Corn fiber is a co-product of commercial ethanol dry-grind plants, which is processed into distillers dried grains with solubles (DDGS) and used as animal feed, yet it holds high potential to be used as feedstock for additional ethanol production. Due to the tight structural make-up of corn fiber, a pretreatment step is necessary to make the cellulose and hemicellulose polymers in the solid fibrous matrix more accessible to the hydrolytic enzymes. A pretreatment process was developed in which whole corn kernels were soaked in aqueous solutions of 2.5, 5.0, 7.5 and 10.0 wt% ammonia at 105oC for 24 h. The pretreated corn then was subjected to a conventional mashing procedure and subsequently ethanol fermentation using a commercial strain of natural Saccharomyces cerevisiae with addition of a commercial cellulase. Pretreatment of the corn with 7.5 wt% ammonia solution plus cellulase addition gave highest ethanol production, which improved the yield in fermentation using 25 wt% solid from 334 g ethanol/kg corn obtained in the control (no pretreatment and no cellulase addition) to 379 g ethanol/kg corn (a 14% increase). The process developed can potentially be implemented in existing dry-grind ethanol facilities as a “bolt-on” process for additional ethanol production from corn fiber, and this additional ethanol can then qualify as “cellulosic ethanol” by the EPA’s Renewable Fuels Standard and thereby receive RINS (Renewable Identification Numbers).

Black variety of tiger nut tubers (Cyperus esculentus) were differently processed in ascorbic acid and alkaline (Ca(OH)2 and Kanwa) solutions at different concentrations and temperatures. The effect of these treatments on the water content (swelling), soluble loss, dehulling efficiency and microbial load was investigated. Water content or swelling of the tiger nut soaked in acid and alkaline solutions can be predicted by Peleg model like with brown variety. This swelling lead to enhance dehulling efficiency of tuber but caused soluble solute loss overall at the highest temperature of soaking in vitamin C solution. Like soaking in water, the constant of Peleg (k1) decrease with the increase of the temperature of soaking, whereas the constant of capacity of Peleg (k2) is approximately 0.018% for all the conditions. Dehulling efficiency also increased with increasing temperatures (65% at 20°C to 70% at 60°C) for tiger nut tubers soaked in water (0 g/L), dehulling efficiency appeared most strongly affected by concentrations and temperatures of soaking solutions. Like dehulling efficiency, ascorbic solutions has given the best results in term of reduction of microbial load compared to the other soaking solutions. This reduction is considerable at the higher temperatures, reaching a maximum of 4.8 log reduction. Soaking and dehulling treatments gave to tiger nut tuber effective decontamination in term of microbial load and obtained good microbiological quality for final process.