Valorisation Proposal of Brewery Spent Grain: Carotenoids and Protein Films Production

The preliminary Brewery Spent Grain (BSG) valorisation proposed is based on the production of cultural media for the growth of the carotenogenic yeast Rhodotorula mucilaginosa; the realisation of protein-rich films is also presented. First experiments, carried out with three BSGs, allowed to define the best extraction set-up, realizing water extraction in agitation (ratio BSG/water= 0.05, at 25 °C, for 2 hrs). Then, using the same water extraction conditions, BSG with the highest total solid content was applied to produce a concentrated syrup (BSG/water= 0.2). Yeast growth and carotenoid production were tested on solid media prepared with water extracts and syrup. Later on, to define the best cultural medium, extracts and syrup were applied in different set of liquid cultures, carried out in 96-well plates, maintained at 25 °C, in agitation. Syrup was utilized as it is or supplemented with inorganic and organic N sources, and the addition of these latter returned better results. Afterward, a scale-up carried out into Erlenmeyer flasks (500 mL) allowed to evidence the possibility of using the syrup as it is for the growth of R. mucilaginosa and carotenoids production. Finally, a high protein content syrup (BSG/water= 0.2), prepared in autoclave (at 121 °C, 2 atm, for 20 min), was evaluated for the production of films: best filming conditions were investigated and amorphous semi-transparent films were obtained.