PURIFICATION AND CHARACTERIZATION OF A NOVEL SOLVENT-TOLERANT LIPASE FROM FUSARIUM-HETEROSPORUM

A microorganism producing a solvent-tolerant lipase was identified as Fusarium (F.) heterosporum. The lipase was purified from the culture filtrate to homogeneity as judged by disc-PAGE and SDS-PAGE. The purification included SP-Sephadex chromatography, gel filtration and isoelectric focusing, and the recovery yield was 38%. The lipase was a monomeric protein with a molecular weight of 31 kDa estimated by SDS-PAGE, and a pI of 7.0. The optimum pH at 40-degrees-C and optimum temperature at pH 5.6 were 5.5-6.0 and 45-50-degrees-C, respectively, when olive oil was used as the substrate. The lipase was stable over a pH range of 4-10 at 30-degrees-C for 4 h, and up to 40-degrees-C at pH 5.6 for 30 min. Furthermore, the enzyme was not inactivated even after incubation at 30-degrees-C in 50% solvent such as dimethylsulfoxide (DMSO), hexane, benzene and ether for 20 h. The activity did not decrease in a reaction with stirring in a mixture containing 50% DMSO or dimethylformamide. The lipase preferably reacted on middle-chain fatty acid triglycerides (6 less-than-or-equal-to C less-than-or-equal-to 12), and cleaved only 1,3-ester bonds of triolein. The enzyme had an N-terminal sequence of Ala-Val-Thr-Val-Thr-Thr-Gln-Asp-Leu-Ser, which has not previously been found in any other protein. We compared the properties of lipases from F. heterosporum and another strain F. oxysporum.