(331e) Incorporating the Effects of Lignin in the Mechanistic Modeling of Enzymatic Hydrolysis of Lignocellulosic Biomass

Authors: 
Zhang, Y., Michigan Technological University
Zhou, W., Michigan Technological University

Lignocellulosic biomass, which are mainly comprised of intertwined cellulose, hemicelluloses and lignin, is the important resource for the production of biofuels and could contribute to reducing the current dependence on traditional fossil fuels. Unlike other two components, lignin is difficult to be hydrolyzed by enzymes and isbelieved to be an obstacle to the enzymatic hydrolysis process. Although there exist heavy pretreatment methods in laboratory to remove or redistribute the lignin component, the cost of such methods are overwhelmingly expensive. It is believed that in a cost-effective industrial-scale plant, only light-pretreatment will be carried out leavingsubstantial amount of lignin in the pretreated biomass. In this work, we try to incorporate two major lignin effects intoa well-establishedmechanistic model for enzymatic hydrolysis of cellulose and hemicelluloses simultaneously. First, lignin may keep adsorbing certain amount of free enzymes and thus hinder the enzymatic adsorption and complexion on cellulose and hemicelluloses. Since lignin has extremely resistance to enzymatic hydrolysis, the ability of lignin adsorbing enzymes maintains stable and the amount of enzymes adsorbed by lignin is only related to the total lignin content within the substrate. Second, lignin could block cellulose and hemicelluloses so that free enzymes cannot adsorb on and hydrolyze the lignin-blocked parts of substrate. The blocking effect of lignin is dynamicandwill finally disappear ifthe space between lignin and the hydrolysable parts of substrate becomes large enough for enzymes to enter.After considering the lignin effects, the model can be applied to study how different pretreatments change the lignin properties in lignocellulosic biomass, such as lignin content and lignin-carbohydrates-complex (LCC) linkages, as well asthe effects of such changes on enzyme accessibility, and help the commercialization of producing biofuels/biochemicals from lignocellulosic biomass by decreasing the costs of pretreatments and enzymes.