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EDGE Process for Ethanol from Winter Barley

29 April 2010

US - US legislation requires the use of advanced biofuels to be made from non-food feedstocks. However, commercialisation of lignocellulosic ethanol technology is more complex than expected and is therefore running behind schedule, according to a study by N P Nghiem, K B Hicks, D B Johnston, G Senske, M Kurantz, M Li, J Shetty and G Konieczny-Janda.

The research, published in Biotechnology for Biofuels 2010, 3:8, shows that this is creating a demand for non-food, but more easily converted, starch-based feedstocks other than corn that can fill the gap until the second generation technologies are commercially viable.

Winter barley is such a feedstock but its mash has very high viscosity due to its high content of -glucans. This fact, along with a lower starch content than corn, makes ethanol production at the commercial scale a real challenge.

A new fermentation process for ethanol production from Thoroughbred, a winter barley variety with a high starch content, was developed.

The new process was designated the EDGE (enhanced dry grind enzymatic) process. In this process, in addition to the normal starch-converting enzymes, two accessory enzymes were used to solve the beta-glucan problem.

First, beta-glucanases were used to hydrolyze the beta-glucans to oligomeric fractions, thus significantly reducing the viscosity to allow good mixing for the distribution of the yeast and nutrients.

Next, beta-glucosidase was used to complete the beta-glucan hydrolysis and to generate glucose, which was subsequently fermented in order to produce additional ethanol.

While beta-glucanases have been previously used to improve barley ethanol production by lowering viscosity, this is the first full report on the benefits of adding beta-glucosidases to increase the ethanol yield.

In the EDGE process, 30 per cent of total dry solids could be used to produce 15 per cent v/v ethanol.

Under optimum conditions an ethanol yield of 402 L/MT (dry basis) or 2.17 gallons/53 lb bushel of barley with 15 per cent moisture was achieved.

The distillers dried grains with solubles (DDGS) co-product had extremely low beta-glucan (below 0.2 per cent) making it suitable for use in both ruminant and mono-gastric animal feeds.

Further Reading

- You can view the full report by clicking here.

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