Bacteria, lactic acid sugar

Certain bacteria (lactic acid bacteria, LAB) ferment milk sugar, lactose, as a source of energy, producing lactic acid as a by-product. When sufficient... 

Yeast (qv) metabolize maltose and glucose sugars via the Embden-Meyerhof pathway to pymvate, and via acetaldehyde to ethanol. AH distiUers yeast strains can be expected to produce 6% (v/v) ethanol from a mash containing 11% (w/v) starch. Ethanol concentration up to 18% can be tolerated by some yeasts. Secondary products (congeners) arise during fermentation and are retained in the distiUation of whiskey. These include aldehydes, esters, and higher alcohols (fusel oHs). NaturaHy occurring lactic acid bacteria may simultaneously ferment within the mash and contribute to the whiskey flavor profile. 

The sugars in fruits such as grapes are feimented by yeasts to produce wines. In winemaking, lactic acid bacteria convert malic acid into lactic acid in malolactic fermentation in fruits with high acidity. Acetobacter and Gluconobacter oxidise ethanol in wine to acetic acid (vinegar). 

Bees and ants are not the only critters that attack using acid. Bacteria, such as those found in plaque, do, too. Saliva usually keeps the mouth at a pH of about 6.8. Any pH of 6.0 or higher does not cause the teeth any problems. Plaque, a bacteria-containing film that builds up on teeth, can cause that pH to plummet. That is because it contains bacteria such as Streptococcus mutans, Lactobacillus casei, and Lactobacillus acidophilus that feed on sugars and make lactic acid. These conditions can lower the pH in the mouth to 5.5 or less. 

Microorganisms have also been developed to produce alternative products, such as lactic acid [65], propane-1,3-diol [67], 3-hydroxypropionic acid [68], butane-2,3-diol [69] and numerous other intermediates. For instance, bacteria such as the Clostridium acetobutylicum ferment free sugars to C4 oxygenates such as butyric acid or butanol. They form the C4 oxygenates by Aldol condensation of the acetaldehyde intermediates. The Weizmann process exploits this property to ferment starch feedstock anaerobically at 37 °C to produce a mixture of w-butanol, acetone and ethanol in a volume ratio of 70 25 5 [3],... 

The main product of anaerobic degradation of sugars by these organisms is lactic acid. Other products of bacterial carbohydrate metabolism include extracellular dextrans (see p. 40)—insoluble polymers of glucose that help bacteria to protect themselves from their environment. Bacteria and dextrans are components of dental plaque, which forms on inadequately cleaned teeth. When Ca salts and other minerals are deposited in plaque as well, tartar is formed. 

Sugar is transformed and reduced to glycerol during fermentation with LactobadUvs mannitopoeus or Lactobacillus lycopersici (heterofer-mentative lactic acid bacteria). This conversion, which has been described by different investigators, may be formulated as follows ... 

Bacteria on the surface of our teeth metabolize sugars to produce lactic acid, which lowers the pH enough to slowly dissolve tooth enamel. Fluoride inhibits tooth decay because it forms fluorapatite, Cal0(PO4)6F2, which is more acid resistant than hydroxyapatite. 

Lactic acid bacteria isolated from wine may use residual sugars or alcohol, or decompose organic acids as a source of carbon for growth and energy. Malic, citric, and tartaric acids may be metabolized, depending on conditions. 

Food can be preserved by fermentation using selected strains nf yeast, lactic acid-producing bacteria, or molds. The production of ethanol, lactic and other organic acids, and anlimicrobial agents in the food, along with the removal of fermentable sugars, can yield a product having an extended shelf life. 

Lactic acid is supplied commercially as an odourless and colourless viscous liquid. It is produced via the fermentation, using lactic acid bacteria, of carbo-hydrates such as com, potato or rice starch, cane or beet sugar, or beet molasses. 

In today s automated process, the water is a poor source of inoculum and light steepwater has a low population of bacteria. Conversion of sugar to lactic acid is not complete at the time steepwater is drawn off for evaporation, but is more complete than expected from observed populations of organisms. A higher population would... 

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