Methods for Preprocessing Reeds to Obtain Enzymatic Hydrolysates with a High Sugar Content

Abstract

Methods of the pretreatment of reeds (grinding, hydrothermal treatment, treatment with acid or alkali solutions, organosolv, deep eutectic solvents) and their effect on the subsequent enzymatic hydrolysis by cellulase and hemicellulase complexes have been studied. Substrates with the highest reactivity were obtained by exposing the reeds to a weakly alkaline deep eutectic solvent (DES) and an alkali solution. The depth of enzymatic hydrolysis of these pretreated substrates was 63 and 59%, and the degree of conversion of polysaccharides (cellulose and hemicellulose) into monosaccharides taking into account the yield of the substrate at the preprocessing stage was 60 and 34%, respectively. After pretreatment of the reeds with acid DES, water steam, water, or a water/organic solution of sulfuric acid, the depth of enzymatic hydrolysis was 45, 25, 20, and 11% and the degree of polysaccharide conversion was 26, 18, 13, and 10%, respectively. The industrial enzyme preparation Agrocell Plus with a predominant content of cellobiohydrolases and endoglucanases was most effective in hydrolyzing the dust fraction of the reed, as was the reed pretreated with a solution of sulfuric acid or DES (acidic or alkaline). The industrial enzyme preparation Agroxil Plus, containing endoxylanase and cellobiohydrolases, was more effective in hydrolyzing the reed after hydrothermal pretreatment or alkali solution. The results of the hydrolysis of the reed pretreated with acidic or weakly alkaline DES under the action of individual (homogeneous) cellulases indicate that in both cases the key enzyme was cellobiohydrolase 1.