– Beer and ale require malting
• Starch converted to glucose
– Aspergillus molds used in
Sake (rice wine)
– Wines made from fruits do not
require malting
– Malolactic fermentation with
grapes
• Leuconostoc convert malic
acid into lactic acid
– Distilled spirits involve
fermentation of fruits, grains,
or vegetables
• Vinegar production
– Aerobic bacteria oxidize ethanol
to acetic acid
– Different flavors due to different
starting materials
– Acetobacter and Gluconobacter
Industrial Microbiology
• Biotechnology
– rDNA technology
• Industrial fermentation
Bioreactors
Primary Metabolites
Formed with new
cells, during the log
phase or
trophophase
Secondary Metabolites
Produced during the
stationary phase or
idiophase
May be due to
conversion of primary
metabolites
Industrial Products
• Food additives and supplements
– Amino acids
– Organic acids
• Citric acid – Aspergillus
• Acetic acid - Acetobacter
– Vitamins
• Pseudomonas, Ashbya fungi, Acetobacter
• Microbial enzymes
– Amylases – Aspergillus
• 1st biological patent
– Pectinase – Clostridium
– Proteases
– Restriction enzymes and polymerases
• Pharmaceuticals
– Antibiotics
• Streptomyces
– Steroids
• Cortisone; estrogen; progesterone
– Hormones
• Insulin; human growth hormone
– Vaccines
• Dyes
– Green jeans
• Alternative fuels
– Renewable resources
– Bioconversion
Biomass
Methane, ethanol, hydrogen
• Microorganisms themselves as products
– Baker’s yeast – Saccharomyces cerevisiae
– Insecticide - Bacillus thurengenisis
• Bt toxin
– Frost inhibitor – Pseudomonas syringae ice-