Applied and Industrial Microbiology

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Chapter 28

• Applied and Industrial Microbiology

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Food Microbiology

• Modern civilization could not survive without
  methods of food preservation
• Many of these methods were discovered by accident
  
• As more foods are prepared at 1 location and
  distributed widely, spread of disease is more
  likely
• Inspection agencies like the FDA and USDA
  minimize this threat

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• Preserving foods by heating a properly sealed
  container is not hard
• Home canning
• The challenge is using the right amount of heat
• Commercial canning requires enough heat to kill
  Clostridium spores without degrading food
• Steam under pressure in a retort, like an
  autoclave
• Not complete sterilization
• Thermophilic bacteria have more resistant spores

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Industrial Food Canning
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• If foods are incubated at high temps,
  thermophilic anaerobic spoilage is common in
  low-acid foods
• Can swells, lowered pH and sour smell
• Clostridium species
• If the can is not swollen- flat sour spoilage
• Bacillus stearothermophilus
• Both types of spoilage are at higher than normal
  temps

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• Mesophilic bacteria can spoil under processed
  canned foods or those contaminated by leaking
• Occurs at normal temps
• Potential botulinal bacteria
• Lower temps are used with acidic foods

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• Few microorganisms are both heat and acid
  resistant
• Byssochlamys fulva produces a heat resistant
  ascospore
• Aspergillus produces a resistant body called a
  sclerotia
• Bacillus coagulans is a spore former that is acid
  resistant

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• Aseptic packaging requires using heat resistant
  materials that are sterilized then formed into
  packages and filled with sterile foods
• Plastics or paper

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• Radiation has been used for large scale food
  preservation
• able to completely sterilize food
• Does not cause it to be radioactive or change
  taste
• Often used on chilled or frozen meats and on
  herbs and spices
• May use gamma rays or electron accelerators
• Must be labeled with a special radura symbol

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Microbes in Food Production

• Cheese US leads world production
• Require formation of curd made up of casein
  protein
• Separated from liquid whey be action of enzyme
  rennin
• Aided by action of lactic-acid producing bacteria
• Curd undergoes microbial ripening
• Cheeses are classified by degree of hardness
• Hard cheeses are ripened by lactic acid bacteria
• Softer cheeses are ripened by Penicillium molds
• Microbial action also provides odors and flavors

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• Other dairy products
• Buttermilk, sour cream, yogurt and fermented milk
  beverages
• Requires inoculation of milk products with
  organisms like Streptococcus thermophilus and
  Lactobacillus bulgaricus
• Non-Dairy fermentations
• Used to make certain plants edible
• Ferment chocolate seeds to release flavor

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• Microbes are used in baking
• Saccharomyces cervisiae ferments bread dough and
  causes it to rise by producing CO2
• Ethanol is burned off when bread is baked
• Some breads like sourdough use lactic acid
  bacteria to produce tart flavor
• Fermentation is also used to produce sauerkraut,
  pickles and olives

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• Alcoholic beverages and vinegar
• Beer, Ale, Malt, Sake and Wine are produced by
  fermenting yeasts, molds and bacteria with either
  grains, rice or fruits
• Aspergillus molds are important in Sake formation
• Lactic acid bacteria convert malic acid into
  lactic acid during wine formation malolactic
  fermentation

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Making Red Wine
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Microbial Metabolism
Saccharomyces cerevisiae
Sugar
Ethyl alcohol CO2
Lactic acid bacteria
Malic acid
Lactic acid
Acetobacter or Gluconobacter
Ethyl alcohol
Acetic acid
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Industrial Microbiology

• Microbes have many industrial uses unrelated to
  food production
• Biotechnology is the application of genetically
  modified microbes
• Industrial fermentation is the large scale
  cultivation of microbes to produce a commercially
  valuable substance
• Vessels for industrial fermentation are called
  bioreactors
• May be the microbe itself or a metabolite

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Fermentation Technology
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Primary Fermentation
Primary metabolites are formed with new cells,
during the log phase or trophophase
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Secondary Fermentation
Secondary metabolites are produced during the
stationary phase or idiophase May be from
conversion of primary metabolites
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Industrial Products

• Amino acids
• Lysine, methionine, phenylalanine and aspartic
  acid
• Citric acid
• Aspergillus niger
• Microbial enzymes
• Amylases 1st biological patent
• Vitamins
• Pseudomonas, Ashbya fungi, Acetobacter

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• Pharmaceuticals
• Streptomyces species produce over 200 antibiotics
• Steroids like cortisone (anti-inflammatory) and
  estrogen and progesterone (birth control)

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• Microorganisms themselves as products
• Bakers yeast Saccharomyces cerevisiae
• Copper Extraction by Leaching
• Thiobacillus ferrooxidans get energy by oxidation
  of iron ore
• Sulfuric acid is a by product

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Biological Leaching of Copper Ores
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• Alternative energy sources using microbes
• As fuel sources diminish interest increases in
  renewable resources
• Biomass is organic matter which microbes can
  convert into energy sources bioconversion
• Methane and ethanol are products of bioconversion
  

Biomass
Methane or ethyl alcohol
Bioconversion