13C nuclear magnetic resonance analysis of glucose and citrate end products in an ldhL-ldhD double-knockout strain of Lactobacillus plantarum

Abstract

We have examined the metabolic consequences of knocking out the two ldh genes in Lactobacillus plantarum using 13 C nuclear magnetic resonance. Unlike its wild-type isogenic progenitor, which produced lactate as the major metabolite under all conditions tested, ldh null strain TF103 mainly produced acetoin. A variety of secondary end products were also found, including organic acids (acetate, succinate, pyruvate, and lactate), ethanol, 2,3-butanediol, and mannitol.

Characterization and Functional Analysis of thepoxBGene, Which Encodes Pyruvate Oxidase inLactobacillus plantarum

“…2A). In order to examine the kinetics of poxB expression during growth, Northern blot analyses were performed with RNA extracted at various times during growth (3,5,7,9, and 11 h) under aerobic conditions with 0.2% glucose (Fig. 2C).…”

“…However, pyruvate dissipation by different metabolic pathways that result in a mixed acid fermentation has also been observed (7). Acetate is the second major fermentation product in L. plantarum (7,31,43). Various pathways for acetate production from pyruvate have been identified in this species (Fig.…”

“…This pathway generates energy and consumes NAD ϩ . Pyruvate is then converted into L-and D-lactate by the stereospecific NAD-dependent lactate dehydrogenases (LDHs), LdhL and LdhD (7), which regenerates NAD ϩ and maintains the redox balance ( Fig. 1).…”

Genetically Engineered Lactobacilli for Technological and Functional Food Applications

“…Homofermentative LAB, which use the glycolytic pathway for sugars fermentation and lack MDH, are also able to produce mannitol under special circumstances (Figure 2). Mutants of L. plantarum and L. casei impaired in NADH regeneration by the lactate dehydrogenase were able to produce small amounts of mannitol from glucose due to a mannitol-1-P dehydrogenase (M1PDH) activity on fructose-6P (Ferain et al, 1996;Viana et al, 2005). M1PDH can recycle NADH rendering mannitol-1P that can be dephosphorylated to mannitol and excreted from the bacterial cell.…”

“…Comparable behaviour has been reported for many LAB where ldhs have been deleted. In this sense, mutation of the genes encoding L-and D-LDHs from L. plantarum, an organism which produces a mixture of 50% D-and 50% L-lactate, never resulted in a complete lack of lactate production (Ferain et al, 1996). An ldhL mutation in L. sakei, a lactic acid bacterium which lacks D-lactate dehydrogenase activity, rendered a strain with strongly reduced L-and D-lactate production (the D isomer was a consequence of the presence of a racemase activity able to transform L-into D-lactate), but small amounts of lactate were still produced (Malleret et al, 1998).…”