Biobutanol production from fiber-enhanced DDGS pretreated with electrolyzed water

DDGS (distiller's dried grains with solubles) is a major co-product in dry-grind ethanol production from corn. A recently developed physical process separates DDGS into two value-added components: a fiber-enriched DDGS and a portion that is rich in oil and protein. Electrolyzed water, a new pretreatment catalyst was employed to pretreat fiber-enriched DDGS. Four temperatures (130, 145, 160, and 175 °C) and three treatment times (10, 20, and 30 min) were examined in the pretreatment with a solid loading of 20% w/w. Other pretreatment methods, such as diluted sulfuric acid, alkaline solution, and hot water, were also tested for comparison purposes. Fifteen FPU cellulase/g cellulose, 40 units β-glucosidase/g cellulose, and 50 units xylanase/g dry biomass were used in the enzymatic hydrolysis at 50 °C and 10% solid loading. The hydrolyzates were fermented by Clostridium beijerinckii BA 101 at 35 °C in an auto-controlled Six-fors fermentor with continuous mixing. The highest sugar yield was achieved when using the acidic electrolyzed water treatment at 175 °C for 10 min, with 23.25 g glucose, xylose and arabinose released from 100 g fiber-enriched DDGS. The C. beijerinckii fermentation produced 5.35 g ABE (acetone, butanol, and ethanol) from 100 g dry fiber-enhanced DDGS. This study demonstrated that DDGS pretreated with electrolyzed water and hydrolyzed with commercial enzymes could be used to produce biobutanol without detoxification.