| Summary: | 碩士 === 國立臺灣大學 === 食品科技研究所 === 94 === This study was conducted to investigate the production of exopolysaccharide (EPS) from several probiotic Lactobacillus and Bifidobacterium species in lactose media. The highest EPS production of Lactobacillus and Bifidobacterium were then assayed for the effects of incubation conditions on their EPS production. Besides, the key enzymes involving in the biosynthesis of EPS in Lactobacillus and Bifidobacterium were assayed. The results show that Lactobacillus salivarius BCRC14759 and Bifidobacteria bifidum BCRC 14615 are the highest EPS producers while they were grown in chemical defined media (CDM) containing lactose. The production of EPS by L. salivarius BCRC14759 and B. bifidum BCRC 14615 were 29.2 mg/L and 8.6 mg/L, irrespectively. While cultivation at 40℃and in CDM that contain 5 g/L lactose, the production of EPS by L. salivarius BCRC14759 was further increased to 50 mg/L. When B. bifidum BCRC 14615 was cultivated in CDM that containing 40 g/L lactose and incubation at 35℃, the production of EPS was increased to 19 mg/L. The glucose utilization was found higher than galactose in L. salivarius BCRC14759 and B. bifidum BCRC 14615. The production of EPS was related to the growth of these bacteria. The α- phosphoglucomutase, UDP-glucose pyrophosphorylase and UDP-galactose-4-epimerase were involved in the biosynthesis of EPS. Their specific activities were higher than other biosynthetic enzymes and utilized in the synthesis of glucose-1-P, UDP-glucose and UDP-galactose. Therefore, the pathway for EPS biosynthesis in L. salivarius BCRC14759 and B. bifidum BCRC 14615 was probably via glucose to UDP-glucose, UDP-galactose, and EPS.
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