Butanol production by Clostridium beijerinckii BA101 using cassava flour as fermentation substrate: enzymatic versus chemical pretreatments

Abstract

Cassava flour (CF), a cost-effective source of starch, was employed as a substrate for successful acetone-butanol-ethanol (ABE) production by batch-fermentation with Clostridium beijerinckii. The effect of temperature, initial concentration of CF and chemical/enzymatic hydrolysis were studied in a 23 factorial design. Results revealed that temperature and initial concentration of substrate exert a significant effect on ABE production, as well as interactions of temperature with the other variables. Solvent production was maximized when working at 40°C, 60 g l−1 CF and enzymatic pretreatment. An average of 31.38 g l−1 ABE was produced after 96 h, with a productivity of 0.33 g l−1 h−1. A posterior randomized block design (3 × 2) showed that enzymatic hydrolysis (with saccharification periods of 6 h at 60°C) enhances both reducing sugar and solvent production if compared to chemical pretreatments. Average ABE production in this case was 27.28 g l−1, with a productivity of 0.28 g l−1 h−1. Results suggest that CF may be a suitable substrate for industrial ABE production.