Enantioselective biocatalytic hydrolysis of (R,S)-mandelonitrile for production of (R)-(-)-mandelic acid by a newly isolated mutant strain.
(R)-(-)-Mandelic acid (R-MA) is an important intermediate with broad uses. Recently, R-MA production using nitrilase has been gaining more and more attention due to its higher productivity and enantioselectivity. In this work, a new bacterium WT10, which exhibited favorable nitrilase activity and excellent enantioselectivity for production of R-MA by enantioselective biocatalytic hydrolysis of (R,S)-mandelonitrile, was isolated and identified as a strain of Alcaligenes faecalis. In order to improve its nitrilase activity for industrial application, the wild-type strain WT10 was further subjected to mutagenesis using a combined LiCl-ultraviolet irradiation and low energy N(+) ion beams implantation technique. A valuable mutant strain A. faecalis ZJUTB10 was obtained. The nitrilase specific activity of the mutant strain was greatly improved up to 350.8 U g(-1), in comparison with wild-type strain WT10 of 53.09 U g(-1). The reaction conditions for R-MA production by mutant strain A. faecalis ZJUTB10 were also optimized. Nitrilase activity in mutant strain showed a broad pH optimum at pH 7.7-8.5. The optimal temperature was 35°C. The highest production rate reached 9.3 mmol h(-1) g(-1). The results showed that mutant strain A. faecalis ZJUTB10 was a new candidate for efficient R-MA production from (R,S)-mandelonitrile and could potentially be used in industrial production.
Xue
Ya-Ping
YP
Institute of Bioengineering, Zhejiang University of Technology, 18 Chaowang Road, Hangzhou, People's Republic of China.
Xu
Sai-Zhen
SZ
Liu
Zhi-Qiang
ZQ
Zheng
Yu-Guo
YG
Shen
Yin-Chu
YC
D000097:Acetonitriles / Q000378:metabolism*; D042481:Alcaligenes faecalis / Q000145:classification / Q000201:enzymology / Q000235:genetics / Q000302:isolation & purification; D000619:Aminohydrolases / Q000378:metabolism; D055162:Biocatalysis; D001709:Biotechnology / Q000379:methods; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008333:Mandelic Acids / Q000138:chemical synthesis*; D008969:Molecular Sequence Data; D009154:Mutation; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012988:Soil Microbiology; D013696:Temperature
D000097:Acetonitriles; D008333:Mandelic Acids; D012336:RNA, Ribosomal, 16S; C045516:mandelonitrile; D000619:Aminohydrolases; C021867:nitrilase; C037938:mandelic acid