Ammonia-Derived Acidic Compound Pretreatment: Fractionation of Lignocellulosic Biomass for Boosting Enzymatic Hydrolysis to Efficiently Produce Bioethanol by Yeast.

Development of pretreatment to reduce biomass recalcitrance is essential to produce fermentable sugars, which is used as carbon sources for microorganisms to synthesize biofuels. Lignin in lignocellulose is generally removed by alkaline pretreatment (e.g., NH4OH, ethanediamine), while the severe environment causes equipment corrosion and forms toxic inhibitors. Using ─NH2/NH4 +-derived acidic compounds (ADACs) might achieve ideal lignin removal efficiency and fermentability. Herein, five ADACs including ammonium chloride (AC), ammonium sulfate (AS), ammonium acetate (AA), butanamide (BuA), and sulfamic acid (SuA) were used for corn stover (CS) pretreatment. The xylan removals were 16.69%-39.49% when pretreating CS by ADAC at 150 °C, which resulted in lower glucose yields of <65%. Elevating the temperature to 180 °C improved lignin and xylan removals to 64.93% and 92.57% under SuA pretreatment. In this case, glucose yield reached 88%, which was 4.27-fold to that of untreated CS. The fermentability of ADAC-pretreated CS hydrolysates was then used for bioethanol production. The obtained ethanol yields reached 88.03% (AC), 72.52% (AS), and 83.35% (SuA). Meanwhile, approximately 25 g/L ethanol was produced by Saccharomyces cerevisiae from SuA-pretreated hydrolysates containing ~60 g/L glucose. Overall, it is the first report to evaluate the typical ADACs for lignocellulose fractionation, which exhibits considerable potential for bioethanol production.