Effect of fermentation additives on the conidium surface-bond enzymatic activity and virulence of Beauveria bassiana.

A Colombian isolate (Bv062) of Beauveria bassiana, previously selected for its pathogenicity against Diatraea saccharalis, was used to evaluate the effect of fermentation additives on conidium surface-bond enzymatic activity and virulence. Genome analysis of this isolate revealed a diverse repertoire of virulence-related factors involved in host infection, including 13 lipases, 18 chitinases, 21 subtilisin-like proteases, and 19 trypsin-like proteases. Comparative genomics with other B. bassiana isolates also identified novel protein candidates not previously annotated in this species. This genomic profile revealed a repertoire of putative hydrolytic enzyme genes previously associated with insect cuticle degradation and host penetration, which guided the selection of the enzymatic groups evaluated in this study. Based on this rationale, three additives (soy protein, wheat bran, and chitosan), previously associated with the induction of N-acetylglucosaminidase, esterase, general protease, and subtilisin-like Pr1 activities, were evaluated. The fungus was mass-produced by semi-solid fermentation using a previously optimized oat-based medium supplemented with the additives. Conidia were harvested and evaluated for yield, germination, enzymatic activity, and virulence. Additives influenced conidiation but did not affect conidial germination. All treatments modulated the enzymatic and insecticidal traits of the produced conidia. Lipase and N-acetylglucosaminidase activities consistently increased in additive-treated conidia, whereas total protease and Pr1 activities did not differ significantly from the control. Insecticidal efficacy was significantly enhanced in conidia produced with soy protein and chitosan at 1 %, and with wheat bran at 0.1 %. Furthermore, the genomic characterization presented here, together with the phenotypic effects of fermentation additives, highlights the need for future transcriptomic studies to investigate whether culture conditions influence the expression of virulence- and fitness-related genes and to identify the regulatory pathways potentially involved.