Optimization of Pseudomonas cepacia lipase preparations for catalysis in organic solvents

The activity of different lipase (from Pseudomonas cepacia) forms, such as crude powder (crude PC), purified and lyophilized with PEG (PEG + PC), cova lently linked to PEG (PEG-PC), cross-linked enzyme crystals (CLEC-PC), and immobilized in Sol-Gel-AK (Sol-Gel-AK-PC) was determined, at various water activities (a(w)), in carbon tetrachloride, benzene and 1,4-dioxane. The re action of vinyl butyrate with l-octanol was employed as a model and both tr ansesterification (formation of 1-octyl butyrate) and hydrolysis (formation of butyric acid from vinyl butyrate) rates were determined. Both rates dep ended on the lipase form, solvent employed, and a(w) value. Hydrolysis rate s always increased as a function of a(w), while the optimum of a(w) for tra nsesterification depended on the enzyme form and nature of the solvent. At proper a(w), some lipase forms such as PEG + PC, PEG-PC, and Sol-Gel-AK-PC had a total activity in organic solvents (transesterification plus hydrolys is) which was close to (39 and 48%) or even higher than (130%) that display ed by the same amount of lipase protein in the hydrolysis of tributyrin-one of the substrates most commonly used as standard for the assay of lipase a ctivity-in aqueous buffer. Instead, CLEC-PC and crude PC were much less act ive in organic solvents (2 and 12%) than in buffer. The results suggest tha t enzyme dispersion and/or proper enzyme conformation (favored by interacti on with PEG or the hydrophobic Sol-Gel-AK matrix) are essential for the exp ression of high lipase activity in organic media. (C) 1999 John Wiley & Son s, Inc.