Chemicals, Enzymes and other Bioactive Molecules

Microbes are not just agents of disease; they are miniature chemical factories. The same metabolic processes that keep them alive produce a wide range of organic acids, alcohols, enzymes, and complex bioactive molecules that we harvest for commercial and medical use. Each product comes from a specific microbe, and understanding which microbe makes what is a standard exam question.

Organic Acids

Several fungi and bacteria are cultivated on an industrial scale to produce organic acids. The key examples are:

• Citric acid: Produced by the fungus Aspergillus niger. Used widely in food, beverages, and pharmaceuticals.
• Acetic acid (vinegar): Produced by the bacterium Acetobacter aceti.
• Butyric acid: Produced by the bacterium Clostridium butylicum.
• Lactic acid: Produced by the bacterium Lactobacillus. This is the same bacterium that curdles milk, but here it is grown in controlled fermenters for bulk acid production.

Alcohols

The yeast Saccharomyces cerevisiae is the workhorse for commercial ethanol production. This is the same yeast used in baking and brewing; under anaerobic conditions, it ferments sugars to produce ethanol and carbon dioxide.

Enzymes

Microbes are a major source of industrial enzymes because they can be grown in large quantities and their enzymes are often more stable than plant or animal enzymes.

• Lipases: Added to detergent formulations. They break down fats and oils, making them effective at removing oily stains from laundry.
• Pectinases and Proteases: Used to clarify bottled fruit juices. Pectinases break down pectin (which causes cloudiness), and proteases break down proteins. This is why commercial juices are much clearer than freshly squeezed juice at home.
• Streptokinase: Produced by the bacterium Streptococcus and modified by genetic engineering. It is used as a "clot buster" — it dissolves blood clots in patients who have suffered a myocardial infarction (heart attack).

Bioactive Molecules (Non-enzyme)

These are complex molecules with specific therapeutic effects, produced by microbes.

• Cyclosporin A: An immunosuppressive agent used to prevent organ rejection in transplant patients. It is produced by the fungus Trichoderma polysporum. …