Selection of hydrolytic enzymes with antifouling activity in seawater

Biofouling represents a severe problem for the shipping industry that needs to have more environmental friendly paints, since several biocides currently used in antifouling coatings are going to be banned by the European legislation because of their poor biodegradability and high toxicity1. Since biofouling starts with the formation of a monolayer of bacterial cells which adhere to surface via biopolymers, hydrolytic enzymes able to degrade natural polymers might prevent bacterial adhesion and biofouling maturation, and might therefore represent potential environmental-friendly antifouling agents2. In this work, the activity and stability of a group of commercially available hydrolytic enzymes in synthetic marine water were characterized, and their ability to reduce biofilm formation by a natural marine microbial community was investigated. A protease, a glycosidase and a lipase were found to display a remarkable specific activity in synthetic marine water (pH 8.0, 25°C), corresponding to 98%, 140% and 62% of their specific activity in buffer under the same conditions, respectively. Mixtures of the 3 enzymes displayed comparable specific activities, except for the lipase activity, that was reduced by 23% in the presence of the protease. In addition, glycosidase and lipase exhibited half lives higher than 56 days in synthetic marine water at 20°C, whereas half life of the protease was 20 days. Finally, none of the three enzymes was able to prevent biofilm formation on microtitre plates by a marine microbial community. However, the mixture of the three enzymes inhibited biofilm growth by 90% as compared to the untreated control, whereas the planctonic growth of microbial community was not affected by enzymes addition. 1EU Biocidal Product Directive, http://ec.europa.eu/environment/biocides/index.htm 2Kristensen et al. 2008. Biotechnology Advances 26, 471–481