1a. Objectives (from AD-416):
The overall objectives of this project are to develop economically viable technology to allow production of fuel ethanol from "Generation 1.5" regional non-corn feedstocks such as winter barley, that are grown outside the Corn Belt on fallow land or land that does not compete with food production. Evolve these ethanol plants into multiple product biorefineries, producing high value food and feeds and then into multi-feedstock biorefineries that can accept fermentable sugars from local lignocellulosic feedstock to produce additional ethanol and valuable coproducts. 1. In conjunction with CRADA partners and other collaborators, develop technologies that enable (1) commercially-preferred processes for converting winter barley into fuel ethanol in ways that significantly reduce biorefinery water usage and (2) commercially-viable, value-added co-products from barley-based biorefineries. 1a: Develop commercially-preferred processes for converting winter barley into fuel ethanol and improved DDGS in ways that increase ethanol yield and significantly reduce biorefinery water usage. 1b: Develop commercially-viable, value-added carbohydrate based co-products from barley kernels, hulls, and/or straw in barley-based biorefineries. 1c: Develop commercially-viable, value-added lipid based co-products from barley kernels, hulls, and/or straw in barley-based biorefineries. 2. In collaboration with NCAUR, develop technologies that enable the commercially-preferred conversion of barley hulls and/or straw into sugar-containing make-up water, allowing the production of ethanol from both starch and cellulose in a barley grain-based biorefinery.
1b. Approach (from AD-416):
In conjunction with CRADA partners and other collaborators, develop technologies that enable commercially-preferred processes for converting winter barley into fuel ethanol and improved DDGS in ways that increase ethanol yield and significantly reduce biorefinery water usage. Develop commercially-viable, value-added carbohydrate based co-products from barley kernels, hulls, and/or straw in barley-based biorefineries. Develop commercially-viable, value-added lipid based co-products from barley kernels, hulls, and/or straw in barley-based biorefineries. In collaboration with NCAUR and other partners, develop technologies that enable the commercially-preferred conversion of barley hulls and/or straw into sugar-containing make-up water, allowing the production of ethanol from both starch and cellulose in a barley grain-based biorefinery.
3. Progress Report:
The arabinoxylan (AX) from barley straw was mixed with chitosan, homogenized using a high pressure homogenizer and mixture was used to make films. AX in combination with chitosan makes a good and stable film with antibacterial activity. The emulsion stability of AX from barley straw is superior to AX from barley hulls. Overall, all these AXs have good emulsion stabilizing capacity for an oil-in-water emulsion system. The emulsifying properties of AXs correlates well with their protein content except AX from barley hull, which has lower emulsifying properties even though it has high protein. The Cellulosic Rich Fraction (CRF) from both barley hulls and straw has high water holding capacity, which could be due to presence of arabinoxylan in the CRF. Developed a chromatographic method to fractionate tocopherols and other functional lipids from barley oil. We are now beginning to develop cost-effective molecular distillation methods to fractionate tocopherols and other functional lipids from barley oil. Molecular distillation methods could be scaled up and used to process large amounts of barley oil. Developed an aqueous enzymatic oil extraction process to extract barley oil from barley germ and wheat germ which achieves oil yields of about 60%. Research is continuing to improve oil yields and to reduce the cost of the process. Barley straw and barley hulls pretreated by dilute acid and alkaline hydrogen peroxide processes developed at the National Center for Agricultural Utilization Research (NCAUR) were hydrolyzed by ACCELLERASE 1500 and ACCELLERASE XY. The effects of enzyme dosages were investigated. Hydrolysates obtained from barley straw and barley hulls pretreated by dilute acid were highly toxic to commercial yeast. Theoretically these hydrolysates can be detoxified prior to fermentation. However, the detoxification process may be too expensive and make production of ethanol using these feedstocks uneconomical. Decision on whether detoxification will be attempted will be made. Preferred conditions for enzymatic hydrolysis of barley straw and barley hulls that had been pretreated with a soaking in aqueous ammonia (SAA) process were established. Experiments on using the hydrolysates as mashing water for ethanol production from dehulled barley (endosperm) are in progress. We worked with a team at Virginia Tech to develop a process to remove toxic mycotoxins from Fusarium-infected, field-grown hulled barley so it can be used for fuel and feed purposes. The hypothesis tested was that removal of the hull from the barley kernel would also remove most of the mycotoxins from the barley. Two different hull removal processes were used including roller milling followed by sieving and a “precision” dehulling process previously developed by us. The precision milling was far more effective than the roller milling at removing mycotoxins from hulled barley, removing the hull and up to 85% of the mycotoxins without significant loss of important kernel components such as starch and protein. This work has been described in a manuscript that has been submitted to a peer reviewed journal.
1. Winter Barley for advanced biofuels. Before 2013, barley was not approved by the Environmental Protection Agency as an official feedstock for U.S. biofuels production under the Renewable Fuel Standard statute. Over the last 5 years, ARS researchers at Wyndmoor, Pennsylvania collaborated with international enzyme companies, plant breeders, entrepreneurs, life-cycle experts, and ethanol plant designers to develop new winter barley varieties, new efficient processes to convert barley into fuel ethanol and to conduct critical analyses on the economics and the environmental benefits of barley ethanol. In response to these accomplishments and the information they contained, the Environmental Protection Agency proposed barley as an acceptable feedstock for renewable fuels and also proposed it as a feedstock for making environmentally preferred “Advanced” biofuels when produced using certain manufacturing processes developed by the team. Because of the important research conducted by ARS and its collaborators and because of the decision by EPA, ethanol plants in the US will soon be able to use barley to make conventional and advanced fuel ethanol and, in the latter case, can receive an economic incentive for using barley over other conventional feedstocks such as corn. Use of winter barley will reduce usage of corn for biofuel production and will lessen stress on food and feed markets for corn. It will also provide economic benefits for farmers and agriculture outside the Corn Belt.
Yoo, C., Nghiem, N.P., Hicks, K.B., Kim, T. 2013. Maximum production of fermentable sugars from barley straw using optimized soaking in aqueous ammonia (SAA) pretreatment. Applied Biochemistry and Biotechnology. 169(8):2430-2441.