20 October 2010
Cross-linked enzyme aggregates have great potential in marine antifouling paints claim Danish scientists.
Paints with antifouling activity are used in the marine industry to prevent undesirable accumulation of microorganisms, plants and animals on ship surfaces below the waterline. Previously tributyltin self-polishing copolymer (TBT-SPC) paints have been used however they were banned in January 2008 due to environmental regulations.
The main alternatives are copper-based paints but these also cause concern for the environment. Consequently it non-toxic alternatives are desirable which is where enzymes can have a niche explains Stepan Shipovskov at Aarhus University, Denmark.
Enzymes can interact directly with microorganisms on the ships surface but organic solvents, such as xylene, are the main base of paints and can inactivate the enzymes. Shipovskov and co-workers tested cross-linked enzyme aggregates (CLEAs) of proteases in artificial sea water and found that they are tolerant to xylene and have great stability in dried paint. Shipovskov explains that 'a stabilisation effect occurs due to the covalent linking between enzyme molecules which prevents enzyme inactivation in organic solvents'.
Environmentally friendly paints for boats use enzymes instead of metals
Additionally, activity of the enzymes becomes 9 times higher when it is immersed in artificial sea water, says Shipovskov. The level of paint hydration continuously increases in seawater leading to an increased amount of molecules leaching from the paint surface, and the cross-linking in the enzyme increases the efficiency of the catalyst, he explains.
Peter Halling at the University of Strathclyde, UK, who researches the use of enzymes in industrial processes, comments: 'CLEA's are a well known method to stabilise enzymes and [this work] is an interesting application and worth researching further.'
Shipovskov now plans to text how long the paints remail active for, 'the technological requirement for antifouling paints is for them to remain active for at least 1 year for private yachts and 6 years for commercial vessels. Therefore, it is crucial to obtain an adequate antifouling effect in addition to the required lifetime,' he says.