Upcycled Animal Feed: Sustainable Solution to Orange Peels Waste

Currently, in an effort to increase their sustainability and reduce their carbon footprint, industries look for ways to valorise their waste instead of simply treating it. At the same time, food insecurity is increasing with alarming rates and thus solutions are sought. To this end, the main objective of this paper was to optimise an innovative valorisation strategy to turn orange juice industry by-products into high-value secondary feedstuff for animals. In this context, a valorisation strategy was designed where a saccharification step of the orange peels and an aerobic fermentation step of the liquid residue were included. Both processes were optimised via factorial deign. The saccharification process was optimised in terms of pectinolytic and cellulolytic enzymes and solid loading, whereas the aerobic fermentation method was optimised in terms of nutrients addition, the yeast to glucose ratio, and pH control. According to the optimised conditions, the final animal feedstuff should be formulated by mixing the solid residue of orange peels after the saccharification process under the optimum conditions (50 °C, 24 h, 7.5% solids loading, Pectinex 25 μL/g TS, CellicCTec3 25 μL/g TS), with the harvested yeast cultivated aerobically on orange peels hydrolysate (30 °C, 24 h, orange peels hydrolysate as sugar source, nutrients addition, yeast to glucose ratio equal to 0.02). Finally, the formulated feedstock should be dried in order to stabilise the product in terms of shelf life and feed safety. The final feedstuff presented 23.11% higher in vitro organic matter digestibility and threefold protein content.