title: Kinetic resolution of racemic styrene oxide at a high concentration by recombinant Aspergillus usamii epoxide hydrolase in an n-hexanol/buffer biphasic system.
abstract: Using the cell-free extract of engineered E. coli/Aueh2, expressing the recombinant Aspergillus usamii epoxide hydrolase (reAuEH2), as a biocatalyst, the kinetic resolution technique of racemic styrene oxide (rac-SO) was examined. In a phosphate buffer system (50mM, pH 7.0), 200mM rac-SO was efficiently resolved, obtaining (S)-SO with 98.1% enantiomeric excess (e.e.), whereas (S)-SO only with 45.2% e.e. was obtained from 750mM rac-SO. The analytical results verified that reAuEH2 shows tolerance towards high substrate concentration but is inactivated at a product concentration of 300mM. To produce (S)-SO with the high concentration, e.e. and volumetric productivity, n-hexanol was selected from a variety of water-miscible and water-immiscible organic solvents to construct an n-hexanol/buffer biphasic system. The optimal phase volume ratio, substrate over enzyme ratio and temperature were 1:1 (v/v), 6:1 (w/w) and 25°C, respectively. In an optimized biocatalytic system, a gram-scale resolution of rac-SO at a high concentration of 1M (120g/L) was performed at 25°C for 2h, obtaining (S)-SO with 98.2% e.e., 34.3% yield (maximum yield of 50%). The substrate concentration and volumetric productivity (1M, 20.6g/L/h) in a biphasic system significantly increased compared with those (0.2M, 3.1g/L/h) in a phosphate buffer system. The efficient resolution of rac-SO at a high concentration in a biphasic system makes it a promising technique for preparing a highly value-added enantiopure (S)-SO with high volumetric productivity.
authors.affiliation: Key Laboratory of Carbohydrate Chemistry & Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, 214122, China.
authors.forename: Die
authors.initials: D
authors.lastname: Hu
authors.affiliation: Key Laboratory of Carbohydrate Chemistry & Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, 214122, China.
authors.forename: Rui
authors.initials: R
authors.lastname: Wang
authors.affiliation: School of Pharmaceutical Science, Jiangnan University, Wuxi, 214122, China.
authors.forename: Xiao-Ling
authors.initials: XL
authors.lastname: Shi
authors.affiliation: School of Pharmaceutical Science, Jiangnan University, Wuxi, 214122, China.
authors.forename: Hui-Hua
authors.initials: HH
authors.lastname: Ye
authors.affiliation: Key Laboratory of Carbohydrate Chemistry & Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, 214122, China.
authors.forename: Qin
authors.initials: Q
authors.lastname: Wu
authors.affiliation: Wuxi Medical School, Jiangnan University, Wuxi, 214122, China. Electronic address: biowmc@126.com.
authors.forename: Min-Chen
authors.initials: MC
authors.lastname: Wu
authors.affiliation: Department of Oncology, Affiliated Hospital, Jiangnan University, Wuxi, 214122, China. Electronic address: wschujianjun@163.com.
authors.forename: Jian-Jun
authors.initials: JJ
authors.lastname: Chu
mesh_terms: D001230:Aspergillus / Q000201:enzymology* / Q000235:genetics; D005591:Chemical Fractionation / Q000379:methods*; D004851:Epoxide Hydrolases / Q000235:genetics / Q000378:metabolism*; D004852:Epoxy Compounds / Q000737:chemistry* / Q000302:isolation & purification*; D000441:Hexanols / Q000737:chemistry*; D007700:Kinetics; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism*; D013237:Stereoisomerism
chemical_list: D004852:Epoxy Compounds; D000441:Hexanols; D011994:Recombinant Proteins; C036260:1-hexanol; C013690:styrene oxide; D004851:Epoxide Hydrolases
keywords: (S)-Styrene oxide; Biphasic system; Epoxide hydrolase; High substrate concentration; Kinetic resolution