food processing

Question 1

Define batch culture

Answer 1

It is the growth of cells in a sealed container (or bioreactor) over a short period of time and under ideal conditions until all the nutrients are used up

Question 2

Define bioreactor

Answer 2

It is a vessel or container in which living cells or their products are used to make a product

Question 3

Define continuous flow

Answer 3

Continuous flow food processing is the growth of cells in an open container (or bioreactor), where nutrients are added and the end products are removed all the time at a rate that maintains the volume of liquid and the number of cells

Question 4

What is single-cell protein production?

Answer 4

The use of bacteria to produce edible forms of protein

Question 5

What are two main methods of production?

Answer 5

Batch culture and continuous flow culture

Question 6

Explain the steps in batch culture

Answer 6

1. A fixed amount of sterile nutrient is added to the micro-organisms in the bioreactor.
2. The micro-organisms go through the lag, log and stationary stages of a typical growth curve.
3. The nutrients are used up and the product is formed. The process is stopped.
4. The bioreactor is emptied and sterilised so that the process can be repeated.

Question 7

What conditions are controlled in the bioreactor?

Answer 7

Suitable temperatures, pressure, aeration and pH.

Question 8

Why is process stopped in the bioreactor before the decline phase?

Answer 8

Because there is very little product formed at this stage.

There is a danger of the micro-organisms bursting or of unwanted side products forming at this stage.

Question 9

Explain the steps in continuous flow culture

Answer 9

1. Nutrients are continuously added to the bioreactor.
2. Bacteria and product are continuously removed.
3. The bacteria are maintained at the log stage of growth.
4. Conditions in the bioreactor are kept constant.

Question 10

What is used more? Batch culture or continuous flow culture

Answer 10

Batch culture is used more often than continuous flow cuture.

Question 11

In batch culture, what can be added for micro-organisms that are aerobic?

Answer 11

Oxygen may be added

Question 12

What happens once the product is formed and after the bioreactor is emptied?

Answer 12

The product is separated from the solution and purified.

Question 13

Give an example of what is produced by batch culture

Answer 13

Yoghurt and many antibiotics

Question 14

What remains constant in the continuous flow method?

Answer 14

The volume of material in the bioreactor remains constant.

Question 15

In continuous flow, why are the organisms said to grow under steady-state conditions?

Answer 15

Factors like pH, temperature, the rate of stirring and the concentrations of nutrients, oxygen and waste products are kept constant.

Question 16

Why is continuous flow limited to a small number of applications?

Answer 16

As it is very difficult to maintain constant conditions

Question 17

Give an example of continuous flow

Answer 17

The production of single-cell protein and some methods of waste water treatment.