An organic solvent-tolerant lipase from Streptomyces sp. CS133 for enzymatic transesterifkation of vegetable oils in organic media

摘要

The enzymatic route for biodiesel production has been noted to be cost ineffective due to the high cost of biocatalysts. Reusing the biocatalyst for successive transesterification cycles is a potential solution to address such cost inefficiency. However, when organic solvent like methanol is used as acyl-acceptor in the reaction, the biocatalyst (lipase) gets severely inactivated due to the inhibitory effect of undissolved methanol in the reaction medium. Thus, organic solvent-tolerant lipase is highly desirable for enzymatic transesterification. In response to such desirability, a lipase (LS133) possessing aforesaid characteristic was extracted from Streptomyces sp. CS133. Relative molecular mass of the purified LS133 was estimated to be 39.8 kDa by SDS-PAGE. Lipase LS133 was stable in pH range 5.0-9.0 and at temperature lower than 50℃ while its optimum lipolytic activity was achieved at pH 7.5 and 40 ℃ It showed the highest hydrolytic activity towards long chain p-nitrophenyl palmitate with K_m and V_(max) values of 0.152 mM and 270.2 mmol min~(-1) mg~(-1), respectively. It showed non-position specificity for triolein hydrolysis. The first 15 amino acid residues of its N-terminal sequence, AIPLRQTLNFQAXYQ, were noted to have partial similarity with some of the previously reported microbial lipases. Its catalytic involvement in biodiesel production process was confirmed by performing enzymatic transesterification of vegetable oils with methanol.