中文摘要：

研究了水／有机溶剂两相体系中，出芽短梗霉SW0202细胞催化4-氯乙酰乙酸乙酯（COBE）不对称还原制备（S）-4-氯-3-羟基丁酸乙酯（CHBE）的过程。有机溶剂的选择表明邻苯二甲酸二丁酯为该反应最适有机溶剂，与单一水相体系相比，水／邻苯二甲酸二丁酯两相体系能明显改善反应效率。通过系统考察一些因素如相体积比、振摇速度、反应温度和pH等对反应速度、摩尔转化率和产物光学纯度的影响发现，这些因素对还原反应的初速度和摩尔转化率有较明显的影响，而对产物的光学纯度影响不明显。优化后的条件为：水与有机溶剂的相体积比1：1，振摇速度180r·min^-1，温度30℃，pH7．0。在该优化反应条件下，水，有机溶剂两相体系中出芽短梗霉SW0202细胞催化COBE生成（S）-CHBE不对称还原反应的最大摩尔转化率和产物的光学纯度分别达到了94．8％和97．9％e.e，在用Na2CO3溶液控制水相pH7.0条件下，有机相中的产物浓度积累达58．2g·L^-1。

英文摘要：

Asymmertric reduction of ethyl 4-chloro-3-oxobutanoate to ethyl （S）-4-chloro-3-hydroxybutanoate with Aureobasidium pullulans SW0202 cells as catalyst was performed in an aqueous/organic solvent biphasic system. The results of the solvent screening indicate that the dibutylphthalate provides the best compromise between the biocompatibility and the partition of substrate and product among the tested solvents. The bioconversion is more efficient in a biphasic system composed of potassium phosphate buffer （0.1 mol·L^-1, pH 6.5） and dibutylphthalate than that in monophasic aqueous system. The suitable values of the factors affecting the reaction, such as the volume ratio of the aqueous phase to the organic phase, shaking speed, reaction temperature and pH value were investigated. The results show that these factors obviously influence the molar conversion and initial reaction rate, but have little effect on the optical purity of the product, which keeps at a higher value when these factors change. The optimum values of volume ratio of the aqueous phase to the organic phase, shaking speed, reaction temperature and pH value are 1：1, 180 r·min^-1, 30℃ and 7.0, respectively. Under above optimum condition, the maximum molar conversion and the optical purity of the product can be obtained as high as 94.8% and 97.9% e.e., respectively. A high product concentration in organic layer was obtained, which could reach 58.2 g·L^-1 by controlling pH at 7.0 with 2 mol·L^-1 Na2CO3 during the process of the asymmertric reduction.