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 hydro lysis 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 interac tions of temperature with the other variables. Solvent pro duction 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 9 2) showed that enzymatic hydrolysis (with sacchari fication 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.