Galactomyces reessii转化β-甲基丁酸生产β-羟基-β-甲基丁酸

Production of β-Hydroxy-β-methylbutyric Acidfrom β-Methylbutyric Acid with Galactomyces reessii

Galactomycesreessii可将 β-甲基丁酸 ( MBA)转化为 β-羟基 - β-甲基丁酸 ( HMB)。摇瓶实验表明发酵过程中提供生长因子的酵母萃取物浓度以 3 g/L较适宜。高浓度钠、铵离子对菌体生长有抑制作用 ,为保证转化 MBA所需 p H可采用混合碱 ( Na OH、KOH、NH4 OH)来调节 ,以防止单一阳离子浓度过高对菌体生长和产物形成的抑制。MBA对菌体生长有明显的抑制作用 ,1 0 g/L的MBA可使菌体浓度减少 3 0 %。分批补料发酵中 ,连续流加葡萄糖和 MBA,控制发酵液中葡萄糖浓度不超过 3 g/L,MBA浓度不超过 4g/L ,1 0 2 h时 HMB浓度达 2 9.0 g/L ,转化率达 5 7.3 % ,HMB平均生产率达 0 .0 98g/( L· h)。

Galactomyces reessii can transform β-methylbutyric acid (MBA) to β-hydroxy-β-methyl-butyric acid (HMB). Shake flask experiments indicated that abundant growth was obtained in the presence of 3g/L yeast extract in the medium. High concentrations of sodium or ammonium ion caused inhibition of the cell growth. In order to avoid the negative effects caused by the cations, the mixture of NaOH, KOH and NH_4OH was used to adjust the culture pH. High MBA concentration inhibited the cell growth. An initial MBA concentration of 10g/L reduced cell growth by 30%. In a fed-batch culture with glucose and MBA maintained at less than 3g/L and 4g/L respectively, the highest HMB concentration of 29.0g/L with a molar conversion yield of 57.3% was obtained at 102h, and the average HMB productivity was 0.098 g/(L·h).