Location: Bioproducts Research2012 Annual Report
1a. Objectives (from AD-416):
Objective 1: Develop enzyme-based technologies (based on cleaving specific covalent crosslinks which underlie plant cell wall recalcitrance) thereby enabling new commercially-viable* saccharification processes. Objective 2: Develop new enzyme-based technologies that enable the production of commercially-viable* coproducts such as specialty chemicals, polymer precursors, and nutritional additives/supplements from raw or pretreated lignocellulosic biomass. Objective 3: Develop pretreatment technologies that enable commercially-viable* biorefineries capable of utilizing diverse feedstocks such as rice straw, wheat straw, commingled wastes (including MSW), sorghum, switchgrass, algae, and food processing by-products. Objective 4: Develop new separation technologies that enable commercially-viable* and energy-efficient processes for the recovery of biofuels, biorefinery co-products, and/or bioproducts from dilute fermentation broths.
1b. Approach (from AD-416):
Novel enzymes for pretreatment of lignocellulosic feedstocks will be developed and improved by (1) creation of new genomic DNA libraries from diverse environments that are known to contain microbes that digest plant biomass, (2) development of novel rapid screening assays for identifying enzymes that have a specific activity, and (3) optimization of different enzyme cocktails for different biomass sources via multivariant, combinatorial optimization protocols. Greener routes toward production of styrene, terephthalic acid, vanillin and ferulic acid derivatives will be developed by a combination of biochemical and chemical synthetic pathways. Enzymes will be applied to created these bioproduct feedstocks. Engineering process models, economic analysis, and process parameters for developing integrated biorefineries using biomass from MSW and other under-utilized biomass sources as feedstock will be developed to create a source of cellulose that is consistent, easily converted to bioenergy and available during all seasons. Develop novel separation methods to reduce energy use and costs for recovering and purifying biofuels/bioproducts from low concentration fermentation broths, especially those resulting from lignocellulosic feedstocks where product concentrations are typically below (sometimes far below) 6 wt%.
3. Progress Report:
Multifunctional enzymes for biomass-to-bioenergy conversion. Converting crop residue such as straw or stover into biofuels is a complex process that can require multiple enzymes working synegistically to release fermentable sugars. ARS researchers in Albany, California, in collaboration with multiple partners (including National Aeronautics and Space Administration and a corporate partner), developed multi-functional enzymes with significantly better biomass-degrading properties. These multi-functional enzymes are built into a protein structure called a chaperon structure that has multiple active sites and can bind up to eighteen different enzymes. Preliminary data showed that enzymes tethered to these chaperonin scaffolds proteins (self-assembling nanostructure chaperonin complex) can exhibit greater synergies than if the same enzymes are free in solution. ARS researchers in Albany, California, received a three year, $479K National Institute of Food and Agriculture grant to continue this research. Bi-functional enzyme that hydrolyzes both mannans and mixed glucans. Several polysaccharides present in the plant cell wall are often difficult to degrade into fermentable sugars for biofuels production, especially those containing mannan. ARS researchers in Albany, California, developed a bi-functional enzyme that enables two hydrolytic reactions to proceed more efficiently than the corresponding individual reactions that releases mannan-derived sugars (mannose) from complex cell wall components. In related work this team employed site-directed mutagenesis and directed evolution to increase the thermal stability of a highly-active beta-xylosidase by eight degrees Celsius, a significant increase in temperature stability with no loss of activity. This beta-xylosidase, which exhibits one third lower end-product inhibition, has about three fourths the activity of the highest beta-xylosidase reported in the literature but has a much broader pH and temperature range, making it potentially interesting in commercial applications. Biorefinery strategies to create polymers and polymer building blocks (i.e. green monomers). In order to optimize biorefinery strategies for the Western States, special effort must be made to ensure that multiple product outputs are developed and commercialized, ensuring that no fraction of the biomass is wasted. In two related projects, ARS researchers in Albany, California, have worked with researchers partners to (1) convert waste methane (biogas) to a biodegradable polymer, poly(hydroxy alkanoate), PHA. (2) convert algae- and kelp-derived sugars using specific enzymes to value added chemicals. The monomers produced will be a range of intersting aldaric acids that have been used in nylon production and in anti-freeze formulations. An ARS partnership with a research partner will continue to test the commercial viability of producing aldaric acids as substrates for polymer production at larger scales.