Submitted to: Journal of Industrial Microbiology and Biotechnology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/19/2004
Publication Date: 7/26/2004
Citation: Jackson, M.A., Payne, A.R., Odelson, D.A. 2004. Liquid culture production of blastospores of the bioinsecticidal fungus Paecilomyces fumosoroseus using portable fermentation equipment. Journal of Industrial Microbiology and Biotechnology. 31:149-154. Interpretive Summary: Limited success in commercializing microbial biocontrol agents is due to a lack of economical production methods, poor product shelf-life and inconsistent pest control under field conditions. It has been suggested that "on-site" or "cottage-industry" production of biocontrol agents may be one approach to overcoming these constraints. Fungi typically grow much slower than bacteria and therefore are susceptible to being overrun by bacterial contaminants. In this study, we evaluated techniques for consistently producing viable spores of the insect biocontrol fungus Paecilomyces fumosoroseus using a commercially available, portable fermentation system. Nutritional and environmental conditions were discovered that would support the rapid production of spores of P. fumosoroseus and at the same time deter the establishment and growth of bacterial contaminants. The use of a low pH, nutritionally rich medium provided a growth environment harmful to bacterial growth yet conducive to rapid fungal spore production. High concentrations of spores of P. fumosoroseus were produced in 40-hour fermentations with very low levels of bacterial contamination. These studies demonstrated that the use of disinfected, portable fermentation equipment has potential for the on-site production of high concentrations of spores of the bioinsecticidal fungus P. fumosoroseus.
Technical Abstract: The production of fungal spores by fermentation is technically constrained. Very little information is available on the production requirements such as medium concentration, inoculum stabilization, required fermentation times and maintenance of axenic growth. In this study, we developed a two-part, liquid concentrate of the production medium that remains stable and soluble at room temperature. We also examined inoculum stability and showed that freeze- or air-dried blastospore preparations were stable for 7 days after rehydration when stored at 4C. The use of a low pH (pH 4), relatively rich complex medium provided a growth environment deleterious to bacterial growth yet conducive to rapid sporulation by P. fumosoroseus. High concentrations of blastospores (7.9 x 10(8)/mL) of P. fumosoroseus were produced in 40-hour fermentations with very low levels of bacterial contamination when the fermentor was charged with a blastospore production medium with a starting pH of 4 and inoculated with blastospores concentrations greater than 1 x 10(6) spores/mL. These studies demonstrated that the use of disinfected, portable fermentation equipment has potential for the on-site production of high concentrations of blastospores of the bioinsecticidal fungus P. fumosoroseus.