Abstract:

In this study, a liquid medium for culturing poplar endophytic Chaetomium globosum ND35 was optimized with an orthogonal design of L₁₆(4⁵). Physical and chemical characteristics of antifungal substances from C. globosum ND35 were preliminarily analyzed by pH paper chromatography and Jack’s eight solvents system paper chromatography as well as UV-Vis spectrum. Bioactive fractions in crude extracts were separated by thin-layer chromatography (TLC) and high performance liquid chromatography (HPLC) and their inhibition to Valsa sordita was examined in agar plate. At the same time, dynamics of the antifungal substances in liquid culture were also tested. The results showed that an optimal medium was obtained with 1% dextrose, 1% sucrose, 0.5% beef extract, 0.02% ferrous sulfate, 0.01% vitamin B₁, pH 7 value. Both intracellular and extracellular substances of liquid cultured mycelia had antibiotic activity, with good heat stability. The antifungal substance were of weak polarity, and able to be easily dissolved in organic solvent, but hard in water relatively. C. globosum ND35 antibiotics had a maximum absorption peak at 221 nm, composed of four components which all showed antifungal activity to Valsa sordita. Analysis of growth dynamics showed that output, absorbency, pH and inhibition rate of the antibiotics were continuous changing in the liquid fermentation process.

Key words: endophytic fungus, Chaetomium globosum ND35, antifungal substance, medium optimization, Valsa sordida, growth dynamics