乳酸桿菌及雙叉桿菌之胞外多醣生成條件與關鍵性酵素活性研究

Abstract

本實驗以常見的益生性乳酸桿菌及雙叉桿菌為研究對象，檢測其在乳糖基質的生長條件下生產胞外多醣的能力，並選取各菌屬中產量最高者，探討影響其生成的培養條件與特性，最後分析胞外多醣生合成的關鍵性酵素活性與代謝的可能途徑。結果顯示，在以乳糖為基質之化學組成培養基(chemical defined medium, CDM)，Lactobacillus salivarius BCRC14759與Bifidobacteria bifidium BCRC 14615有最高的胞外多醣產量( 29.2 mg/L, 8.6 mg/L )；在不同培養條件下，L. salivarius BCRC14759 於含5 g/L乳糖濃度培養基，以40℃的培養溫度下，有最高的胞外多醣產量(50 mg/L)，B. bifidium BCRC 14615則在含40 g/L乳糖培養基，35℃培養溫度下，胞外多醣產量最高(19 mg/L)。L. salivarius BCRC14759與B. bifidium BCRC 14615之胞外多醣產量與菌體生長有相關性，對培養基中的葡萄糖利用性較半乳糖高；兩菌株的胞外多醣生合成酵素α- phosphoglucomutase 、UDP-glucose pyrophosphorylase及 UDP-galactose-4-epimerase 的比活性皆比其他生成酵素高，有利於glucose-1-P、UDP-glucose與UDP-galactose之生成，推測其合成胞外多醣途徑係經由葡萄糖轉變成UDP-glucose至UDP-galactose，最後生成胞外多醣。

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.