Location: Sustainable Biofuels and Co-products Research
2015 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
Grain Sorghum was utilized for fermentations utilizing a process that was analogous to the corn dry grind ethanol process. Fermentation of grain sorghum using the identical process for corn resulted in small but statistically significant reductions in both rate and yield of ethanol relative to corn. This would have a serious negative economic impact for fuel ethanol facilities. Further testing showed that modification to grinding and enzyme supplementation could improve the conversion. Additional work is continuing to address the necessary modifications for successful implementation of grain sorghum into existing ethanol facilities.
Sweet sorghum juice was used in ethanol fermentation using an industrial yeast strain of Saccharomyces cerevisiae. Final ethanol concentrations obtained with and without addition of commercial starch hydrolysis enzymes were the same, which indicated that the sweet sorghum juice used in these experiments did not contain significant levels of starch. The fermentation rates, however, were significantly faster when nutrients were added, which indicated the sweet sorghum juice required nutrients for efficient ethanol fermentation.
Accomplishments
Review Publications
Zhang, X., Nghiem, N.P. 2014. Pretreatment and fractionation of wheat straw for production of fuel ethanol and value-added co-products in a biorefinery. Mathematical Biosciences and Engineering (MBE) Journal. 1(1):40-52.
Nghiem, N.P., Senske, G.E. 2014. Capture of carbon dioxide from ethanol fermentation by liquid absorption for use in biological production of succinic acid. Applied Biochemistry and Biotechnology. 175:2104-2113.
Challa, R., Johnston, D., Singh, V., Tumbleson, M., Rausch, K. 2014. Fouling characteristics of model carbohydrate mixtures and their interaction effects. Journal of Food and Bioproducts Processing. 93:197-204.
