ARS | Publication request: Production of Microsclerotia of Metarhizium anisopliae Using Deep-Tank Liquid Fermentation

Submitted to: Society for Invertebrate Pathology Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: August 18, 2009
Publication Date: October 18, 2009
Citation: Jackson, M.A., Jaronski, S. 2009. Production of Microsclerotia of Metarhizium anisopliae Using Deep-Tank Liquid Fermentation [abstract]. Society for Invertebrate Pathology Annual Meeting. Abstract No. 114.

Technical Abstract: The entomopathogenic fungus Metarhizium anisopliae is a pathogen of numerous soil-dwelling insects and has been registered in the United States and other countries as a bioinsecticide. Recent studies using various strains of M. anisopliae showed that small sclerotia (microsclerotia) were produced in high concentrations in liquid culture under the appropriate nutritional and cultural conditions. Granules containing microsclerotia of M. anisopliae were desiccation tolerant, germinated sporogenically when rehydrated, and when soil incorporated, infected and killed the sugar beet root maggot, Tetanops myopaeformis. In this study, we evaluated the potential for using deep-tank fermentation for the large-scale production of microsclerotia of M. anisopliae F52. Sixteen 100-L deep-tank fermentations of M. anisopliae were conducted using glucose and acid hydrolyzed casein as the carbon and nitrogen sources, respectively. Mean values for biomass and microsclerotia yields for cultures of M. anisopliae were 20.9 g/L and 6.4 x 10e7 microsclerotia/L, respectively. A diatomaceous earth (DE) filter aid was added to the fermentation broth containing microsclerotia of M. anisopliae; and the fungal biomass was separated from the culture supernatant using a rotary drum vacuum filter. Dewatered microsclerotia–DE preparations were granulated and air-dried to approximately 2.5% moisture. When rehydrated on water agar and incubated at 28ºC, virtually all microsclerotia-DE granules (97-100%) germinated hyphally. After 8 days incubation on water agar at 28ºC, mean conidia production by the microsclerotia–DE granules was 1.1 x 10e9 conidia/gram dried microsclerotial preparation. Following one-year storage under vacuum in polyethylene bags at 4ºC, the mean value for conidia production by air-dried microsclerotia–DE preparations was 5.8 x 10e8 conidia/gram. These results suggest that deep-tank fermentation is a promising method for the large-scale production of stable microsclerotia of M. anisopliae.