Evaluation of tomato based agro-industrial byproducts as substrates for Trichoderma harzianum cultivation and bioinoculant potential

Antonia Esposito¹Valeria Scala²Nikolay Vassilev³Maria Aragona²Loredana Canfora⁴Alessandro Polito²Riccardo Fiorani²Stefano Mocali^1*

• ¹Research Centre for Agriculture and Environment (CREA-AA), Council for Agricultural Research and Economics, Florence, Italy
• ²Research Centre for Plant Protection and Certification (CREA-DC), Council for Agricultural Research and Economics, Rome, Italy
• ³Department of Chemical Engineering, Universidad de Granada Facultad de Ciencias, Granada, Spain
• ⁴Research Centre for Agriculture and Environment (CREA-AA), Council for Agricultural Research and Economics, Rome, Italy

Trichoderma harzianum is a well-known biocontrol agent with growing interest as a multifunctional bioinoculant due to its diverse metabolic capabilities. Despite its promising potential, the transition from laboratory-scale cultivation to industrial-scale production still presents challenges, particularly in optimizing biomass and spore yield at low cost. This study focused on testing a new medium for spore/mycelium production of T. harzianum integrating traditional growth media with gazpacho, a tomato-based by-product of Andalusian food as cheap substrate. We also assessed its multifunctional activity, including the tolerance to salt stress, solubilization of rock phosphate and the antagonistic activity against three major tomato pathogens (Botrytis cinerea, Fusarium oxysporum, and Pyrenochaeta lycopersici) through dual culture assays. The results showed that media supplemented with 3% and 6% (v/v) gazpacho significantly increased T. harzianum biomass and sporulation in solid and submerged state fermentations, while 10% reduced spore formation in liquid submerged fermentation, probably due to pH-related stress. Interestingly, biomass and sporulation were further improved in media containing 3–6% (v/v) gazpacho combined with 100 mM NaCl, highlighting the strain resilience under saline conditions. Trichoderma harzianum was able to grow and sporulate in solid media with up to 100 mM NaCl, demonstrating strong salt tolerance. Moreover, the strain showed phosphate solubilization activity on gazpacho-containing media in submerged fermentation, and effectively inhibited over 70% of pathogenic mycelial growth, with B. cinerea showing the highest inhibition (78.40%). Overall, these findings highlight T. harzianum strain's multifunctional potentials in different fermentation conditions using cheap agro-industrial residues as additives to growth media, thus representing a promising approach toward cost-effective bioinoculant production and a support to circular economy in microbial technology. Furthermore, both salt tolerance and phosphate solubilization further encourage T. harzianum as a robust candidate for bioformulations in challenging agro-environment.