Submerged fermentation of Colletotrichum truncatum for biological control of scentless chamomile
Colletotrichum truncatum is being developed for biocontrol of scentless chamomile (Matricaria perforata). For potential mass production, a study was conducted to determine the possibility of submerged culturing. Fungal cultures were grown in V8-juice broth or a basal-salts liquid supplemented with carbon (C) and nitrogen (N) sources (C:N ratio at 10:1) in 500-ml flasks at 16 °C, 22 °C, or 28 °C in darkness to determine the impact of temperature. Sporulation was highest in the basal-salts medium at 16 °C, yielding about 1 x 106 sp/ml after two weeks. Further improvements were explored by examining the effects of various C and N sources, C concentrations, and C:N ratios. After comparison of nine C sources and eight organic and inorganic N sources, glucose and casamino acids were considered to be effective supplements to the basal-salts medium. Increasing glucose concentration from 5 to 40 g/L enhanced spore yields, but decreased biocontrol efficacy when glucose was 20 g/L or higher. In comparison to non-treated controls, spores produced at 5 g/L glucose reduced fresh weight of scentless chamomile by approximately 75% as opposed to only 39% by spores produced at 40 g/L glucose. Media amended with 10 g/L glucose supported high levels of sporulation without compromising the efficacy of spores. No significant difference in sporulation or efficacy was observed among C:N ratios ranging from 5:1 to 40:1.
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