Role of mycelium and extracellular protein in the biodegradation of 2,4,6-trichlorophenol by Phanerochaete chrysosporium

Abstract

The biodegradation of 2,4,6-trichlorophenol (2,4,6-TCP) by Phanerochaete chrysosporium was studied in batch systems. In experiments with mycelial suspension, the degradation of 2,4,6-TCP was found to occur in the absence of ligninase. Chloride ion was recovered in nearly stoichiometric amounts at the end of the process. The microorganism did not retain its degradation ability for more than 6 days under substrate-deficient conditions. Neither the mycelium nor the extracellular protein alone could degrade 2,4,6-TCP; both were required for complete degradation to occur. In experiments in which 2,4,6-TCP was exposed to the culture supernatant separated from its mycelium, negligible degradation was obtained and no chloride ion was recovered. No degradation was observed even when the supernatant was supplemented with hydrogen peroxide as a possible cosubstrate. In experiments performed with washed mycelium separated from its supernatant, no degradation took place until the mycelium released additional extracellular protein 5 to 6 h into the incubation. Additions of washed mycelium separated from its supernatant to active cultures also produced an increase in the rate of degradation in correspondence with the protein release. The protein release was independent of the presence of 2,4,6-TCP. The addition of cycloheximide to inhibit the synthesis of de novo proteins completely suppressed the release of protein by the mycelium and resulted in no 2,4,6-TCP degradation. Additions of culture supernatants containing a high concentration of extracellular protein to active cultures produced an increase in the rate of 2,4,6-TCP degradation. The results of this work indicate that the concentration of extracellular protein is the limiting factor in 2,4,6-TCP degradation but that no degradation can take place unless the mycelium is simultaneously present. This can be interpreted as an indication that sequential steps requiring both extracellular and cellular enzymes are involved in the degradation of 2,4,6-TCP by P. chrysosporum.

Process optimization and modeling of trichlorophenol degradation by Phanerochaete chrysosporium

“…The mycelium left in the bottles was washed, resuspended, and centrifuged three times using a wash solution having the same composition of the growth medium but containing no glucose and nitrate in order to prevent fungal growth. 2 The washed mycelium was transferred to a single container to which an aliquot of the 2,4,6-TCP stock solution was added. After adjusting the pH, the suspension was brought up to 500 mL with wash solution and transferred to four replicate 250-mL Erlenmeyer flasks (100 mL/flask).…”

“…Armenante et a1 . 2 have recently shown that the degradation of 2,4,6-TCP by P. chrysosporium is a process that requires the simultaneous presence of both the mycelium and the extracellular enzyme system released by the mycelium to initiate degradation. These investigators have also shown that the rate-limiting step in the process is the concentration of extracellular protein and that the concentration of mycelial biomass does not affect the rate of degradation, although the presence of some biomass is necessary for degradation to occur.…”

Rat cytochrome P450-mediated transformation of dichlorodibenzo-p-dioxins by recombinant white-rot basidiomycete Coriolus hirsutus

“…Extracellular lignin-degrading enzymes such as lignin peroxidase (LiP) and manganese peroxidase (MnP) produced by white-rot basidiomycete fungi have been reported to be involved in transformation of various CDDs (and various chlorophenols etc.) (Armenante et al 1994;Bumpus et al 1985;Joshi and Gold 1993;Joshi and Gold 1994;Reddy and Gold 2000;Takada et al 1996;Valli et al 1992). Through various metabolic pathways, the white-rot basidiomycete fungi convert the chlorinated aromatic compounds to CO 2 and H 2 O.…”

Aerobic degradation and dechlorination of 2–chlorophenol, 3-chlorophenol and 4-chlorophenol by a Pseudomonas pickettii strain

“…The biodegradation of low-chlorinated phenols has been studied in both aerobic and anaerobic systems (Steiert et al 1987;Larsson et al 1988;Larsson and Lemkemeier 1989;Kramer and Kory 1992;Kafkewitz et al 1992;Kiyohara et Armenante et al 1994). Considerable efforts have also been made to develop biological treatments for some of these chemicals (Balfanz and Rehm 1991 ;Armenante et al 1992 ;Menke and Rehm 1992 ;Armenante et al 1993).…”