Optimization of Culture Conditions and Production of Bio-Fungicides from Trichoderma Species under Solid-State Fermentation Using Mathematical Modeling

Abstract

Agro-industrial wastes suitable for economical and high mass production of novel <i>Trichoderma</i> species under solid-state fermentation were identified by optimizing the culture conditions using a mathematical model and evaluating the viability of the formulated bio-product. Fourteen inexpensive, locally available, organic substrates and cereals were examined using a one-factor-at-a-time experiment. The fungus colonized nearly all substrates after 21 days of incubation, although the degree of colonization and conidiation varied among the substrates. A mixture of wheat bran and white rice (2:1 <i>w/w</i>) was found to support maximum growth of <i>T. asperellum</i> AU131 (3.2 × 10⁷ spores/g dry substrate) and <i>T. longibrachiatum</i> AU158 (3.5 × 10⁷ spores/g dry substrate). Using a fractional factorial design, the most significant growth factors influencing biomass production were found to be temperature, moisture content, inoculum concentration, and incubation period (<i>p ≤</i> 0.05). Analysis of variance of a Box-Behnken design showed that the regression model was highly significant (<i>p ≤</i> 0.05) with <i>F</i>-values of 10.38 (<i>P</i> = 0.0027, <i>T. asperellum</i> AU131) and 12.01 (<i>p</i> < 0.0017, <i>T. longibrachiatum</i> AU158). Under optimal conditions, maximum conidia yield of log₁₀ (8.6) (<i>T. asperellum</i> AU131) and log₁₀(9.18) (<i>T. longibrachiatum</i>) were obtained. For wettable powder <i>Trichoderma</i> species formulations, it was possible to maintain conidial viability at room temperature (25 °C) for eight months at concentrations above 10⁶ CFU/g.