Scale-up of Ethanol Production from Winter Barley by the EDGE (Enhanced Dry Grind Enzymatic) Process in Fermentors up to 300 l

Abstract

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.

Production of Ethanol From Newly Developed and Improved Winter Barley Cultivars

“…Among all the winter barley lines tested, AMAZE 10 stood out as the best feedstock with the highest ethanol yield. The yield of 292 gal/ac obtained for this feedstock was considerably higher than the values obtained for Thoroughbred (255 gal/ac) and EVE (231 gal/ac), which were the two barley lines used for development of the fermentation process in the previous studies [4,10].…”

“…The grain composition and production data of the five hulled and five hull-less winter barley lines are shown in Tables 1 and 2, respectively. Since both starch and β-glucan could be hydrolyzed with suitable enzymes to produce glucose, which in turn could readily be fermented by S. cerevisiae [4,10], a barley feedstock with high total starch plus β-glucan as well as high grain yield would be ideal for ethanol production. The other components, which included oil, protein, and fiber, although not directly affecting ethanol production, determine the quality of the DDGS co-product.…”

“…The other analyses, which included starch, β-glucan, oil, protein, fiber, and ash, were performed according to the procedures described in a previous study [10] and are described here.…”

“…The grain composition and other pertinent information have been reported in a recent publication [13]. Our main objective was to determine the potential use of the newly developed barley lines for improvement of ethanol production compared to the results obtained with the old cultivars in previous studies (4,10). In the present study, we report the results of ethanol fermentation experiments using five hulled and five hull-less winter barley lines that have recently been developed.…”

“…It was demonstrated that the added β-glucanases hydrolyzed β-glucans to oligomers and the added β-glucosidase further hydrolyzed these oligomers to glucose, which was readily fermentable by the yeast Saccharomyces cerevisiae [4]. The fermentation process, which was developed using shake flasks, was successfully scaled up in 7.5-, 70-, and 300-L fermentors using both hulled (Thoroughbred) and hull-less barley (Eve) [10]. An economic analysis of this process indicated the benefit of adding the enzymes to obtain extra ethanol production in all cases except one where the highest β-glucosidase cost allowance and lowest barley cost were used [11].…”