Optimizing Acid Hydrolysis of Jerusalem Artichoke-Derived Inulin for Fermentative Butanol Production

In this study, a central composite design and response surface methodology were used to study the effect of various hydrolysis variables (temperature, pH, and time) on the acid hydrolysis of Jerusalem artichoke-derived inulin using three different mineral acids (HCl, H2SO4, and H3PO4). Numerical optimization was used to maximize the sugar yield of Jerusalem artichoke powder within the experimental range for each of the mentioned acid. The influence of each acid on the formation of hydroxymethylfurfural (HMF; a known by-product and inhibitor for fermentative organisms) was also investigated. H2SO4 was found to have a better potential for sugar yields compared to two other acids (HCl and H3PO4) since it can hydrolyze the highest amount of inulin (98.5 %) under optimal conditions (temperature of 97 °C, pH of 2.0, and time period of 35 min) without producing inhibiting HMF concentrations. The sulfuric hydrolysate of Jerusalem artichoke was fermented via solventogenic clostridia to acetone-butanol-ethanol (ABE). An ABE yield of 0.31 g g−1 and an overall fermentation productivity of 0.25 g l−1 h−1 were obtained, indicating the suitability of this feedstock for fermentative ABE production.