Enzymes

Enzymes are biological protein molecules, polymers made from amino acids. They are responsible for catalysing most living processes and essential for all living organisms, both synthesising products and degrading of polymers. The single enzyme is organised in a tertiary structure with an active site, which is responsible for the catalysed reaction. Enzymes are classified according to their specificities and their mode of action, for example they can be hydrolytic and degrade specific polymers (e.g. proteases, glucanases). An enzyme is a catalyst, which means it participates in a chemical reaction but is not used in the process. Therefore the same enzyme molecule can be used over and over again. When incorporated in antifouling coatings they can help weaken the adhesion forces of fouling species. They do this by attacking the adhesive glues used by fouling species, for example barnacles, algae and mussels.

Methodology

Enzymes can be incorporated into antifouling coatings to either resist initial settlement of fouling or to facilitate the removal of fouling.

Key Factors Positive

- Enzymes are very powerful molecules that are able to degrade the glue of fouling organisms at very low concentrations.
- Enzymes are easily biodegraded themselves in nature by microorganisms into amino acids and finally into carbon dioxide and water. Coatings with enzymes therefore potentially provide a “natural”, non-toxic solution to biofouling.

Key Factors Negative

- Only experimental coatings exist, mostly based on enzymes which degrade proteins (proteases) (see for example www.biolocus.com). The formulations tested within CRAB were not sufficiently effective.
- Each fouling species has its own bio-adhesive, which means that a mixture of enzymes would be needed.
- All actives including enzymes are regarded as biocides by the BPD (EU Biocidal Products Directive) so need to go through normal registration procedures (which is a time-consuming and costly process).
- Price could be an issue. Enzymes can be costly.

Cost Benefit

Commercial products have not yet been developed for aquaculture.

Conclusions/ Discussion

Theoretically enzymes are powerful chemicals to be used as active ingredients in net coatings. However, currently in practice their application and efficacy has posed too many challenges to make them commercially viable.