OBJECTIVES (S)-Mandelate dehydrogenase (SMDH) and laccase were immobilized on chitosan. The bi-enzymatic system with immobilized SMDH and immobilized laccase was taken to catalyze the stereoselective transformation of racemic mandelic acid and (R)-mandelic acid was obtained from its racemic mixture. RESULTS Characteristics of the immobilized enzymes were valuated. The optimum pH and temperature of the immobilized SMDH were found to be pH 3.4 and 45 °C, and these of the immobilized laccase were about pH 6.0 and 55 °C, respectively. The Km value of the immobilized SMDH for racemic mandelic acid was 0.27 mM and that of the immobilized laccase for ferrocyanide was 0.99 mM. The thermal and storage stabilities of these enzymes were improved with immobilization. The enantiomeric purity of the bi-enzymatically produced (R)-mandelic acid was determined to be over 99%. CONCLUSION The immobilized bi-enzymatic system for the stereoselective transformation of racemic mandelic acid showed higher productivity, faster reaction velocity, and more stable catalytic ability.Graphical abstract.

中文翻译：

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使用固定的漆酶和（S）-扁桃酸脱氢酶进行消旋扁桃酸的立体选择性生物转化。

目的（S）-扁桃酸脱氢酶（SMDH）和漆酶固定在壳聚糖上。采用固定化SMDH和固定化漆酶的双酶体系催化外消旋扁桃酸的立体选择性转化，并从其外消旋混合物中获得（R）-扁桃酸。结果评价了固定化酶的特性。固定的SMDH的最佳pH和温度分别为pH 3.4和45°C，固定的漆酶的最佳pH和温度分别约为pH 6.0和55°C。固定化SMDH的外消旋扁桃酸的Km值为0.27 mM，固定化漆酶的亚铁氰化物的Km值为0.99 mM。固定化可以提高这些酶的热稳定性和储存稳定性。经测定，双酶法生产的（R）-扁桃酸的对映体纯度超过99％。结论外消旋扁桃酸立体选择性转化的固定化双酶体系具有较高的产率，更快的反应速度和更稳定的催化能力。