Cloning, Expression, and Characterization of a Cold-Active and Organic Solvent-Tolerant Lipase from Aeromicrobium sp SCSIO 25071

The gene encoding lipase (Lip98) from Aeromicrobium sp. SCSIO 25071 was cloned and functionally expressed in Escherichia coli. Lip98 amino acid sequence shares the highest (49%) identity to Rhodococcus jostii RHA1 lipase and contains a novel motif (GHSEG), which is different from other clusters in the lipase superfamily. The recombinant lipase was purified to homogeneity with Ni-NTA affinity chromatography. Lip98 showed an apparent molecular mass of 30 kDa on SDS gel. The optimal temperature and pH value for enzymatic activity were recorded at 30Q degrees C and 7.5, respectively. Lip98 exhibited high activity at low temperatures with 35% maximum activity at 0 degrees C and good stability at temperatures below 35 degrees C. Its calculated activation energy was 4.12 kcal/mol at the low temperature range of 15-30 degrees C. Its activity was slightly affected by some metal ions such as K+, Ca2+, and Na+. The activity of Lip98 was increased by various organic solvents such as DMSO, ethanol, acetone, and hexane with the concentration of 30% (v/v) and retained more than 30% residual activity in neat organic solvent. The unique characteristics of Lip98 imply that it is a promising candidate for industrial application as a nonaqueous biocatalyst and food additive.