Proactive management of fermentation and formulation interactions to improve biocontrol product performance

The key components of biocontrol product development; discovery, fermentation, and formulation, are interactively linked to each other and ultimately, to product performance. The fermentation environment can be managed to maximize the quantity and quality of biomass and bioproducts produced which, in turn, impacts success in formulating a biocontrol product. Multistrain mixtures of biocontrol agents can foster greater and more consistent reductions of plant disease. Microbial mixtures commonly are produced by blending separately produced fermentation products but co-cultivation of strains to equivalent biomass yields in a single fermentation would provide mixture advantages without incurring the cost disadvantages of multiple fermentation and processing protocols. As a first step in determining the feasibility and efficacy of co-cultured fermentor products active against Fusarium head blight (FHB) of wheat, three strains of Cryptococcus spp. that have demonstrated individual efficacy against the disease in one or more field tests were grown in bi-and tripartite fermentations. Growth rate inequalities between cocultured strains were overcome via establishing consistent initial culture optical desities (OD) using weighted ratios of each component strain. Growth curves of each component strain were determined by plating on a medium that contained melezitose as a sole carbon source and produced colonies of individually distinguishable sizes. After 48 h, co-cultures of Cryptococcus flavescens OH 182.9 and C. aureus OH 71.4 had near equivalent cell counts and represented the only treatment that reduced FHB disease severity (32%, P<0.05, Dunnett's t test) when averaged across four greenhouse studies