吐温/缓冲液体系中酶法合成(R)-对氯环氧苯乙烷

Enzymatic synthesis of(R)-p-chlorostyrene oxide in Tween/buffer system

利用环氧化物水解酶突变体Pv EH1Z4X4-59制备了(R)-对氯环氧苯乙烷〔(R)-p CSO〕。以E.coli/pveh1Z4X4-59全细胞作为生物催化剂,在磷酸盐缓冲液体系(Na2HPO4-Na H2PO4,100mmol/L,pH=7.0)中有效拆分250mmol/L对氯环氧苯乙烷(rac-p CSO)制备(R)-p CSO(ees>99%)。随后,依据6种非离子型表面活性剂对E.coli/pveh1Z4X4-59全细胞酶活力和对映选择性的影响,筛选吐温-20作为最佳添加剂,构建并优化吐温-20/缓冲液反应体系。在最优反应条件下,吐温-20的添加量为4%(体积分数),E.coli/pveh1Z4X4-59全细胞的添加量为200 g/L,反应时间为12 h,初始底物浓度显著提高至800 mmol/L(123.7 g/L),获得(R)-p CSO的ees和产率分别为99%和45.7%(理论产率为50%),时空产率高达4.71 g/(L·h)。反应体系放大至100 mL后,制备4.5 g(R)-p CSO的总收率为36.3%。

Whole cells of E.coli/pveh1 Z4 X4-59 expressing a Phaseolus vulgaris epoxide hydrolase mutant Pv EH1 Z4 X4-59 was used as biocatalyst to catalyze hydrolytic kinetic resolution of 250 mmol/L racemic p-chlorostyrene oxide(rac-p CSO)in Na2 HPO4-NaH2 PO4 buffer system(100 mmol/L,pH=7.0)to prepare(R)-p-chlorostyrene oxide[(R)-p CSO)with an over 99%enantiomeric excess(ees).The effects of six nonionic surfactants on the activity and enantioselectivity of whole cells of E.coli/pveh1 Z4 X4-59 were investigated.It was found that Tween-20 was the best reaction additive.Thus,a Tween-20/buffer system was constructed and optimized.The optimized conditions were as follows:dosage of Tween-20 in Tween-20/buffer system was 4%(volume fraction),dosage of whole cells of E.coli/pveh1 Z4 X4-59 was 200 g/L,and reaction time was 12 h.Under these conditions,the initial substrate concentration was significantly increased to 800 mmol/L(123.7 g/L),(R)-p CSO with 99%ees,45.7%yield(theoretical yield 50%)and 4.71 g/(L·h)space-time yield was obtained.When the reaction system was amplified to 100 mL,the total yield of 4.5 g(R)-p CSO was 36.3%.