Gibberellic acid (GA3) is the most important gibberellin that affects various plant developmental processes. As such, it has an international market value of $106 million dollars. However, it is costly in the market because of high downstream processing cost that is linked to its current mode of production via submerged fermentation. Solid-state fermentation, in contrast, minimizes this limitation of cost when optimal process parameters are used. Hence, this study utilized orange waste as a cheap substrate in the bio-production of gibberellic acid through the optimization of three process parameters (incubation temperature, pH and substrate concentration). The study also investigated the interactive effects of these parameters on the yield of gibberellic acid. Using Design Expert® software, a 19-run experiment, varied at five levels, was generated. Accordingly, each fermentation reaction that had been supplemented with 0.03% FeSO4.7H2O and 0.01% (NH4)2SO4 was inoculated with a constant fungal inoculum. The highest yield of gibberellic acid was with a combination of 19.5 g of substrate set at 30 °C incubation temperature with a pH of 5.5. The interaction between the three factors was a linear relationship. The bio-production of gibberellic acid using orange waste as an alternative substrate suggests the possibility of a further reduction in cost of production of high-end value metabolites when proper optimization is carried out.
Ja’afar Nuhu Ja’afar and Muhyideen Muazu
