Substrate specificity and effects of water-miscible solvents on the activity and stability of extracellular lipase from Streptomyces rimosus

Abstract

Substrate specificity, regioselectivity and transesterification activity of purified extracellular lipase from Streptomyces rimosus were investigated. The enzyme showed pronounced lipolytic activity toward a number of triacylglycerols and oils of vegetable and animal origin. It hydrolyzed most efficiently medium chain length fatty acid glycerol esters (C8–C12). There was preference for the esters of C16 and C18 unsaturated fatty acids over C16 and C18 saturated fatty acid esters, as well as for triacylglycerol substrate with cis double bond (triolein) versus trans double bond (trielaidin). Streptomyces rimosus lipase hydrolyzed primary and secondary ester bonds in triacylglycerols (triolein and 2,3-dimercapto-1-propanol tributyrate). The lipase catalyzed the hydrolysis of poly(oxyethylene) sorbitan monoesters (Tween 20–80) with rate comparable for that determined with triacylglycerols and oils. Several water-miscible solvents enhanced the lipase activity. 1,4-Dioxane activated the enzyme in a broad concentration range, up to 4-fold. Lipase was stable in solvent mixtures containing 50% (v/v) ethanol, 1,4-dioxane, acetonitrile or acetone. Tetrahydrofuran and N,N-dimethylformamide (both 50%) inactivated the enzyme with t 1/2 of 5 min and t 1/2 of 2 h, respectively. Transesterification of racemic 1-phenyl ethanol with vinyl acetate, catalyzed by extracellular lipase from Streptomyces rimosus in n-hexane, proceeded with partial R-enantioselectivity.