Biorefining Protein from UK Grasslands - Can We Combine Novel Protein with Surplus Bread Crusts to Sustainably Feed Healthier Food to More People?

British grassland farming covers 72% (12.6 million ha) of the utilised agricultural area, supporting 9.7 and 34 million cattle and sheep respectively1. Coupled with the drive towards zero-carbon 2040, diversification away from livestock production and plant-protein imports (e.g. Soya and other pulses) to alternative on-shore grown plant-protein fit for human consumption may provide longer-term environmentally beneficial economic security for UK farmers.

The opportunity for plant-protein production on an existing agricultural level exists within the UK. Approximately 70% of the UK's commercial forage grass (Loillium/Festuca spp. <10% crude protein) and clover (Trifolium spp. <20% crude protein) varieties have been bred at Aberystwyth University (AU). Previous research has demonstrated that this protein is readily extractable as a liquid stream following pressing of grass and/or clover, while the remaining fibre can be used as an animal feed showing nutritional equivalence with the original grass (lamb trials-STARS project AU, beef trials-Aarhus University2,3).

Furthermore, grass contains soluble fructan (-2,1 and -2,6-fructosylpolysaccharides, 20% DM), an effective pre-biotic (AU; UK & European Patent, US patent filed). Red clover juice, also contains secondary metabolites (phytoestrogens and pinitol etc.) with known nutraceutical/functional properties. Both of these perennial crops sequester carbon, while clovers have the added advantage of nitrogen fixation, thereby reducing fertiliser inputs.

A method to convert this protein-rich material into a protein-rich food ingredient and/or product is through co-fermentation processes (e.g. tempeh production). However, most of the native bacteria used are pathogenic (i.e. Klebsiella pneumoniae)4, thus the investigation of alternative co-culture with a GRAS status organism, will not only be of nutritional value, but also regulatory and marketing benefit.

Vegetarian and flexitarian diets are a growing, long-term trend, with the latter achieving 9% growth per annum. Among the future needs of these discerning consumers are a strong preference for non-GM, ethically sourced plant-protein supported by traceable supply chain credentials ensuring environmental and socially responsible farm to fork manufacture.

Samworth Brothers Ltd (SBL) are a leading UK sandwich provider; producing 30-50 tonnes per week of excess bread crusts from their manufacturing operations whose disposal route is as animal feed. Using plant-protein from UK grown crops to keep this bread in the human food chain is a future aspiration of Samworth Brothers.

The development of new protein-rich ingredients involves many challenges to the food industry as the product must have a high nutritional value (amino acid profile and digestibility), no allergenicity, adequate technological properties (e.g. solubility, foamability etc.), acceptable flavour and mouthfeel (astringency). Through co-fermentation anti-nutritional factors can be degraded, protein structures are developed, and other metabolites (vit B12) and flavours (umami) are produced; thus, controlling the substrate, organism and process could help develop a novel biorefining process producing high quality vegetable protein-rich food product(s).

The hypothesis to be tested in this studentship is: Protein-rich juice extracted from forage grass/clover and combined with surplus bread crusts can undergo bioconversion by mixed microbial consortia producing a safe, sustainable, novel human food ingredient from grasslands (fig1). The objectives of this studentship are:

1) Optimisation of extraction, concentration and purification of grass/clover juice rich in protein and nutraceuticals (fructans, phytoeostrogens and pinitol).

2) Development of a biorefining process for protein-rich juice through solid-state Lactobacillus spp., Propionibacterium freundenreichii (GRAS) and Rhizopus spp fermentation, using excess bread crusts as a scaffold (laboratory and pilot plant s