Abstract
Objective: An instrument-free assay was developed for simultaneous detection of laccase activity in a large number of samples as diverse as screening of laccase-producing microbial cultures or chromatographic fractions. Method: Dried paper discs previously impregnated with 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) were placed on a flat-bottom microplate (a simple way to avoid misidentification) and loaded with an aliquot from each sample. Results: Discs corresponding to samples containing laccase activity become green-bluish colored within first ten minutes of reaction, allowing direct detection through simple naked-eye inspection. Conclusion: As an example, this easy process was applied to the laccase purification in order to eliminate chromatographic fractions that did not contain laccase activity, thus reducing the number of spectrophotometric assays.
Highlights
Laccases and laccase-like metalloxidases [1] are glycoenzymes that belong to the family of multicopper oxidases
The laccase activity in culture media fermented by the white-rot fungus used in this work (G. resinaceum) or other laccase-producing white-rot fungal strains, such as Trametes versicolor, Phlebia rufa and Fomes fomentarius, are routinely detected in our laboratory using the proposed easy assay for rapid screening of laccase activity
The use of G. resinaceum in this study “per se” is not important or relevant to this work, since it was only used as a laccaseproducing strain
Summary
Laccases (benzenediol: oxygen oxidoreductase, EC 1.10.3.2) and laccase-like metalloxidases [1] are glycoenzymes that belong to the family of multicopper oxidases They catalyze non-specific oxidation of natural or synthetic substrates such as phenolic or non-phenolic aromatic compounds, amines and inorganic ions or molecules, with a concomitant four-electron reduction of molecular oxygen to water. In recent years, these enzymes have received increasing attention due to their potential for wide-ranging biotechnological applications [2, 3] including environmental pollution abatement [4, 5]. Chromatographic processes yield a large number of fractions that have to be analyzed for the presence of enzyme activity, usually by
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