Ethanol Production from Soybean Fiber, a Co-product of Aqueous Oil Extraction, Using a Soaking in Aqueous Ammonia Pretreatment

• Published in: Journal of the American Oil Chemists' Society Vol. 89; no. 7; pp. 1345 - 1353
• Main Authors: Karki, Bishnu, Maurer, Devin, Box, Shannon, Kim, Tae Hyun, Jung, Stephanie
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01-07-2012; Springer; Springer Nature B.V
• Subjects: Agriculture; Alkaline pretreatment; Ammonia; Ammonia steeping; Aqueous chemistry; Aqueous extraction; Biological and medical sciences; Biomass; Biomaterials; Biotechnology; Chemistry; Chemistry and Materials Science; coproducts; Crop production; Delignification; enzymatic hydrolysis; Ethanol; ethanol production; Extrusion; Fat industries; Fermentation; Fibers; Food engineering; Food industries; Food Science; Fundamental and applied biological sciences. Psychology; General aspects; glucose; Hydrolysis; Industrial Chemistry/Chemical Engineering; insoluble fiber; Lignocellulose; Oils & fats; Original Paper; saccharification; soaking; Soybean fiber; Soybeans; temperature; Soybeans; Alkaline pretreatment; Ammonia steeping; Ethanol; Lignocellulose; Aqueous extraction; Soybean fiber; Extrusion; Delignification; Biomass; Soybean; Oils and fats industry; Grain legume; Oil; Production; Extraction; Pretreatment
• ISSN: 0003-021X; 1558-9331
• DOI: 10.1007/s11746-012-2016-z

The effectiveness of soaking in aqueous ammonia (SAA) as a pretreatment method for the conversion of soybean fiber to ethanol via simultaneous saccharification and fermentation (SSF) was investigated. Insoluble fiber is a co-product from oil and protein extraction using two-stage, countercurrent, enzyme-assisted, aqueous extraction processing of full-fat soybean flakes (FFSF) and extruded FFSF. The fiber fractions were soaked in 15 wt% aqueous ammonia at 1:10 solid-to-liquid ratio. The effects of operating variables, including treatment times (6, 12, and 24 h), treatment temperatures (60 and 80 °C), and cellulase loadings (15 and 60 FPU/g-glucan) on the degree of enzymatic hydrolysis were determined. The best SAA conditions were 80 °C for 12 h followed by an enzyme loading of 15 FPU/g-glucan, which produced a 152-mg/g glucose yield after 48 h of hydrolysis. This was 8.7 times the amount produced from the same fiber not pretreated with SAA. The glucose yield increased to 381 mg/g when fiber obtained from extruded FFSF was submitted to SAA. SAA (80 °C, 12 h) on extruded fiber subjected to SSF increased ethanol yield from 0.06 g of ethanol/g [40% of theoretical yield] (for non SAA pretreated fiber) to 0.25 g of ethanol/g [92% of theoretical yield]. The combination of extrusion and SAA was an efficient means for converting the fiber-rich soybean fraction into ethanol.