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An amazing enzyme by directed evolution

Scientists at the CSIC have obtained a laccase enzyme which can have very different uses: from fuel cell to oxygen detection, bioremediation or ecological pulp bleaching.

The enzime is blood tolerant therefore can be used in biomedical implants. It can also be used in fuel cells, oxygen detection, bioremediation or ecological pulp bleaching.Laccases enzymes with high redox potential (high capacity for producing  reduction- oxidation reactions) happen naturally in white rot fungi. These enzymes are considered the ecological biocatalysts of the future, as they can oxidize hundreds of molecules using the oxygen from the air and releasing it just water. Nevertheless, they are naturally adapted to environments with very acidic pH, therefore they are not functional at neutral or slightly alkaline pH. That prevents their use in biotechnological sectors like biomedicine or environmental decontamination.

Scientists at the Instituto de Catálisis y Petroleoquímica of the CSIC have obtained a laccase enzyme through directed molecular evolution. This methodology is based on the introduction of random mutations and recombinations into the enzyme genes; afterwards, the modified enzymes are introduced into an artificial environment, with conditions selected by the scientists. It is like reproducing the natural evolution process in a test tube and addressing it towards goals which don’t exist in nature.

Miguel Alcalde, researcher at the CSIC and leader of the project, explains: “After several cycles of forced evolution in the laboratory, we obtained a new enzyme which was active at conditions of slightly alkaline pH and high concentration of mineral salts. These are the conditions given in blood and human plasma, and where normally fungal lacasse enzymes are not functional”.

It has been obtained by directed evolution, which is like reproducing and forcing the natural evolution process in a test tube

With the newly modified enzyme, scientists are developing a first application: a biological battery which is composed of a cathode, which includes the modified enzyme, and an anode, with a different enzyme. In this battery, the lacasse enzyme is capable of taking the electrons that come from the anode, where another enzyme oxidizes blood glucose. This generates a continuous electrical flow that can power small devices such as biosensors. The bio battery has been implemented in an implantable nanodevice to detect several molecules in blood, like glucose and oxygen. The device is being developed in the European project 3D-nanodevice of the VII Frame.

Uses

The modified enzyme can be used as well in biosensors for detecting oxygen in physiological fluids, says Miguel Alcalde. Another interesting use is in the paper industry. In nature, adds the scientist, these enzymes participate in wood lignin degradation in very acidic environments. The modified enzyme, which can be functional at neutral pH, could be used to degrade lignin at some stages of the pulp bleaching process. Also it could be used in bioremediation processes, as the enzyme has the capacity of degrading Polycyclic aromatic hydrocarbons (PAH’s), pollutants related to the use of fossil fuels.

The laccase enzyme can be expressed in yeast Saccharomyces cerevisiae and Pichia pastoris, which guarantees its production in enough quantities. The enzyme has been patented by the CSIC. Nowadays, companies interested in developing and commercializing devices with the new modified enzyme are sought.

Results of this work were published in the magazine Chemistry & Biology (Maté et al. 2013 20: 223-231).

Contact:

Sara Junco Corujedo
Instituto de Catálisis y Petroleoquímica del CSIC
Tel.:  34 - 91 585 46 33
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Scientists at the CSIC have obtained a laccase enzyme which can have very different uses: from fuel cell to oxygen detection, bioremediation or ecological pulp bleaching.