Nanoassembly of immobilized ligninolytic enzymes for biocatalysis, bioremediation and biosensing
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Extracellular enzymes, lignin peroxidase (LiP) and manganese peroxidase (MnP) from white rot fungus Phanerochaete chrysosporium, have been shown to degrade various harmful organic compounds ranging from chlorinated compounds to polycyclic aromatic hydrocarbons (PAH) to polymeric dyes. The problems in using immobilized enzymes for biocatalysis/bioremediation are their loss of activity and long-term stability. To address these issues, adsorption by layer-by-layer assembly (LbL) using polyelectrolytes, entrapment using gelatin, and chemisorption using coupling reagents have been investigated. In order to increase surface area for catalysis, porous silicon, formed by electrochemical etching of silicon, has been considered. The efficacy of these extremely stable nanoassemblies towards degradation of model organic compounds -veratryl alcohol (VA) and 2,6-dimethoxyphenol (DMP)-in aqueous and in a mixture of aqueous/acetone has already been demonstrated. In parallel, we are pursuing development of sensors using these immobilized enzymes. Experiments carried out in solution show that NO can reversibly bind Ferri-LiP to produce a diamagnetic complex with a distinct change in its optical spectrum. NO can be photolyzed off to produce the spectrum of native paramagnetic fern-species. Preliminary data on the detection of NO by LiP, based on surface plasmon resonance (SPR) using fiber optic probe, are presented.