Comparative of alkaline hydrogen peroxide pretreatment using NaOH and Ca(OH)2 and their effects on enzymatic hydrolysis and fermentation steps

In this work, alkaline hydrogen peroxide pretreatment (AHP), at low concentrations of chemical reagents and mild temperature, on sugarcane bagasse was evaluated for production of bioethanol via enzymatic hydrolysis using Cellic (R) CTec3 from Novozymes (R) and fermentation using Saccharomyces cerevisiae wild-type strain AR5. Sodium hydroxide NaOH and calcium hydroxide Ca(OH)(2) as alkaline reagents were used and combined with hydrogen peroxide (H2O2) as oxidant reagent. AHP pretreatment with NaOH increased cellulose content up to 78% and holocellulose content up to 90%, resulting in 35% more of cellulose and holocellulose contents compared with AHP pretreatment with Ca(OH)(2). Results of enzymatic hydrolysis of substrate coming from pretreatment with NaOH achieved high holocellulose-to-reducing sugar yield up to 81% in 7 h of reaction time, 30% higher production than using Ca(OH)(2). Besides, for the fermentation process, the necessity and effectiveness of removing remaining solids after enzymatic hydrolysis are not reported in the open literature. Finally, the maximum theoretical yield (95%) was obtained using bothalkaline reagents for the fermentation experiments, producing a maximum ethanol concentration of 39 g/L when AHP pretreatment with NaOH was used, as well the ethanol production balances of 28.9% and 19.1%, were achieved according to the pretreatments with NaOH and Ca(OH)(2), respectively.

Automated summary

This study found that alkaline hydrogen peroxide pretreatment using NaOH can significantly increase cellulose and holocellulose content of the substrate, as well as the yield of bioethanol production through enzymatic hydrolysis and fermentation. In terms of alkaline reagent selection, NaOH is more effective than Ca(OH)2.