Biochemical characterization of a new thermostable lipase from Bacillus pumilus strain

Abstract

Objective: Research and characterization of new thermostable lipases from bacterial strains isolated from tannery waters in the old medina of Fez. Methods: Gene which encodes the 16S ribosomal RNA for a bacterial species was amplified via PCR and sequenced (Bacillus pumilus HF544325). The extracellular lipase from B. pumilus is purified by gel filtration (Sephacryl S-200) and cation exchange chromatography (Mono S sepharose cation exchanger). The N-terminal sequences of purified Bacillus pumilus lipase were determined by automated Edman’s degradation, using an Applied Biosystems 470 A protein sequencer equipped with PTH 120A analyser. The activity of lipase was examined within the pH range of 6.0-10.0 and the effect of pH on lipase stability was determined by incubating the lipase fraction in various buffer solutions ranging from 3.0 to 10.0 for 24 h at room temperature. Results: The results showed that Bacillus pumilus is a strain that produce non-inducible lipase. This enzyme has a molecular weight of 27 kDa and presents a maximal activity at pH 8 and 45°C. The 18 N-terminal amino acid residues showed a high degree of homology with other Bacillus lipase sequences. After treatment in 100°C for 5 min, the thermostable enzyme maintains 60% of its activity, which is greater than that those founded in previous works. The enzyme retained 100% of its activity after 30 min incubation at 70°C. Conclusion: This newly isolated lipase is thermostable and it has a significant difference which was observed when the biochemical properties of the Bacillus pumilus lipase were compared to others microbial lipases. The Bacillus pumilus lipase can be considered as a good candidature for industrial and biotechnological applications.