Modification of purified lipases from Candida rugosa with polyethylene glycol:: A systematic study

Semipurified lipase and pure isoenzymes [lipase A (CRLA) and lipase B (CRLB)] of Candida rugosa were chemically modified using pNPCF-PEG. The modified enzymes can be stored at 4 degrees C for 6 months without losing activity. The chemically modified lipases were more stable than the native enzymes and were stored at 50 degrees C in isooctane. The chemically modified enzymes were used in i) hydrolysis of triolein; ii) esterification of oleic acid; and iii) enantioselective esterification of(R,S) ibuprofen. Lipase activity was less than esterase activity as a result of the chemical modification of the lipase. The influence of purification and chemical modification degrees in the i) storage stability; ii) catalytic activity; iii) stability with respect to isooctane; and iv) stereoselectivity is discussed. We modulated the hydrophobicity of the biocatalyst by changing the modification degree of the lipase. This effect allowed us to select the optimum biocatalyst to achieve the maximum yield for esterification in different organic solvents. Only the purification of C. rugosa lipase increased the activity and enantioselectivity. Purification and chemical modification did not change the enantiopreference of the lipase. (C) 1998 Elsevier Science Inc.