Optimization of pretreatment process of cassava rhizome for bio-succinic fermentation by Actinobacillus succinogenes

Cassava rhizome is an attractive agricultural residue from cassava-processing industry. With its lignocellulosic structure, cassava rhizome can be converted to simple sugars such as glucose, which is a precursor for succinic acid production. In this study, ozonation and alkaline pretreatments were chosen to enhance liberation of fermentable sugars from cassava rhizomes. Lignin removal and cellulose content were used as the criteria for the pretreatment performance. The maximum lignin removal of 56.47% ww−1 was obtained from alkaline pretreatment under the condition using 2% NaOH at 120 °C and 30 min reaction time, while ozonation pretreatment for 60 min reaction time achieved 18.7% ww−1 lignin removal. The extended reaction time for ozonation did not increase the lignin degradation while the cellulose content slightly increased. Higher concentration of NaOH resulted in decreases on the net weight of cassava rhizome after the pretreatment process. Fermentation of the enzymatic hydrolysate of alkaline-pretreated cassava rhizome led to the maximum succinic acid concentration (11.25 gL−1) and glucose utilization (99.53% ww−1). This study provided an alternative option to convert cassava rhizomes to biochemical products in biorefineries.