This study investigated the design of a tray bioreactor for solid-state fermentation, applying Rhizopus oryzae to oilseed meals as the substrate. Two process variables were continuously monitored in the bioreactor to ensure precise control of the environmental conditions: temperature and relative humidity (RH). The comprehensive analysis covered the effects of different fermentation conditions on the protein content, technological properties, and molecular distribution of the samples. The study revealed that the configuration factors suffered a stratification within the three trays of the bioreactor. Notably, the upper tray registered the largest dispersion, with a range of 1.5 °C. When analyzing the differences between sensors within each tray, the largest difference was found in the lower tray (10.9%). Furthermore, higher EAI (Emulsifying Activity Index) values were observed in the upper tray (T3) for rapeseed. As for ESI (Emulsion Stability Index) values, no differences were observed between the trays or fermentation periods. Using the changes induced by Rhizopus oryzae fungal enzymes, the study quantitatively examined the changes in the by-product valorization. While the bioreactor factors did not affect the protein quantity itself, they had significant impacts on specific changes within the molecular weight protein fraction. The findings of this study offer significant insights into the complex dynamics of solid-state fermentation processes. The outcomes of this study not only advance understanding of solid-state fermentation but also offer practical guidance for the design and operation of fermenters in industrial applications.

This study explores the development of functional fermented beverages using fibre-rich residues derived from olive pruning, vineyard pruning, chicory root, and red onion, obtained after subcritical water extraction of polyphenols. Two microbial strains, Lactiplantibacillus plantarum and Bacillus subtilis, were evaluated for their fermentation performance across different fibre matrices, with and without sugar supplementation. Key parameters including microbial growth, pH evolution, and reducing sugar content were monitored, and Lactiplantibacillus plantarum showed superior acidification and viability (>9 log CFU/mL), especially in sugar-enriched formulations, while Bacillus subtilis showed a limited performance. Based on fermentation efficiency, three sugar-supplemented formulations were selected to scale-up: olive pruning fibre and vineyard pruning fibre fermented with Lactiplantibacillus plantarum and olive pruning fibre fermented with Bacillus subtilis. Red onion fibre extract was excluded from scale-up experiments due to its high viscosity, which made it impossible to measure reducing sugars, consistent with its high water-holding capacity. Fermentation significantly increased antioxidant capacity, reaching up to 750 µmol Trolox equivalents/L and 18 mg of gallic acid equivalents/L in L. plantarum-fermented samples, confirming microbial release of bound phenolics and formation of bioactive metabolites. The resulting beverages were microbiologically stable (final pH < 4.5), sensorially acceptable, and potentially antioxidant-rich, supporting their role in sustainable food system development and circular bioeconomy.