Industrial and Food Microbiology
Domain 10 tests industrial fermentation, downstream processing and food microbiology. Questions often ask which organism makes a product, why fermentation conditions matter, and how food spoilage and preservation work.
Core rules and concepts
- Industrial fermentation uses selected microbes in bioreactors under controlled temperature, pH, aeration and substrate. Upstream processing prepares the inoculum and medium; downstream processing harvests, purifies and formulates the product.
- Products: ethanol by Saccharomyces cerevisiae; citric acid by Aspergillus niger; penicillin by Penicillium chrysogenum; glutamic acid by Corynebacterium glutamicum; enzymes and single-cell protein from various microbes.
- Food spoilage is caused by bacteria, yeasts and moulds; preservation includes refrigeration, drying, salting, acidification, canning and irradiation. Pasteurization reduces pathogens but does not sterilize.
- Foodborne pathogens include Salmonella, Staphylococcus aureus (toxin), Clostridium botulinum (anaerobic canned foods) and Listeria.
Worked example
Citric acid production uses Aspergillus niger grown on molasses. Reasoning: the medium supplies sucrose, and the fungus is cultured aerobically at controlled pH and temperature. Citric acid accumulates in the broth, then is recovered by filtration, precipitation and purification. The process is aerobic, so adequate aeration is critical; anaerobic conditions would favour unwanted fermentation.
Mark-losing traps
- Pasteurization is not sterilization; spoilage organisms and spores can survive.
- Clostridium botulinum is an anaerobe associated with improperly canned low-acid foods.
- Penicillin is not produced by Penicillium notatum in modern industrial processes; P. chrysogenum is used.
- Not all fermented foods are safe by default; starter cultures and hygiene control the process.