Biology: Biotechnology

biotechnology is the industrial use of living organisms (or parts of living organisms) to produce food, drugs or other products

explain why microorganisms are often used in biotechnological processes

Grow rapidly in favourable conditions, with a generation time of as little as 30 minutes

Often produce proteins or chemicals that are given out into the surrounding medium and can be harvested

Can be genetically engineered to produce specific products

Grow well are relatively low temperatures, much lower than those required in the chemical engineering of similar processes

Can be grown anywhere in the world and are not dependent on climate

Tend to generate products that are in a more pure form than those generated via chemical processes

Can often be grown using nutrient materials that would otherwise be useless or even toxic to humans

describe, with the aid of diagrams, and explain the standard growth curve of a microorganism in a closed culture

Lag phase

Organisms are adjusting to the surrounding conditions. This may mean taking in water, cell expansion, activating specific genes and synthesising specific enzymes. The cells are active but not reproducing so population remains fairly constant. The length of this period depends on the growing conditions

Log phase

The population size doubles each generation as each individual has enough space and nutrients to reproduce. In some bacteria the population can double every 20-30 mins. The length of this phase depends on how quickly the organisms reproduce and take up the available space and nutrients

Stationary phase

Nutrient levels decrease and waste products like Carbon Dioxide and other metabolites build up. Individual organisms die at the same rate at which new individuals are being produced. In an open system this would be the carrying capaciry

Death phase

Nutrient exhaustion and increased levels of toxic waste products and metabolites leads to the death rate increasing above the reproduction rate. Eventually all of the organisms will die in a close system

describe how enzymes can be immobilised

Adsorption

Enzyme molecules are mixed with the immobilising support and bind to it due to a combination of hydrophobic interactions and ionic links.

Covalent bonding

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

Entrapment

Enzymes are trapped, for example in a gel bead or network of cellulose fibres. Substrate and product molecules can pass through the material to the enzyme, but the enzyme cannot pass through to the solution

Membrane separation

Enzymes are physically separated from the substrate mixture by a partially permeable membrane. The substrate and product molecules can pass through the membrane, but the enzymes cannot

explain why immobilised enzymes are used in large-scale production

Enzymes can be recovered easily and used many times

The product is not contaminated by the enzyme

Protection by the immobilising material means the enzyme is more stable in changing temperatures or pH

Enzyme activity can be controlled more easily

compare and contrast the processes of continuous culture and batch culture

Batch Culture 

Growth rate is slower because nutrient level declines with time

Easy to set up and maintain

Less efficient- fermenter is not in operation all of the time 

Very useful for processes involving the production of secondary metabolites

Continuous Culture

Growth rate is higher as nutrients are continuously added to the fermentation tank

 Set up is more difficult, maintenance of required growing conditions can be difficult to achieve

If contamination occurs, only one batch is lost If contamination occurs, huge volumes of product may be lost

More efficient- fermenter operates continuously

Very useful for processes involving the production of primary metabolites

describe the differences between primary and secondary metabolites

Primary metabolites are substances produced by an organism as part of its normal growth. The production of primary metabolites matches the growth in population of the organism

Secondary metabolites are substances produced by an organism that are not part of its normal growth. The production of secondary metabolites usually begins after the main growth period of the organism and so does not match the growth in population of the organism

explain the importance of manipulating the growing conditions in a fermentation vessel in order to maximise the yield of product required

The growing conditions can be manipulated and controlled in order to ensure that the microorganism is growing in its optimum conditions, and so the yield can be maximised

Temperature

Too hot and enzymes will be denatured, too cold and growth will be slowed

Type and addition of nutrient

This depends on whether the product is a primary or a 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 and a reduction in growth rate

pH

Chances in pH can reduce the activity of enzymes and therefore reduce growth rates

explain the importance of asepsis in the manipulation of microorganisms

Asepsis is the absence of unwanted microorganisms which could:

Compete with the culture microorganisms for nutrients and space

Reduce the yield of useful products from the culture microorganisms

Cause spoilage of the product

Produce toxic chemicals

Destroy the culture microorganisms and their products