Lactate, utilization

Duncan, S. H., Louis, P., and Flint, H. J. (2004). Lactate-utilizing bacteria, isolated from human feces, that produce butyrate as a major fermentation product. Appl. Environ. Microbiol. 70,5810-5817. 

Stansen C, Uy D, Delaunay S et al (2005) Characterization of a Corynebacterium glutamicum lactate utilization operon induced during temperature-triggered glutamate production. Appl Environ Microbiol 71 5920-5928... 

Cardiovascular and septic shock, with resultant tissue hypoperfusion, are the most common causes of lactic acidosis. Poor tissue perfusion and hypoxia influence enzymatic pyruvate and lactate metabolism to stimulate anaerobic glycolysis and to decrease lactate utilization. This leads to hyperlactatemia and lactic acidosis. The mortality rate of this type of lactic acidosis may be as high as 80% and correlates with the degree of hyperlactatemia. 

Lactic acidosis can also result from inhibition of lactate utilization in gluconeoge-nesis (e.g., hereditary fructose intolerance, which is due to a defective aldolase gene). If other pathways that use glucose-6-P are blocked, glucose-6-P can be shunted into glycolysis and lactate production (e.g., glucose 6-phosphatase deficiency). 

Lactate in cheese may be oxidized to acetate. Pediococci produce 1 mol of acetate and 1 mol of CO2 and consume 1 mol of O2 per mole of lactate utilized (Thomas et al, 1985). The concentration of lactate in cheese far exceeds that required for optimal oxidation, and lactate is not oxidized until all sugars have been exhausted. The oxidation of lactate to acetate in cheese depends on the NSLAB population and on the availability of O2, which is determined by the size of the block and the oxygen permeability of the packaging material (Thomas, 1987). Acetate, which may also be produced by starter bacteria from lactose (Thomas et al., 1979) or citrate or from amino acids by starter bacteria and lactobacilli (Nakae and Elliott, 1965), is usually present at fairly high concentrations in Cheddar cheese and is considered to contribute to cheese flavor, although high concentrations may cause off-flavors (see Aston and Dulley, 1982). Thus, the oxidation of lactate to acetate probably contributes to Cheddar cheese flavor. 

The most critical parameters for the total current from an S. oneidensis biofilm are biofilm thickness, fraction of electrons recoverable for current, biofilm density, maximum specific lactate utilization rate, and electron equivalence of lactate ... 

The membrane-bound electron transport chains (ETC) catalyzes the transfer of reducing equivalents (protons and electrons) from NADH, glycerol-3-phosphate and lactate to oxygen, nitrate or fumarate (Sone, 1972 de Viies et al, 1972, 1977). P. pentosaceum contains a constitutive nitrate reductase and can reduce nitrate as a terminal electron acceptor during lactate utilization. Nitrate respiration is linked with the ATP synthesis (van Gent-Ruijters et al, 1975). 

The growth, acid production and lactate utilization by propionibacteria (especially P. freudenreichii and P. shermanii) are inhibited by long-chain fatty acids (10-100 mg/1 each) lauric (C o), myristic (C o), oleic (Cis i) and linoleic (Ci8 2) acids (Boyaval et al, 1995), present in milk lipids. However, the inhibitory effects of these acids were only observed in lactate-yeast extract medium (YEL), but not in milk or curd. The work was undertaken in connection with the often poor eyes formation in Swiss-type cheese. 

Many studies that characterized carbohydrate fermentation patterns applied methods that focused on utilization of single carbohydrates (Davis etal., 1988 Edwards and Jensen, 1992 Edwards etal., 1993 1998a 2000). It is therefore possible that these bacteria can metabolize glycerol to acrolein if other sugars or lactic acid are present. NADH produced as a byproduct of carbohydrate (or lactate) utilization is speculated to be reoxidized to NAD from the reduction of 3-HPA to 1,3-propandiol (Schiitz... 

Selenomonas ruminantium, a Gram-negative anaerobe and one of the major species present in the rumen, accumulates succinate as a major end product in the presence of lactate, if malate is added to stimulate lactate uptake. Without malate present, the major end products are acetate and propionate. When succinate reached the concentration of the added malate, malate utilization ended. From a practical standpoint, malate could be added to ruminant diets high in rapidly fermentable carbohydrates. Because high rumen lactate is undesirable, the presence of malate could stimulate lactate utilization (Evans and Martin 1997). 

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