Glucose lactic 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. 

Lactic acid bacteria were immobilized in Ca-alginate beads prepared from different concentration of Na-alginate (1.0%, 2.0%, 4.0%, 6.0% and 8.0% w/v) and their fermentation efficiencies were investigated in liquid pineapple waste containing 31.3 gL of glucose... 

Some lactic acid bacteria of the genus Lactobacillus, as well as Leuconostoc mesenteroides and Zymomonas mobilis, carry out the heterolactic fermentation (Eq. 17-33) which is based on the reactions of the pentose phosphate pathway. These organisms lack aldolase, the key enzyme necessary for cleavage of fructose 1,6-bisphosphate to the triose phosphates. Glucose is converted to ribulose 5-P using the oxidative reactions of the pentose phosphate pathway. The ribulose-phosphate is cleaved by phosphoketolase (Eq. 14-23) to acetyl-phosphate and glyceraldehyde 3-phosphate, which are converted to ethanol and lactate, respectively. The overall yield is only one ATP per glucose fermented. 

Taniguchi, M., Tokunaga, T., Horiuchi, K., Hoshino, K., Sakai, K., and Tanaka, T. 2004. Production of L-lactic acid from a mixture of xylose and glucose by cocultivation of lactic acid bacteria. Appl. Microbiol. Biotechnol., 66,160-165. 

Some microorganisms can specifically produce mannitol from glucose or fructose without making a sorbitol byproduct (Smiley et al., 1967 Song et al., 2002 Wisselink et al, 2002 Saha, 2003). Mannitol, at 180g/L, can be easily recovered from the fermentation broth by cooling crystallization. Thus, research efforts have been directed toward production of mannitol by fermentation and enzymatic means (Vandamme and Soetaert, 1995). In this paper, the authors review the production of mannitol by lactic acid bacteria. 

Figure 21.1. Pathway of glucose metabolism by homofermentative lactic acid bacteria.

Figure 21.2. Pathway of glucose and fructose (1 2) metabolism by heterofermentative lactic acid bacteria.

Dextran is a natural, branched polymer of glucose linked by a 1-6-linked glucoyranoside, and some branching of 1,3-linked side chains (Figure 30.3c). Dextran is synthesized from sucrose by certain lactic acid bacteria, the best known being Leuconostoc mesenteroid.es and Streptococcus mutans. Its molecular weight ranges from 3000 to 2,000,000 Da. 

Although of limited importance in Saccharomyces sp. the enzyme glucose-6-phosphate dehydrogenase is used in the metabolism of glucose by the bacterium Zymomonas (Entner-Doudoroff pathway) and lactic acid bacteria fphosphoketolase pathway) (see Chapter 21). 

Lactic acid bacteria and muscle tissue also catabolize glucose by the BMP pathway but regenerate NAD- by reducing pyruvic acid to lactic acid using the enzyme lactate dehydrogenase ... 

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