Streptomyces sp. IPV2742: solid-state fermentation on defatted wheat bran and application as candidate biocontrol agent

Fungal pathogens represent a major threat to global crop production. Generally, they are controlled by fungicides. However, fungicides can have negative effects on the biosphere, posing risks for environment and human health. The sustainability of the agricultural sector is strongly bound with development of new biological approaches as an alternative to chemicals. Streptomyces species play a key role in the biocontrol of phytopathogens thanks to the high number of secondary metabolites with antimicrobial activity produced. Moreover, growing Streptomyces spp. on unconventional substrates like agri-food waste can both re-valorise agricultural waste and, at the same time, reduce crop loss. In this study, the spore morphology of Streptomyces sp. IPV2742, isolated from Vitis vinifera, was characterized by scanning electron microscope (SEM). It was observed that IPV2742 strain produces rugose ornamented spores. Moreover, the growth in solid-state fermentation (SSF) strain was evaluated. Streptomyces sp. IPV2742 grew well on defatted wheat bran, reaching the maximum concentration of 108 CFU/g seven days after the inoculation. The crude extracts obtained from fermented substrates were tested against Sclerotinia sclerotiorum, Fusarium culmorum, Botrytis cinerea and Fusarium oxysporum f.sp. basilici. The crude extract showed stronger antimicrobial activity against F. culmorum (35%), while the activity against F. oxysporum f.sp. basilici was less significant (10%). These results suggest that IPV2742 can be considered a possible biocontrol agent against phytopathogens and as a source of new bioactive molecules.