Numerous studies have indicated that fruits and vegetables are considered as significant sources of bioactive compounds. The generated by-products, which are derived from the food industry, reveal similar or higher antioxidant activity. On the other hand, intense industrialization results in the production of large volumes of by-products, raising serious environmental issues. Therefore, this situation creates the necessity to develop new strategies in order to exploit the generated wastes, securing the ability to develop new high-added-value products. This review aims to summarize the exploitation of fruit wastes, namely, apple and citrus, as well as vegetable by-products which are derived from tomato, potato and carrot cultivation. All the aforementioned by-products have found wide applications in the development of new high-added-value products in the food and feed industry owing to their improved nutritional profiles. Furthermore, these wastes are characterized by a strong antioxidant activity, justifying their valorization in other fields such as cosmetics and pharmaceutical industries.

Solid-State fermentation (SSF) is a valuable process used for the enhancement of the nutritional profile of agro-industrial by-products. The main objective of the present study concerns the exploitation of a mixture consisting of Cottonseed Cake (CSC) and Lathyrus clymenum pericarp (LCP) at a ratio of 80–20% w/w, which was utilized as substrate for the initiated by Pleurotus ostreatus SSF process. The final goal is the improvement of their nutritional value and the parallel reduction in their gossypol content. The obtained results revealed a statistically significant increase (p < 0.05) in protein content by 34.91%, while 1,3-1,6 β-glucans exceeded a 5-fold statistically significant increment (p < 0.05) at Day 11. Furthermore, lignin was reduced significantly (−26.71%) at Day 11. Free gossypol’s presence was lowered by 12.45%, while SSF presented a profound effect concerning the total gossypol level since the latter underwent a statistically significant reduction (p < 0.05) that exceeded 9-fold at Day 11. The study herein highlights SSF’s efficiency as a potential means to reduce free and total gossypol content with a parallel upgrade of its nutritional value. The fermentation outcome reveals its potential as a feed supplement and contributes to the reduction in the environmental footprint within the framework of a circular economy.

The present study examined the supplementation of Spirulina platensis (SP) in various ratios in the basal diet of laying hens targeting the determination of the optimum amount that is required for the improvement of egg quality parameters and oxidative stress. A total of 300 24-week-old Lohmann Brown laying hens were selected and kept at a commercial farm (Vasileios Kompoulis Ltd. farm, Megara, Attiki, Greece). The employed farm was supplied with 25 similar cages. The control group was fed the basal diet, whereas the experimental feedstuff was fortified with SP by 0.1, 0.2, 2 and 5% w/w. At the end of the trial the addition by 5% w/w improved the egg weight, the yolk color, carotenoids, protein content and enhanced the eggshell strength. Additionally, the specific treatment improved the oxidative stress of the employed laying hens by recording the lowest values in TBARS and CARBs content. On the contrary the fortification with 5% w/w enhanced TAC, GSH and CAT activity. Overall, SP addition forms an intriguing approach for the improvement of the performance, physiology, and health of laying hens, with a parallel contribution to the development of more sustainable and viable feed ingredients for poultry production systems.