Activity of different Candida antarctica lipase B formulations in organic solvents

The activity of different formulations of Candida antarctica lipase B (CALB ), such as crude CALB, purified CALB, purified CALB lyophilized with PEG (C ALB + PEG) or oleic acid (CALB + GA), and the commercial formulation Novozy m 435, was determined in toluene, carbon tetrachloride, and 1,4-dioxane at various water activities (a(w)). The reaction between vinylacetate and l-oc tanol was used as the model reaction and both transesterification (formatio n of 1-octylacetate) and hydrolytic (formation of acetic acid from vinylace tate) activities were determined. For equal amounts of lipase protein, CALB + PEG land to a lesser extent CALB + OA) displayed higher activity than th at of the other formulations; for instance, in toluene (a(w) < 0.1), it was 260-, 13-, and 1.8-fold more active than crude CALB, purified CALB, and No vozym 435, respectively. Moreover, the transesterification activity of CALB + PEG was of the same order of magnitude (51%) of the activity shown by th e enzyme in the hydrolysis of vinylacetate in aqueous buffer. These results suggest that PEG and oleic acid could act as lyoprotectants, preventing th e formation of intermolecular interactions during the lyophilization proces s that might be responsible for protein denaturation. No diffusional limita tion was observed for CALB + PEG-catalyzed reactions. Purified CALB, in con trast to the other formulations, showed a marked activity increase (2.1 to 7.8-fold) as a function of a(w) and, in 1,4-dioxane, it was 3.5-fold more a ctive when it was added to the solvent after previous dissolution of the ly ophilized powder in water. <(c)> 2001 John Wiley & Sons, Inc.