Dark fermentative hydrogen production from cassava starch: A comprehensive evaluation of the effects of starch extrusion and enzymatic hydrolysis

Abstract

Hydrolysis could be rate-limiting for the dark fermentative H2 production from cassava starch (CS) due to its semicrystalline nature. Therefore, the effects of CS extrusion and enzymatic hydrolysis on improving dark fermentation (DF) were studied. Preliminary DF experiments were conducted to investigate the effects of inoculum (sludge) heat-pretreatment, which increased H2 production from untreated-CS by over 154%. Likewise, 15 g/L starch was considered best for H2 production. Extruded-CS presented a maximum H2 yield of 1.58 mol H2/mol glucose with a 76% reduction in the fermentation adaptive phase and 43% increase in maximum H2 productivity compared to untreated-CS. Meanwhile, extruded-CS hydrolysate presented a maximum H2 yield of 1.8 mol H2/mol glucose with a 63% reduction in the fermentation adaptive phase and 18% increase in H2 productivity. A comprehensive assessment of the H2 yield, process time, production rate, and process simplification revealed extruded-CS as the most promising feedstock under the evaluated conditions.