Shuichi Yanahira

Formation of oligosaccharides from lactitol by Aspergillus oryzae β-d-galactosidase

Six oligosaccharides were first formed from lactitol by a transgalactosylation reaction catalyzed by Aspergillus oryzae beta-D-galactosidase. From the results of methylation analysis, MS, and 1H- and 13C-NMR studies, it was concluded that these oligosaccharides are O-beta-D-galactopyranosyl-(1----4)-O-beta-D-galactopyranosyl-(1----4)-D- glucitol, O-beta-D-galactopyranosyl-(1----3)-O-beta-D-galactopyranosyl-(1----4)-D- glucitol, O-beta-D-galactopyranosyl-(1----4)-[O-beta-D-galactopyranosyl-(1----6)]- D- glucitol, O-beta-D-galactopyranosyl-(1----6)-O-beta-D-galactopyranosyl-(1---4)- glucitol, O-beta-D-galactopyranosyl-(1----4)-[O-beta-D-galactopyranosyl- (1----5)]-D-glucitol, and O-beta-D-galactopyranosyl-(1----4)-[O-beta-D-galactopyranosyl-(1----1)]- D-glucitol. The last three are newly observed oligosaccharides.

Multilocus variable-number of tandem repeat analysis (MLVA) for Clostridium tyrobutyricum strains isolated from cheese production environment

Clostridium tyrobutyricum is a gram-positive spore-forming anaerobe that is considered as the main causative agent for late blowing in cheese due to butyric acid fermentation. In this study, multilocus variable-number of tandem repeat (VNTR) analysis (MLVA) for C. tyrobutyricum was developed to identify the source of contamination by C. tyrobutyricum spores in the cheese production environment. For each contig constructed from the results of a whole genome draft sequence of C. tyrobutyricum JCM11008(T) based on next-generation sequencing, VNTR loci that were effective for typing were searched using the Tandem Repeat Finder program. Five VNTR loci were amplified by polymerase chain reaction (PCR) to determine their number of repeats by sequencing, and MLVA was conducted. 25 strains of C. tyrobutyricum isolated from the environment, raw milk, and silage were classified into 18 MLVA types (DI=0.963). Of the C. tyrobutyricum strains isolated from raw milk, natural cheese, and blown processed cheese, strains with identical MLVA type were detected, which suggested that these strains might have shifted from natural cheese to blown processed cheese. MLVA could be an effective tool for monitoring contamination of natural cheese with C. tyrobutyricum in the processed cheese production environment because of its high discriminability, thereby allowing the analyst to trace the source of contamination.