A2/A-level Biology - Biotechnology and Gene Technologies (2)

• The products of metabolism (the sum of all of the chemical reactions in an organism), e.g. new cells and cellular components, chemicals such as hormones and enzymes, waste products such as carbon dioxide, oxygen, urea, ammonia, nitrates.

• Substances produced by an organism as part of its normal growth, e.g. amino acids, proteins, enzymes, nucleic acids, ethanol, lactate.
• The production of primary metabolites matches the growth in population of the organism.

• Substances produced by an organism that are not part of its normal growth, e.g. antibiotic chemicals.
• The production of secondary metabolites usually begins after the main growth period of the organisms – does not match the growth in population of the organism.

• Commercial applications of biotechnology often require the growth of a particular organism on an enormous scale.
• An industrial-scale fermenter is essentially a huge tank, which may have capacity of tens of thousands of litres.
• The growing conditions in it can be manipulated and controlled in order to ensure the best possible yield of the product.

The conditions that affect the microorganisms being cultured include:
 

(1) Temperature   

• Too hot – enzymes will denature and growth will be slowed.
• Too cool – enzymes work less efficiently and growth will be slowed.

(2) Type and time of addition of nutrient   

• Growth of microorganisms requires a nutrient supply, including sources of carbon, nitrogen and any essential vitamins and minerals.
• The timing of the nutrient addition can be manipulated, depending on whether the process is designed to produce a primary or secondary metabolite.

(3) Oxygen concentration   

• Most use aerobic conditions, so sufficient oxygen most be available.
• A lack of oxygen leads to the unwanted products of anaerobic respiration and a reduction in growth rate.

(4) pH   

• Changes in pH within the fermentation rank can reduce the activity of enzymes and so reduce growth rates.

• The absence of unwanted microorganisms.

• It refers to the measures to ensure that unwanted microorganisms do not contaminate the culture that is being grown or the products that are extracted.
• The nutrient medium in which the microorganisms grow could also support the growth of many unwanted microorganisms.
• Any unwanted microorganism is called a contaminant.
• Unwanted microorganisms:
  - Compete with the culture microorganisms for nutrients and space.
  - Reduce the yield of useful products from the culture microorganisms.
  - May cause spoilage of the product.
  - May produce toxic chemicals.
  - May destroy the culture microorganism and their products.

That's the end of the topic!

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