Bio 3 - Microbiology - Large-scale microbe production

It is very difficult to produce microorganisms on an industrial scale

Increasingly, we want to make use of materials made by the microbes (Drugs or food)

This means we have to keep a very large fermentation going for a long time so we can harvest the products.

In ideal conditions, bacteria can double every 20 minutes. However, these ideal condidtions are rare.

As the numbers of the microorganisms increase, the conditions change. The food is used up, and the metabolisms of millions of microorganisms causes the temperature to rise. Oxygen levels fall as it is used up in respiration.

The CO2 waste from respiration can alse alter the pH of the culture. If the pH changes, the activity of the enzymes in the culture can be affected so it stops growing or dies. Other waste products may begin to build up and poison the culture. In industrial fementations, very large microbe cultures are involved. So problems like these can develop very rapidly

When we grow microbes on an industrial scale we use large vessels known as fermenters. These industrial fermenters are designed to overcome the problems which stop a culture from growing well. They react to changes, keeping the condidtions as stable as possible. This in turn means we can get the maximum yield. These industrial fermenters usually have: 

- An oxygen supply to provide oxygen for respiration of the microorganisms

- A stirrer to keep the microorganisms in suspension. This maintains an even temperature and makes sure oxygen and food are evenly spread out through the culture

- A water-cooled jacket which removes the excess heat produced by the respiring microorganisms. Any rise in temperature is used to heat water which is constantly removed and replaced with more cold water

- Measuring instruments which constantly monitor factors such as the pH and temperature so that changes can be made if necessary

Recently a completely new food based on fungi has been developed. It is known as Mycoprotein, which means protein from fungus. 

It is produced using the fungus Fusarium. This grows and reproduces rapidly on a relatively cheap sugar syrup in large specialised fermenters. It needs Aerobic conditions to grow successfully. Then it can double its mass every five hours!

The fungal biomass is harvested and purified. Then it is dried and processed to make Mycoprotein. This is a pale yellow solid with a faint taste of mushrooms.