Sorbitol utilization by Pediococcus parvulus 2.6

ADRIÁN PEREZ RAMOS; MARIA LAURA WERNING; MARI LUZ MOHEDANO; GIUSEPPE SPANO; PALOMA LÓPEZ

Navarra

Otro; VIII Reunion de Bacterias Lácticas; 2014

Pediococcus parvulus 2.6 isolated from cider secretes a 2-substituted (1,3)-β-D-glucan exopolysaccharide (EPS) synthetized by the GTF glycosyltransferase using UDP-glucose as substrate. The potential of P. parvulus 2.6 as a probiotic strain has previously been established. In this work, the ability of this bacterium to utilize sorbitol has been detected, its genetic determinants identified and its interplay with the 2-substituted (1,3)-β-D-glucan synthesis investigated. Metabolomic analysis revealed that P. parvulus 2.6 can use sorbitol as a carbon source. DNA sequencing of the P. parvulus 2.6 genome and subsequent analysis showed the existence of a sorbitol utilization operon in a plasmid carried by this bacterium. The operon consists of six genes (gutFRMCBA). GutF encodes a sorbitol-6-phosphate dehydrogenase; gutRM genes encoding two putative regulators; and gutCBA genes encoding the proteins EIIC, EIIBC and EIIA which are components of a phosphoenolpyruvate-dependent sorbitol phosphotransferase system (PTSGut). Homology of these gene products with those of the Lactobacillus casei gut operon indicate that regulation of gut operon expression in P. parvulus could be carried out in a similar way to that described for L. casei. Metabolomic analysis of P. parvulus grown in the presence of sorbitol and glucose revealed a co-metabolism accompanied by a diauxic growth. A inhibition ELISA assay was optimized to allow direct and specific quantification of 2-substituted (1,3)-β-D-glucan in culture supernatants. EPS quantification showed that indeed the 2-substituted (1,3)-β-D-glucan is synthesized when sorbitol was used as the only carbon source and that this synthesis is very efficient since a similar rate of production of the EPS was observed in cultures grown in media containing either glucose or sorbitol.