文献类型：期刊文献

英文题名：Significant enhancement of (R)-mandelic acid production by relieving substrate inhibition of recombinant nitrilase in toluene-water biphasic system

作者：Zhang, Zhi-Jun[1];Pan, Jiang[1];Liu, Jun-Feng[1];Xu, Jian-He[1];He, Yu-Cai[2];Liu, You-Yan[3]

机构：[1]E China Univ Sci & Technol, State Key Lab Bioreactor Engn, Lab Biocatalysis & Bioproc, Shanghai 200237, Peoples R China;[2]Changzhou Univ, Coll Chem & Chem Engn, Changzhou 213164, Peoples R China;[3]Guangxi Univ, Coll Chem & Chem Engn, Nanning 530004, Peoples R China

年份：2011

卷号：152

期号：1-2

起止页码：24

外文期刊名：JOURNAL OF BIOTECHNOLOGY

收录：;WOS:【SCI-EXPANDED(收录号:WOS:000288745600004)】；

基金：This work was financially supported by the National Natural Science Foundation of China (no. 20902023), Ministry of Science and Technology, P.R. China (nos. 2009ZX09501-016 and 2009CB724706), China National Special Fund for State Key Laboratory of Bioreactor Engineering (no. 2060204) and Shanghai Leading Academic Discipline Project (no. B505).

语种：英文

外文关键词：Aqueous-organic biphasic system; Recombinant nitrilase; Enantioselective hydrolysis; High substrate tolerance; (R)-(-)-Mandelic acid; Escherichia coli whole cells

摘要：The enantioselective hydrolysis of mandelonitrile with whole cells of a recombinant Escherichia coli expressing nitrilase activity was severely inhibited by the substrate at high concentrations (> 300 mM), which resulted in a low yield of the target product (R)-(-)-mandelic acid. To relieve the substrate inhibition and to enhance the (R)-(-)-mandelic acid productivity, eight water-organic solvent biphasic systems were attempted in this work. Toluene was found to be the most suitable solvent as the organic phase among the solvents tested. Various parameters were systematically examined and optimized in shake flasks. The phase volume ratio, buffer pH and reaction temperature were shown to be sensitive parameters affecting both the yield and the enantiopurity of product in the biphasic system. Under the optimized conditions, significant enhancement of substrate tolerance from 200 mM to 500 mM and average productivity from 179.6 g l(-1) d(-1) to 352.6 g l(-1) d(-1) were achieved. Subsequently, the biocatalytic hydrolysis of mandelonitrile was successfully carried out in a stirred reactor (2-l scale) by repeated use of the calcium alginate entrapped cells for 5 batches, affording 110.7 g (R)-(-)-mandelic acid in 98.0% ee (enantiomeric excess) and a specific production of 13.8 g (mandelic acid) g(-1) (cell), respectively. (C) 2011 Elsevier B.V. All rights reserved.