Growth of Bifidobacterium pseudocatenulatum in medium containing N-acetylsucrosamine: enzyme that induces the growth of this bacterium via degradation of this disaccharide.

Bifidobacterium pseudocatenulatum grows well in the early stages of cultivation in medium containing sucrose (Suc), whereas its growth in medium containing the analogue disaccharide N-acetylsucrosamine (SucNAc) tends to exhibit a considerable delay. To elucidate the cause of this phenomenon, we investigated the proliferation pattern of B. pseudocatenulatum in medium containing D-glucose (Glc) and SucNAc and identified the enzyme that degrades this disaccharide. We found that B. pseudocatenulatum initially proliferates by assimilating Glc, with subsequent growth based on SucNAc assimilation depending on production of the β-fructofuranosidase, which can hydrolyze SucNAc, after Glc is completely consumed. Thus, B. pseudocatenulatum exhibited a diauxic growth pattern in medium containing Glc and SucNAc. In contrast, when cultured in medium containing Glc and Suc, B. pseudocatenulatum initially grew by degrading Suc via the phosphorolysis activity of Suc phosphorylase, which did not react to SucNAc. These observations indicate that B. pseudocatenulatum proliferates by assimilating Suc and SucNAc via different pathways. The β-fructofuranosidase of B. pseudocatenulatum exhibited higher hydrolytic activity against several naturally occurring Suc-based tri- or tetrasaccharides than against Suc, suggesting that this enzyme actively catabolizes oligosaccharides other than Suc.