Application Of Lignin-based Amphiphilic Polymer On Enhancing Enzymatic Hydrolysis Of Lignocellulose And Its Mechanism Research

Lignocellulose, containing cellulose, hemicellulose and lignin, is renewable andabundant. Hemicellulose and cellulose in the pretreated substrates can be digested into sugarssuch as glucose and xylose which can be used to produce chemicals and ferment into ethanoland butanol. However, nonproductive cellulase adsorption on lignin in the substrate throughstrong affinity was inevitable, which reduced the enzymatic hydrolysis efficiency of celluloseand increased the cost. Amphiphilic polymers were used to improve substrate enzymaticdigestibility (SED) in this study. The effects of molecular weight, founction group andstructure of kinds of amphiphilic polymers on the improvement of SED of lignocellulose werestudied. The relevant mechanism was proposed from the point of blocking nonproductiveadsorption of cellulase on lignin. Then the nonionic copolymer composed by lignin andpolyethylene glycol was proved to have better improvement on the SED of lignocellulose.At first, four fractions of lignosulfonate (SXP) with different molecular weight got byultrafiltration classification were used in the enzymatic hydrolysis process of filter paper andlignocellulose. It was found that SXP with higher molecular weight（SXP2,10000~50000Da）had better improvement. Besides, four SXP frictions could effectively block non-productiveadsorption of cellulase on lignin film measured by quartz crystal microgravimetry withdissipation monitoring（QCM-D）, and the blocking effect became stronger with the increasingmolecular weight. Based on the experimental results, the mechanism about the improvementof SED by adding SXP was proposed.And then, three linear amphiphilic polymers with different founction groups includingsulfanilic acid-phenol-formaldehyde condensate (ASP), formaldehyde naphthalene sulfonatecondensate (FDN) and sulfonated acetone-formaldehyde condensate (SAF), were used in theenzymatic hydrolysis process of cellulose and lignocellulose and the inhibition of thenon-productive adsorption of cellulase on the lignin surface. It was found that all the threeamphiphilic polymers could effectively block more non-productive adsorption of cellulase onlignin than SXP. However, they could not enhance the enzymatic hydrolysis of cellulose orlignocellulose.The possible reason behind was related to the decreasing adsorption ofcellulase on cellulose and enayme activity.Through the above study, nonionic amphiphilic polymer (AL-PEG1000) synthesized bylignin with three-dimensional net structure and linear polyethylene glycol was used toenhance the enzymatic hydrolysis of lignocellulose. It was found that AL-PEG1000hadstronger enhancement than ASP and PEG1000. Because AL-PEG1000not only improved the the cellulase activity to cellulose, but also blocked the non-productive cellulase adsorption onlignin surface.With the proportion of20~35%in lignocellulose biomass and being the by-product ofbiological refining, lignin was cheap in price and abundant in source.Using lignin tosynthesize amphiphilic polymer to improve the enzymatic hydrolysis of lignocellulose wasimportant and significant, which could improve utilization of lignocellulose biomass andpromote the development of cellulosic ethanol industry and the social sustainabledevelopment...