Degradation of humic acids by manganese peroxidase from the white-rot fungus Clitocybula dusenii

✍ Scribed by Dirk Ziegenhagen; Martin Hofrichter

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 165 KB
• Volume: 38
• Category: Article
• ISSN: 0233-111X
• DOI: 10.1002/(sici)1521-4028(199809)38:4<289::aid-jobm289>3.0.co;2-h

✦ Synopsis

The depolymerization of humic acids (HAs) obtained from low-rank coal (lignite) to fulvic acids (FAs) was investigated in a cell-free system (in vitro) using manganese peroxidase (MnP) from the white-rot fungus Clitocybula dusenii b11. MnP was produced in surface cultures of C. dusenii which were induced with manganese(II) ions (Mn 2+ , 300 µM). The optimum conditions for the action of MnP were determined by varying following parameters of the enzyme assay: i) concentration of Mn 2+ , ii) concentration of hydrogen peroxide (H 2 O 2 ), iii) pH value and iv) temperature. Optimum parameters determined were used in subsequent in vitro depolymerization studies of humic acids. For that purpose, following parameters of the reaction mixture were additionally varied: concentration of HAs, concentration of the thiol mediator glutathione (GSH), presence and concentration of organic solvents. As the result, following parameters were found to be optimal for the MnP-catalyzed in vitro depolymerization of HAs into low-molecular weight FAs (MnP activity 0.12 U/ml): 250 µg/ml HAs, 1 mM MnCl 2 , 46 µM/min H 2 O 2 (continuously supplied by glucose oxidase), 600 µM GSH, 4% (v/v) N,N-dimethylformamide (DMF), pH 4.0, and 37 °C.