Purification and Characterisation of an Acidic and Antifungal Chitinase Produced by a Streptomyces sp.

Abstract

An extremely acidic extracellular chitinase produced by a Streptomyces sp. was purified 12.44-fold by ammonium sulphate precipitation, ion-exchange chromatography and gel-permeation chromatography and further characterised. The molecular mass of the enzyme was estimated to be about 40 kDa by SDS–PAGE. The optimum pH and temperature of the purified enzyme were pH 2 and 6, and 50 °C respectively. The enzyme showed high stability in the acidic pH range of 2–6 and temperature stability of up to 50 °C. Additionally, the effect of some cations and other chemical compounds on the chitinase activity was studied. The activity of the enzyme was considerably retained under salinity conditions of up to 3%. The Km and Vmax values of the enzyme were determined to be 6.74 mg mL−1 and 61.3 U mg−1 respectively using colloidal chitin. This enzyme exhibited antifungal activity against phytopathogens revealing a potential biocontrol application in agriculture.