Characterization of a novel alkaline esterase (E22) from a marine bacterium Altererythrobacter epoxidivorans CGMCC 1.7731T

Abstract:

[Objective] To clone and express an esterase gene e22 from marine bacterium Altererythrobacter epoxidivorans CGMCC 1.7731T and characterize the enzyme. [Methods] Screening of the genome of strain CGMCC 1.7731T obtained an esterase-encoding gene, e22. The gene was amplified by PCR and cloned into the expression vector pET-28a. Then, the recombinant plasmid was transformed into Escherichia coli BL21(DE3) for heterogenetic expression. After purified by affinity chromatography, the enzyme was characterized. [Results] The amino acids sequence analysis indicated E22 belongs to Family II of lipolytic enzyme. The enzymatic property assay revealed that E22 had maximum activity using p-nitrophenyl butyrate as substrate. It was an alkaline esterase that had highest activity at pH 10.5. The optimal reaction temperature was 55 °C. After incubated at 60 °C for 2 h, E22 still remained over 50% activity, which showed its moderate thermal stability. The activity of E22 was not significantly affected by the presence of 1% methanol, 1% Triton X-100 or 0.1% SDS. On the contrary, the addition of 10 mmol/L Ba2+ and Ca2+ would apparently inhibit the catalytic capacity of E22. [Conclusion] E22 is a novel marine esterase with excellent properties such as thermostability, and alkaline, organic solvent and detergent tolerance. These characteristics suggest its application prospects in the industrial production.

Key words:Marine bacterium, Alkaline esterase, Characterization, Cloning and expression