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Cloning, Expression and Characterization of a Lipase from Bacillus Subtilis Strain I4 with Potential Application in Biodiesel Production

A lipase gene from sequencing genomic DNA of Bacillus subtilis strain I4 (I4-2) was cloned and expressed in E. coli. The deduced amino acid (aa) sequences for the lipase I4-2 was composed of 31-amino-acid signal sequence and a 181-amino-acid mature part, corresponding to a molecular mass (Mr) of 19.33 kDa. Based on the Mr and the protein sequence, the lipase I4-2 was belong to the lipase family1.4. The activity of the purified recombinant lipase I4-2 was apparently optimal at 45°C and pH 7.0. The enzyme was stable at 25°C, and more than 56% of the initial activity after incubation in buffer pH 7.0 for 120 min at 37°C. In addition, lipase I4-2 was mixed with methanol (50, v/v) for 30 min and residual activity was 45%. lipase I4-2 can catalyzed biodiesel production from soybean oil at methanol : soybean (molar ratio of methanol to oil = 3:1), 10% n-hexane, 3.5% water. The results of GC–MS analysis demonstrated that a 3-stepwise process resulted in a 98% conversion yield after 8 h of reaction at 37°C.