With the global population on the rise, meeting the demand for protein has become paramount. Fish, being a rich protein source, has seen an increase in production, both through wild-catch and aquaculture. However, this surge in production has led to a corresponding increase in fish waste, with approximately 50% of processed fish being classified as by-products. Among these, tuna meal, a protein-rich leftover, is used in aquaculture in the fish meal. In this study we are trying to improve the nutritional value of the tuna meal by microbial fermentation. Then fermented product will be used in a feeding trial for barramundi to see the impact of repurposed tuna meal and non-reproposed tuna meal on the protein profile of the fish brain, liver and intestine. The intricate interplay between gut-brain peptides, microbial metabolites, and appetite regulation will provide valuable insights into the regulation of feeding behaviour of the fish.
Initially, the study evaluated the most effective extraction and fractionation method for characterizing tuna meal using shotgun proteomics. The results demonstrated that employing TCA-Acetone/Methanol-Chloroform, followed by HpH fractionation, enabled the identification of 923 proteins and 3020 peptides in tuna meal. Subsequently, tuna meal underwent controlled fermentation using Lactobacillus plantarum and Bacillus Sabtilis. This process aimed to assess the proteolytic capabilities of different microorganisms in hydrolyzing proteins and enhancing the amino acid profile of the tuna meal. Protein extraction was performed on both the fermented and non-fermented tuna meal, employing molecular cut-off sizes of 10 kDa and 5 kDa to filter out small proteins and peptides for further analysis. The protein extract was then subjected to a 60-minute gradient on the Orbitrap Exploris 480 for comprehensive evaluation.
The second phase of the study involves collecting samples of brain, liver and intestine from farm raised barramundi fed on different diets. Proteomic analysis will be performed on tissue samples, with the aim of discerning how different formulations of protein in the diets can have an effect on protein expression in tissues.
Keywords: Shotgun proteomics, Tuna meal, Bioactive peptides, Fermentation, L.plantarum, B. Sabtilis