Solid-state fermentation as green technology to improve the use of plant feedstuffs as ingredients in diets for European sea bass (Dicentrarchus labrax) juveniles

The fish trial was performed following the ARRIVE (Animal Research: Reporting of In Vivo Experiments) Guidelines for Reporting Animal Research, and was approved by the ORBEA Animal Welfare Committee of CIIMAR (ORBEA; reference ORBEA_CIIMAR_27_2019) according to the European Union directive 2010/63/EU and the Portuguese Law DL 113/2013.This study aimed to evaluate the utilization by juvenile European sea bass of a SSFed PF mixture with Aspergillus niger CECT 2088. A 22-day digestibility and a 50-day growth trial were performed testing four diets, including 20 or 40% of an unfermented or SSFed PF mixture (rapeseed, soybean, rice bran, and sunflower seed meals, 25% each). SSF of the PF added cellulase and β-glucosidase activity to the diets. Mycotoxin contamination was not detected in any of the experimental diets except for residual levels of zearalenone and deoxynivalenol (100 and 600 times lower than that established by the European Commission Recommendation-2006/576/EC). In diets including 20% PF, SSF did not affect growth but increased apparent digestibility coefficients of protein and energy, feed efficiency, and protein efficiency ratio. On the contrary, in diets including 40% PF, SSF decreased growth performance, feed intake, feed and protein efficiency, and diet digestibility. SSF decreased the intestinal amylase activity in the 40% SSFed diet, while total alkaline proteases decreased in the 20% and 40% SSFed diets. Hepatic amino acid catabolic enzyme activity was not modulated by SSF, and plasma total protein, cholesterol, and triglyceride levels were similar among dietary treatments. In conclusion, dietary inclusion of moderate levels of the SSFed PF, up to 20%, improves the overall feed utilization efficiency without negatively impacting European sea bass growth performance. The replacement of PF with the SSFed PF mixture may contribute to reducing the environmental footprint of aquaculture production.This study was funded by the Ocean3R project (ref. NORTE-01-0145-FEDER-000064) within the research line “Decarbonising our waters and ocean”, founded by the Northern Regional Operational Programme (NORTE2020) through the European Regional Development Fund (ERDF). This research was also supported by national funds through FCT—Foundation for Science and Technology within the scope of UIDB/04423/2020 and UIDP/04423/2020 and through a BioTecNorte operation (NORTE-01-0145-FEDER-000004). Lúcia Vieira was supported by the grant Ocean3R-HP-2021-029, Diogo Filipe by an FCT grant (2020.05525.BD), Rui Magalhães by an FCT grant (SFRH/BD/115870/2016), Nicole Martins by an FCT grant (SFRH/BD/137919/2018), and Marta Ferreira by an FCT grant (SFRH/BD/143614/2019).