双层固定化酵母催化还原4-氯-乙酰乙酸乙酯的研究

以海藻酸钠为内层载体,利用机械强度良好的聚乙烯醇(PVA)改性海藻酸钠混合物作为外层载体,双层固定化高活性酵母,得到固载的生物催化剂,用于由磷酸缓冲溶液和环己烷组成的双相体系,对4-氯-乙酰乙酸乙酯(COBE,ethyl 4-cloro-3-oxobutyrate)进行不对称催化加氢合成(S)-4-氯-3-羟基丁酸乙酯(S)-CHBE],ethyl(S)-4-chloro-3-hydro butanoate].在最适条件下,双层固定化酵母的不对称催化还原反应优于游离细胞和单层固定化细胞.在底物COBE的最佳浓度和进料速率分别为170mmol/L,125mL/h的连续操作条件下,最高(S)-CHBE转化率为94.2%,最高对映体过量值为98%.与游离细胞催化COBE相比,反应转化率提高3%,最佳底物浓度比游离细胞增加1倍;与单层固定化细胞催化还原相比,对映体过量值提高8%.连续性实验表明,双层固定化酵母细胞在连续使用5d,其转化率和对映选择性没有明显下降.

STUDY ON THE CATALYTIC REDUCTION OF ETHYL 4-CLORO-3-OXOBUTYRATE BY DOUBLE-LAYERS IMMOBLIZED YEAST

The supported biocatalysis was prepared with the highly active yeast double-layer immobilized by alginate as the inner layer and alginate improved by polyvinyl alcohol with good mechanical property as outer layer,which was applied in the asymmetric catalytic hydrogenation of COBE(ethyl 4-cloro-3-oxobutyrate) in the biphase of phosphate buffer solution for the preparation of(S)-CHBE.The best converting yield was 94.2% and the best e.e% was 98% under the optimal concentration 170mmol/L and flow rate 125mL/h.Comparing with the free yeast,the converting yield increased 3%,the concentration of substrate increased 100%.Comparing with the one layer immobilized yeast,the enantioselectivity excess increased 8%.The continuous experiment showed that double layer immobilized yeast can be recycled to use in 5 days without significant decrease in the bioreduction of COBE.