Liquid Fermentation Technology for Experimental Production of Biocontrol Fungi

Abstract

Large batches of biomass of Gliocladium virens, Trichoderma hamatum, T. harzianum. T. viride and Talaromyces flavus were produced in liquid fermentation in 20-l vessels simulating industrial conditions by utilizing commercially available, inexpensive ingredients (molasses and brewer''s yeast). The maximum biomass yield of Trichoderma harzianum, T. viride and G. virens was obtained after 15 days of agitated incubation and that of T. hamatum at 10 days. The biomass of Talaromyces flavus consisted of hyphae devoid of spores and that of Trichoderma and Gliocladium of mycelial fragments, conidia, and chlamydospores. At 6 and 10 days of incubation, about half of the spores were mature chlamydospores, and at 15 days 75% were mature chlamydospores. About 80-90% of the chlamydospores in the fresh biomass germinated on a medium selective for Trichoderma. Air-dried mats were ground and mixed (25 or 50%, wt/wt) with a commercially available pyrophyllite carrier. Conidia of Trichoderma in pyrophyllite survived better at -5, 5, 15, 25, and 30.degree. C than biomass propagules (BP) alone. The best temperatures to prolong shelf life of conidia and BP in pyrophyllite were -5 and 5.degree. C and the worst were 25 and 30.degree. C. Biomass propagules of Talaromyces flavus had 44% survival at room temperature after 5 mo. Biomass propagules of Gliocladium and Trichoderma, added to soil at 5 .times. 103 colony-forming units per gram, fragmented or proliferated greatly and attained numbers from 2 .times. 106 to 6 .times. 106. In no case did conidia of Trichoderma or Gliocladium, added without a food base, proliferate in soil.