CONICET | Buscador de Institutos y Recursos Humanos

L-arabinose isomerase is a technological relevant enzyme because can isomerizes D-galactose, contained in cheese whey lactose, to D-tagatose, a natural rare sugar. Actually, all L-arabinose isomerases have been isolated in a recombinant way but this methodology implies a reduced technological application. For this reason, 29 bacterial strains, some of them previously characterized as L-arabinose isomerase producers, were assayed as L-arabinose fermenting strains employing conveniently designed culture mediums with 0.5% (w/v) L-arabinose as main carbon source. From all evaluated bacterial strains, Enterococcus faecium DBFIQ E36, Enterococcus faecium DBFIQ ETW4 and Pediococcus acidilactici ATCC 8042 were, in this order, the best L-arabinose fermenting strain. Afterward, to compare L-arabinose metabolization and L-arabinose isomerase activity, cell-free extract and cell-free extract saline precipitated of the three bacterial cultures were obtained and production of ketoses was determined by cysteine carbazole sulfuric acid method. Results have shown that the more L-arabinose metabolization ability, the more enzymatic activity obtained, so Enterococcus faecium DBFIQ E36 was selected to continue with production, purification and characterization studies. This work describes a simply microbiological method to select potential L-arabinose fermenting bacteria to produce the enzyme L-arabinose isomerase.