Lactic bacteria, acid tolerant

Patel, M. A., Ou, M., Harbrucker, R., Aldrich, H., Buszko, M., Ingram, L., and Shanmugam, K. 2006. Isolation and characterixation of acid-tolerant, thermophilic bacteria for effective fermentation of biomass-derived sugars to lactic acid. Appl. Environ. Microbiol., 72, 3228-3235. 

Acid-tolerant lactic acid bacteria would solve this latter problem and have indeed been obtained from screening [44] and via whole genome shuffling [45]. Alternatively, a lactate dehydrogenase gene could be inserted in a yeast, such as S. cerevisiae. These grow well at low pH and efficiently channel carbon into the glycolysis pathway under anaerobic conditions [46, 47]. Such constructs were indeed found to produce up to 55 g L-1 of lactic acid at pH 3.6 [46]. 

Saccharomyces cerevisiae Lactic acid production A muscle bovine lactate dehydrogenase gene (LDH-A) was expressed in S. cerevisiae, a nd lactic acid was produced in titers of 20 g/liter with productivities of 11 g/liter/h due to the acid tolerance of S. cerevisiae this organism may serve as an alternative for substitution of bacteria for lactic acid prxrduction 108... 

Bactericidal activity Lactobacilli ferment lactose to lactic acid, thereby reducing the pH to a level that harmful bacteria cannot tolerate. Hydrogen peroxide is also produced, which inhibits the growth of Gram-negative bacteria, ft has also been reported that lactic acid producing bacteria of the Streptococcus and Lactobacillus species produce antibiotics. 

P. cyclohexanicum sp. nov. was isolated recently from spoiled orange juice (Kusano et al., 1997). The results of phylogenetic analysis of the 16S rRNA gene indicated the highest level of homology with the classical propionibacterium P. freudenreichii, to which it is also similar pheno-typically. co-Cyclohexyl undecanoic acid, an alicyclic fatty acid rarely found in bacteria, is the major cellular fatty acid in the new propionibacterium. P. cyclohexanicum produces large amounts of lactic acid, is acid-tolerant and heat-resistant, which differentiates the new species from the other propionibacteria. 

Acidogenic, producing mainly lactic acid, and acid tolerant. The pH optimum for growth is 5-5 which is sufficiently low to inhibit most other bacteria. Found in very low concentrations in plaque but predominate in active carious lesions. Require a source of B vitamins. 

Evidently, adaptation phenomena (probably similar to those described for lactic bacteria) occur, ensuring their ethanol tolerance in wine. Acidity and ethanol concentration simultaneously influence the physiology and the resistance of acetic acid bacteria. 

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. 

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