3 forms of microbial fermentation
Three basic forms of microbial fermentation are known in microbiology:
Lactic acid fermentation
Lactobacillus species use sugars, carbohydrates and starches to extract energy and produce lactic acid. It is very common in food production: dairy products like yogurt and related probiotics. In the pharmaceutical industry, lactic acid is used in implants, pills, dialysis, surgical sutures, and controlled drug release systems. In the cosmetic industry, lactic acid is used in the manufacture of hygiene and aesthetic products because of its moisturizing, antimicrobial, and rejuvenating effects on the skin.
Yeasts digest sugars to produce ethanol and carbon dioxide. Such yeasts are commonly used in breweries, wine-making and bakeries. Pharmaceutical ethanol fermentation is used as a solvent to dissolve the active ingredient in some medicines, or as an extraction solvent in herbal medicinal products. Ethanol has also been used as an antimicrobial preservative, possessing bactericidal and fungicidal activity.
Acetic acid fermentation
Sugars are converted into acetic, propionic and butyric acids and other flavorings, which give vinegar the complex sour taste. In medicine, acetic fermentation has antiseptic properties that are used to cure bacterial infections.
Of course, the characterization of the involved microorganisms has led to the development of biotechnology tools to harness them for scale-up in bioreactors to secure the large supply demands.
Where does microbial fermentation occur?
Fermentation is a general biochemical tool for energy generation during times of scarce oxygen supply. Even in human bodies, fermentation processes occur in muscles when energy is needed more quickly than oxygen can be transported to the tissue - picture sprinters or weightlifters who produce huge power outputs in short amounts of time.
Interestingly, microbial fermentation occurs in animals as well: in their gastrointestinal tracts. Microorganisms feed on digested food and help our bodies break it down to valuable building blocks. Herbivores couldn’t extract enough energy from their plant-based nutrition without the help of methane-releasing microbes.