OCR Biology F215: Biotechnology

(a) State that Biotechnology is the industrial use of living organisms (or parts of living organisms) to produce food, drugs or other products

(b) Explain why microorganisms are often used in biotechnological processes
--> Reproduce asexually - genetically identical & carry out the same metabolic processes
--> Have a fast life cycle & growth rate so large populations can be built up quicklyCan produce chemicals which are released into the growth medium which can be harvested
--> Can be genetically modified to produce specific products
--> Grow rapidly in favourable conditions - generation time can be as little as 30 mins
--> Can be grown on waste materials from industry which would be useless or towix to humans
--> Can be grown anywhere in the world, not climate dependant e.g. some bacteria has evolved and enzymes can work in hot environments
--> Tend to generate products that are in a more pure form than those generated via chemical processes
--> No ethical questions

(c) Describe, with the aid of diagrams, and explain the standard growth curve of a microorganism in a closed culture
Sigmoid Growth Curve

.. Explaining the sigmoid growth curve:

1) Lag Phase - Growth is slow, organisms are adjusting to the surrounding conditions. The cells are active but not reproducing. The length of this period depends on the growing conditions

2) Log Phase - Rapid rate of growth, dividing at max rate as each individual has enough space & nutrients. The limiting factor is their growth rate, this phase depends on how quickly the organisms reproduce

3) Stationary Phase - Birth rate = Death rate. Nutrients are being used up & waste products are building up

4) Death Phase - Nutrients become exhausted & a build up of toxic waste leads to the death rate to increase above the rate of reproduction. Eventually all organisms will die in a closed system

(d) Describe how enzymes can be immobilised

--> Absorption - Enzyme molecules are mixed with the immobilising support & bind to it due to a combination of hydrophobic interactions & ionic links

--> Entrapment - Enzymes are trapped e.g. in a gel bead/network of cellulose fibres. Substrate & product can pass through the material to the enzyme, but the enzyme can't pass through to the solution

--> Covalent bonding - Enzyme molecules are covalently bonded to a support, often by covalently linking enzymes together to an insoluble material using a cross-linking agent

--> Encapsulation

--> Membrane separation

(e) Explain why immobilised enzymes are used in large scale production
--> Enzymes can be recovered easily & used again many times
--> The product isn't contaiminated by the enzyme
--> Protection from the immobilising material means the enzyme is more stable in changing temps or pH
--> Enzyme activity can be controlled more easily

(f) Compare & contrast the processes of continuous culture & batch culture

• Nutrients added: only at start / continuously
• Product removed: when fermentation stops / continuously (organisms held in log/growth phase giving higher productivity so can be on a smaller scale)
• Growth rates & product fermentation are slower because of limiting factors
• slower growth rates = larger vessels used
• Easy to set up & maintain / an be difficult to maintain conditions for log phase
• Contamination? Only one batch is wasted / can affect huge volumes
• Less efficient / more efficient use of time
• Quality can vary / quality is consistant
• Useful for processes involving secondary metabolites / primary metabolites
  

(g) Describe the differences between primary & secondary metabolites

Primary metabolites --> substances produced by an organism as part of its normal growth e.g. amino acids, proteins, enzymes, nucleic acids, ethanol & lactate. Production matched the growth in population of the organism.

Secondary metabolites --> substances produced by an organism that are not part of its normal growth phase. Production usually begins after main growth period of the organism & doesn't match the growth in population of the organism. Antibacterial chemicals are mainly secondary metabolites. Only a small mumber of micro-organisms produce secondary metabolites, often when there is a depletion in nutrients or a build up of waste products

(h) Explain the importance of manipulating the growing conditions in a fermentation wessel in order to maximise yield of product required

Growing conditions can be manipulated & controlled in order to ensure that the microorganism is growing in its optimum conditions = maximisation of product:
--> Temperature - Too hot = enzymes denature. Too cold = growth will be slow
--> Type & addition of nutrient - depends on whether the product is a primary or secondary metabolite
--> Oxygen concentration - most organisms are grown under aerobic conditions so there must be a sufficient supply of oxygen to prevent the unwanted products of anaerobic respiration & a reduction in growth rate
--> pH - changes in pH can reduce the activity of enzymes & .'. reduce growth rates

(i) Explain the importance of asepsis in the manipulation of microorganisms

Asepsis is the absence of unwanted microorganisms which could:
--> compete with the culture for nutrients & space
--> reduce the yield of useful products form the culture
--> spoil the product (contamination)
--> produce toxic chemicals
--> destroy the culture & their products