Expression and characterization of a novel cold-adapted lipase from psychrotolerant bacteria Psychrobacter sp. S1B

@#Aim: This study aimed to isolate, express and characterize the lipase derived Psychrobacter sp. S1B in Escherichia coli expression system. Methodology and results: Exploration towards S1B lipase characteristic was conducted where shotgun cloning method was applied to obtain lipase encoded gene and E. coli expression system through pET28a was used to overexpress S1B lipase. Lipase activity was measured by using p-nitrophenol method. The S1B lipase gene is 1005 bp in length with molecular weight of 46 kDa, optimum pH was 10.0, showed hydrolytic activity preference toward p-nitrophenyl caprylate (C8) and p-nitrophenyl hexanoate (C6) substrates (C6 < C8). The best temperature for S1B lipase activity was at 30 °C while exhibited high activity at lower temperature (10-25 °C) with above 90% of maximum activity, therefore it is classified as cold adaptive lipase. In addition, S1B lipase showed stability against various metal ions, including Cu2+ and Zn2+ which commonly act as inhibitors of lipases derived from Psychrobacter species. Moreover, S1B lipase exhibited great tolerance against up to 50% (v/v) hexane and some non-ionic detergents such as 1% (v/v) DMSO and 1% (v/v) Triton X-100. Conclusion, significance and impact of study: The study proposes a novel cold-adapted lipase which has potential as a biocatalyst for synthesis caprylic acid ester

Analysis of the Structure-stability Relationship of Cold-adapted Lipase PsLip1 from Homology Modeling

Two initial models of cold-adapted lipase PsLip1 have been constructed, based on homology with the bacterial lipases Chromobacterium viscosum(CvLip) and Pseudomonas cepacia(PcLip), whose X-ray structures have been solved and refined to high resolution. The mature polypeptide chains of these lipases have 84% similarity. The models of Mod1 and Mod2 have been compared with the tertiary structures of CvLip and PcLip, respectively, and analyzed in terms of stabilizing interactions. Several structural aspects that are believed to contribute to protein stability have been compared: the number of conserved salt bridges, aromatic interactions, hydrogen bonds, helix capping, and disulfide bridges. The 3-dimensional structural model of PsLip1 has been constructed in order to elucidate the structural reasons for the decreased thermostability of the enzyme in comparison with its mesophilic counterparts.