High solids loading biorefinery for the production of cellulosic sugars from bioenergy sorghum

Authors: CHENG, MING-HSUN - University Of Illinois; KADHUM, HAIDER JAWAD - Oregon State University; MURTHY, GANTI - Indian Institute Of Technology; Dien, Bruce; SINGH, VIJAY - University Of Illinois

Submitted to: Bioresource Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/21/2020
Publication Date: 8/26/2020
Citation: Cheng, M., Kadhum, H., Murthy, G., Dien, B.S., Singh, V. 2020. High solids loading biorefinery for the production of cellulosic sugars from bioenergy sorghum. Bioresource Technology. 318. Article 124051. https://doi.org/10.1016/j.biortech.2020.124051.
DOI: https://doi.org/10.1016/j.biortech.2020.124051

Interpretive Summary: Bioenergy sorghum is a promising feedstock for production of chemicals and fuels because it required low inputs, has high crop yields, and can be grown on marginal farmland. However, converting it commercially to a fuel or chemical requires first extracting the plant carbohydrates as sugars at high concentrations. This is difficult because it requires processing the feedstock to sugars, which is a complex multi-step process, at solids contents of 30-50%. At these solids level the slurry resembles a moist solid. In this paper, two pilot scale unit operations were paired and biomass successfully processed at 40% solids with a sugar yield that 61% was of the maximum. Further process variations at laboratory scale are described that improve sugar yields while still maintaining high sugar concentrations. This work is of direct value to agriculture processors because it demonstrates production of commercially attractive sugar syrups using industrial type equipment and provides direction towards future process improvements.

Technical Abstract: A novel process applying high solids loading has been developed to produce sugars from bioenergy sorghum. The hydrothermal pretreatment with 50% solids loading was performed in a pilot scale continuous reactor followed by disc refining. Sugars were extracted from the enzymatic hydrolysis at 10% to 50% solids content using fed-batch operations. Three surfactants (Tween 80, PEG 4000, and PEG 6000) were evaluated to increase sugar yields. The hydrolysis using 2% PEG 4000 had the highest sugar yields. Glucose concentrations of 105, 130, and 147 g/L were obtained from the reaction at 30%, 40%, and 50% solids content, respectively. Additionally, the two-stage enzymatic hydrolysis was used to improve the sugar yields for the hydrolysis of 40% and 50% solids loadings. The total glucose yields of 78.02% and 73.14%; and xylose yields of 68.75% and 65.25% were obtained from the hydrolysis at 40% and 50% solids content, respectively.