Location: Sustainable Biofuels and Co-products Research
2020 Annual Report
Objectives
1: Develop technologies that enable the integrated processing of sorghum grains and sweet sorghum juice at existing biofuels production facilities and that enable the commercial production of new co-products at sorghum-based biorefineries.
1A: Develop technologies that enable the integrated processing of sorghum grains at existing biofuels production facilities.
1B: Develop technologies that enable the integrated processing of sweet sorghum juice at existing biofuels production facilities.
1C: Develop technologies that enable the commercial production of new co-products at sorghum-based biorefineries.
2: Develop technologies that enable the commercial production of marketable C5-rich and C6-rich sugar streams from sorghum lignocellulosic components.
2A: Develop technologies that enable the commercial production of marketable C5-rich sugar streams from sorghum lignocellulosic components.
2B: Develop technologies that enable the commercial production of marketable C6-rich sugar streams from sorghum lignocellulosic components.
3: Develop technologies that enable the commercial conversion of sorghum lignocellulosic components into fuels and industrial chemicals.
3A: Develop technologies that enable the commercial production of industrial chemicals from the C5-rich sugar stream obtained from the enzymatic hydrolysis of pretreated sorghum cellulosic components.
3B: Develop technologies that enable the commercial production of additional ethanol and industrial chemicals from the C6-rich sugar stream obtained from the enzymatic hydrolysis of the cellulose-enriched residue.
3C: Develop technologies that enable the use of byproducts and wastes generated in ethanol and other fermentation processes in the sorghum biorefinery for production of energy and chemicals.
Approach
In conjunction with collaborators, develop technologies that enable commercially-preferred bio/chemical processes for converting all components of sorghum plants, including grains, juice, and bagasse, into fuels, industrial chemicals and consumer products. Develop commercially viable processes for incorporation of sorghum grains into existing commercial corn-based ethanol plants and evaluate the effects of this process modification on overall water balances in the existing plants. Develop commercially viable technologies for using sweet sorghum juice and sorghum biomass, including both carbohydrates and lignin, for the production of important platform chemicals, i.e. chemicals that can be used as precursors for production of a wide range of industrial chemicals and consumer products. Develop technologies for capturing the carbon dioxide gas generated in ethanol fermentation for use in other fermentation processes that requires CO2 as a secondary feedstock in addition to fermentable sugars. Develop technologies for conversion of the wastes generated in cellulosic ethanol and industrial fermentation processes into methane for internal use as an energy source. Develop an integrated process combining the aforementioned process components for a sorghum-based biorefinery.
Progress Report
New NP306 OSQR approved project entitled “Integrated Biological/Chemical Biorefining for Production of Chemicals and Fuels” is currently being established.
Objective 1: The process models previously developed integrating grain sorghum have been utilized for economic analysis for comparison with the existing corn-to-ethanol model. Distiller’s dried grains with solubles (DDGS) from laboratory scale production were completed and compositionally analyzed for importation components that relate to the commercial value of the coproduct. Work on a manuscript that compares and contrasts the two variations for ethanol production is being prepared for publication late in FY 2020 or early FY 2021. Models will be shared publicly upon request, as is currently done with all of our previously developed models.
Objective 2. Lignin was extracted by NaOH in high yields from enzymatic hydrolysis residue of pretreated sweet sorghum bagasse. The dissolved lignin fractions were recovered by precipitation by lowering the pH of the aqueous extract solution. After washing and freeze drying, the powdered lignin was sent to collaborators at Michigan State University for analysis. The collaborators characterized the lignin fractions for ash content, molecular weight, chemical functional groups, and thermal stability. Discussion with the collaborators at Michigan State University determined that the properties of the sweet sorghum bagasse lignin fractions make it an attractive component in the production of biobased epoxy resins. These preliminary results were included in a collaborative research proposal with professors at Michigan State University that was submitted to the USDA NIFA Agriculture and Food Research Initiative (AFRI) Foundational and Applied Science Program. The proposed research will recover lignin from organic solvent pretreatment of agricultural feedstocks and utilize the lignin in high value material applications.
Objective 3: Fermentable sugars were generated following enzymatic hydrolysis of low moisture anhydrous ammonia (LMAA) pretreated sweet sorghum bagasse. The resulting hydrolysate contained 40 g/L glucose and 20 g/L xylose. This hydrolysate was then utilized in fermentation experiments with the bacteria strain Clostridium tyrobutyricum to generate butyric acid. By using a 2 L bioreactor with pH control around 12 g/L of butyric acid could be generated with an average yield of 0.3 g butyric acid per g sugar consumed with complete glucose utilization. Only limited quantities of xylose were converted during fermentation. Butyric acid can be recovered from the fermentation broth and be utilized as an intermediate chemical for a wide range of markets including chemical upgrading to butanol as an advanced biofuel.
Accomplishments
Review Publications
You, J., Johnston, D., Dien, B.S., Singh, V., Engeseth, N.J., Tumbleson, M., Rausch, K.D. 2020. Effects of nitrogenous substances on heat transfer fouling using model thin stillage fluids. Food and Bioproducts Processing. 119:125-132. https://doi.org/10.1016/j.fbp.2019.10.010.
Stoklosa, R.J., Nghiem, N.P., Latona, R.J. 2019. Xylose enriched ethanol fermentation stillage from sweet sorghum for xylitol and astaxanthin production. Fermentation. 5(4):1-17. https://doi.org/10.3390/fermentation5040084.
