Purification and characterization of Streptomyces albidoflavus antifungal components

Chitinolytic strain Streptomyces albidoflavus was isolated from soil of the central region of Poland. Its identification was based on analysis of 16S rRNA gene sequence. The colloidal chitin was revealed as the finest substrate for the production of chitinases by S. albidoflavus. The enzyme catalyzed the hydrolysis of the disaccharide 4-methylumbelliferyl-β-D-N,N′,N″-triacetylchitotriose most efficiently and was, therefore, classified as an endochitinase. The chitinase of S. albidoflavus was purified by applying the two-step procedure: fractionation with ammonium sulphate and chitin affinity chromatography. The molecular weight of the purified enzyme determined by SDS-PAGE was approximately 50 kDa. The enzyme was characterised as thermostable during 180 min of preincubation at the temperature of 35°C and 40°C. The activity of the enzyme was strongly inhibited in the presence of Hg²⁺ and Mn²⁺ ions, SDS but stabilized by Ca²⁺ and Mg²⁺ ions. Both purified and crude chitinases from S. albidoflavus inhibited the development of fungal phytopathogens. Purified chitinase inhibited the growth of Alternaria alternata, Fusarium culmorum, Fusarium oxysporum and Botrytis cinerea. Additionally, the crude chitinase inhibited the growth of Fusarium solani.