In vivo functional expression of an extracellular Ca2+-independent Bacillus pumilus lipase in Bacillus subtilis WB800N

A strain showing distinct lipase activity was isolated from food factory sewage and identified as Bacillus pumilus (named Bacillus pumilus Nws-bp1) by 16S rRNA sequence analysis. The wild-strain Nws-bp1 showed maximum lipase activity of 2.91 U/ml. Meanwhile, the lipase gene (named lip BP) was obtained from strain Nws-bp1 with the assistance of homology analysis. The gene has an open reading frame of 648 bp encoding 215-amino-acid lipase (LipBP) with 34-amino-acid putative signal peptide, and shows highest identity with the lipase from Bacillus pumilus MTCC B6033 (CP007436.1). Also, the lip BP gene without signal peptide sequence was expressed in Bacillus subtilis WB800N using amyQ (encoding an amylase) signal peptide. The lipase total enzyme activity was 44.15 U/ml which was about 15 times higher than that of the parent strain, and in supernatant was 32.29 U/ml (about 73 % of the total activity). The pH and temperature optima were pH 10.0 and 40 °C, respectively. Moreover, the recombinant LipBP showed apparent stability under alkaline conditions especially at pH 9.0–11.0. Also, LipBP showed stability under normal temperature and retained 85 % of the residual activity after incubation at 40 °C for 8 h without substrate. The specific activity of purified LipBP was 2650 ± 117 U/mg (pNPP substrate). The K m and V max values of purified LipBP were 1.36 mM and 208.25 μmol/(ml·min), respectively. This is the first report of Bacillus pumilus lipase expressed in Bacillus subtilis using amyQ signal peptide, and the pH stability and organic solvent tolerance recombinant lipase provide its potential value in industrial applications.