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Laccases
Laccases are oxidoreductases belonging to the multinuclear copper-containing oxidases. Interest in these essentially 'ecofriendly' enzymes has grown significantly in recent years: their uses span from the textile to the pulp and paper industries, and from food applications to bioremediation processes. Laccases also have uses in organic synthesis, pharmaceutical and nanothechnological sectors. These oxidase enzymes catalyse substrates at the expense of molecular oxygen and produce water as the only by-product.
Laccase market
Industrial enzyme market is valued at $2 billion per annum with a potential annual growth rate of 3 to 5%. Laccase stakes in this market is about 40% thus making it a potential $800 million market cap.
Challenges in laccase industrialization
The fungal laccases, most widely used because of the high redox potential, present various drawbacks: they are expensive to produce, slow grower and they are endogenously expressed at very low concentrations. Bacterial laccases represent an attractive alternative to the fungal enzymes, but a substantially lower redox potential limiting their industrial application.
MetGen Solution
MetGen addresses challenges in laccase application by blending structural/functional features of the efficient fungal laccases into robust bacterial protein to produce affordable and efficient lignin degrading enzyme
We design specific set of variations in the amino acid sequence of laccase protein. We construct a DNA sequence library containing all the desired mutations which are further cloned into expression plasmid. Each mutant is thereafter screened against the substrates of interest in all desired conditions in combination with the selected mediators. Positively active candidates are used further as bases for sequence enrichment (additional mutation stages to cumulate positive mutations) and later screening procedures. All these steps yield into new strains expressing optimally mutated laccases for the desired conditions.
MetGen Offers
- Laccase process development using toolbox of MetGen laccases
- Development of tailored enzymes adapted to customer conditions. For further details visit page.
Laccases in Pulp and Paper Industry
In pulp and paper industries, laccases are used for the delignification of woody fibres, particularly during the bleaching process. In most of these applications, laccases are used together with a chemical mediator. The main sources of these lignin degrading enzymes are fungal and bacterial. The fungal laccases obtained from Pycnoporus cinnabarinus, Trametes trogii or Trametes vesicolor present various drawbacks: they are expensive to produce, slow grower and they are endogenously expressed at very low concentrations. Furthermore, the bacterial expression of fungal lignin biodegradation enzymes is not possible and, when expressed as recombinant proteins in yeast, the levels obtained are still 40 times lower than their bacterial counterparts. In addition, the stability and tolerance to hard conditions (high temperatures, extreme pH,…) of these fungal oxidase enzymes are tremendously reduced when compared to bacterial ligninolytic proteins. However fungal laccases display higher oxidation potential for lignin degradation in comparison to the bacterial oxidase enzyme.
The bacterial enzyme for biodegradation of lignin was obtained from Bacillus subtilis and is recombinantly expressed in Escherichia coli. This laccase enzyme can be easily and cheaply overexpressed and fulfill most of the requirements for industrial enzyme applications. Nevertheless, the bacterial laccase activity is still not optimal.
In addition, efficient improvement of the use of ecological mediators with recombinant laccases can be tested in order to offer better reaction yield and less polluting side products.
Laccases in other industrial applications
Several further applications of laccases have been proposed. In organic synthesis, the typical substrates for laccase enzymes are phenols and amines, and the reaction products are dimers and oligomers derived from the coupling of reactive radical intermediates. Specifically, the direct substrate oxidation of phenol derivatives has been investigated in bioremediation efforts to decontaminate industrial wastewaters and soils. The polymeric polyphenolic derivatives that result from the laccase-catalyzed oxidative couplings are usually insoluble and can be separated, easily, by filtration or sedimentation. The selective removal of phenol derivatives is also required for the stabilization of beverages, such as fruit juices, wine and beer, although, here, the enzymes must be immobilized because they have not been approved for use as a food additive. Additionally, a laccase has been commercialized, recently, for preparing cork stoppers for wine bottles, whereby the enzyme oxidatively diminishes the characteristic cork taint and/or astringency that is frequently imparted to aged bottled wine. At present, the main technological applications of laccases are in the textile, dye or printing industries in processes related to decolourisation of dyes. Future potential applications for laccase enzymes could be clean alternatives to expensive and polluting rare metals in fuel cells and batteries.
Oxidation by enzymes with little impact on nature, simplicity of production and usage presents rising interest in the industrial community. Novel industrial applications and development of existing procedures implicating modified laccases could be considered once more robust, highly expressed, more specific for less toxic and natural mediators, and more tolerant for non biological conditions will be produced. Industrial processes such as textile, pulp and paper, food, bioremediation, pharmaceutical and nanobiotechnological processes involving strong pollutants and energy consuming steps could be by-passed or attenuated by the usage of a more 'ecofriendly' modified laccase.
Extras:
Fig.1 Laccase - essentially green catalyst - they work with air and produce water as the only by-product
Fig.2 Laccase mediators
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