Submitted to: Journal of Industrial Microbiology and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/26/2005
Publication Date: 7/12/2005
Citation: Cliquet, S., Jackson, M.A. 2005. Impact of carbon and nitrogen nutrition on the quality, yield, and composition of blastospores of the bioinsecticidal fungus Paecilomyces fumosoroseus. Journal of Industrial Microbiology and Biotechnology. 32:204-210. Interpretive Summary: The fungus Paecilomyces fumosoroseus is being developed as an environmentally friendly, microbial biocontrol agent for numerous insect pests including the silverleaf whitefly and Formosan termite. This fungus grows yeast-like in deep-tank fermentors to produce spores that infect and kill whiteflies and termites. In this study, we evaluated the impact of nutrition during growth on the stability and infection potential of these fungal spores. Results from these studies showed that fungal spores of P. fumosoroseus grown on a diet rich in nitrogen germinated more rapidly and survived drying better than spores grown on diets rich in carbohydrate and/or low in nitrogen. These results demonstrated that the nutritional components of the fungal diet can be altered to improve the stability and potential infectivity of this insect biocontrol agent. Understanding how to improve the effectiveness of biological control agents through nutrition is critical to the commercial success and acceptance of these non-chemical insect control measures.
Technical Abstract: Cultures of Paecilomyces fumosoroseus grown in media containing higher levels of Casamino acids (13.2 g/L) produced significantly higher blastospore yields [13.2-18.5 x 10(7) blastospores/ml] and blastospore viability (79-82%) compared to cultures grown in media containing lower concentrations (1.32 g/L) of Casamino acids [0.4-2.3 x 10(7) blastospores/ml, 52-62% viability]. In addition, blastospores produced in media with higher Casamino acid content germinated more rapidly than those produced in media with lower concentrations of Casamino acids. Chemical analyses of blastospore composition showed that accelerated blastospore germination may be related to increased proteinaceous reserves rather than to glycogen, carbohydrate or lipid accumulation. Tolerance to freeze-drying by blastospores suspended in spent medium was enhanced by a higher Casamino acid concentration in the culture medium and by residual glucose in the spent medium. Storage of blastospores in liquid suspensions at 4 degrees C was detrimental to spore viability regardless of the culture conditions, whereas freeze-dried blastospores stored at 4 degrees C or 20 degrees C survived better when produced in media with higher levels of Casamino acids.