Isolation, Identification and Investigation of Fermentative Bacteria from Sea Bass (Dicentrarchus labrax): Evaluation of Antifungal Activity of Fermented Fish Meat and By-Products Broths

High-added-value compounds recovery from supercritical fluid extraction-defatted European sea bass (Dicentrarchus labrax) viscera by lactic acid bacteria (L. plantarum and L. casei) assisted fermentation

In this study, supercritical-CO2 (25.0 MPa, 40 °C, 75 min, 10.0 mL/min) was used to defeat sea bass viscera to facilitate the fermentation process. Then, the defatted samples were used as raw material to be fermented by lactic acid bacteria (Lactobacillus plantarum and Lactobacillus casei) over 72 h. After fermentation, solid matrices and supernatants were separated by centrifugation and analyzed for protein content, bioactive peptides, and minerals. Both LAB strains significantly (P < 0.05) increased protein content (24.9 % and 27.4 %) in the supernatants. Six bioactive peptides were identified, demonstrating antioxidants, anti-inflammatory, anticancer, antithrombotic, immunomodulatory, and hypolipidemic properties. Some 28 antioxidant peptide sequences were found, especially for EL (glutamic acid-phenylalanine) and KD (lysine-aspartic acid). Moreover, the mineral results showed the possibility of mineral accessibility, while the LAB strains also notably enhanced the antioxidants of the supernatants. This study highlights the potential of fish side streams in generating bioactive compounds through fermentation.

Obtaining Antioxidants and Natural Preservatives from Food By-Products through Fermentation: A Review

Industrial food waste has potential for generating income from high-added-value compounds through fermentation. Solid-state fermentation is promising to obtain a high yield of bioactive compounds while requiring less water for the microorganism’s growth. A number of scientific studies evinced an increase in flavonoids or phenolics from fruit or vegetable waste and bioactive peptides from cereal processing residues and whey, a major waste of the dairy industry. Livestock, fish, or shellfish processing by-products (skin, viscera, fish scales, seabass colon, shrimp waste) also has the possibility of generating antioxidant peptides, hydrolysates, or compounds through fermentation. These bioactive compounds (phenolics, flavonoids, or antioxidant peptides) resulting from bacterial or fungal fermentation are also capable of inhibiting the growth of commonly occurring food spoilage fungi and can be used as natural preservatives. Despite the significant release or enhancement of antioxidant compounds through by-products fermentation, the surface areas of large-scale bioreactors and flow patterns act as constraints in designing a scale-up process for improved efficiency. An in-process purification method can also be the most significant contributing factor for raising the overall cost. Therefore, future research in modelling scale-up design can contribute towards mitigating the discard of high-added-value generating residues. Therefore, in this review, the current knowledge on the use of fermentation to obtain bioactive compounds from food by-products, emphasizing their use as natural preservatives, was evaluated.

Bio-Preservative Potential of Microorganisms Isolated from Red Grape against Food Contaminant Fungi

Fungal spoilage is one of the main reasons of economic losses in the food industry, especially in the wine sector. Consequently, the search for safer and new preservation techniques has gained importance in recent years. The objective of this study was to investigate the antifungal and anti-mycotoxigenic activity from 28 microorganisms (MO) isolated from red grape. The antifungal activity of a cell free supernatant of fermented medium by the isolated MO (CFS) was tested with the agar diffusion method and the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) assay. Additionally, different antifungal compounds from the CFS were identified and quantified (organic acids, phenolic compounds, and volatile organic compounds). Finally, the most active CFS were tested as red grape bio-preservative agents. Results evidenced that CFS fermented by the strain UTA 6 had the highest antifungal activity, above all isolates, and produced a wide pool of antifungal compounds. The use of UTA 6 CFS as bio-preservative agent showed a reduction of 0.4 and 0.6 log₁₀ spores per gram of fruit in grapes contaminated by A. flavus and B. cinerea, respectively. Moreover, UTA 6 CFS treatment reduced the occurrence of aflatoxin B₁ and fumonisin (B₂, B₃, and B₄) production in grapes contaminated by 28-100%.