Deepika Dahiya: Synergism with novel expansin-related proteins for cellulose processing

Abstract: 

The demand for environmentally sustainable materials has accelerated the use of renewable biomass, such as lignocellulose from plant fibers. This study focuses on innovative biotechnological methods to enhance the conversion of lignocellulosic biomass into valuable products, thereby promoting circular economy principles. Specifically, the research investigates the production and application of microbial expansin-related proteins (EXLX), particularly loosenin-like proteins, to improve enzymatic hydrolysis processes for biomass conversion. 

The study employs Pichia pastoris strains SMD1168H and KM71H to produce and scale up these proteins, and further assessing their impact on converting softwood kraft pulp to nanocellulose. Key objectives include evaluating these proteins' ability to synergize with cellulolytic enzymes, enhancing sugar release from softwood kraft pulps, and facilitating the production of cellulose nanocrystals (CNCs). Advanced techniques such as Biological Small Angle Neutron Scattering (Bio-SANS) were used to analyze the structural impact of the proteins on holocellulose. 

Results demonstrate that recombinant expansin-related proteins can significantly boost enzymatic hydrolysis efficiency. This enhancement is attributed to the proteins' ability to increase enzyme accessibility by modifying fiber morphology. The integration of these proteins in enzymatic cocktails showed a marked improvement in glucose and xylose yields from various cellulosic substrates. Furthermore, the study explores the enzymatic production of CNCs with enhanced stability and dispersibility, suitable for applications in conductive inks and other advanced materials. The findings underscore the potential of these proteins to reduce enzyme loadings, thereby lowering production costs and environmental impact. Future research directions include optimizing process parameters for large-scale applications and investigating synergistic effects with other enzyme systems. 

In conclusion, the incorporation of microbial expansin-related proteins in biomass processing holds significant promise for advancing sustainable production technologies. This research provides foundational insights into their mode of action and range of applications, paving the way for more efficient and eco-friendly biomass conversion methods.

Opponent: Professor Chunlin Xu, Åbo Akademi University, Finland

Supervisor: Professor Emma Master, Aalto University School of Chemical Engineering

Link to electronic thesis: LINK

Link to the remote defence: LINK