Regional Competitive Grants

Project Title: Mechanisms of Surfactant Effects on Biomass Conversion

Principal Investigators and affiliations:

• PI: Maren Roman (Virginia Tech, Department of Wood Science and Forest Products)
• Co-PI: Alan Esker (Virginia Tech, Department of Chemistry)
• Co-PI: Wolfgang Glasser (Virginia Tech, Department of Wood Science and Forest Products)

Start Date: 9/1/2007      End Date: 8/31/2010

Project Abstract:

The overall goal of this research is to develop a comprehensive understanding of the mechanisms by which surfactants enhance the enzymatic hydrolysis of lignocellulosic biomass. The results of this research will provide valuable insight into the interactions between cellulolytic enzymes and lignocellulosic substrates and their influence on enzyme performance. The specific objectives of the proposed research are: (1) Quantify adsorption of cellulolytic enzymes and various surfactants per se on model cellulose and lignin surfaces (2) Determine the effect of surfactants on adsorption of cellulolytic enzymes on model cellulose and lignin surfaces (3) Determine the effect of surfactants on enzymatic cellulose hydrolysis rates (4) Develop a model for the effect of surfactants on enzymatic cellulose hydrolysis NON-TECHNICAL ABSTRACT: Several studies in the literature report beneficial effects of surfactants on the conversion of lignocellulosic biomass to ethanol. Surfactants were found to increase glucose as well as ethanol yields, increase reaction rates, and lower the amount of enzyme required for conversion. The mechanism by which surfactants accelerate the process is unclear. The goal of this research is to develop a comprehensive understanding of the mechanisms by which surfactants enhance the enzymatic hydrolysis of lignocellulosic biomass. Adsorption and hydrolytic activity of enzymes on model cellulose surfaces in the presence and absence of surfactants will be studied by several analytical methods. The results will be used to develop a adsorption and kinetic models. The data generated and models developed will yield technology that can instantly cause a significant reduction in ethanol production costs and bring us closer to the federal target for ethanol production costs of $1.07 per gallon ethanol.

The adsorption and enzymatic hydrolysis, if applicable, of cellulase and beta-glucosidase on model cellulose and lignin surfaces will be studied by surface plasmon resonance spectroscopy, ellipsometry, and quartz crystal microbalance. Once our understanding of enzyme adsorption and hydrolysis on these model surfaces is complete, surfactants will be added and the adsorption and enzymatic hydrolysis studied in the presence of surfactants. In addition to adsorption and hydrolysis on model surfaces, saccharification experiments with cellulose nanocrystal suspensions will be carried out to measure hydrolysis rates in suspension.

To reduce the nation’s dependence on foreign oil, President Bush created the 'Advanced Energy Initiative' (AEI) in early 2006. The specific goal of the AEI is to replace more than 75% of oil imports with domestic, renewable alternatives by 2025. To meet the President’s goal, the Office of Energy Efficiency and Renewable Energy of the Department of Energy’s Biomass Program has implemented the ‘Biofuels Initiative’ (BFI) with the following two specific R&D goals: (1) to make cellulosic ethanol (= ethanol from non-grain biomass resources) cost competitive with gasoline by 2012, and (2) to replace 30% of 2004 motor gasoline (60 billion gallons) with bioethanol by 2030 (“30 x 30 Vision”). The official 2012 cost target for cellulosic ethanol production is $1.07 per gallon of ethanol (year 2002 dollars). To meet this target, from currently $2.16 per gallon of ethanol (year 2006 dollars), several critical R&D needs have been identified. The proposed research directly contributes to five of the federally identified R&D needs. Addition of surfactants increases the saccharification efficiency (rate and yield) and allows for lower enzyme loadings, thus reducing the cost of purchased enzyme per gallon of ethanol. Furthermore, this research will further our understanding of the effect of lignin on enzyme kinetics. The novel aspect of this research is the unique and powerful combination of model systems and methods that will be used to study the interactions of enzymes, cellulose, lignin, and surfactants. This proposal targets funding priority #5 of the Department of Transportation and Southeastern Sun Grant Initiative: new or improved conversion processes for production of fuels, bioproducts, and chemicals.

Our experiments will yield adsorption parameters for both, enzymes and surfactants, on cellulose and lignin, as well as enzymatic hydrolysis rates in the absence and presence of surfactants. Comparing our results from the three different surface techniques will allow us to refine our adsorption and kinetics models through an iterative approach, thereby yielding the best possible adsorption parameters, hydrolysis rates, and ultimately model for the effect of surfactants on enzymatic cellulose hydrolysis. The data generated and models developed will yield technology that can instantly cause a significant reduction in ethanol production costs.

Reports and Publications:

Quarter 1 - 2008
Quarter 2 - 2008
Quarter 3 - 2008
Quarter 4 - 2008

Quarter 1 - 2009
Quarter 2 - 2009