title: Efficient production of methionine from 2-amino-4-methylthiobutanenitrile by recombinant Escherichia coli harboring nitrilase.
abstract: Methionine as an essential amino acid has been attracting more attention for its important applications in food and feed additives. In this study, for efficient production of methionine from 2-amino-4-methylthiobutanenitrile, a codon-optimized nitrilase gene was newly synthesized and expressed, and the catalytic conditions for methionine production were studied. The optimal temperature and pH for methionine synthesis were 40 °C and 7.5, respectively. The recombinant nitrilase was thermo-stable with half-life of 5.52 h at 40 °C. The substrate loading was optimized in given amount of catalyst and fixed substrate/catalyst ratio mode to achieve higher productivity. Methionine was produced in 100 % conversion within 120 min with a substrate loading of 300 mM. The production of methionine with the immobilized resting cells in packed-bed reactor was investigated. The immobilized nitrilase exhibited good operation stability and retained over 80 % of the initial activity after operating for 100 h. After separation, the purity and the total yield of methionine reached 99.1 and 97 %, respectively. This recombinant nitrilase could be a potential candidate for application in production of methionine.
authors.affiliation: Institute of Bioengineering, Zhejiang, University of Technology, Hangzhou, 310014, People's Republic of China.
authors.forename: Li-Qun
authors.initials: LQ
authors.lastname: Jin
authors.forename: Zong-Tong
authors.initials: ZT
authors.lastname: Li
authors.forename: Zhi-Qiang
authors.initials: ZQ
authors.lastname: Liu
authors.forename: Yu-Guo
authors.initials: YG
authors.lastname: Zheng
authors.forename: Yin-Chu
authors.initials: YC
authors.lastname: Shen
mesh_terms: D000619:Aminohydrolases / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D055162:Biocatalysis; D018914:Cells, Immobilized; D042621:Comamonadaceae / Q000201:enzymology; D004795:Enzyme Stability; D004926:Escherichia coli / Q000235:genetics*; D006207:Half-Life; D006863:Hydrogen-Ion Concentration; D008670:Metals / Q000737:chemistry; D008715:Methionine / Q000096:biosynthesis / Q000138:chemical synthesis*; D009570:Nitriles / Q000737:chemistry* / Q000378:metabolism
chemical_list: C000593270:2-amino-4-methylthiobutanenitrile; D001426:Bacterial Proteins; D008670:Metals; D009570:Nitriles; D008715:Methionine; D000619:Aminohydrolases; C021867:nitrilase
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