Fermentation of Trichoderma for biological control using local inputs in Costa Rica

Introduction. Supply chain issues have driven up raw material costs and reduced the availability of materials for producing biological control agents. These delays in application could result in increased disease pressure and reduced farm yields. Objective. To determine the effect of different amounts of starch and the use of local ingredients for small and commercial-scale fermentation processes for Trichoderma harzianum. Materials and methods. All trials took place in San José, Costa Rica, between 2016 and 2018. Flask trials were executed to investigate the potential reduction or elimination of starch in commercial fermentation media. Additionally, fermentation vessel trials were conducted to assess the effectiveness of an alternative local medium, encompassing three treatments: 1) Commercial medium as a control, 2) 10% molasses medium, and 3) 10% molasses mediaum with 0.5% yeast extract. Viable spore counts were performed to determine colony forming units (CFU/mL). Results. Reducing starch to 10% of the original medium had no impact on CFU/mL. However, the absence of starch led to uneven growth during fermentation, resulting in solid mycelium accumulations. Molasses medium yielded roughly half the CFU/mL compared to the commercial medium, but it still exceeded the 107 CFU/mL threshold commonly used in studies for biological plant pathogen control. Results from a commercial-scale fermenter mirrored those from pilot-scale fermentation. Conclusion. While reducing starch content in the commercial medium didn't affect growth, the absence of starch caused solid mycelium accumulations, potentially posing issues in commercial production. Employing locally sourced molasses medium on a commercial scale appears feasible while maintaining a viable spore count meeting the minimum field-use specifications. Overall, these findings support the use of these media for Trichoderma production in biological control applications.