The essentials
Microbes are grown on a large scale in huge vessels called fermentors to make products useful to humans. This branch is called industrial microbiology.
Beverages: Saccharomyces cerevisiae, called brewer's yeast here, ferments malted cereals and fruit juices to produce ethanol. Wine and beer are made without distillation, while whisky, brandy and rum are made by distilling the fermented broth.
Antibiotics: Antibiotics are chemical substances produced by some microbes that can kill or retard the growth of other, disease-causing microbes. Penicillin was the first antibiotic to be discovered. Alexander Fleming noticed that the mould Penicillium notatum stopped the growth of Staphylococcus bacteria around it. Its full potential as an effective antibiotic was later established by Ernst Chain and Howard Florey, and penicillin was widely used to treat wounded soldiers in World War II. Fleming, Chain and Florey shared the Nobel Prize in 1945.
Organic acids, alcohol and enzymes: Microbes also produce useful chemicals and enzymes.
Bioactive molecules: Cyclosporin A, produced by the fungus Trichoderma polysporum, is used as an immunosuppressive agent in organ-transplant patients. Statins, produced by the yeast Monascus purpureus, lower blood cholesterol by competitively inhibiting the enzyme responsible for cholesterol synthesis.
Key points
- Aspergillus niger (fungus) – citric acid.
- Acetobacter aceti (bacterium) – acetic acid.
- Clostridium butylicum (bacterium) – butyric acid.
- Lactobacillus (bacterium) – lactic acid.
- Lipases – used in detergents to remove oily stains.
- Pectinases and proteases – make bottled fruit juices clearer.
- Streptokinase from Streptococcus, modified by genetic engineering – a "clot buster" for blood clots in heart-attack patients.
Exam tips
- Match each product with its organism and its type (bacterium, fungus or yeast); this is a classic question pattern.
- Remember that statins act by competitive inhibition of an enzyme of cholesterol synthesis.