1. Applied and Industrial Microbiology
Chapter 28
Applied and Industrial Microbiology
Lectures prepared by Christine L. Case
© 2013 Pearson Education, Inc.

3. Food Microbiology
28-1 Describe thermophilic anaerobic spoilage and flat sour spoilage by mesophilic bacteria.
28-2 Compare and contrast food preservation by industrial food canning, aseptic packaging, radiation, and high pressure.
28-3 Name four beneficial activities of microorganisms.

4. Historically…
Drying
Osmotic pressure (salt or sugar)
Fermentation

5. Foods and Disease Hazard Analysis and Critical Control Point (HACCP)
FDA
USDA

6. Washing, sorting, blanching
Figure 28.1 The commercial sterilization process in industrial canning.
Blanching in hot water or steam softens the product to easily fill the can.
Washing, sorting, blanching
Steam box
This treatment lowers the microbial population and destroys enzymes that might alter color, flavor, or texture.
Cans are filled to capacity, leaving minimal dead space.
Steam is used to exhaust, or drive out, dissolved air.
The cans are sealed.
Cans are sterilized by pressurized steam in a retort, similar to an autoclave.
Cans are then cooled by submersion in a water bath or by spraying them with water.
Cans are labeled, stored, and delivered for sale.

7. Figure 28.2 Commercial canning retorts.

8. Formation of a double seam for top or bottom
Figure 28.3 The construction of a metal can.
Sealing compound
Formation of a side seam
Formation of a double seam for top or bottom

9. Commercial Sterilization
Destroys C. botulinum endospores
12D treatment kills 1012 endospores
Thermophilic anaerobic spoilage: surviving endospores multiply, causing the can to swell from gas
Or flat sour spoilage

10. Low-acid canned food spoilage
Flat sour
Geobacillus stearothermophilus
Can is not swollen
Thermophilic anaerobic
Thermoanaerobacterium thermosaccharolyticum
Swollen can
Putrefactive anaerobic
Clostridium sporogenes, C. botulinum

11. Food Preservation
Aseptic packaging: presterilized materials assembled into packages and aseptically filled

12. Figure 28.5 Irradiation logo.

13. Table 28.2 Approximate Doses Of Radiation Needed To Kill Various Organisms (Prions Are Not Affected)

14. Ionizing Radiation Low dose 1 kGy Killing insects Pasteurizing dose
Meats and poultry
High dose
>10 kGy
Sterilizing spices

15. Irradiation sources lifted from storage pool for processing period
Figure 28.6 A gamma-ray irradiation facility.
Irradiation sources lifted from storage pool for processing period
Shielding
Material to be irradiated
Shielding
Conveyors to move material in and out of processing position
The irradiation source is submerged in the storage pool. The blue glow is Cerenkov radiation caused by charged particles exceeding the speed of light in water.
An irradiation facility, showing the path of the material to be irradiated

16. Figure 28.7 Electron-beam accelerator.
Bending magnet
Electron gun

17. High Pressure Prewrapped, precooked foods 87,000 psi
Kills Salmonella, Listeria, E. coli
Preserves color and flavor well

18. Cheese Curd: solid casein from lactic acid bacteria and rennin
Whey: liquid separated from curd
Hard cheeses are produced by lactic acid bacteria
Semisoft cheeses are ripened by Penicillium on surface

19. Figure 28.8 Making cheddar cheese.
The milk has been coagulated by the action of rennin (forming curd) and is inoculated with ripening bacteria for flavor and acidity. Here the workers are cutting the curd into slabs.
The curd is chopped into small cubes to facilitate efficient draining of whey.
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.

20. Figure 28.9 The basic steps in making red wine.
Grapes are tested and picked.
Sulfite is added to kill undesirable yeasts and bacteria.
Yeast inoculum is added.
Result is pressed to separate 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.

21. Alcoholic Beverages and Vinegar
Beer and ale are fermented starch
Malting: germinating barley converts starch to maltose and glucose
For sake, rice starch is converted to sugar by Aspergillus
Wine is fermented plant sugars
Yeast ferment sugars to ethanol and CO2
Grape wine requires bacterial malolactic fermentation
Acetobacter and Gluconobacter convert ethanol to acetic acid

22. Microbial Metabolism Sugar Ethanol + CO2 Malic acid Lactic acid
Saccharomyces cerevisiae
Malic acid
Lactic acid
Lactic acid bacteria
Ethanol
Acetic acid
Acetobacter or Gluconobacter

23. Is botulism a greater danger in spoilage of canned goods under thermophilic or under mesophilic conditions? 28-1
Canned foods are usually in metal cans. What sorts of containers are used for aseptically packaged foods? 28-2
Roquefort and blue cheeses are characterized by blue-green clumps. What are these? 28-3

24. Industrial Microbiology
28-4 Define industrial fermentation and bioreactor.
28-5 Differentiate primary from secondary metabolites.
28-6 Describe the role of microorganisms in the production of industrial chemicals and pharmaceuticals.
28-7 Define bioconversion, and list its advantages.
28-8 List biofuels that can be made by microorganisms.

25. Biotechnology
Use of microorganisms, cells, or cell components to make a product
Classical: fermentation
Recombinant DNA

26. Section of a continuously stirred bioreactor
Figure 28.10a Bioreactors for industrial fermentations.
Acid/base
for pH control
Motor
Steam for sterilization
Foam breaker
Liquid level
Flat-bladed impeller
Culture broth
Baffle
Cooling jacket
Diffuser
Sterile air
Harvesting drain
Section of a continuously stirred bioreactor

27. Bioreactor tank, at left
Figure 28.10b Bioreactors for industrial fermentations.
Bioreactor tank, at left

28. Cells Ethanol produced Cell weight or numbers Time
Figure 28.11a 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.

29. Tropophase Idiophase Cells Cell weight or numbers Penicillin produced
Figure 28.11b Primary and secondary fermentation.
Tropophase
Idiophase
Cells
Cell weight or numbers
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).

30. Figure 28.12 Immobilized cells.
Bacteria
Silk fibers

31. Industrial Products Xanthan Amino acids Citric acid Enzymes Vitamins
Antibiotics
Steroids

32. Xanthan Applications of Microbiology, unnumbered figure, page 808.
Xanthomonas campestris producing gooey xanthan.

33. Figure 28.14 Biological leaching of copper ores.
Leaching: Fe3+ in acidic leaching solution oxidizes insoluble copper sulfide (Cu+) to soluble CuSO4 (Cu2+).
Pregnant
(metal-bearing)
solution, CuSO4
Copper for industrial uses
Leach dump of
copper sulfide ore
Fe0 (metallic scrap iron)
Pump
Oxygen in aerated pond
Oxidation pond:
T.Ferrooxidans oxidizes FeSO4 to Fe3+ + H2SO4 (acidic leaching solution).
Barren solution,
no copper, iron
as FeSO4
CuSO4 precipitates as copper (Cu0); Fe3+ is changed to FeSO4 (Fe2+).

34. Alternative Energy Sources Using Microbes
Cellulose digested by cellulase
Sugars fermented to ethanol or higher alcohols or hydrogen
Algal oils
Biomass
Methane
Ethanol
Hydrogen
Bioconversion

35. Microturbines produce electricity from methane
Figure Methane production from solid wastes in landfills.
Gas flaring stacks
Microturbines produce electricity from methane

36. Industrial Microbiology and the Future
Food processing
Pharmaceuticals from rDNA technology
Ethanol and hydrogen
And more

37. Are bioreactors designed to operate aerobically or anaerobically? 28-4
Penicillin is produced in its greatest quantities during the trophophase of fermentation. Does that make it a primary or secondary metabolite? 28-5
At one time, citric acid was extracted on an industrial scale from lemons and other citrus fruits. What organism is used to produce it today? 28-6

38. Landfills are the site of a major form of bioconversion—what is the product? 28-7
How can microbes provide fuels for cars and electricity? 28-8