HYDROLYTIC ENZYMES SECRETED BY PAECILOMYCES-LILACINUS CULTURED ON SCLEROTIA OF ASPERGILLUS-FLAVUS

Sclerotia, the survival stage of Aspergillus flavus, are compact masse s Of mycelia capable of withstanding harsh climatic conditions. Six st rains of Paecilomyces lilacinus, originally isolated from sclerotia of A. flavus var. flavus or A. flavus var. parasiticus, were also able t o colonize the sclerotia from four different strains of A. flavus unde r laboratory conditions. P. lilacinus strains did not differ significa ntly in their colonization ability, but host susceptibility appeared t o be an important factor. P. lilacinus strains were cultured in vitro for 96 h on a basal salt medium containing either ground sclerotia of A. flavus or glucose plus asparagine. Activities of hydrolytic enzymes such as polysaccharidases, proteases, and chitinases were determined in the culture supernatants. Supernatants from fungal cultures grown i n the basal medium containing glucose plus aspargine medium showed ver y little or no enzyme activity, whereas fungi grown on ground scleroti a produced a variety of enzymes. Specifically, all strains produced ch itinases (endochitinase and N-acetyl glucosaminidase), beta-1,3-glucan ase, chymoelastase and chymotrypsin, suggesting that these enzymes may be required for colonization of sclerotia. Production of beta-1,4-glu canase, dextranase, cellulase, and trypsin was strain variable, sugges ting that these enzymes may not be required.