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ARS Home » Northeast Area » Wyndmoor, Pennsylvania » Eastern Regional Research Center » Sustainable Biofuels and Co-products Research » Research » Publications at this Location » Publication #347701
Research Project: Sorghum Biorefining: Integrated Processes for Converting all Sorghum Feedstock Components to Fuels and Co-Products

Location: Sustainable Biofuels and Co-products Research

Title: Near theoretical saccharification of sweet sorghum bagasse using simulated green liquor pretreatment and enzymatic hydrolysis

Author
item PHAM, HUONG - Kongiu National University
item Nghiem, Nhuan
item KIM, TAE - Hanyang University

Submitted to: Energy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2018
Publication Date: 6/2/2018
Citation: Pham, H.T., Nghiem, N.P., Kim, T.H. 2018. Near theoretical saccharification of sweet sorghum bagasse using simulated green liquor pretreatment and enzymatic hydrolysis. Energy. 157:894-903.

Interpretive Summary: Sweet sorghum is a potential feedstock for production of fuel ethanol and industrial chemicals. It is a type of sorghum that is bred to contain high levels of sugar in its stems. Due to its ability to withstand harsh environmental conditions such as heat and drought, sweet sorghum can be grown in regions that are not suitable for corn. Sweet sorghum contains a juice having high contents of readily fermentable sugars. The fiber-rich residues (bagasse) obtained after extraction of the juice from the stalks can also be converted to ethanol and/or chemicals by breaking down the fibrous carbohydrates into sugars and fermenting them to ethanol. This research focused on a method to improve production of fermentable sugars, which are the feedstocks for conversion to fuels and chemicals. The method used green liquor, which is a by-product readily available in Kraft paper mills. The major component of the green liquor, sodium carbonate, also can easily be made from carbon dioxide produced in ethanol and other industrial fermentations. The method therefore offers a low-cost option for sweet sorghum bagasse conversion to useful products.

Technical Abstract: A pretreatment method using simulated green liquor (GL) consisting of sodium carbonate and sodium sulfide was investigated for improving the enzymatic saccharification of sweet sorghum bagasse (SSB). The GL pretreatment method was optimized by using response surface methodology (RSM) at various times (15–110 min), temperatures (160–200 degree C), liquid/solid (L/S) ratios (4–16), total titratable alkali (TTA) charges (10–18%), and sulfidity (0–40%). The optimum pretreatment conditions for the highest total sugar yield (glucan and xylan + galactan + mannan (XMG)) were determined to be 110 min, 160 degrees C, L/S ratio of 7, TTA of 18%, and sulfidity of 40%. The optimal sugar yield predicted by the model was 83.2%. The predicted value was confirmed in an experiment where 82.6% of the overall sugar yield (91.3% of glucan and 69.5% of XMG) was obtained.