牛瘤胃分离菌株静息细胞培养体系生物转化黄豆苷原

Biotransformation of daidzein by resting cell system of bacterial strain isolated from bovine rumen gastric juice

摘要:

从牛瘤胃胃液中分离了一株在厌氧条件下能利用其生长细胞将大豆异黄酮黄豆苷原高效还原为二氢黄豆苷原的革兰氏阳性细菌菌株Niu-O16。研究了菌株Niu-O16静息细胞体系转化黄豆苷原的最佳转化条件，通过单因素试验确定菌株Niu-O16静息细胞转化黄豆苷原的最佳条件是：初始pH 6.0?8.0，静息细胞浓度32?64 mg/mL (湿重)，加入底物浓度0.8?1.2 mmol/L。通过正交试验确定了静息细胞浓度、加入底物浓度及转化时间的最佳组合为：静息细胞浓度32 mg/mL、加入底物浓度0.8 mmol/L、转化时间24 h；最佳转化条件下底物转化率最高为63.9％。该结果为厌氧菌的静息细胞转化及工业应用提供了参考。

Abstract:

In previous study we isolated a gram-positive bacterial strain, designated Niu-O16, from bovine rumen gastric juice. The growing cells of bacterial strain Niu-O16 is capable of biotransforming isoflavone daidzein into dihydrodaidzein efficiently under anaerobic conditions. In this study we investigated the optimal bioconversion conditions for the resting cells of bacterial strain Niu-O16 to convert daidzein into dihydrodaidzein. Single factor test showed that the optimal conditions for the initial pH of phosphate buffer, the concentration of the resting cell and the concentration of the substrate daidzein were 6.0–8.0, 32–64 mg/mL (wet weight) and 0.8~1.2 mmol/L, respectively. Orthogonal experiments were used to determine the optimal combination of the resting cell concentration, substrate concentration and biotransformation time. The results showed that the optimal combination included resting cell concentration 32 mg/mL, substrate concentration 0.8 mmol/L and the biotransformation time 24 h. Furthermore, the biotransformation kinetics under optimal conditions were studied, under which conditions the highest bioconversion rate was 63.9% in the resting cell system. The results might provide information for resting cell biotransforming of anaerobes as well as its industrial application.