Fermentation, lactic acid formation

Lactic acid formation occurred to a different extent when paper sludge hydrolysate was used. Although the same batch of hydrolysate was used for all experiments under identical conditions, lactate production was observed from the early stage (Fig. 2, condition D2) of the fermentation or lactate was only found in the fermentation broth in the very late phase of the process (condition Dl). 

Discovery of yeast as the origin of fermentation (Erxleben) Scientific explanation of lactic acid formation (Pasteur)... 

L-Lactic acid formation by fermentation of glucose or lactose Lactobacillus... 

Most bacteria convert malic acid to lactic acid with an intermediate formation of pyruvic acid, while Oenococcus oeni (previously classified as Leuconostoc oenos) expresses the malolactic enzyme to directly convert malic acid in one-step reaction. O. oeni has been extensively studied for controlled MLF of wine due to its higher tolerance to ethanol, low pH, and Yeasts like Schizosaccharomyces pombe and Saccharomyces strains can also convert malic acid through a maloethanolic-type fermentation. Lactic acid is less acidic than malic acid, and as a conseqnence, MLF leads to improvement of the sensory properties and biological stability of the wines. Additionally, the production of various other by-products of the MLF reaction may affect wine flavor positively. 

Hohl, L. A., and Joslyn, M. A. 1941b. Lactic acid formation in alcoholic fermentation by yeast. Plant Physiol. 16, 343-360. 

The acidification of the seed tissue together with a significant rise in temperature caused by the exergonic process of acetic acid formation leads to the cocoa-specific aroma precursor formation. There are various factors influencing the biochemical outcome of the fermentation process and thus the quality of the raw cocoa. Important factors are, for instance, fruit ripeness, overall amount of seeds used, degree of acetic and lactic acid formation, and rise as well as homogeneity in temperature and oxygen. 

The pH of fresh milk is 6.5 6.75. When the pH decreases to 4.6, due to lactic acid formation, caseins precipitate, leaving a yellowish solution of whey (serum). The acidification (fermentation of lactose to lactic acid) is not only the spontaneous activity of contaminating microorganisms during storage of milk, but also a result of the activity of arange of cultural microorganisms used in dairy industry. 

The production of soda crackers is also based on a mixed fermentation. Doughs for cracker production are inoculated with very smaH amounts of bakers yeast. During the first 3—5 h of the 18-h fermentation, yeast activity predominates thereafter bacterial fermentation causes a rapid decrease in pH through formation of lactic acid. 

The B. licheniformis JF-2 strain produces a very effective surfactant under conditions typical of oil reservoirs. The partially purified biosurfactant from JF-2 was shown to be the most active microbial surfactant found, and it gave an interfacial tension against decane of 0.016 mN/m. An optimal production of the surfactant was obtained in cultures grown in the presence of 5% NaCl at a temperature of 45° C and pH of 7. TTie major endproducts of fermentation were lactic acid and acetic acid, with smaller amounts of formic acid and acetoin. The growth and biosurfactant formation were also observed in anaerobic cultures supplemented with a suitable electron acceptor, such as NaNO3[1106]. 

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