Capacity of soybean carbohydrate metabolism in Leuconostoc mesenteroides, Lactococcus lactis and Streptococcus thermophilus

Few studies have focused on the capacity of lactic acid bacteria in utilizing soybean carbohydrates by genetic and phenotypic approaches. In the current study, genetic and phenotypic characteristics of soybean carbohydrate metabolism in Leuconostoc mesenteroides, Lactococcus lactis and Streptococcus thermophilus were investigated. The results indicated that all the 3 species have the potential capacity to utilize sucrose with a sucrose phosphoenolpyruvate-dependent phosphotransferase system (PTS) pathway mainly consisted of scrA, sacA, scrK and scrR. Among the 15 strains, only 1 L. lactis strain possessed both sucrose permease and PTS pathway. On the other hand, only Leu. mesenteroides among the 3 species have the genes related to α-galactosidases for potential capacity to metabolize raffinose-family oligosaccharides (RFO) in soybean. Four Leu. mesenteroides strains, DQHXN_Q03M16, FSDLZ60M2, DSCAB2M6 and DQHXN_Q38M5, possessed the complete α-galactosidases gene clusters of lacS-galA-galK-galT and high α-galactosidases activity, which contributed to the capacity of these strains to utilize RFO. These findings provide an approach to investigate the genetic and the phenotypic characteristics of Leu. mesenteroides, L. lactis and S. thermophilus in soybean carbohydrate metabolism for suitable strain selection in soybean fermentation.