Extraction and recovery of lignin derived phenolic inhibitors to enhance enzymatic glucose production

Abstract

Laccase mediated delignification of lignocellulosic biomass generates phenolic compounds which normally inhibits the enzymatic hydrolysis of cellulose and suppresses the reaction rate drastically. To overcome the inhibitory effects and maximize productivity, pretreatment is requisite. This work proposes the extraction of phenolic compounds at the pretreatment stage to increase glucose yield in the enzymatic hydrolysis of lignocellulosic biomass-Bambusa Bamboo. In addition, recovery of lignin derived phenolic compounds is also targeted by adsorption followed by desorption. For adsorbent preparation, chemically modified cenospheres from waste coal fly ash and chitosan were cross-linked to form syntactic foam adsorbent. Adsorption and desorption studies were carried out on synthesized adsorbent using gallic acid as a phenolic equivalent. In our investigation, 40.31% delignification was achieved when the feed of the average particle size of 60 μm was operated in a batch reactor. The extraction of phenolic compounds significantly increases glucose yield and 1.4 times higher glucose yield was obtained for delignified plus extracted biomass than that of only delignified biomass. Syntactic foam adsorbent has shown excellent adsorption capacity for phenolic compounds with a rapid rate of adsorption in initial hours and exhibited maximum adsorption capacity as 1.07 mmol of gallic acid per gram of adsorbent. Thus, extraction of lignin derived phenolic inhibitors prior to enzymatic hydrolysis, and recovery of these phenolic compounds by adsorption can make the process more viable for the sustainable production of biofuels in the biorefinery.