Assessment of the chemical pre-treatment methods for the delignification of sugarcane bagasse

For the extraction of sugars and their subsequent conversion into ethanol, removing lignin from sugarcane bagasse is a major challenge attributed to its recalcitrant nature. This study compares the efficacy of green deep eutectic solvents with conventional acid/alkali pre-treatments for the delignification of sugarcane bagasse. Among different deep eutectic solvent pre-treatments, the maximum removal of lignin i.e. 77.37% was reported when bagasse was treated with choline chloride: formic acid (1:2) for 6 h. The comparison between deep eutectic solvents and conventional acid/alkali pretreatments revealed that acid (H2SO4) pre-treatment showed no significant reduction in lignin content. However, the alkaline pre-treatment with 1 M NaOH for 60 min resulted in significant removal of lignin content (83.17%) from bagasse compared to deep eutectic solvent pre-treatment. Fourier transform infrared spectroscopy and scanning electron microscopic results of bagasse indicated significant structural alterations after the pre-treatment. The saccharification of alkali-pretreated bagasse with in-house cellulase resulted in a maximum reducing sugar concentration of 54.50 g/L with a hydrolytic efficiency of 67.01%. The batch fermentation of bagasse hydrolysate with Saccharomyces cerevisiae resulted in an ethanol concentration of 9.55 g/L with a fermentation efficiency of 53.81%. This study made a median attempt to identify an effective pre-treatment method to delignifying sugarcane bagasse, ultimately enhancing the enzymatic accessibility and increasing the efficiency of cellulose hydrolysis into fermentable sugars.