Identification, purification and characterization of a novel glycosidase (BgLm1) from Leuconostoc mesenteroides

This study describes the identification and characterization of a novel recombinant Leuconostoc mesenteroides glycosidase (BgLm1). Since the protein encoded by LEUM_0847 gene was annotated as putative beta-glucosidase, characterization procedures were done using p-nitrophenyl-beta-D-glucopyranoside as substrate. A high yield of purified recombinant BgLm1 was obtained (12 mg/L). The enzyme showed an optimal activity at pH 6.0 and 40 degrees C and preserved 65% of residual activity after 48 h of incubation at 25 degrees C. Ca2+ and Mn2+ ions greatly increased the beta-glucosidase activity. Moreover, BgLm1 demonstrated beta-galactosidase and beta-fucosidase activities. Kinetic parameters of BgLm1 revealed its low affinity to p-nitrophenyl-beta-D-glucopyranoside (K-m of 9.93 mmol/L). Then, although LEUM_0847 gene was annotated as a beta-glucosidase, our results suggest that BgLm1can be indeed considered as a beta-galactosidase since high hydrolysis using skimmed milk (lactose) as natural substrate and high affinity (K-m of 0.56 mmol/L) and specific constant (2254 mmol/L-1 s(-1)) to p-nitrophenyl-beta-D-galactopyranoside were observed. In conclusion, the enzymatic properties observed in this study, support the interest of BgLm1 for food industrial applications.