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The Southeastern Regional
Sun Grant Center
2506 Jacob Drive
Knoxville, TN 37996-4570
Phone: (865) 946-1124
Fax: (865) 946-1109
Email: sungrant@tennessee.edu

Regional Competitive Grants

Project Title:  Evaluation of Reduced Lignin Softwood and Hardwoods for Improved Conversion to Bioethanol

Principal Investigators and affiliations:

  • PI: Gary Peter (University of Florida, School of Forest Resources and Conservation)
  • Co-PI: Lonnie Ingram (University of Florida, Department of Microbiology and Cell Science)
  • Co-PI: James Preston (University of Florida, Department of Microbiology and Cell Science)
  • Collaborator: Maud Hinchee (CTO, ArborGen, LLC) 

Start Date: 9/1/2007      End Date: 8/31/2008

Project Abstract:

A number of processes have been developed to convert biomass to ethanol; however, currently, they are not cost competitive. Improvements in all conversion steps are required to make ethanol from biomass commercially competitive. Plant feedstocks with reduced amounts of lignin and increased amounts of fermentable carbohydrates represent an important area of current research to improve the efficiency and cost of biofuels produced from plant biomass. In the proposed research we will quantify the improvements in yield and efficiency of converting increased carbohydrate and reduced lignin softwood and hardwoods into ethanol. The scientific rationale for this proposal is that greater amounts of lignin in plant feedstocks are thought to limit the efficiency of conversion due to 1) lower absolute amounts of carbohydrate available per unit mass for conversion, 2) lower porosity and permeability of cell walls, thereby limiting access of cellulases to the cellulose and decreasing the rate of enzymatic degradation, 3) nonspecifically sequester cellulases, thereby increasing the amount of cellulase needed for hydrolysis and 4) increase the amounts of cellulase inhibitors derived from lignin produced during some pretreatment methods. Thus, decreasing the amount of lignin in plant feedstocks is expected to enhance the yield and efficiency of converting biomass carbohydrates to ethanol. Knowledge of the degree to which conversion is limited by lignin content will provide valuable information for scientists working on plant biomass conversion about what structural alterations within the cell walls of plants may make biomass materials more amenable to bioconversion processes. These results will also permit more detailed studies into the mechanisms by which reduced lignin, altered lignin, size and chemical composition may increase the efficiency of bioconversion.

The objectives of this research will include: 1. Quantify the composition and yield of hemicelluloses extracted during pretreatment of wild-type and reduced lignin wood from loblolly pine and Eucalyptus. Wood chips will be pretreated by dilute acid hydrolysis at elevated temperature and pressure. The soluble compounds, mainly the hemicellulose sugars, will be washed from the chip and analyzed. The amount of hemicellulose and the sugar composition will be determined using standard methods. We expect that greater amounts of hemicellulose will be extracted in the reduced lignin wood. 2. Quantify the yield of carbohydrates during saccharification and the efficiency and yield of ethanol production during simultaneous saccharification and fermentation of reduced lignin content of wood from loblolly pine and Eucalyptus. Pretreated woody biomass will be incubated with commercially available cellulases under standard conditions. The amount of sugars hydrolyzed will be quantified and compared between the wild type and low lignin woods. The yield and efficiency of these hydrolyses will be determined. In addition, cellulase and ethanol producing bacteria will be added simultaneously in a co-fermentation approach as this can improve the yield of sugars. The amount and efficiency of ethanol production will be compared.

Reports and Publications:

Quarter 1 - 2008
Quarter 2 - 2008