Biochemical analysis and antimicrobial potential of Mastacembelus armatus epidermal mucus

The epidermal mucus of fish plays an important role in innate immunity, providing both physical and biochemical protection through a complex matrix of bioactive molecules. The present study explored the biochemical characterization, bactericidal, and fungicidal activities of Mastacembelus armatus (Zig-Zag eel) epidermal mucus treated with Aeromonas hydrophila. Extracts of epidermal mucus (ethanolic and acidic) of Mastacembelus armatus showed antimicrobial activity against selected resistant bacteria and fungi. The zone of inhibition (ZOI), which was measured in millimetres, revealed differences in activity between different fungi and bacteria. The acidic extract demonstrated noticeably higher ZOI values against various MDR bacteria and fungi was more effective than the ethanolic extract. Strong peaks in the Fourier transform infrared (FTIR) spectrum of Mastacembelus armatus indicated the presence of metabolic components in the epidermal mucus. The O-H and N-H stretching vibrations, which are indicative of water content and protein-based molecules such as mucins or amide, are shown by a large peak at 3272.60 cm^-1. This result suggests that fish epidermal mucus has the potential to contribute enormously to the defence of fish against bacteria and fungi. Therefore, this study could be evidence in favour of the substitution of chemical antibiotics with fish epidermal mucus as a new 'antimicrobial' introduced in aquaculture and in humans against bacterial infections.