Development of a process scheme for the production of high value functional products from DDGS

DDGS is the major co-product of bioethanol fermentation and is produced at very large quantities annually worldwide. Currently, DDGS is a low value agro-industrial product produced by distillers or bioethanol factories, and is primarily used as a protein-rich animal feed. A major issue with this application, which reduces its utilisation compared to soybean and canola meals, is its compositional variability, which consequently affects its nutritional quality and digestibility.

The aim of the proposed work is to develop a novel, scalable and economically viable process that will transform DDGS into several medium to high value products, namely a prebiotic food ingredient, gluten protein for film packaging, betaine and choline for use as nutritional supplements, and crude dietary fibre. The proposed process is based on the biorefinery concept in which the agricultural raw material is transformed into several value-added streams, which are either end-products or starting materials for secondary processing. Developing such a multi-stream process using DDGS as the raw material would be pioneering for the biorefinery industry as it would add considerable value to DDGS.

Prebiotics are non-digestible food ingredients that have a beneficial effect on health through their selective metabolism by bacteria in the intestinal tract, and are attractive prospects in the digestive health market. The objective will be to transform arabinoxylan (AX), which consists 30-50% of DGGS, into arabinooligosaccharides (AXOS); these have been shown to have prebiotic activities and over the last five years have attracted considerable commercial interest. A commercially attractive prospect is to target the production of AXOS with relatively high molecular weights (MW) in an effort to increase the persistence of the prebiotics in the colon and target delivery into the distal region. This would increase the beneficial effects of prebiotics as most of the colonic diseases, principally ulcerative colitis and bowel cancer, predominantly originate in the distal region. Gluten on the other hand consists 30-40% of DDGS and will be used to produce biodegradable film packaging material. The research will focus on extracting and characterising the gluten and evaluating the properties of the films. This will open up new applications for DDGS gluten with high market potential and economic benefits. Finally, betaine and choline have important biological functions for human health and as such they have received a lot of commercial interest as nutritional supplements. They are present in wheat and consequently in DDGS at much higher concentrations than in other natural food sources, and therefore extraction of these compounds from DDGS has considerable economic and market potential.

The proposed process consists of several scalable unit operations including the separation of DDGS into a soluble and non soluble stream, the fractionation of the soluble steam into gluten, AX, betaine and choline, the controlled hydrolysis of AX to AXOS, and the purification of AXOS. Key factors influencing the efficiency, scalability and economic feasibility of the process are (i) the development of efficient processing steps for the separation of the raw material into the target compounds, with high yields and purities, (ii) the utilisation of highly active enzymes that lead to the controlled synthesis of AXOS with specific MW and prebiotic activities and (iii) the production of gluten films with suitable morphological and functional properties for commercial use. The work will be carried by a multidisciplinary team of researchers from the University of Reading and Rothamsted Research and will bring together unique expertise in wheat biochemistry, bioprocessing, protein science, food ingredient functionality and gut microbiology.

The aim of the proposed work is to develop a process for the transformation of DDGS, produced by distillers and bioethanol factories into arabinoxylooligosaccharides (AXOS) with prebiotic activities, gluten for biodegradable film packaging, nutritional supplements betaine and choline, and crude dietary fibre. The focus of the research will be to use a combination of thermal and alkali treatment followed by physical separation methods, such as absorption and/or ethanol precipitation, to separate DDGS into a soluble stream and then fractionate it into gluten and arabinoxylan (AX) and separate out the betaine and choline. The target is to achieve high recovery yields and purities for each type of product in their respective process streams. The gluten fraction will be characterised by SDS PAGE and HPLC and will be used to produce film packaging. The microstructure, morphology and oxygen and moisture permeability of the films will be studied aiming to produce a product with potential for commercial applications. Betaine and choline will be separated by anion exchange chromatography. AX will be hydrolysed in a control manner by commercial or novel endo-beta-1,4 xylanases to produce AXOS fractions, which will be collected by size exclusion preparative chromatography, and their prebiotic activity evaluated in vitro using the gut model systems at UoR. On the basis of the data from the prebiotic testing, the enzymatic process will be subsequently re-visited targeting the production of a mixture of AXOS with a specific molecular weight range, at high yields, and following that a scalable membrane filtration process will be developed to separate the AXOS from small molecular weight components. The proposed work is innovative as it offers a completely novel approach to the utilisation and upgrade of DDGS, and is technically challenging as the aim is to develop a process that is efficient, scalable and cost effective, which can be transferred into commercial scale.

The research will have a socioeconomic impact to various beneficiaries including: (i) the commercial private sector, mainly companies involved in the production of DDGS by distillers and bioethanol factories, functional food ingredients, nutritional supplements and biodegradable packaging materials, (ii) the UK economy and (iii) the general public.

The transformation of DDGS, which is currently sold as animal feed, into medium and high value products will open up new markets for DDGS producers, more specifically the prebiotics, nutraceuticals and bioplastics markets.

In 2010, the total European food and beverage prebiotics market was valued at 316 million Euro, coresponding to a volume of approximately 100 kt. By 2015, the market is estimated to be valued at about 767 million Euro, with a unit volume of 205 kt and an annual growth rate of 13.7 % (Frost and Sullivan, 2010 report). The market value in the US for prebiotics is currently about $110 million and is expected to double over the next 5 years, whereas in Asia, it was approximately 141$ million in 2009 and is estimated to reach 232$ million by 2014. The market share of arabinoxylooligosaccharides is at the moment much smaller than that of the established inulin, fructooligosaccharides and galactooligosaccharides, but they are the most investigated compounds out of the emerging prebiotics and have attracted a lot of commercial interest over the last five years.


Bioplastics make up about 0.1% of the global market in plastics, which currently stands at about 260 million tonnes per annum, and is predicted that by the end of 2011 this will reach over 1500 kt (HGCA report). Among these, the bioplastics that are used as food packaging materials are mainly starches (~60% of market), cellulose acetate (~15% of market), and polylactic acid (PLA) (~15% of market) (HGCA report). Providing that the production costs are low, gluten-based bioplastics could eventually replace cellulose-based bioplastics as gluten has unique viscoelastic properties and can form films which are good oxygen barriers at low relative humidities.

Betaine has an established market within the nutritional supplements sector, which primarily includes sports nutrition; it is estimated that the betaine market is between 300-400 kt and is growing fast. Choline is mainly used as an animal health ingredient but has promising human applications as a nutritional supplement, as it has been associated with brain and memory health.

Considering the above market volume data and taking also into account the fact that in 2012 800 to 1000 kt of DDGS are expected to be produced annually in the UK, it can be deduced that a significant market potential exists for producing the above components from DDGS. In terms of the economics, currently the cost of DDGS is around £60-100 per tonne whereas the cost of a prebiotic is around £2000-4000 per tonne and the cost of betaine and choline are about £300 to 500 per tonne. The cost of gluten film packaging is likely to be considerably high; for comparative purposes the cost of biodegradable cellulose films is between £1,000-4,000 per tonne. The above figures indicate a potentially large economic impact to the UK economy by the transformation of DDGS through investment and product sales. The success of the project will also increase the possibility for attracting further funding to the UK academia from industry, the UK research councils, or the EU.

The societal and environmental impact of the project will also be significant. DDGS derived gluten plastics are sustainable products that can offer an alternative to synthetic petrochemical plastics, and are also fully biodegradable, which can help reduce waste and pollution. Moreover, the project's outcomes will result in an improvement in the quality of life and the health of consumers, through the development of functional health ingredients that can be incorporated into food products or nutritional supplemnts.