Collaborative Research: Harnessing synergism between biosurfactants and enzymes to enable efficient valorization of cellulose: towards a sustainable materials bioeconomy

University Of California-Davis, Davis CA

Investigators

Abstract

Cellulose is an abundant, renewable, and environmentally-sustainable resource that can be used to produce nanocellulose and value-added fuels and chemicals. As such, cellulose is an ideal feedstock for building a circular bioeconomy. To realize this potential, however, scalable and sustainable methods are needed to efficiently convert cellulose into nanocellulose. Current chemical and mechanical nanocellulose production processes are efficient but unsustainable, as they require high energy and water inputs, use toxic and corrosive solvents, and generate large amounts of greenhouse gas emissions and high-volume waste streams. Enzymatic processes enable sustainable nanocellulose production but suffer from low yields. Petroleum-derived surfactants are often added to enhance enzymatic bioconversion of cellulose, but selecting an ideal surfactant is not straightforward and incorporates non-renewable resources into the process. Saprophytic fungi decompose cellulosic biomass by secreting an enzyme-laden mixture that includes cellulases as well as naturally-occurring biosurfactants called hydrophobins. Hydrophobins have been implicated in enhancing enzymatic cellulose decomposition and, thus, offer a potential green alternative to petrochemical surfactants. However, the role hydrophobins play in enhancing cellulase activity on cellulose remains unclear. The goal of this project is to develop a scalable, environmentally-sustainable process for nanocellulose production by leveraging the surface activity of hydrophobins to improve cellulose deconstruction and modification. This research will result in new tools to improve enzymatic cellulose conversion, thereby enabling the cellulose-based circular bioeconomy. This project is motivated by the need for scalable and sustainable processes to convert cellulosic biomass into nanocellulose and value-added fuels and chemicals. The investigation focuses on improving the rate and extent of enzymatic hydrolysis of cellulose by incorporating hydrophobin biosurfactants, which appear to synergistically enhance cellulase performance. The project aims to elucidate the mechanisms of biosurfactant-enhanced enzyme-cellulose interfacial interactions such that the kinetics of cellulose hydrolysis and functionalized nanocellulose production can be controlled. The project has three specific aims. Aim 1 will examine how hydrophobins interact with cellulose to affect surface and material properties and determine how hydrophobins facilitate enzymatic interactions and turnover with cellulose. Aim 2 will build an understanding of how the evolutionary diversity of hydrophobins leads to differences in cellulose and enzyme adsorption. This knowledge will be used to engineer novel hydrophobins with improved interfacial interactions that increase nanocellulose production. Aim 3 will evaluate the integration of enzymes, hydrophobins, and cellulose to engineer ideal conditions for consolidated bioprocessing, considering both in vitro and cell-based systems using Trichoderma reesei as a host. Ultimately, this work will lead to new knowledge of how biological systems modify interfaces during cellulose deconstruction, which is key to developing enzymatic approaches for efficient nanocellulose production. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.