Molecular aspects of lignocellulosic biomass degradation: dynamics of enzymes and plant cell wall nanoarchitecture

Author(s)

Rodrigo Leandro Silveira

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Química
• Defense date: 2014-12-05

Examining board members

Munir Salomão Skaf; Richard John Ward; Roberto Dias Lins Neto; Camila Alves de Rezende; Nelson Henrique Morgon

• Advisor: Munir Salomão Skaf

Abstract

Biofuel production from lignocellulosic biomass involves physico-chemical and enzymatic processes that challenge its economic viability. The lignocellulosic biomass is recalcitrant against degradation and is made up of cellulose, hemicellulose and lignin. This structure and the enzyme mechanisms are not fully understood. In this thesis, molecular dynamics simulations and the statistical mechanical theory 3D-RISM were employed to assess molecular aspects of the biomass degradation, including: (1) structural dynamics of cellulases; (2) molecular basis of the thermophilicity of laminarinases; (3) non-hydrolytic disruption of biomass by expansins; (4) primary cell wall nanoarchitecture; and (5) thermodynamic forces of the secondary cell wall. In the topic (1), we observed that cellulase substrate accessibility can be modulated through changes in its primary structure, with consequences to the enzymatic activity. Moreover, the product inhibition is related to conformational changes of residues located close to the substrate binding site. In addition, changes of the intrinsic dynamics allow cellulases change their function according to the hydrolysis step. In the topic (2), we show that the substrate binding site conformation of laminarinases is sensitive to temperature variations. In the topic (3), we observed that the expansin can translade over the cellulose surface and induce torsions in free glucan chains, suggesting the possibility of disruption of cellulose-cellulose and cellulose-xyloglucan hydrogen bonds as a ziper. In the topic (4), the results showed that the aggregation of cellulose nanofibrils takes place through their hydrophilic face and that hemicellulose plays roles in stabilizing such aggregation. In the topic (5), we observed that the cohesion forces within the secondary cell wall are of entropic origin and that the lignin chemical composition modulates the lignin-lignin and lignin-hemicellulose interactions (AU)

• FAPESP's process: 10/08680-2 - Molecular aspectos of lignocellulosic biomass degradation: dynamics of enzymes and plant cell wall nanoarchitecture
• Grantee: Rodrigo Leandro Silveira
• Support Opportunities: Scholarships in Brazil - Doctorate