38 DECEMBER 2022 • WORLD AQUACULTURE • WWW.WA S .ORG because of their toxicity. Biokos is a new natural agent that can fill the need for an effective solution to Ich in aquaculture as well as in ornamental fish. It is a cyclic lipopeptide that kills the Ich parasites by affecting their cellular membrane integrity. Here we have shown that Biokos at very low concentrations can cure goldfish from Ich infection, confirming similar earlier results with rainbow trout. We have also shown that Biokos does not affect the health and functionality of biofilter bacteria needed for conversion of ammonia to nitrate. This means that it can be applied to RAS systems (and ornamental fish tanks) without problems for fish or biofilter health. Finally, we have shown that microorganisms in mature aquaculture and fish tank water will inactivate and degrade Biokos within hours or days into harmless components. Application of Biokos is expected to be as solid formulation tablets (Fig. 6). These studies demonstrate that Biokos can be an efficient and effective remedy for large-scale use in foodfish aquaculture and in the ornamental fish industry. Acknowledgments We thank GUDP (Grønt Udviklings- og Demonstrations Projekt), The BioInnovation Institute, and Vækstfonden (the Danish Growth Fund) for funding. We thank collaborators at University of Copenhagen Collaborators and the Blue Planet public aquarium for help and discussions. Notes M.J. Hansen, F. Mehrdana, E.H. Hansen, G. Salerno and J. Hansen Sundew ApS, Ole Maaløes Vej 3, DK-2200 Copenhagen N, Denmark. Email: info@sundew.bio References Al-Jubury, A., C. Lu, P.W. Kania, L. von G. Jørgensen, Y. Liu, I. de Bruijn, J. Raaijmakers and K. Buchmann. 2018. Impact of Pseudomonas H6 surfactant on all external life cycle stages of the fish parasitic ciliate Ichthyophthirius multifiliis. Journal of Fish Diseases 41:1147–1152. D’Costa, V.M., T.A. Mukhtar, T. Patel, K. Koteva, N. Waglechner, D.W. Hughes, G.D. Wright and G. De Pascalea. 2020. Inactivation of the lipopeptide antibiotic daptomycin by hydrolytic mechanisms. Antimicrobial Agents and Chemotherapy 56:757-764. Korbut, R., L.M. Skjolding, H. Mathiessen, R. Jaafar, X. Li, L. von G. Jørgensen, P.W. Kania, B. Wu and K. Buchmann. 2022. Toxicity of the antiparasitic lipopeptide biosurfactant SPH6 to green algae, cyanobacteria, crustaceans and zebrafish. Aquatic Toxicology 243:106072. Li, X., R. Jaafar, Y. He, B. Wu, P.M. Kania and K. Buchmann. 2022. Effects of a Pseudomonas H6 surfactant on rainbow trout and Ichthyophthirius multifiliis: In vivo exposure. Aquaculture 547:737479. Liu, Y., E. Rzeszutek, M. van der Voort, C. Wu, E. Thoen, I Skaar, V. Bulone, P.C. Dorrestein, J.M. Raaijmakers and I. de Bruijn. 2015. Diversity of aquatic Pseudomonas species and their activity against the fish pathogenic oomycete Saprolegnia. PLoS ONE 10(8): e0136241. Mathiessen, H., M.H. Marana, R. Korbut, B. Wu, A. Al-Jubury, A.M. Karami, P.W. Kania and K. Buchmann. 2021. Inflammatory reactions in rainbow trout fins and gills exposed to biocides. Diseases of Aquatic Organisms 146:9-21. Nielsen, T.H. and J. Sørensen. 2003. Production of cyclic lipopeptides by Pseudomonas fluorescens strains in bulk soil and in the sugar beet rhizosphere. Applied Environmental Microbiology 69:861-868. FIGURE 6. The Biokos product formulated into dosing tablets.
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