Growth and sporulation of Beauveria bassiana and Metarrhizium anisopliae on media containing various amino acids

Natural isolates of two entomogenous fungi, Beauveria bassiana and Metarrhizium anisopliae, were cultured in liquid culture media containing 24 amino acids and KNO₃ to determine their effect on growth and sporulation. In addition, the growth and medium pH changes for each isolate grown on an asparagine-containing medium were compared. Tryptophan and alanine were most effective for growth and sporulation of B. bassiana, although glutamine and KNO₃ also produced large numbers of regularly shaped spores. Tryptophan, glutamic acid, and histidine were all well utilized for both growth and sporulation of M. anisopliae. Nitrogen sources containing sulfur were poorly utilized for sporulation by M. anisopliae. In general, B. bassiana produces greater mycelial mass and much larger numbers of spores than M. anisopliae. Both fungi attained nearly the same growth maximum on asparagine medium though B. bassiana exhibited an initially more rapid growth rate. In both fungi this rapid growth phase was accompanied by a decline in medium pH followed by a rise in pH during the decline phase of growth.