Lipase from Aeromonas caviae AU04: Isolation, purification and protein aggregation

An extracellular thermostable lipase producing bacteria was isolated and identified as Aeromonas caviae AU04. The optimum temperature and pH for lipase secretion was found to be 30 °C and pH 7.0, respectively. The enzyme was purified 3.3-fold with 28.7% recovery by ammonium sulphate precipitation and hydrophobic interaction chromatography. The enzyme showed a strong tendency to aggregate in solution. The purified enzyme did not penetrate into stacking gel and also eluted in the void volume of the column in gel permeation chromatography. The aggregated lipase was partially solubilised by the addition of non-ionic detergent Triton X-100. The optimum temperature and pH for activity of the enzyme was found to be 60 °C and pH 7.0, respectively. The purified lipase was found to be stable in the presence of hydrophobic organic solvents with log P value more than 2.0. Incubation of enzyme with 1-hexane and toluene increased the lipase activity two fold. The thermostability and tolerance to organic solvents makes it an attractive and promising biocatalyst for enzyme mediated synthesis.