Over-expression and properties of a purified recombinant Bacillus licheniformis lipase: a comparative report on Bacillus lipases

The gene coding for an extracellular lipase of Bacillus licheniformis was cloned using PCR techniques. The sequence corresponding to the mature lipase was subcloned into the pET 20b(+) expression vector to construct a recombinant lipase protein containing 6 histidine residues at the C-terminal. High-level expression of the lipase by Escherichia coli cells harbouring the lipase gene-containing expression vector was observed upon induction with IPTG at 30°C. A one step purification of the recombinant lipase was achieved with Ni-NTA resin. The specific activity of the purified enzyme was 130 units/mg with p-nitrophenyl-palmitate as substrate. The enzyme showed maximum activity at pH 10–11.5 and was remarkably stable at alkaline pH values up to 12. The enzyme was active toward p-nitrophenyl esters of short to long chains fatty acids but with a marked preference for esters with C6 and C8 acyl groups. The amino acid sequence of the lipase shows striking similarities to lipases from Bacillus subtilis and Bacillus pumilus. Based on the amino acid identity and biochemical characteristics, we propose that Bacillus lipases be classified into two distinct subfamilies of their own.