Biotechnology is the use of living organisms — usually microorganisms such as bacteria, yeast and fungi — to make useful products or to carry out useful processes. People have used it for thousands of years to make bread, cheese and alcohol; modern biotechnology now extends to medicines, fuels and genetic engineering. In CSEC Biology you should be able to describe everyday examples, explain why microorganisms are so useful, and outline the basic ideas of genetic modification and its social implications.
Why microorganisms are used
Microorganisms make excellent "factories" because they:
- reproduce very rapidly, doubling in number in minutes to hours;
- have simple growth requirements (a sugar source, warmth and, for some, oxygen);
- carry out useful chemical reactions quickly because of their enzymes;
- can be grown in large vessels (fermenters) under controlled conditions.
Everyday biotechnology
Bread. Yeast is mixed into dough. The yeast respires the sugars, and in the warm dough it carries out anaerobic respiration (fermentation): glucose → ethanol + carbon dioxide. The carbon dioxide forms bubbles that make the dough rise; the ethanol evaporates during baking.
Alcohol (brewing and wine-making). Yeast ferments the sugars in grain or fruit juice to produce ethanol and carbon dioxide. Here it is the ethanol that is wanted; the process is carried out without oxygen so that fermentation, not aerobic respiration, takes place.
Yoghurt and cheese. Bacteria (e.g. Lactobacillus) ferment the sugar lactose in milk to lactic acid. The acid lowers the pH, which thickens (clots) the milk proteins, giving yoghurt its texture and sour taste, and helps preserve it.
In every case the key idea is the same: a microorganism's enzymes convert a cheap raw material into a valuable product.
Industrial production — the fermenter
On a large scale, microorganisms are grown in a fermenter (bioreactor), a large stainless-steel vessel in which conditions are carefully controlled to maximise the product. You should be able to explain why each condition is controlled:
- Temperature — kept optimum; too high denatures enzymes, too low slows the reaction. The vessel has a cooling water jacket because respiration releases heat.
- pH — monitored and adjusted to keep enzymes working efficiently.
- Oxygen — sterile air is bubbled in for aerobic processes.
- Nutrients — sugar and other nutrients are added.
- Sterility — everything is sterilised first to keep out unwanted microbes that would compete or contaminate the product.
- Stirring (agitation) keeps the microbes, nutrients, oxygen and heat evenly distributed.
Products made this way include antibiotics such as penicillin (from the mould Penicillium), enzymes for washing powders, and single-cell protein for food.
Genetic engineering
Genetic engineering (genetic modification) is changing the genetic material of an organism by inserting a gene from another organism. The classic example is the production of human insulin:
- The human gene for insulin is identified and cut out using enzymes.
- The gene is inserted into a small loop of bacterial DNA (a plasmid), which acts as a vector.
- The modified plasmid is put back into a bacterium.
- The bacterium, now carrying the human gene, is grown in a fermenter and produces large quantities of human insulin, which is purified for use by people with diabetes.
This insulin is identical to human insulin, can be made in huge amounts cheaply, and avoids using insulin extracted from animals.
Other applications include genetically modified (GM) crops with improved yield, pest resistance or vitamin content.
Social and ethical issues
CSEC expects you to discuss benefits and concerns of biotechnology:
- Benefits: cheaper medicines, larger and more reliable food supplies, less use of chemical pesticides, new vaccines and fuels (e.g. ethanol biofuel).
- Concerns: possible effects of GM organisms on wild species and biodiversity; ethical worries about "tampering" with genes; questions over who owns and controls the technology; the need for clear labelling so consumers can choose.
A strong answer gives a balanced view rather than simply saying biotechnology is "good" or "bad."
Enzymes in biotechnology
Many biotechnology processes depend on isolated enzymes rather than whole organisms, and CSEC may ask about these. Enzymes can be extracted from microorganisms and used directly because they are fast, specific and work under mild conditions. Examples to remember:
- Pectinase breaks down pectin in fruit to release more juice and make it clearer.
- Protease (protein-digesting) is added to washing powders to remove food and blood stains, and is used to "pre-digest" baby foods.
- Lipase digests fats and is also used in biological detergents.
- Carbohydrase / amylase converts starch to sugar syrup in the food industry.
A major advantage is the use of immobilised enzymes — enzymes fixed onto an inert support such as beads. The substrate flows over them, the product is collected, and the enzymes are not washed away, so they can be reused and the product is not contaminated with enzyme. Immobilised lactase, for example, is used to make lactose-free milk for people who cannot digest lactose.
Why anaerobic conditions matter in brewing and baking
A point students often miss is why brewing is done without oxygen. Yeast can respire either aerobically (giving CO₂ and water and lots of energy) or anaerobically (fermentation, giving ethanol and CO₂). If oxygen were freely available, the yeast would respire aerobically and produce little or no alcohol. So brewers deliberately exclude air to force anaerobic respiration and maximise ethanol. In baking, by contrast, it is the carbon dioxide that matters, and any small amount of alcohol simply evaporates in the oven — so the same organism, Saccharomyces, is used for two quite different purposes depending on which product is wanted.
Common exam mistakes
- Confusing the products: in bread the useful product is the CO₂ (gas), in brewing it is the ethanol, in yoghurt it is the lactic acid.
- Forgetting to say why fermenter conditions are controlled — the marks are for the reason, not just naming the condition.
- Writing that genetic engineering "creates a new gene" — it transfers an existing gene from one organism to another.
Key terms to remember
- Biotechnology — using living organisms or their enzymes to make useful products.
- Fermentation — anaerobic respiration in microorganisms (e.g. yeast → ethanol + CO₂).
- Fermenter (bioreactor) — a large vessel with controlled conditions for growing microorganisms.
- Pasteurisation / sterilisation — heat treatment to kill unwanted microbes.
- Genetic engineering — transferring a gene from one organism into another.
- Plasmid — a small loop of bacterial DNA used as a vector to carry a gene.
- Immobilised enzyme — an enzyme fixed to a support so it can be reused and does not contaminate the product.
- GM organism — a genetically modified organism carrying a gene from another species.
Quick recap
- Biotechnology uses microorganisms (and their enzymes) to make useful products; they reproduce fast and need only simple conditions.
- Bread, alcohol and yoghurt are everyday fermentation examples — know the raw material and the product for each.
- Industrial production uses fermenters with controlled temperature, pH, oxygen, nutrients, sterility and stirring.
- Genetic engineering transfers a gene (e.g. the human insulin gene) into bacteria using a plasmid vector.
- Be ready to weigh the benefits against the ethical and environmental concerns.