[Expression of Candida antarctica lipase B on yeast surface and synthesis of ethyl hexanoate catalyzed by CALB].

Short-chain esters play a significant role in the food industry as flavor and aroma constituents. Candida antarctica lipase B (CALB) is one of the most effective catalysts for organic synthesis. We constructed a CALB-displaying yeast whole-cell biocatalyst and applied it to esterification from caproic acid and ethanol. CALB was fused with the alpha-agglutinin C-terminal and the signal peptide of Glucoamylase in pICAS, a yeast surface display vector, to construct plasmid pICAS-CALB. An extremely Asn-rich linker, named celAL was inserted in the Xho I of pICAS-CALB to construct plasmid pICAS-celAL-CALB. The fused gene was under the control of GAPDH promoter. After incubated at 30 degrees C for 96 h the lipase hydrolytic activity of the yeast whole cells reached a plateau, 26.26 u/(g x dry cell). In nonaqeous media, the yield of 98.0% ethyl hexanoate was obtained after 24 h esterification from caproic acid and ethanol (the molar ratio of caproic acid : ethanol = 1 : 1.25) using lyophilized CALB displaying yeast whole cells.