In vitro, optimization of growth and bioactivity of antibacterial metabolite produced by Rhizoctonia solani Kuhn

Abstract

The aim of this study was to optimize the cultural conditions for optimal fungal growth and metabolic bioactivity of Rhizoctonia solani isolated from potato tubers in Basra, Iraq. Different culture media, temperatures, pH and carbon and nitrogen sources were used to elucidate their effects on the fungal growth response and bioactivity of the fungal metabolite against two bacteria strains E. coli and S. aureus. R. solani grew better on Trypto Soyo broth medium at pH 6 and temperature 30 C. Starch (C- source) and NaNO3 (N-source) were most suitable for the fungus growth. Highest dry weight of fungal crude extract was obtained by using TS broth medium at pH 6 and incubation temperature 30 C. A disc diffusion technique was applied to examine the bioactivity of fungal crude extract against two strains of bacteria E. coli and S. aureus. The fungus exhibited higher antibacterial metabolic bioactivity (30 mm and 34 mm inhibition zones diam) against E. coli and S. aureus, respectively, by using TS broth medium amended with starch and (NH4)2SO3 at pH 6 and 25 C temperature.