Cloning, expression and characterization of cold active esterase (EstN7) from Bacillus cohnii strain N1: A novel member of family IV

Esterases and lipases from extremophiles have attracted great attention due to their unique characteristics and wide applications. In the present study, an open reading frame (ORF) encoding a novel cold active esterase (EstN7) from Bacillus cohnii strain N1 was cloned and expressed in Escherichia coli. The full-length esterase gene encoding a protein of 320 amino acids with estimated molecular weight of 37.0 kDa. Amino acid sequence analysis revealed that the EstN7 belongs to family IV lipases with a characteristic penta-peptide motif (GXSXG), the catalytic triad Ser, Asp, His and the conserved HGGG motif of the family IV. The recombinant enzyme was purified to apparent homogeneity using nickel-affinity chromatography with a purification fold of 5 and recovery 94.5%. The specific activity of the purified enzyme was 336.89 U/mg. The recombinant EstN7 showed optimal activity at 5 degrees C moreover, EstN7 displayed full robust stability in the presence of wide range of organic solvents. The purified enzyme had K-m and V-max of 45 +/- 0.019 mu M and 1113 mu mol min(-1) mg(-1), respectively on p-NP-acetate. These promising characteristics of the recombinant EstN7 would underpin its possible usage with high potential in the synthesis of fragile compounds in pharmaceutical industries. (C) 2018 Published by Elsevier B.V.