Adsorption of inhibitors using a CO2-activated sugarcane bagasse fly ash for improving enzymatic hydrolysis and alcoholic fermentation in biorefineries

Abstract

Many compounds released during the pretreatment of lignocellulosic biomass inhibit enzymes and yeasts, leading to a negative impact on the overall efficiency of biorefineries. Here, we propose the removal of phenolic compound and furaldehyde inhibitors by adsorption using CO2-activated sugarcane bagasse fly ash in order to improve both the enzymatic hydrolysis of cellulose and the alcoholic fermentation processes. The activation of fly ash resulted in a substantial enhancement of the specific surface area and pore volume of the adsorbent, improving the adsorption capacity for phenolics by 4.5-fold. The treatment of an inhibitor cocktail with 2% (w/v) activated fly ash resulted in removal of 97% of the phenolic compounds. The enzymatic hydrolysis of microcrystalline cellulose in the presence of the treated inhibitor cocktail resulted in glucose concentration values equivalent to that obtained for the control without the inhibitors. Moreover, the alcoholic fermentation performed using the fly ash-detoxified hydrolysate resulted in a remarkable 5.5-fold increase of the fermentation efficiency. These findings demonstrated that the CO2 activation of the fly ash resulted in an efficient adsorbent for the removal of inhibitors from both the enzymatic hydrolysis and the alcoholic fermentation processes, and could be used to improve the overall efficiency of future biorefineries.