Food production using micro-organisms

What is a disadvantage of using microorganisms to make food for human consumption?

A Competition from contaminating microorganisms can reduce yield.

B Food produced by microorganisms is low in fat.

C Microorganisms can be grown on waste materials.

D Use of microorganisms for food production raises fewer ethical concerns than use of animals.

Batch fermentation with microorganisms is used to produce a range of useful substances.

Which of the following are important for achieving maximum yield during a batch fermentation process?

1. Temperature should be maintained close to the optimum.

2. Temperature should be low to reduce costs.

3. Substrate should be constantly added to maintain a high concentration.

A 1, 2 and 3

B Only 1 and 2

C Only 2 and 3

D Only 1

Microorganisms can be used to produce food.

Which option is not seen as an advantage of using microorganisms to produce food compared to traditional food production methods?

A Microorganisms grow more rapidly than plants or animals.

B Production can be easily varied to meet demand.

C Production can occur at low temperatures and pressures.

D There are no animal welfare issues.

Escherichia coli is a bacterium that is used widely in scientific experiments and in biotechnology.

This is a transmission electron micrograph of E. coli.

Name the structure labelled A.

Based on your knowledge, estimate the diameter of the E. coli cell.

Give your answer in m.

A student carries out a serial dilution of an E. coli culture.

This is the method the student uses:

• Transfer 10 cm³ of E. coli culture to a sterilised test tube from an original culture that has a volume of 50 cm³.

• Carry out four 10-fold serial dilutions. Each dilution involves transferring 1 cm³ of culture from one test tube to another test tube containing 9 cm³ of distilled water.

• Transfer 1 cm³ of the final 10 cm³ diluted culture to an agar plate. Evenly spread 1 cm³ of liquid across the plate using a sterilised spreader.

• Use a micropipette for each transfer.

• Incubate the agar plates for 24 h.

• Count the number of colonies that develop on the plate. Each colony is assumed to develop from a single bacterium.

• Estimate the E. coli population in the original 50 cm³ culture.

Describe two improvements to the student’s method, other than using different equipment, that could improve the accuracy of their population estimate.

The student counts 22 colonies on the agar plate.

Calculate the total number of E. coli cells in the original 50 cm³ culture.

Give your answer in standard form.

Total number of E. coli cells in 50 cm³ =........

E. coli can be genetically modified to produce useful proteins.

State two other reasons why E. coli is a suitable microorganism to use in biotechnology.

Microorganisms can be used to produce a variety of food products.

Microorganisms have simple nutrient requirements, which helps to reduce production costs.

List two other advantages of using microorganisms in food production.

Yoghurt is a food produced from milk using microorganisms.

Yoghurt production involves two bacteria: Lactobacillus delbrueckii and Streptococcus thermophilus.

The bacteria convert the lactose present in milk into lactic acid.

Lactic acid is an important contributor to the flavour of yoghurt. Lactic acid also helps to give yoghurt a longer shelf life than milk.

Suggest how lactic acid helps to extend the shelf life of yoghurt.

Both bacteria also break down some of the protein casein, which is present in milk.

Name the product of protein breakdown and describe the type of reaction that takes place.

The microorganism that is used to produce mycoprotein is a fungus.

The diagram is of a fermenter used for mycoprotein production.

Use the diagram to name the type of fermentation process used for mycoprotein production.

Justify your answer.

Suggest and explain why a cooling system is necessary.

The air inlet provides the fungus with oxygen for respiration, and ammonia.

Suggest and explain why the fungus is provided with ammonia.

Mycoprotein foods contain protein.

The presence of protein in a solution can be detected using biuret reagent.

In the presence of protein, biuret reagent turns from blue to violet.

A colorimeter can be used, along with biuret reagent, to determine the concentration of protein in a solution.

Outline how to use a colorimeter to determine the concentration of protein in a solution.

State one alternative method for determining the concentration of protein in a solution.

Bacteria and fungi can be used to make food for human consumption. The use of microorganisms in food production creates fewer ethical issues than the use of animals.

On an industrial scale, microorganisms can be cultured using either batch fermentation or continuous fermentation.

The table below lists statements about industrial culturing of microorganisms.

Place ticks (✓) in the table to indicate whether each statement applies to batch or continuous fermentation.

A student carried out a different serial dilution to estimate the size of another bacterial population.

The serial dilution resulted in four colonies developing on an agar plate.

Explain why the student’s estimation of this bacterial population is likely to be inaccurate.

Some microorganisms can be used by humans in industry. Some microorganisms are pathogenic.

Pathogenic microorganisms are transmitted in various ways.

Complete the following passage about the transmission of pathogenic microorganisms using the most appropriate terms.

Some pathogens are carried between host organisms by animals, which are often insects.

These animals suffer no symptoms of the disease and are known as........

Other pathogens, such as P. infestans that causes potato blight, produce reproductive structures

called........, which can be carried on air currents to infect other hosts.