Cross-linking of multi-enzyme aggregates - Combi-CLEAs of two laccases with broadened pH-spectrum
(2011) 5th European Bioremediation Conference — Location: Chania, Greece (4.July.2011)
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- Authors
Agathos, Spiros N. 
- Abstract
- The immobilization of enzymes is one of the prerequisites for their successful application in industrial processes as it often improves desired properties such as stability. Furthermore, immobilization of enzymes facilitates their retention in reactor systems as well as their reuse. Beside carrier-based immobilization approaches, the cross-linking of enzyme aggregates (CLEAs), developed by the group of R.A. Sheldon, has gained considerable attention during the last decade. CLEAs are produced by precipitating the protein(s) of interest with a suitable precipitant (e.g. ammonium sulphate, acetone or polyethylene glycol) and subsequently link the protein aggregates covalently to each other (e.g. with a bifunctional cross-linker like glutaraldehyde). This methodology is simple, does not need highly purified enzymes and results in biocatalysts of high specific activity, solely consisting of protein. Laccases are enzymes able to oxidize a high variety of pollutants like phenols, endocrine disrupting chemicals or polycyclic aromatic hydrocarbons only needing molecular oxygen as final electron acceptor. They are thus of high interest for biotechnological applications. In our group, laccase-CLEAs have been successfully produced and applied for the treatment of endocrine disruptors in adapted reactor systems. These emerging pollutants are of concern as they pass conventional wastewater treatment plants (WWTP) and enter the environment where they can modulate or disrupt the endocrine system of animals even at very low concentrations. The EU-project MINOTAURUS is aiming at the development of intensified processes for pollutant removal based on different immobilization approaches. One of the goals is the development of an enzymatic polishing step to be applied to conventionally treated wastewaters, thus providing a viable solution for the problem of endocrine disruptors. To reach this goal, several obstacles have to be overcome. Laccases usually possess an activity-optimum in the acidic pH-range against phenolic substrates, which limits their applicability in neutral or even alkaline matrices. Here, we present first results to combine laccases from Coriolpsis polyzona, with an acidic pH-optimum, and from Coprinopsis cinerea, with a neutral pH-optimum, in a single biocatalyst. The production of combined CLEAs of both laccases was optimized. The obtained combi-CLEAs showed activity over a broad pH-range implying their suitability for the treatment of wastewaters with varying pHs. These results are promising, thus next steps will include a comprehensive characterization of the developed biocatalysts and an application in a lab-scale bioreactor system for the treatment of a real WWTP-effluent. We thank M. Ruehl from the laboratory of Prof. U. Kües - Molecular Wood Biotechnology and Technical Mycology - at the University of Göttingen, Germany, for providing the C. cinerea laccase.
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Citations
Junghanns, C., Demarche, P., Nair, R., & Agathos, S. N. (2011). Cross-linking of multi-enzyme aggregates - Combi-CLEAs of two laccases with broadened pH-spectrum. 5th European Bioremediation Conference, Chania, Greece. https://hdl.handle.net/2078.5/214857