Detoxification of polycyclic aromatic hydrocarbons by fungi

Summary The polycyclic aromatic hydrocarbons (PAHs) are a group of hazardous environmental pollutants, many of which are acutely toxic, mutagenic, or carcinogenic. A diverse group of fungi, includingAspergillus ochraceus, Cunninghamella elegans, Phanerochaete chrysosporium, Saccharomyces cerevisiae, andSyncephalastrum racemosum, have the ability to oxidize PAHs. The PAHs anthracene, benz[a]anthracene, benzo[a]pyrene, fluoranthene, fluorene, naphthalene, phenanthrene, and pyrene, as well as several methyl-, nitro-, and fluoro-substituted PAHs, are metabolized by one or more of these fungi. Unsubstituted PAHs are oxidized initially to arene oxides,trans-dihydrodiols, phenols, quinones, and tetralones. Phenols andtrans-dihydrodiols may be further metabolized, and thus detoxified, by conjugation with sulfate, glucuronic acid, glucose, or xylose. Although dihydrodiol epoxides and other mutagenic and carcinogenic compounds have been detected as minor fungal metabolites of a few PAHs, most transformations performed by fungi reduce the mutagenicity and thus detoxify the PAHs.     

Utilization of oligosaccharides by three imperfect fungi

Summary The utilization of oligosaccharides (maltose, sucrose, lactose and raffinose) by three imperfect fungi viz.Alternaria tenuis Auct.,Colletotrichum capsici (Syd.)Butler &Bisby andColletotrichum gloeosporioides Penz. isolated from diseased leaves of tomato,Scindapsus pictus andPolyscias balfuriana respectively, was studied chromatographically. Except for lactose, all the sugars were utilizzed through a hydrolytic pathway and almost all proved to be a suitable source of carbon for the growth of fungi. Along with the utilization of sucrose, a simultaneous synthesis of an oligosaccharide was also observed in case of two species ofColletotrichum. C. gloeosporioides, however, also synthesized an oligosaccharide, maltotriose if it is grown in the medium containing maltose. During the utilization of raffinose, melibiose and fructose were detectted in the culture medium ofA. tenuis. Melibiose was further broken down into glucose and galactose by the two species ofColletotrichum.All the sugars were consumed from the media within 15 days except for lactose which persisted in the media even after 15 days.     

Utilization and polymerization of lignosulfonates by wood-rotting fungi

The susceptibility of lignosulfonates to the action of lignin-degrading wood-rotting fungi was studied by submitting commercial lignosulfonate (Peritan Na) and fractions of calcium lignosulfonate of different molecular weights to the action of selected white rot fungi. As shown by gel filtration chromatography and determinations according to the nitroso method, lignosulfonates, even in conditions which did not support fungal growth, underwent strong polymerization when brought in contact with typical, extracellular polyphenol oxidase-producing white-rot fungi. Owing to the polymerization, nitroso determinations showed a seeming decrease of lignosulfonate. Polyporus dichrous, an “atypical” white-rot fungus which does not produce extracellular polyphenol oxidase and hence does not cause polymerization of lignosulfonates, was found to degrade 11% of the lignosulfonate available in a solid malt extract medium during 19 days. Addition of lignosulfonate to a rich synthetic liquid growth medium increased the mycelial yield of several white-rot fungi. Trametes versicolor was able to grow on a calcium lignosulfonate fraction with molecular weight 1350 which served as sole source of carbon and energy, but not on fractions of higher molecular weight. The utilization/polymerization of lignosulfonates was shown to depend on concentration and on the presence of additional utilizable sources of carbon.     

Removal and mineralization of polycyclic aromatic hydrocarbons by litter-decomposing basidiomycetous fungi

Nine strains of litter-decomposing fungi, representing eight species of agaric basidiomycetes, were tested for their ability to remove a mixture of three polycyclic aromatic hydrocarbons (PAHs) (total 60 mg l(-1)) comprising anthracene, pyrene and benzo(a)pyrene (BaP) in liquid culture. All strains were able to convert this mixture to some extent, but considerable differences in degradative activity were observed depending on the species, the Mn(II) concentration, and the particular PAH. Stropharia rugosoannulata was the most efficient degrader, removing or transforming BaP almost completely and about 95% of anthracene and 85% of pyrene, in cultures supplemented with 200 micro M Mn(II), within 6 weeks. In contrast less than 40, 18, and 50% BaP, anthracene and pyrene, respectively, were degraded in the absence of supplemental Mn(II). In the case of Stropharia coronilla, the presence of Mn(II) led to a 20-fold increase of anthracene conversion. The effect of manganese could be attributed to the stimulation of manganese peroxidase (MnP). The maximum activity of MnP increased in S. rugosoannulata cultures from 10 U l(-1) in the absence of Mn(II) to 320 U l(-1) in Mn(II)-supplemented cultures. The latter degraded about 6% of a (14)C-labeled BaP into (14)CO(2) whereas only 0.7% was mineralized in the absence of Mn(II). In solid-state straw cultures, S. rugosoannulata, S. coronilla and Agrocybe praecox mineralized between 4 and 6% of (14)C-labeled BaP within 12 weeks.     

Degradation of aromatic hydrocarbons by white-rot fungi in a historically contaminated soil

Phanerochaete chrysosporium NRRL 6361 and Pleurotus pulmonarius CBS 664.97 were tested for their ability to grow under nonsterile conditions and to degrade various aromatic hydrocarbons in an aged contaminated soil that also contained high concentrations of heavy metals. After 24 days fungal incubation, carbon-CO2 liberated, an indicator of microbial activity, reached a plateau. At the end of the incubation time (30 days), fungal colonization was clearly visible and was confirmed by ergosterol and cell organic carbon determinations. In spite of unfavorable pH (around 7.4) and the presence of heavy metals, both fungi produced Mn-peroxidase activity. In contrast, laccase and aryl-alcohol oxidase were detected only in the soil treated with P. pulmonarius CBS 664.97 and lignin-peroxidase in that with P. chrysosporium NRRL 6361. No lignin-modifying enzyme activities were present in non-inoculated soil incubated for 30 days (control microcosm). Regardless of the fungus employed, a total removal of naphtalene, tetrachlorobenzene, and dichloroaniline isomers, diphenylether and N-phenyl-1-naphtalenamine, was observed. Significant release of chloride ions was also observed in fungal-treated soil, in comparison with that recorded in the control microcosm. Both fungi led to a significant decrease in soil toxicity, as assessed using two different soil contact assays, including the Lepidium sativum L. germination test and the Collembola mortality test.     

Biodegradation of polycyclic aromatic hydrocarbons by new isolates of white rot fungi.

Eight rapid Poly R-478 dye-decolorizing isolates from The Netherlands were screened in this study for the biodegradation of polycyclic aromatic hydrocarbons (PAH) supplied at 10 mg liter(-1). Several well-known ligninolytic culture collection strains, Phanerochaete chrysosporium BKM-F-1767, Trametes versicolor Paprican 52, and Bjerkandera adusta CBS 595.78 were tested in parallel. All of the strains significantly removed anthracene, and nine of the strains significantly removed benzo(a)pyrene beyond the limited losses observed in sterile liquid and HgCl2-poisoned fungus controls. One of the new isolates, Bjerkandera sp. strain Bos 55, was the best degrader of both anthracene and benzo(a)pyrene, removing 99.2 and 83.1% of these compounds after 28 days, respectively. Half of the strains, exemplified by strains of the genera Bjerkandera and Phanerochaete, converted anthracene to anthraquinone, which was found to be a dead-end metabolite, in high yields. The extracellular fluids of selected strains were shown to be implicated in this conversion. In contrast, four Trametes strains removed anthracene without significant accumulation of the quinone. The ability of Trametes strains to degrade anthraquinone was confirmed in this study. None of the strains accumulated PAH quinones during benzo(a)pyrene degradation. Biodegradation of PAH by the various strains was highly correlated to the rate by which they decolorized Poly R-478 dye, demonstrating that ligninolytic indicators are useful in screening for promising PAH-degrading white rot fungal strains.     

Biodegradation of polycyclic aromatic hydrocarbons by new isolates of white rot fungi.

Eight rapid Poly R-478 dye-decolorizing isolates from The Netherlands were screened in this study for the biodegradation of polycyclic aromatic hydrocarbons (PAH) supplied at 10 mg liter(-1). Several well-known ligninolytic culture collection strains, Phanerochaete chrysosporium BKM-F-1767, Trametes versicolor Paprican 52, and Bjerkandera adusta CBS 595.78 were tested in parallel. All of the strains significantly removed anthracene, and nine of the strains significantly removed benzo(a)pyrene beyond the limited losses observed in sterile liquid and HgCl2-poisoned fungus controls. One of the new isolates, Bjerkandera sp. strain Bos 55, was the best degrader of both anthracene and benzo(a)pyrene, removing 99.2 and 83.1% of these compounds after 28 days, respectively. Half of the strains, exemplified by strains of the genera Bjerkandera and Phanerochaete, converted anthracene to anthraquinone, which was found to be a dead-end metabolite, in high yields. The extracellular fluids of selected strains were shown to be implicated in this conversion. In contrast, four Trametes strains removed anthracene without significant accumulation of the quinone. The ability of Trametes strains to degrade anthraquinone was confirmed in this study. None of the strains accumulated PAH quinones during benzo(a)pyrene degradation. Biodegradation of PAH by the various strains was highly correlated to the rate by which they decolorized Poly R-478 dye, demonstrating that ligninolytic indicators are useful in screening for promising PAH-degrading white rot fungal strains.     

Comparative studies on lignin and polycyclic aromatic hydrocarbons degradation by basidiomycetes fungi

A total of 130 wild basidiomycetes fungi were collected and identified. The polycyclic aromatic hydrocarbons (PAHs) degradation by the potential Phellinus sp., Polyporus sulphureus (in liquid state fermentation (LSF), solid state fermentation (SSF), in soil) and lignin biodegradation were compared with those of a bacterial isolate and their corresponding cocultures. The PAHs degradation was higher in LSF and the efficiency of the organisms declined in SSF and in soil treatment. Phellinus sp. showed better degradation in SSF and in soil. Bacillus pumilus showed higher degradation in LSF. B. pumilus was seen to have lower lignin degradation than the fungal cultures and the cocultures could not enhance the degradation. Phellinus sp. which had higher PAHs and lignin degradation showed higher biosurfactant production than other organism. Manganese peroxidase (MnP) was the predominant enzyme in Phellinus sp. while lignin peroxidase (Lip) was predominant in P. sulphureus.     

Utilization of fuel oils by fungi isolated from oceanic tar balls

Filamentous fungi were isolated from approximately half of 300 tar balls collected from the north Atlantic and the north Pacific Oceans. Forty-two isolates were tested for their ability to utilize no. 2 and no. 4 fuel oils as the sole carbon source at 2 different concentrations. Isolates of Aspergillus, Graphium, Humicola , Lophotrichus, Penicillium , and Tetracoccosporium were found that produced extensive growth.     

Taxonomic value of the property of fungi to assimilate hydrocarbons

A wide range of fungi were tested for their ability to assimilate a series of hydrocarbons, which includedn-paraffins, aromatic hydrocarbons and petroleum fractions.The property is not evenly distributed among the various fungal classes, but is to be found mainly in two orders, the Mucorales and the Moniliales. Within the latter order, the generaAspergillus andPenicillium are rich in hydrocarbon-assimilating strains. In other genera, the property of assimilating hydrocarbons is relatively rare.Hydrocarbon assimilation is not necessarily common to related species, nor proper to one species, but more the property of individual strains. Different strains belonging to the same species differ in metabolic activity when they are tested against a series of hydrocarbons. The property of assimilating hydrocarbons appears to lack taxonomic value. Species of the same genus show only a tendency to behave in a similar way, e.g.Penicillium strains usually assimilaten-decane and light gas oil whereasAspergillus strains seldom do so. Aspergillus species sporulate better on long chainn-paraffins. On some hydrocarbons, they develop particular pigments. n-Paraffins with at least ten carbon atoms support better growth than petroleum fractions. Individual strains are very sensitive to minor changes in hydrocarbon composition or structure. Only sparse delayed growth is observed on aromatic hydrocarbons.n-Heptane, petroleum ether, naphtha and kerosene are often toxic whereas aromatic hydrocarbons are usually non-toxic.