The antibacterial activity of fish skin mucus with various extraction solvents and their in-vitro evaluation methods

Epidermal mucus is known to facilitate fish survival due to its multifunctional barrier with various cellular and humoral components, especially to combat invading pathogens. The research on the antibacterial properties of fish skin mucus has been expanding over the years, with more refined protocols being developed and more fish species being investigated. The vast information generated from these researches requires a systematic and comprehensive review, to provide consistent knowledge and guidelines for researchers to effectively apply in their research in future. This article reviewed the protocols relating to the fish epidermal mucus collection and extraction. The collection of mucus was further categorised into destructive and non-destructive ways, and the extraction methods were divided into three major types, namely aqueous, organic and acidic. The commonly- used antibacterial bioassays (i.e. agar disk diffusion, agar well diffusion, broth micro-dilution, bacterial cell growth curves, etc.) of the fish mucus against a total of 46 bacterial species were also discussed. Despite the methodological variation, slight modifications of the standardized protocols are warranted for a better experimental approach. The antibacterial effectiveness (bactericidal activity) of fish epidermal mucus extracts was exhibited by 47 fish species from three out of the five classes, which suggests their great potential in aquaculture and possibly in human-health applications. To acquire a deeper understanding of fish epidermal mucus, it is imperative to conduct purification and characterization of its antimicrobial components. Copyright © 2020 The Author(s).