Composition and dynamics of volatile organic compounds during solid-state fermentation: a new source of antifungal compounds

Background Solid state fermentation (SSF) is a biotechnological process in which microorganisms grow in the absence or near-absence of flow-free water. Recently, this process has re-gained attention due to the possibility to use raw materials and by-products as SSF substrates to produce value-added products. In this work, the volatilome produced by Streptomyces sp. DEF603 during solid-state fermentation (fVOCs) on defatted wheat bran has been characterised to identify molecules active against fungal phytopathogens. Results Untargeted HS–SPME–GC–MS, combined with statistical analysis, highlighted a clear separation ( i ) between inoculated and non-inoculated samples and ( ii ) among inoculated samples collected at different time points. Variable Importance in Projection (VIP) statistics identified 21 potential volatile markers that significantly contributed to distinguishing different variables. Interestingly, the relative amount of 12 fVOCs increased during fermentation, including known antimicrobial compounds such as 2-pentanone, dimethyl trisulfide, and 2-methyl-1-butanol. Accordingly, the antifungal activity of fVOCs against Botrytis cinerea , Fusarium culmorum, and Alternaria alternata increased over time, reaching 98.5% inhibition of mycelium growth and complete inhibition of spore germination in Alternaria alternata . Conclusion The results support the use of defatted wheat bran, a common agri-food waste, as a substrate for producing VOCs to be applied as novel, environmentally friendly biofumigants. Graphical abstract Created in BioRender. Bulgari, D. (2026) https://BioRender.com/yk3z5s3