Mechanism Study On Surface Intervention Of Polyethylene Glycol In The Enzymatic Hydrolysis Of Cellulose

Aiming at solving the various problems during the saccharification of cellulose,amphiphilic molecule polyethylene glycol (PEG) was added to enhance digestibility oflignocelluloses using composite enzymes. During this process, PEG was self-assemblyadsorbedon the surface of insoluble substrate and enzyme by non-covalent force. Using thisstrategy, a new technology of lignocelluloses saccharification was proposed on the basis of PEGsurface intervention in enzymatic hydrolysis, which is technologically reasonable andeconomically viable. Moreover, its mechanism behind the effect was also studied. The mainconclusions are as follows:(1) A set of PEG surface intervening methodsin cellulose hydrolysis process were established toenhance the efficiency of glycoside hydrolase on digesting insoluble substrate andfacilitating the recycle use of enzymes. PEG surface intervention in the enzymatichydrolysis of PH101leads to the increase of cellulose conversion from42.4%to66.4%. Fornatural lignocelluloses, cellulose conversions were raised to89.2%and57.4%for ASCSand BSP, respectively.(2) During the process of PEG surface intervention, the dynamic distribution of PEG, enzymesand cellulose and their interactions were investigated to clarify the mechanism of PEGsurface intervention in enzymatic hydrolysis. It was found that PEG intervention in thehydrolysis process could produce two new systems: PEG-substrate and PEG-enzymespontaneously with non-covalent force. It was the first time to be confirmed that PEGself-assembly occurs in two aspects: enzyme and the surface of substrate. The latter seemedto contribute more to the effect of intervention and promotion of hydrolysis.(3) For the natural lignocellulosic material, PEG could adsorbed to cellulose as well as lignin,and the latter was obviously more superiority. During the hydrolysis, degradation ofcellulose could accelerate PEG adsorption on lignin. Especially for ASCS, which has largersurface area, nearly half of the PEG was adsorbed on the residual after hydrolysis. PEG’spositive effect on the conversion of ASCS could be attributed to that PEG adsorption onlignin effectively reduced the unproductive adsorption of enzyme on lignin.(4) The influence of PEG surface intervention enzymatic hydrolysis of cellulose was positivelycorrelated with the adsorption between enzyme and substrate. PEG self-assembly couldreduce the adsorption of enzyme to lignin and cellulose. This desorption was deeplyinfluenced by the structure and properties of substrate, which were the key factor leading tothe successful PEG surface intervention by self-assembly.(5) The studies on properties characterization of PEG self-assembly cellulose indicated that theenhancement effect of PEG on cellulase activities and the relief of enzyme protein aggregation were also partly responsible for the promotion of hydrolysis. It was also foundfor the first time that PEG self-assembly promoted the intermolecular repulsion amongenzymes, improved enzyme aggregation under the condition of enzymatic hydrolysis, andled to the enhancement of solubility and stability of enzyme in the aqueous phase.