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Toxic drying agents used in paints and coatings may soon be swapped with an environmentally friendly option, according to a group of Austrian researchers.
While most effective, traditional cobalt-based catalysts used in water-based paints to dry alkyd resins have been proved to be carcinogenic, according to researchers at the Austrian Centre of Industrial Biotechnology in Graz, Austria.
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Though more research is needed, a laccase-mediator system may be a non-toxic alternative to colbalt-based drying agents.
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In looking for non-toxic alternatives, the team says it has demonstrated that a laccase-mediator system can work in lieu of the colbalt-based catalyst as a drying agent.
The team's research, "Banning toxic heavy-metal catalysts from paints: enzymatic cross linking of alkyd resins," was recently published in the journal Green Chemistry.
Turning to Nature’s Enzymes
Laccases are copper-containing enzymes found in many plants, fungi and bacteria and are known to catalyze the oxidation of phenolic substrates, according to a report on the research in Chemistry World. The report notes that laccases are already used in a variety of fields, including the textile, food, and the pulp and paper industries.
In their research, the scientists used 1-Hydroxybenzotriazole as a mediator for the enzyme, which proved to be “effective” for laccase in the oxidation of the alkyd resin, the researchers said. A mediator is described as “small molecule that can be used to broaden the substrate scope of an enzyme by acting as an ‘electron shuttle’ between the enzyme and substrate,” according to the report.
More Research Needed
The laccase-mediator system performed “remarkably well” but was “not as fast” as the cobalt-catalyzed drying process, according to the report. The team found that the laccase-mediator reaction worked in aqueous media as well as solid film, where enzyme diffusion is limited.
“Within the catalytic cycle, the mediator oxidizes the alkyd resin and is regenerated by the laccase, which is uniformly distributed within the drying film as evidenced by confocal laser scanning microscopy,” according to the research description.
However, the scientists note that further researcher is needed into the “kinetics of the reaction.”
Moreover, the team plans to utilize a new optical sensor that monitors oxygen consumption during the cross-linking reaction to search for “novel mediators with higher performance and from renewable sources,” Chemistry World reported.
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