Effect of Formic Acid and Furfural on the Enzymatic Hydrolysis of Cellulose Powder and Dilute Acid-Pretreated Poplar Hydrolysates

Biomass pretreatment often leads to the formation of compounds that are inhibitory to enzymatic hydrolysis. To remove inhibitory compounds prior to enzymatic hydrolysis, pretreated biomass is washed with at least 3 volumes of water. However, this washing step would be difficult to manage in commercial operations because of the unsustainable water consumption. This study reports on the effects of formic acid and furfural on Accellerase 1500 with cellulose powder and dilute acid-pretreated poplar as substrates. Using cellulose powder as the substrate for enzymatic hydrolysis with the addition of 5 or 10 mg/mL formic acid, glucose recovery was reduced by 34% and 81%, respectively, in comparison to the control. The addition of furfural, at 2 or 5 mg/mL, to the enzymatic system reduced glucose recovery by 5% and 9%, respectively. When 5 mg/mL of formic acid was combined with 5 mg/mL of furfural, glucose recovery in the cellulose powder enzymatic system was reduced by 59%. Inhibition of sugar recovery was more pronounced when dilute acid-pretreated poplar was used as a substrate for enzymatic hydrolysis. At 24 h incubation, recovery reductions were 94%, 97%, and 93% in the presence of 5 or 10 mg/mL formic acid or the 5 mg/mL combination.