Production and properties of Beauveria bassiana conidia cultivated in submerged culture

Abstract

Under submerged growth in a defined medium (TKI broth), the entomopathogenic fungus, Beauveria bassiana, produced conidia; it produced only blastospores in complex media. Production of such "submerged" conidia depended on the nature of the carbon source and the presence of nitrate as a nitrogen source. Maximum yield of conidia (5 × 108 mL) was obtained when glucose was the carbon source and when the glucose to nitrate ratio was 5:1. Other carbon sources gave rise to both conidia and blastospores. Reducing the phosphate concentration resulted in the production of conidia which resembled "aerial" conidia in morphology and germination rates. The surfaces of "submerged" conidia were relatively smooth, but had a tendency to acquire the rough, warty, brittle surface characteristics of aerial conidia. Blastospores produced in defined media gave rise to conidia through microcycle conidiation without going through the vegetative phase of growth. In more complex media, blastospores did not undergo microcycle conidiation.