Microorganisms have been used to make food for thousands of years. Their metabolism changes the raw material into a product with a new taste, texture or keeping quality.Bread: yeast (Saccharomyces cerevisiae) is mixed with flour, water and sugar. Yeast respires the sugars, and the carbon dioxide produced makes the dough rise. Any ethanol evaporates during baking.Brewing (beer and wine): yeast respires sugars anaerobically (alcoholic fermentation), producing ethanol. In beer the sugars come from germinated barley; in wine they come from grapes.Yoghurt: bacteria such as Lactobacillus bulgaricus ferment lactose in milk to lactic acid. The fall in pH makes the milk proteins coagulate, thickening the milk, and gives the sharp taste.Cheese: bacteria turn milk sour by producing lactic acid, and the enzyme chymosin (rennet) coagulates the milk into solid curds, which are separated from the liquid whey. Moulds such as Penicillium are added to make blue cheeses.Single-cell protein (SCP): microorganisms grown as food themselves. Mycoprotein (Quorn) is made from the fungus Fusarium venenatum.
• Advantages: very fast growth, high protein and low fat, grown on waste or cheap substrates, no animal welfare issues, needs little land.
• Disadvantages: conditions must be sterile to avoid contamination, the protein must be purified, it may taste poor unless flavoured, and some people dislike eating food grown from fungi or bacteria.
• Advantages: very fast growth, high protein and low fat, grown on waste or cheap substrates, no animal welfare issues, needs little land.
• Disadvantages: conditions must be sterile to avoid contamination, the protein must be purified, it may taste poor unless flavoured, and some people dislike eating food grown from fungi or bacteria.