Effect of biosynthetic intermediates and citrate on the phenyllactic and hydroxyphenyllactic acids production by Lactobacillus plantarum CRL 778

Abstract

Aim: To evaluate the influence of biosynthetic precursors, intermediates and electron acceptors on the production of antifungal compounds [phenyllactic acid (PLA) and hydroxyphenyllactic acid (OH‐PLA)] by Lactobacillus plantarum CRL 778, a strain isolated from home‐made sourdough. Methods and Results: Growth of fermentative activity and antifungal compounds production by Lact. plantarum CRL 778 were evaluated in a chemically defined medium (CDM) supplemented with biosynthetic precursors [phenylalanine (Phe), tyrosine (Tyr)], intermediates [glutamate (Glu), alpha‐ketoglutarate (α‐KG)] and electron acceptors [citrate (Cit)]. Results showed that the highest PLA production (0·26 mmol l−1), the main antifungal compound produced by Lact. plantarum CRL 778, occurred when greater concentrations of Phe than Tyr were present. Both PLA and OH‐PLA yields were increased 2‐folds when Cit was combined with α‐KG instead of Glu at similar Tyr/Phe molar ratio. Similarly, glutamate dehydrogenase (GDH) activity was significantly (P < 0·01) stimulated by α‐KG and Cit in Glu‐free medium. Conclusion: Phe was the major stimulant for PLA formation; however, Cit could increase both PLA and OH‐PLA synthesis by Lact. plantarum CRL 778 probably due to an increase in oxidized NAD+. This effect, as well as the GDH activity, was enhanced by α‐KG and down regulated by Glu. Significance and Impact of the Study: This is the first study where the role of Glu and GDH activity in the PLA and OH‐PLA synthesis was evidenced in sourdough lactic acid bacteria (LAB) using a CDM. These results contribute to the knowledge on the antifungal compounds production by sourdough LAB with potential applications on the baked goods.

Metabolic mechanism of phenyllactic acid naturally occurring in Chinese pickles

“…These finding could be explained by the fact that Phe was the precursor of PLA metabolism in LAB (Vermeulen et al, 2006) and to some extent the production of PLA in pickles was positively correlated with the content of Phe in foodstuff. Besides, other researches on the production of PLA also indicated the stimulant effect of Phe (Dallagnol, Catalán, Mercado, Font de Valdez, & Rollán, 2011;Mu, Yu, Zhu, Jiang, & Zhang, 2012;Valerio et al, 2004). Simultaneously, this speculation was also verified in this study shown in Fig.…”

“…Similarly, the research on PLA production by L. plantarum TMW 1.468 also showed relatively low conversion rate (Vermeulen et al, 2006). In terms of the reason leading to the different PLA concentration in various types of pickles, biosynthetic intermediates (glutamate, alpha-ketoglutarate) and electron acceptors (citrate) could probably be the major factors in addition to the precursor (Phe) (Dallagnol et al, 2011). The work regarding the effect of biosynthetic intermediates and electron acceptors on the production of PLA in pickles was being done by our research group.…”

Identification of Antioxidants Produced byLactobacillus plantarum

“…[6][7][8] Certain strains of L. plantarum from sourdough have been reported to produce HPLA and PLA 8) and reported to be antifungal compounds. 8,9) An aromatic aminotransferase has been shown to be active with tyrosine, phenylalanine, tryptophan, methionine and leucine.…”

Phenyllactic Acid: A Potential Antimicrobial Compound in Lactic acid Bacteria

“…This regulatory effect was observed in L. plantarum resulting in enhanced production of PLA in presence ά-ketoglutarate [28,30]. In presence of substrates like glucose, citric acid and fructose acting as electron acceptor, glutamate dehydrogenase activity is enhanced leading to formation of ά-ketoglutarate which in turn upregulate the PhLA synthesis [32]. The other precursor is PPA which can be reduced to PhLA with help of enzymes such as reductases or dehydrogenases present in LAB.…”

“…The enzyme AAT transfer the amino acid group from phenyl alanine to any suitable ά-keto-acid preferably ά-ketoglutarate in LAB. Hence ά-ketoglutarate is an important that effects the both catabolism of phenylalanine and regulation of PhLA synthesis indirectly [32]. This regulatory effect was observed in L. plantarum resulting in enhanced production of PLA in presence ά-ketoglutarate [28,30].…”