Optimization of Succinic Acid Production by Mixed-Fungal Culture in Two-Step Fermentation Process using Response Surface Methodology

Optimization of Succinic Acid Production by Mixed-Fungal Culture in Two-Step Fermentation Process using Response Surface Methodology

Succinic acid, a platform chemical for various industrially important polymers, is conventionally produced via bacterial fermentation. This study used consolidated bioprocessing technology that employed lignocellulolytic and acidogenic fungal co-cultures to produce succinic acid from non-pretreated lignocellulosic biomass. The consolidated bioprocessing technology involves a two-step fermentation process: solid-state fermentation pre-culturing, followed by slurry fermentation. The fungal succinic acid fermentation was optimized by Box-Behnken Design (BBD) using response surface methodology (RSM). The conditions optimized were mass fraction of birch wood chip substrate, initial buffer pH, and solids loading. The optimum conditions for the fungal succinic acid fermentation were a mass fraction of birch wood chip of 0.37, an initial buffer pH of 4.80, and a solids loading of 16.36%. Factor effects and interactions were investigated, and a regression model was created to predict the maximum succinic acid production. The maximum succinic acid production predicted by the model was 22.06 g/L. This method of production is a hopeful and promising alternative to the conventional bacterial succinic acid production means due to minimal requirements for substrate pretreatment, which may potentially reduce the overall production costs of the platform chemical.