An alternative method for the determination of lignocellulolytic enzymatic activities of white rot fungi

IRG/WP 98-10261

D Muñoz-Mingarro, F Llinares, F Rubio, M Yuste, C Rodríguez-Borrajo, J Jiménez, M T De Troya

Some lignocellulolytic activities of wood decay fungi can be evaluated in an indirect way through the study of the decolorization that white rot fungi produces in culture media in the presence of dyes. In this assay, ten dyes were selected, which were added in concentrations of 0.00 1% - 0.003% (P/V) to four-day cultures of Trametes versicolor containing 1% of beech sawdust in a basal salt medium. After the addition of the dye and at seven-day intervals, aliquots were taken in aseptic conditions in order to determine the following parameters: pH, loss of colour, and laccase and Mn-peroxidase activity. All of the cultures and determinations were carried out in triplicate and contrasted with noninoculated controls, as well as with controls that were inoculated, but with no stain added. The results obtained showed that the fungi produced decolorization in all of the cases. The linear regression analysis of the data of residual color (as absorbance), contrasted with the lignocellulolytic activities, showed significant regression coefficientes (p<0.05) in the cultures with Methyl Red, Safranine, Crystal Violet and Blue Eosin. In an additional experiment, sonicated and non-sonicated extract were incubated with Methyl Red solutions (significant regression coefficient) and Bromophenol Blue (non-significant regression coefficient), independently, for three hours. The results showed that there are no notable differences between the sonicated samples and those that were not sonicated in a medium with Methyl Red, whereas in a medium with Bromophenol Blue, decolorization was produced only in the presence of the sonicated extract. This would indicate that the decolorization of Methyl Red can be carried out by extracellular components of the culture, while Bromophenol Blue requires the action of intracellular components to become degraded. This might explain the significant correlation mentioned earlier.On the other hand, the nature of the dyes may influence the magnitude of the activities described: thus it is seen that with Bromophenol Purpel and Crystal Violet, significantly higher values of activities than those of the control without a dye are obtained, while with Malachite Green, the activity is significantly lower.


Conference: 98-06-14/19 Maastricht, The Low Countries

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