6.2.1 - (h-i)

Question 1

What are the phases to a Standard Growth Curve of a microorganism?

Answer 1

1. Lag Phase: Bacteria acclimatising to new environment, synthesising necessary enzymes.
2. Log Phase: Rapid reproduction, binary fission every 20 minutes, no limiting conditions and few cells die
3. Stationary Phase: Total growth rate is 0. Death rate = reproduction rate
4. Decline/Death Phase: Reproduction almost ceased, and death rate is rising due to limiting conditions
   
   • High temperature
   • Limited nutrients or oxygen
   • Build up of waste products (carbon dioxide or ethanol)

Question 2

Define immobilised enzyme

Answer 2

Enzymes which are fixed to an inert support system to which the substrate passes over. This is so the enzymes don’t mix with the substrate and contaminate the product

Question 3

What are the advantages of immobilised enzymes?

Answer 3

• They are not lost and can be reused immediately
• Enzymes are specific to the process – few by-products that need to be removed from final product
• Greater temperature tolerance – immobilised enzymes less easily denatured and work over wider temperature range making bioreactor costs cheaper
• Do not contaminate end product as they are not freely mixing with the solution

Question 4

What are the disadvantages of immobilised enzymes?

Answer 4

• Reduced efficiency – immobilising an enzyme reduces its activity rate
• High initial costs – immobilised enzymes are expensive, but do not need to be constantly replaced

Question 5

What are the methods for immobilising an enzyme?

Answer 5

Adsorption: The enzymes are bonded (ionically or hydrophobic interactions) to an inorganic carrier surface – e.g. silica, carbon, clay

Surface Immobilisation – covalent: Covalent bonding of enzymes to a surface

Entrapment: In a matrix, e.g. of polysaccharides or entrapped in a membrane

Separation: From substrate by a partially permeable membrane

Question 6

Name 5 examples of immobilised enzymes

Answer 6

1. Glucose isomerase
2. Penicillin Acylase
3. Lactase
4. Aminoacylase
5. Glucoamylase

Question 7

What are the industrial uses of:

Glucoe Isomerase

Penicillin Acylase

Answer 7

Glucose Isomerase

• Converts glucose to fructose
• Fructose is sweeter than glucose, so can be used as industrial sweetener

Penicillin Acylase

• Makes semi-synthetic penicillins – e.g. amoxicillin, ampicillin
• Some bacteria are resistant to naturally occurring penicillin, but many bacteria are vulnerable to the semi-synthetic penicillin

Question 8

What are the industrial uses of:

Lactase

Aminoacylase

Question 9

What are the industrial uses of:

Glucoamylase

Answer 9

Glucoamylase

• Converts short-chain carbohydrates (dextrins) into glucose
• Used to convert raw starch pulp to glucose, which can be fermented for other products