6.4.8 Microorganisms & Biotechnology

Microorganisms & Biotechnology

Biotechnology harnesses the processes in living organisms to
- Produce useful products, such as foods and medicines
- Carry out useful services, such as sewage treatment, composting and bioremediation
Microorganisms are the most useful group of organisms that carry out biotechnological processes because they
- Have simple growth requirements
  - Their food is cheap and readily available
  - They occupy very little space
- Reproduce quickly
- Do not have non-productive tissues and organs
- Can be grown on an industrial scale to perform duties useful to large numbers of the human population

Brewing uses yeast species, eg. Saccharomyces cerevisiae, Saccharomyces pastorianus to respire sugars from barley malt and produce ethanol and CO₂
The process is anaerobic, and is known as fermentation
Ethanol is the primary product, and CO₂is a by-product
Some alcoholic drinks have a higher alcohol content than fermentation alone can produce, so these drinks are first fermented, then distilled to concentrate the alcohol
- Whisky and bourbon are distilled from a barley beer
- Brandy is distilled from grape wine
- Other spirits use generic fermented ethanol distilled through botanicals (berries, herbs and spices) to extract flavours
  - E.g. Gin, which uses mainly juniper berries

Wheat or rye flour is mixed with yeast and other ingredients to make dough
The culture of yeast is in fact a mixture of several different naturally occurring species
Commercial bakeries carefully control the species of yeast used
Artisan bakeries sometimes use wild yeast cultures, preserved and cultivated regularly (sometimes called 'starter cultures')
Yeast enzymes begin by hydrolysing the starch in flour to maltose
Maltose is then hydrolysed to produce monosaccharides which can be used for aerobic respiration
When oxygen runs out, yeast begin to respire anaerobically
Both aerobic and anaerobic respiration produce CO₂ in bubbles throughout the dough, causing the dough to rise
Baking kills the yeast and causes the gas pockets in the dough to expand, so the bread rises further

Pasteurised milk is used as a raw material
Bacteria are used to digest lactose, producing lactic acid
Lactic acid lowers the pH of the milk
The low pH causes proteins in the milk to denature, leading to separation of curds (solids) and whey (liquids)
Curds are pressed and processed into hard cheeses eg. Red Leicester
Mould spores from saprotrophic fungi such as Penicillium glaucum can be artificially introduced into blue-veined cheeses eg. Gorgonzola

A starter culture of Lactobacillus bulgaricus and Streptococcus thermophilus bacteria are introduced to pasteurised milk
The bacteria use sugars in the milk to respire and produce lactic acid as a waste product
Lactic acid denatures the proteins in the milk, causing them to coagulate (stick together). This produces the thick texture and and sour taste of yoghurt
Flavours can be added at this stage to produce flavoured yoghurt

Species of mould from the Penicillium genus can be cultured in industrial fermenters
The technique is known as deep-tank fermentation
Extraction and purification of the product produces large volumes of the drug for therapeutic use
Penicillin became one of the first 'wonder drugs' as a result of being produced on a large scale

Batch fermenter penicillin, downloadable AS Level & A Level Biology revision notes

A batch fermenter for the commercial production of penicillin

Large scale production of human insulin can be carried out using biotechnology
Previously, diabetics had to be treated with pig insulin, which is hard to isolate, expensive and not as effective as human insulin
Recombinant DNA technology can incorporate the gene for human insulin into the genome of the bacterium, Escheriscia coli
Recombinant bacteria are grown in batch fermenters, and each bacterial cell expresses insulin
Insulin is released into the batch medium and can be purified for medicinal use at a later stage

Mycoprotein is a meat substitute product used to make vegetarian, meat-like products like burgers and sausages
Mycoprotein is low-fat and high in fibre, so making it an attractive alternative to meat
- This could play a part in ensuring that a growing human population eats enough protein
The prefix 'myco' means fungus
The microorganism used is Fusarium venenatum, a filamentous fungus
A source of glucose is added to the tank
Oxygen is also supplied to ensure aerobic respiration can occur, which yields maximal growth of hyphae (the part that forms the meat-like material)
Nitrogen is introduced in the form of ammonia
Quorn^TM is a well-known brand name for mycoprotein
The product in mycoprotein is the fungus itself, rather than a substance produced by microorganisms

Humans can contaminate land and water with toxic substances through their activity
Remediating this land can remove the pollutants and restore the land to its natural state
Examples are oil spills, industrial accidents, acidic damage from mining and cleanup of crime scenes
Many bioremediation techniques rely on oxidative digestion of pollutants
Bioventing is sometimes all that is needed, a process which allows oxygen to reach the contaminants
- Naturally occurring microorganisms perform aerobic digestion of the contaminants and release non-polluting products
Biostimulation also relies on naturally occurring microorganisms but adds nutrients that promote microbial digestion of pollutants
Genetic engineering has been trialled to create microorganisms that are capable of bioremediation

As well as the established processes listed above, research on biotechnology has identified possible roles in these emerging processes
- Production of biofuels (to replace the use of fossil fuels)
- Production of vaccines and antibodies for the treatment of disease
- Production of hardy crop plants that can grow in arid conditions
- Counteracting threats from bioterrorism or bio-warfare
All of these potential applications are in their infancy but are in research and development trials