Properties of a neutral, thermally stable and surfactant-tolerant pullulanase from worker termite gut-dwelling Bacillus safensis as potential for industrial applications

Abstract

The gut of termite has been observed to host communities of bacteria which exhibited pullulan-degrading ability. Bacillus safensis displayed maximum pullulanase (a debranching enzyme) activity and it was therefore selected for production, purification and characterization of pullulanase which was the aim of the study. The crude enzyme obtained from the pullulanase production medium was subjected to ammonium sulphate precipitation, ion exchange and gel-filtration chromatography and the physicochemical properties of the purified was thereafter characterized. A purified pullulanase with the yield of 13% and 24-fold purification was obtained and its homogeneity was established by molecular weight of 42 kDa. The optimum pH 7 and 60 °C were obtained while the enzyme was stable between 40-60 °C and pH 4–5 and 7–8 respectively with significant amount of residual activities recorded. The purified pullulanase was stimulated in the presence of Ca2+, urea and SDS while Al3+, Fe2+, Co2+, Cu2+, Mg2+ and chelating agent, EDTA mildly inhibited the activity of the enzyme in a concentration-dependent manner. The Km and Vmax were found to be 0.324 μmol/ml/min and 6.85 mg/ml respectively. The exceptional physicochemical properties of B. safensis pullulanase could find application in several industrial processes.

Keywords

• Termites' gut
• Pullulanase
• Purification
• Biochemical properties
• Surfactants