Effect of ultraviolet C irradiation on growth and antibacterial activity of Fomitopsis betulina (Bull.) B.K. Cui, M.L. Han and Y.C. Dai

The using of ultraviolet C (UVC) irradiation is nowadays one of the effective ways of obtaining a new mutant mushroom species with higher yield and synthesis of biologically active metabolites. Of particular interest is the acquisition by mutant mushrooms the new therapeutic properties. Effect of UVC irradiation on the mycelium growth and antibacterial activity of Fomitopsis betulina culture liquid has been studied.  The cultures of F. betulina grown in glucose-peptone-yeast agar culture medium (GPY) three and ten days were exposed to UVC radiation (λ=254 nm)  with durations from five to sixty minutes at distance of 0.3 m and twelve-days-old cultures were subcultured on GPY for further study of biomass production and inhibition of bacteria growth. F. betulina mycelium growth increased after 15 min of UVC exposure but not significantly changed by among all treatments, as well as color and odor. This duration of UVC radiation exposure with dose of radiation 0.85 kJ/sm2 caused a stimulating effect of biomass production irrespective of the growth phase of irradiated culture (at the beginning of growth or at actively growing period). Antibacterial activity of F. betulina culture liquid against Bacillus subtilis decreased with increase in the time of exposure.  The highest action against Staphylococcus aureus recorded after 5 min of UVC exposure (0.28 kJ/sm2 radiation dose), and then also decreased. Antibacterial ability of F. betulina culture liquid against Escherichia coli increased significantly compared to the control and the highest action was found after UVC irradiation for 15 min (0.85 kJ/sm2 radiation dose). The obtained knowledge can be applied to obtain new mushroom strains with better therapeutic properties.