Scale-up of ethanol production from winter barley by the EDGE (enhanced dry grind enzymatic) process in fermentors up to 300 l

摘要

A fermentation process, which was designated the enhanced dry grind enzymatic (EDGE) process, has recently been developed for barley ethanol production. In the EDGE process, in addition to the enzymes normally required for starch hydrolysis, commercial β-glucanases were used to hydrolyze (1,3)(1,4)-β-d-glucans to smaller molecules, thus reducing the viscosity of the mash to levels sufficiently low to allow transport and mixing in commercial equipment. Another enzyme, a developmental β-glucosidase, then was used to hydrolyze the resulting oligomers to glucose, which subsequently was fermented to produce additional ethanol. The EDGE process was developed with Thoroughbred, a winter hulled barley, using a shake flask model. To move toward commercialization, it is necessary to prove that the developed process would be applicable to other barley varieties and also to demonstrate its scalability. Experiments were performed in 7.5, 70, and 300-l fermentors using Thoroughbred and Eve, a winter hull-less barley. It was shown that the process was scalable for both barley varieties. Low levels of glucose throughout the course of the fermentations demonstrated the high efficiency of the simultaneous saccharification and fermentation process. Final ethanol concentrations of 14% (v/v) were achieved for initial total solids of 28.5-30% (w/w), which gave an ethanol yield of 83-87% of the theoretical values. The distillers dried grains with solubles co-products contained very low levels of β-glucans and thus were suitable for use in feed formulations for all animal species.