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ARS Home » Southeast Area » New Orleans, Louisiana » Southern Regional Research Center » Commodity Utilization Research » Research » Publications at this Location » Publication #363037
Research Project: Developing Technologies that Enable Growth and Profitability in the Commercial Conversion of Sugarcane, Sweet Sorghum, and Energy Beets into Sugar, Advanced Biofuels, and Bioproducts

Location: Commodity Utilization Research

Title: Development of an enzyme processing cocktail for sweet sorghum processing by-products

Author
item COLE, MARSHA - Oak Ridge Institute For Science And Education (ORISE)
item Eggleston, Gillian
item Gaines, Deriesha
item HECKEMEYER, MATTHEW - Heckemeyer Mill
item Klasson, K Thomas

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 3/7/2019
Publication Date: 11/6/2019
Citation: Cole, M., Eggleston, G., Gaines, D., Heckemeyer, M., Klasson, K.T. 2018. Development of an enzyme processing cocktail for sweet sorghum processing by-products. In: Lima, I., Eggleston, Gl, Clayton, C. (eds.). Proceedings of the Advances in Sugar Crop Processing and Conversion 2018 Conference. 2:207-219. 366 pp.

Interpretive Summary: Soluble matter in sweet sorghum juices and syrups are mainly Soluble matter in sweet sorghum juices and syrups are mainly sugars that can be converted to ehtanol during fermentation.Recently, it was found that sweet sorghum contains a substantial amount of starch in the insoluble form in juice sediment and/or clarification mud. These are untapped sources of fermentable sugars. In this study, we optimized hydrolysis, liquefaction, and saccharification conditions and develop an enzyme cocktail for the bioconversion and fermentation of juice sediment and clarification mud. Yeast fermentation showed that the utilization of insoluble starch from some sweet sorghum products significantly increased the final ethanol concentration by 135 and 15% for the juice sediment and clarification mud, respectively. The presence of organic acids and other compounds had no effect on the ethanol production rate. More research is warranted on understanding how these chemical impurities may have affected the enzymes activities in the sediment and clarification mud.

Technical Abstract: Soluble carbohydrates in sweet sorghum juices and syrups are the main sugars that are converted to ethanol during fermentation. Recently, it was found that sweet sorghum contains a substantial amount of starch in the insoluble form in juice sediment and/or clarification mud, and is an untapped source of fermentable sugars. In this study, a response surface method was used to optimize hydrolysis, liquefaction, and saccharification conditions and develop an enzyme cocktail for the bioconversion and fermentation of juice sediment and clarification mud. Optimal hydrolysis was best achieved at 80C in 90 min when <18% w/w starch was used since the solid concentration significantly (P<0.05) affected hydrolysis efficiency. Subsequent studies revealed that a cocktail comprised of 63% SAN Extra L,16% Promozyme, and 21% Viscozyme L was most effective in improving the saccharification of insoluble starch to fermentable sugars at 60C in 90 min. Application of the optimal conditions tripled fermentable glucose and doubled total sugars in juice sediment, showing insignificant improvement in clarification mud. Saccharomyces cerevisiae fermentation showed that the utilization of insoluble starch from sweet sorghum products significantly increased the final ethanol concentration by 135 and 15% for the juice sediment and clarification mud, respectively. The presence and/or bioaccumulation of aconitic acid, succinic acids, lactic acids, acetic acid, or glycerol in the samples or from fermentation had no effect (P<0.05) on the ethanol production rate. More research is warranted on understanding how these chemical impurities affected the enzymes activities in the sediment and clarification mud.