Microorganisms and biotechnology
Useful microorganisms
Microorganisms are widely exploited in industry, medicine and food production.
Fermentation
Fermentation (in biology) is anaerobic respiration carried out by microorganisms, producing useful products.
Yeast (a fungus) carries out alcoholic fermentation: Glucose → Ethanol + Carbon dioxide (+ small amount of ATP)
Lactobacillus bacteria carry out lactic acid fermentation: Glucose → Lactic acid
Applications:
| Microorganism | Process | Product |
|---|---|---|
| Yeast | Alcoholic fermentation | Bread (CO₂ makes dough rise), beer, wine |
| Lactobacillus | Lactic acid fermentation | Yoghurt, cheese |
| Penicillium (fungus) | Secondary metabolite | Penicillin (antibiotic) |
| E. coli (GM) | Gene expression | Insulin, human growth hormone |
Industrial fermenters
A fermenter (bioreactor) is a large sterile vessel used to grow microorganisms under controlled conditions:
- Temperature: controlled by water jacket; optimum for enzyme activity.
- pH: monitored; adjusted to maintain enzyme activity.
- Oxygen: stirrer + air supply for aerobic fermentation (or kept anaerobic for yeast).
- Nutrients (growth medium): glucose or other carbon source added.
- Sterility: steam-sterilised before use to prevent contamination by other organisms.
Antibiotics
Penicillin was the first antibiotic, discovered by Alexander Fleming (1928) when he noticed Penicillium mould killing bacteria on a petri dish.
Modern penicillin production uses industrial fermenters:
- Penicillium inoculated into sterile growth medium.
- Grown under controlled conditions (temperature, pH, oxygen, nutrients).
- Penicillin extracted and purified.
Genetic modification (GM)
Genetic modification (genetic engineering) involves inserting a gene from one organism into another to produce a desired protein.
Producing human insulin by GM bacteria
- Gene for human insulin identified in human DNA.
- Gene cut out using restriction enzymes (cut DNA at specific sequences).
- Plasmid (circular DNA from bacteria) cut with the same restriction enzyme → same sticky ends.
- Insulin gene inserted into plasmid using DNA ligase (joins sticky ends).
- Recombinant plasmid inserted into E. coli bacteria.
- Bacteria multiply in fermenter → produce human insulin.
- Insulin extracted and purified.
Benefits and concerns of GM
| Benefits | Concerns |
|---|---|
| Cheaper insulin production | Unforeseen ecological effects |
| GM crops with pest resistance → higher yield | Ethical objections (playing God) |
| GM crops tolerant to herbicide/drought | Spread of GM genes to wild plants |
| Golden Rice (vitamin A) → tackle malnutrition | Reduced biodiversity (monocultures) |
Food production using microorganisms
Mycoprotein (Quorn): made from Fusarium venenatum (a fungus). Grown in a fermenter on glucose syrup; harvested and processed into a high-protein meat substitute.
Yoghurt: pasteurised milk inoculated with Lactobacillus bacteria → ferment lactose to lactic acid → lowers pH → milk proteins denature and set.
Bread: yeast ferments glucose → CO₂ causes dough to rise; ethanol evaporates during baking.
⚠Common mistakes
- Saying yeast produces lactic acid in bread — yeast produces ethanol and CO₂ (alcoholic fermentation).
- Confusing restriction enzymes and DNA ligase — restriction enzymes CUT; ligase JOINS.
- Forgetting that fermenters must be sterilised before use to prevent contamination.
- Stating GM bacteria produce human insulin "from their own DNA" — the human insulin gene is inserted into the bacterial plasmid.
AI-generated · claude-opus-4-7 · v3-ccea-biology