Some microorganisms are very useful to us. Under natural conditions, they can convert raw materials into end productions that are of value to humans.
- Bacteria Lactobacillus convert milk to yoghurt under warm conditions. They are also used in the production of cheese, beer and other fermented foods.
- Yeast carries out anaerobic respiration and produces carbon dioxide. The characteristic of yeast, called fermentation, is seen in the production of bread. The carbon dioxide raises the dough, making the bread soft.
- Bacteria act on alcohol to produce vinegar.
- In the textile industry, bacteria are mixed with plant stems. When the bacteria have decomposed the soft tissues, the fibres that are left behind are used to make cloth and ropes.
- In leather processing, bacteria produce enzyme proteases, which digest the animal tissues that are still attached to the hides. When the hides are cleaned, leather-made bags, furniture and shoes can then be manufactured.
- In the petroleum industry, bacteria are used to "clean" oil by "eating up" the impurities.