Fractionation and exploitation of the component value of DDGS

Some fermentation processes, eg brewing, use cereal starch as their source of carbohydrate. Typically, the residue of the cereal grain is not separated until the end of the fermentation process. In distilleries or in processes designed to produce alcohol for fuel, the liquid stream then goes through distillation which leaves a liquid residue ("thin stillage"). In large scale operations, the liquid and grain residues are dried to produce "distillers dried grain and solubles" (DDGS) which can be used as animal feed. In the UK, at least 2 large-scale wheat to alcohol plants will soon be operating. These will convert low-grade feed-wheat (of which the UK typically has a surplus) to alcohol for use as an automotive fuel, co-producing large quantities of DDGS, of a fairly consistent composition. The industrial members of IBTI have set a challenge of adding value to this DDGS, which this project addresses.
Apart from the starch, cereal grain is composed mainly of protein, fibre and other non-starch carbohydrate and fats. The main animal feed value is contained in the protein, but the high fibre content means that DDGS is only useful for ruminant animals. In this project we intend to separate some of the protein, carbohydrate and fats and use them to produce higher value products, while still retaining the option to use the protein component as an animal feed, possibly for poultry. The latter is important as using DDGS as animal feed replaces imported soybean and thus, can reduce the greenhouse gas (GHG) emissions associated with soybean production and importation. Therefore, the challenge breaks down into 2 parts: 1) devising methods to remove the non-starch carbohydrate and fat from the DDGS without destroying the feed value, and 2) finding ways to gain added value from the extracted components. For the first part we have assembled a multidisciplinary team who are experts in addressing the engineering, biological and animal nutrition components of this project. From a process engineering perspective it would actually make sense to use the separated distiller's grain, before addition of the "solubles", as our starting material. This would be difficult to obtain, so we will recover the grain component from the DDGS. Removal of the fats could be done with an organic solvent, but this might leave undesirable residues in the animal feed. As an alternative we will investigate the use of super-critical carbon dioxide (SCCO2) extraction; a gentle, residue free method used for making decaffeinated coffee. The fibre and other carbohydrates will be removed mainly with enzymes, but we will need to find gentle physical pre-treatments (hot water or a short steam treatment) to facilitate enzyme access to the carbohydrates.
In (2), we will focus on upgrading the carbohydrate and protein components. The carbohydrate could be used in a second fermentation process, if an organism was available that could convert the carbohydrates to useful products. To reduce the cost of this process we would need to find/create an organism that could use most of the carbohydrate polymers directly, rather than adding separate enzymes, so this part of the programme will focus on identifying suitable enzymes and the genes that encode them to put into established process organisms. Producing additional fuel or other chemicals by a secondary fermentation will not only improve the economics but also the GHG balance of the process. The proteins contained in wheat grain are rather specialised in their make-up, having a high frequency of certain amino acids. Availability in large volumes offers a unique opportunity to make specific chemicals, and the feasibility of exploiting this renewable chemicals approach will comprise a second strand of activity. If successful, this will also have a GHG benefit.
Together with projected uses of the fatty fraction we will combine data from the whole exercise into an economic model for independent evaluation by potential users.

The large scale availability of DDGS from UK feed-wheat based bioethanol plants provides an opportunity to consider enhancing its value. DDGS is made by separating the residue of the wheat grain, post-fermentation (distillers grain) with a "solubles" syrup created by concentration of the "thin stillage" recovered post-distillation. We argue that the best place to add value is to extract material at the distillers grain stage. Furthermore, we maintain that extraction should be gentle enough to maintain the animal feed value of the protein in the residue, once combined with the "solubles". For reasons of practicality we will initially use a surrogate "distillers grain" by recovering the solids from DDGS, but through collaborations with Vivergo, may be able to access the real product as the project progresses.
The ultimate aim is to extract fat/oil using supercritical CO2, use the distillers grain in a second fermentation by hydrolysis and microbial metabolism of the non-starch carbohydrates and use some of the protein in biocatalytic upgrading to defined chemical products. In the first stage of the project, where we will be developing methods to extract fat/oil, release and hydrolyse the carbohydrate and selectively metabolise certain protein components, we will benchmark the suitability of the methods by the level of retention of the animal feed value of the residue. Not only do we intend to retain the feed value, but also investigate whether it can be enhanced for use with poultry, having removed the bulk of the fibre. We believe that there is scope for novelty in the use of explosive decompression in SCCO2 treatment, to open up the grain structure to enzyme action.
In the second part of the programme we will develop new metabolically versatile bacterial strains able to degrade most of the non-starch carbohydrate and convert it to 1-butanol, and selective proteolytic and tandem biocatalytic methods to convert part of the protein to value-added chemical products.

Who will benefit from this research? This is a full proposal invited based on an outline submission to the IBTI club. As an industry club, the immediate beneficiaries will be the club members who have contributed to its foundation, some of whom have a direct interest in increasing the value of DDGS arising from first generation biofuel production while others have a broader interest in thermophilic bacteria and/or producing chemicals from renewables. In the longer term, if we can gain added value from DDGS such that the economics of first generation wheat to ethanol processes are improved, a second group of beneficiaries will be UK farmers who will gain a stable alternative market for their feed wheat. Given that we intend to produce additional products from the DDGS, including running a second fermentation, this will dramatically improve the greenhouse gas balance of a "wheat to ethanol + other products biorefinery". Through displacement of the use of fossil hydrocarbons for this purpose, the wider environmental benefit will help UK government reach its mandated targets and, more importantly, help reverse the trajectory of global warming which threatens social and economic disruption. In addition, the residual material that will be produced is likely to be of increased feed value for pigs and poultry compared with traditional DDGS because of its reduced fibre content. This will enhance its value as a protein supplement in pig and poultry diets and thereby reduce the reliance of the animal feed industry on imported soyabean meal. This will further increase the environmental benefit of UK-based wheat to ethanol production.
How will they benefit? Industrial club members of IBTI will benefit via a number of routes. Firstly, club members have first refusal on the right to license an IP arising from the programme. Secondly, they will get the opportunity to see documents prepared for publication in advance of submission. In this way they will get a unique opportunity to secure any unforeseen IP contained in the work. Finally, by attending dissemination meetings (see below) they will gain access to early stage results in the research programme, which could assist their own research. This benefit could be realised within the next 5 years. UK farmers will benefit through market stabilisation and subsequent long term supply contracts, giving them the confidence to expand their activities, potentially in a 5-7 year timeframe. The global development of biorefineries which supplant fossil fuel usage and some imports, will ultimately benefit us all by reduction of net CO2 emissions. The timescale of this depends on other factors, outside of our control. PDRAs on the project will gain valuable experience on working on feedstocks in the context of a biorefinery and the interdisciplinary nature of the team.
What will be done to ensure that they have the opportunity to benefit? IBTI runs meetings at 6 monthly intervals where the results of IBTI funded research are presented under an agreement of confidentiality. This provides early access for IBTI club Industrial members to arising results. IBTI club members will also get sight of any documents planned for publication, 4 weeks prior to submission. We will also use the forum of IBTI meetings to explore the opportunity to add value to this work by internal collaboration with IBTI funded groups, and use our links in BSBEC to look for further synergies, given the overlap between biofuel production and chemicals from biomass.
Any IP arising from work done within the programme will be secured by Imperial Innovations on behalf of the consortium members. Funding through IBTI will create a contractual obligation to offer licences to IBTI club companies in the first instance and, given their remit, Imperial Innovations will actively pursue the possibility of licensing the technology as rapidly as possible. The PI and CoIs all have experience of working with Industry (see Pt1A of the proposal).