The development of a silage-based biorefinery to deliver the maximum nutritional benefit for human consumption from UK grasslands

Abstract

In this work we aimed to increase the food potential of UK pasture by coupling targeted mechanochemical processing and novel biotechnology to convert silage into edible protein and lipid fractions. To this end, the water-soluble protein and vitamins were extracted from silage using a twin-screw extruder at room temperature. The extrusion of the silage was optimized in water with no additional chemicals. Under optimal conditions, 22 wt% of the silage was solubilized, with this fraction containing 52% of the protein present from the original material. The protein contained key essential amino acids with a profile similar to soy protein. Vitamins B₁, B₂, B₃ (nicotinamide and nicotinic acid) and B₆ (pyridoxine, pyridoxal and pyridoxamine) were also extracted. The resulting solids from the extruder, which contained further insoluble protein and the carbohydrates from the silage, were then depolymerized and used to culture the oleaginous yeast Metschnikowia pulcherrima producing further mycoprotein and lipid from the system. The mycoprotein contained a balanced amount of vital amino acids, while the yeast lipid had a fatty acid profile containing high levels of monounsaturated lipids. The silage was also found to contain high value lipids, rich in omega-6 linolenic acid. The work presented here represents a preliminary study but highlights the possibility of extracting edible nutrients from grass feasibly, with the potential to make UK agriculture far more resilient and sustainable.This article is part of the theme issue 'Transforming terrestrial food systems for human and planetary health'.

Keywords: fermentation; grass; lipid; mechanochemical; protein; yeast.

Figure 1.

Flow chart demonstrating the ‘pasture to plate’ concept producing three food products from silage including a grass protein fraction with further soluble nutrients, a mycoprotein and myco-lipid fraction.

Figure 2.

The amino acid composition of the essential amino acids, as a percentage of the total essential amino acids, for the silage used in this study, protein extract of silage (*), M. pulcherrima and examples of staple and alternative proteins.

Figure 3.

The single-factor analysis (A) and response surface plot (B) of the silage extrusion for protein extraction.