Media and Fermentation Processes for the Rapid Production of High Concentrations of Stable Blastospores of the Bioinsecticidal Fungus

In shake flask andfermentor studies, various media components and culture inocula were tested to improve P. fumosoroseus spore production rates, yield and stability. To evaluate inoculum potential and inoculum scale-up for fermentor studies, conidia and liquid culture-produced spores of various strains ofP. fumosoroseus were compared as inoculum. Inoculation of liquid cultures with blastospores at concentrations of at least 1 x 10 spores mL -1 resulted in the rapid production of high concentrations of blastospores (,..., 1 X 10 spores mL -1, 48 h fermentation time) for all strains tested. The rapid germination rate ofblastospores (90% after 6 h incubation) compared to conidia (> 90% after 16 h incubation) and the use of higher inoculum rates reduced the fermentation time from 96 to 48 h for maximal spore yields. A comparison of various complex nitrogen sources showed that liquid media supplemented with acid hydrolyzed casein or yeast extract supported the production of high concentrations of blastospores that were significantly more desiccation-tolerant (79-82% survival after drying) when compared to blastospores produced in media supplemented with other nitrogen sources (12-50% survival after drying). For rapid spore production, requirements for trace metals and vitamin supplementation were dependent on the type of hydrolyzed casein used in the medium. Fermentor studies with two strains ofP. fumosoroseus showed that high concentrations (1.31.8 x 10 spores mL -1) of desiccation-tolerant blastospores could be produced in 48-h fermentations. These studies have demonstrated that the infective spores of various strains of the fungal bioinsecticide Paecilomyces fumosoroseus can be rapidly produced using deep-tank, liquid culture fermentation techniques.