title: Pretreatment of Dried Distiller Grains with Solubles by Soaking in Aqueous Ammonia and Subsequent Enzymatic/Dilute Acid Hydrolysis to Produce Fermentable Sugars.
abstract: Dried distillers grains with solubles (DDGS), a co-product of corn ethanol production in the dry-grind process, was pretreated by soaking in aqueous ammonia (SAA) using a 15 % w/w NH4OH solution at a solid/liquid ratio of 1:10. The effect of pretreatment on subsequent enzymatic hydrolysis was studied at two temperatures (40 and 60 °C) and four reaction times (6, 12, 24, and 48 h). Highest glucose yield of 91 % theoretical was obtained for the DDGS pretreated at 60 °C and 24 h. The solubilized hemicellulose in the liquid fraction was further hydrolyzed with dilute H2SO4 to generate fermentable monomeric sugars. The conditions of acid hydrolysis included 1 and 4 wt% acid, 60 and 120 °C, and 0.5 and 1 h. Highest yields of xylose and arabinose were obtained at 4 wt% acid, 120 °C, and 1 h. The fermentability of the hydrolysate obtained by enzymatic hydrolysis of the SAA-pretreated DDGS was demonstrated in ethanol fermentation by Saccharomyces cerevisiae. The fermentability of the hydrolysate obtained by consecutive enzymatic and dilute acid hydrolysis was demonstrated using a succinic acid-producing microorganism, strain Escherichia coli AFP184. Under the fermentation conditions, complete utilization of glucose and arabinose was observed, whereas only 47 % of xylose was used. The succinic acid yield was 0.60 g/g total sugar consumed.
authors.affiliation: Sustainable Biofuels and Co-products Research Unit, Eastern Regional Research Center, Agricultural Research Service, USDA, Wyndmoor, PA, 19038, USA. john.nghiem@ars.usda.gov.
authors.forename: Nhuan P
authors.initials: NP
authors.lastname: Nghiem
authors.affiliation: Sustainable Biofuels and Co-products Research Unit, Eastern Regional Research Center, Agricultural Research Service, USDA, Wyndmoor, PA, 19038, USA.
authors.forename: Justin
authors.initials: J
authors.lastname: Montanti
authors.affiliation: Department of Environmental Engineering, Kongju National University, Cheonandae-Ro, 1223-24, Cheonan, Chungnam, 31080, South Korea.
authors.forename: Tae Hyun
authors.initials: TH
authors.lastname: Kim
mesh_terms: D000641:Ammonia / Q000737:chemistry; D001089:Arabinose / Q000096:biosynthesis / Q000737:chemistry; D000431:Ethanol / Q000737:chemistry* / Q000378:metabolism; D005285:Fermentation; D005947:Glucose / Q000096:biosynthesis / Q000737:chemistry* / Q000302:isolation & purification; D006868:Hydrolysis; D007220:Industrial Waste; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000235:genetics; D013696:Temperature; D014867:Water / Q000737:chemistry; D014994:Xylose / Q000096:biosynthesis / Q000737:chemistry; D003313:Zea mays / Q000737:chemistry*
chemical_list: D007220:Industrial Waste; D014867:Water; D000431:Ethanol; D000641:Ammonia; D014994:Xylose; D001089:Arabinose; D005947:Glucose
keywords: Dilute acid/enzyme hydrolysis; Dried distillers grains with solubles; Ethanol fermentation; Soaking in aqueous ammonia pretreatment; Succinic acid