Increasing the expression yield of active Candida antarctica lipase B (CAL-B) in Escherichia coli was achieved by using a codon-optimized synthetic gene and by mutagenesis to introduce hydrophilic residues on the surface of CAL-B. Five residues (four leucines and one isoleucine) on the surface of CAL-B were selected and changed with aspartate after codon optimization. While the codon-optimized synthetic gene of CAL-B did not increase the expression yield, the mutation increased the activity of the enzyme three-fold (3.3 mg/l of culture) compared to the wild type. The mutant enzyme had similar hydrolytic activity toward hydrolysis of p-nitrophenyl acetate or p-nitrophenyl butyrate and enantioselectivity toward hydrolysis of (R, S)-1-phenylethyl acetate compared to the wild-type enzyme.