František Nerud

Decolorization of synthetic dyes by the Fenton reagent and the Cu/pyridine/H2O2 system

Representative azo, triphenylmethane, heterocyclic and polymeric synthetic dyes have been decolorized by two biological non-ezymatic systems, copper/pyridine/H2O2 and the Fenton reagent. With the former system, intensive decolorization measured after 1 h was obtained with phenol red (89%), tropaeolin 00 (58%), Evans blue (95%), eosin yellowish (84%), and Poly B-411 (92%). The rate of decolorization was not affected by pH in the range of 3-9 and increased with increasing temperature. The use of the radical scavengers thiourea and superoxide dismutase showed that hydroxyl radicals rather than superoxide anions are involved in the reaction. Omission of pyridine led to a substantial decrease in the extent of decolorization (20-50% decolorization). The use of organic peroxide instead of H2O2 resulted in slightly slower decolorization, similar values of decolorization being obtained only after a 2-h incubation. Decolorization of the dyes by the Fenton reagent was also very effective but slower than that obtained with the first system. Except for phenol red and eosin yellowish, (decolorization 8% and 52%, respectively) the dyes were decolorized up to 99% after 1-day incubation.

PCB congener selective biodegradation by the white rot fungus Pleurotus ostreatus in contaminated soil.

Six strains of white rot fungi were tested for their biodegradation ability of low chlorinated polychlorinated biphenyl (PCB) commercial mixture (Delor 103) in real soil system. Phanerochaete chrysosporium and Trametes versicolor did not show any ability to degrade PCBs in soil. On the contrary, four strains of Pleurotus ostreatus were able to remove about 40% of Delor 103 in two months. All P. ostreatus strains decomposed PCBs selectively with the preference for congeners with chlorine atoms in ortho > meta > para position. Degradation efficiency decreased with increasing number of chlorination.

Decolorization of structurally different synthetic dyes using cobalt(II)/ascorbic acid/hydrogen peroxide system

The cobalt(II)/ascorbic acid/hydrogen peroxide system was used for decolorization of azo, acridine, anthraquinone, thiazine and triphenylmethane dyes. More than 90% decolorization was obtained with all dyes except Remazol Brilliant Blue R (75%). With other transition metals the system was less efficient. With copper, higher concentration and prolonged incubation time was necessary to obtain the same extent of decolorization. The rate of decolorizaton was not affected by pH in the range of 3-9. The reaction is very fast, with more than 90% decolorization being attained within 15 min. The system produces hydroxyl radicals which are responsible for the decolorization.

Influence of iron and copper nanoparticle powder on the production of lignocellulose degrading enzymes in the fungus Trametes versicolor

White rot fungi are one of the key group of microorganisms that help to enrich the soil via degradation of wood. In the current communication, influence of iron and copper nanoparticles on the production of lignocellulolytic enzymes by Trametes versicolor have been investigated. The production of enzymes in the presence of the two nanoparticles was compared to that of ferrous and cupric ions respectively. Results show that both the tested nanoparticles alter the production profile of the lignocellulolytic enzymes when compared to the control set. The production of laccase was not influenced by iron nanoparticles but was effected by copper nanoparticles within 24h of incubation. Both the nanoparticles decreased the production of beta-glucosidase, beta-xylosidase and cellobiohydrolase significantly. However, the production profile of Mn-peroxidase and remained statistically similar to that of control when the organism was incubated with iron and copper nanoparticles. The production profiles were also different when one compares the ionic form of metals and the nanoparticles, suggesting different mechanism of action of the particles on the organism. The difference in the production profile was not growth related as no significant difference was recorded for either form of iron and copper on the growth of T. versicolor.

Effect of cadmium on the ligninolytic activity ofStereum hirsutum andPhanerochœte chrysosporium

An inhibitory effect of cadmium on the growth and ligninolytic activity of the wood-rotting basidiomycetesPhanerochœte chrysosporium, Pleurotus ostreatus, Pycnoporus cinnabarinus andStereum hirsutum was observed. Delayed decolorization of the polymeric dye Poly R-478 was observed in samples with 0.10 mmol/L Cd. Addition of 0.25 mmol/L Cd to the cultivation medium strongly reduced the activity of both Mn-dependent and Mn-independent peroxidases ofStereum hirsutum, while the activity of laccase was not affected to a similar extent. The maximum of MnP activity in these samples was found during the exponential phase of growth whereas control samples showed the highest activity after the onset of the stationary phase (days 15–21). Cadmium at concentrations higher than 0.50 mmol/L significantly inhibited the activity of all enzymes tested in bothS. hirsutum andP. chrysosporium.

The effectiveness of biological treatment of wheat straw by white-rot fungi

Out of 13 species ofBasidiomycetes growing on wheat straw, 9 species enhanced thein vitro dry matter digestibility of the substrate. The detergent fiber content (acid and neutral) of the substrate was significantly reduced by most of the fungi tested. Hemicellulose showed the largest proportionate loss, whereas lignin the smallest one.

Cryopreservation of basidiomycete strains using perlite.

A new alternative method using perlite as a particulate solid carrier in the growth medium with a cryoprotectant was successfully tested for cryopreservation of several basidiomycete species from different genera (Armillaria, Pleurotus, Pluteus, Polyporus) which failed to survive or retain their properties in cryopreservation procedures routinely used in our laboratory. Frozen basidiomycete strains were kept in cryovials submerged in liquid nitrogen and were either immediately after the freezing process or after a 6-month storage thawed and checked for viability, purity and changes in growth, morphology and biochemical characteristics. All cultures survived the cryopreservation procedure and no negative effects of cryopreservation by this method have been observed after 6 months of storage in liquid nitrogen.

Distribution of ligninolytic enzymes in selected white-rot fungi

Ten white-rot fungi have been screened for the production of ligninase, manganese peroxidase and laccase. Although the fungi degraded lignin efficiently, they significantly differed in the occurrence of individual ligninolytic enzymes. Based on the enzyme pattern produced under N-limited conditions, the fungi can be divided into the following four groups:1. ligninase-manganese peroxidase-laccase group,2. ligninase-manganese peroxidase group,3. manganese peroxidase-laccase group,4. laccase group.

Production of ligninolytic exoenzymes and14C-Pyrene mineralization byPleurotus sp. in lignocellulose substrate

Pleurotus sp. was grown in liquid medium and on a solid straw substrate, and activities of laccase and manganese-dependent peroxidase (MnP) were recorded. The activities were the highest in a rich, glucose corn-steep liquid medium. In straw cultures, laccase activity was about ten times lower. Under solid state conditions, MnP production was the highest during days 20–40, when laccase activity already had declined. In straw cultures, mineralization of14C-pyrene was measured as release of14CO2. The highest rates of pyrene mineralization occurred during days 20–45,i.e. the period of high MnP activities, suggesting a role of this enzyme in PAH degradation. Within 60d, 24% of pyrene was mineralized.

Degradation of polycyclic aromatic hydrocarbons by the copper(II)-hydrogen peroxide system

A non-enzymic system containing CuSO4 (10 mmol/L) and hydrogen peroxide (100 mmol/L) was used for the degradation of three polycyclic aromatic hydrocarbons: phenanthrene, fluoranthene, and pyrene (all at 10 mmol/L). The system degraded the compounds rapidly and efficiently. After 1 d at room temperature, more than 80 % of pyrene, phenan-threne, and fluoranthene disappeared. Several products are formed during the reaction including a black precipitate.