Effect of soil bacteria on the ability of polycyclic aromatic hydrocarbons (PAHs) removal by Trametes versicolor and Irpex lacteus from contaminated soil

The effect of bacteria represented by indigenous soil microflora or a mixture of soil bacteria Pseudomonas aeruginosa and Rhodococcus erythropolis on fungal growth, extracellular enzyme production and polycyclic aromatic hydrocarbons (PAHs) biodegradation efficiency in soil of white-rot fungi Trametes versicolor and Irpex lacteus was investigated. Both fungi were able to colonize soil. The growth yields measured by ergosterol were about two-fold in I. lacteus after 10 weeks. Laccase was produced in T. versicolor cultures in the presence or absence of bacteria but live bacteria reduced the laccase levels in soil about 5 times. Manganese-dependent peroxidase (MnP) was not detected in T. versicolor cultures. The amounts of MnP and laccase in I. lacteus cultures were not affected by the presence of bacteria. T. versicolor was more efficient in PAH removal for all PAHs tested although its capacity to colonize soil was lower. The removal rates of PAHs by T. versicolor in sterile soil were 1.5-fold, 5.8-fold and 1.8-fold for 2-3-ring, 4-ring and 5-6-ring PAHs, compared to I. lacteus, respectively. I. lacteus showed a low efficiency of removal of pyrene, benzo[a]anthracene and benzo[k]fluoranthene, compared to T. versicolor, whereas chrysene and benzo[b]fluoranthene were degraded by neither fungus. The main effect of the presence of the indigenous microflora or R. erythropolis and P. aeruginosa was a significant decrease of degradation of total PAHs by both T. versicolor and I. lacteus. Weak fungal/bacterial synergistic effects were observed in the case of removal of acenapthylene, benzo[a]pyrene, dibenzo[a,h]anthracene and benzo[g,h,i]perylene by I. lacteus and acenapthylene by T. versicolor. However, the bacterial effects were different in the two fungi. PAH abiotic losses represented 15 and 21% of the total PAHs after 5 and 10 weeks, respectively; naphthalene and acenaphthene were removed from the soil due to volatilization.     

Breakdown Products in the Metabolic Pathway of Anthracene Degradation by a Ligninolytic Fungus Polyporus sp. S133

Polyporus sp. S133 fungi were selected based on their ability to degrade anthracene in liquid media. The degradation efficiency of anthracene increased by adding 0.5% Tween 80 to reach 71%; agitation at 120 rev/min increased the degradation to 92% after 30?days of incubation. Enzymes such as manganese peroxidase (MnP), lignin peroxidase (LiP), laccase, 1,2-dioxygenase and 2,3-dioxgenase were produced by Polyporus sp. S133 during incubation, and the highest enzyme activity was 182.3 U l^?1 by 1,2-dioxygenase after 20?days of incubation. These results indicate that ligninolytic and dioxygenase enzymes secreted from Polyporus sp. S133 could play an important role in anthracene degradation efficiency. The metabolites detected through the degradation pathway were anthraquinone, phthalic acid, benzoic acid and catechol.     

Degradation of isoproturon by the white rot fungus Phanerochaete chrysosporium

The ability of the white rot fungus Phanerochaete chrysosporium to degrade isoproturon was tested in solid substrate fermentation (SSF) cultures using straw as substrate/carrier material. The role of the lignin degrading enzymes, lignin peroxidase (LiP) and manganese peroxidase (MnP), in the degradation of the herbicide was also studied. Isoproturon concentration and LiP and MnP activities were followed in sterile straw cultures of the fungus. In vitro degradation tests with pure LiP and MnP were performed. P. chrysosporium in straw cultures was able to degrade 91% of the herbicide isoproturon in 14 days of incubation. A sharp decrease of isoproturon coincided with the largest MnP activity. Although LiP activity was also present, its role in SSF is unclear. The in vitro tests showed a strong isoproturon oxidation by LiP and a slower oxidation by MnP in the presence of Tween 80 probably by a lipid peroxidation process. Two N-demethylated metabolites were identified in pure enzyme tests and in SSF cultures. Several unidentified isoproturon derivatives, most likely hydroxylated, were also formed in both systems. The different pattern of derivatives detected in pure LiP and MnP tests showed a completely different metabolism by these two enzymes.     

Basidiomycetes from Compost and their Dye Degradation and Enzyme Activities

The degree of decolorization of Poly R-478, a highly recalcitrant anthraquinone dye, by three basidiomycetes belonging to Polyporales isolated from compost was investigated together with the enzymes involved. Decolorization tests in two liquid cultures, one with a simple mycelium inoculum, the other with an inoculum of mycelium grown on straw, resulted in 70% and 87% decolorization respectively in 7 days. However, the efficiency did not increase significantly in the presence of the lignocellulose substrate. The three strains produced laccase and/or manganese peroxidase activity during the decolorization, whereas lignin peroxidase activity was not observed. Previous growth on straw enhanced the synthesis of ligninolytic enzymes, though there was no correlation between enzyme activity and decolorization. The three fungi can be proposed as promising candidates for the treatment of colored industrial effluents and probably for soils contaminated by complex polymers, such as polycyclic aromatic hydrocarbons.     

Bioaugmentation and biostimulation effects on PAH dissipation and soil ecotoxicity under controlled conditions

The degradation of spiked anthracene (ANT), pyrene (PYR) and benzo[a]pyrene (B[a]P) in soil (3000 mg ∑ 3 PAHs kg⁻¹ dry soil) was studied in aerobically incubated microcosms for 120 d. The applied treatments aimed at enhancing PAH removal from the heavily contaminated soils are: (i) bioaugmentation by adding aged PAH-contaminated soil (ACS) containing activated indigenous degraders; and (ii) combined bioaugmentation/biostimulation by incorporating sewage sludge compost (SSC) and decaying rice straw (DRS). The adopted treatments produced higher PAH dissipation rates than those observed in unamended PAH-spiked soils, especially for ANT and PYR in the presence of DRS or ACS (>96%). However, B[a]P was the most recalcitrant hydrocarbon to biodegradation. Extracellular enzyme investigation revealed the existence of ligninolytic activities in all soil treatments, including control but no relationship could be found with PAH dissipation. The ecotoxicological assessment indicated that regardless of applied treatment, PAH-spiked soils were chronically lethal to ostracod Heterocypris incongruens and confirmed the sensitivity of the microcrustacean to the concomitant presence of these three hydrocarbons. Lettuce root elongation inhibition was correlated with PAH level but the presence of SSC conferred a strong phytotoxic capacity to PAH-spiked soils. DRS amendment may constitute a cost-effective alternative for hydrocarbon bioremediation as it has impacted positively on soil microbial activity and enhanced PAH removal with no apparent changes in soil physico-chemical properties.     

Production of lignocellulose-degrading enzymes and degradation of leaf litter by saprotrophic basidiomycetes isolated from a Quercus petraea forest

Due to the production of lignocellulose-degrading enzymes, saprotrophic basidiomycetes can significantly contribute to the turnover of soil organic matter. The production of lignin- and polysaccharide-degrading enzymes and changes of the chemical composition of litter were studied with three isolates from a Quercus petraea forest. These isolates were capable of fresh litter degradation and were identified as Gymnopus sp., Hypholoma fasciculare and Rhodocollybia butyracea. Within 12 weeks of incubation, H. fasciculare decomposed 23%, R. butyracea 32% and Gymnopus sp. 38% of the substrate dry mass. All fungi produced laccase and Mn-peroxidase (MnP) and none of them produced lignin peroxidase or other Mn-independent peroxidases. There was a clear distinction in the enzyme production pattern between R. butyracea or H. fasciculare compared to Gymnopus sp. The two former species caused the fastest mass loss during the initial phase of litter degradation, accompanied by the temporary production of laccase (and MnP in H. fasciculare) and also high production of hydrolytic enzymes that later decreased. In contrast, Gymnopus sp. showed a stable rate of litter mass loss over the whole incubation period with a later onset of ligninolytic enzyme production and a longer lasting production of both lignin and cellulose-degrading enzymes. The activity of endo-cleaving polysaccharide hydrolases in this fungus was relatively low but it produced the most cellobiose hydrolase. All fungi decreased the C/N ratio of the litter from 24 to 15-19 and Gymnopus sp. also caused a substantial decrease in the lignin content. Analytical pyrolysis mass spectrometry of litter decomposed by this fungus showed changes in the litter composition similar to those caused by white-rot fungi during wood decay. These changes were less pronounced in the case of H. fasciculare and R. butyracea. All fungi also changed the mean masses of humic acid and fulvic acid fractions isolated from degraded litter. The humic acid fraction after degradation by all three fungi contained more lignin and less carbohydrates. Compared to the decomposition by saprotrophic basidiomycetes, litter degradation in situ on the site of fungal isolation resulted in the relative enrichment of lignin and differences in lignin composition revealed by analytical pyrolysis. It can most probably be explained by the participation of non-basidiomycetous fungi and bacteria during natural litter decomposition.     

Degradation of phenolic and non-phenolic aromatic pollutants by four Pleurotus species: the role of laccase and versatile peroxidase

The ability of Pleurotus eryngii, Pleurotus ostreatus, Pleurotus pulmonarius and Pleurotus sajor-caju to degrade the aromatic pollutants 2,4-dichorophenol (2,4-DCP) and benzo(a)pyrene [B(a)P] in liquid culture and microcosm (using wheat straw as growth substrate and sea sand as a xenobiotic carrier) was investigated by HPLC and ¹⁴CO₂ release from labeled pollutants. We found that 100 μM 2,4-DCP was very quickly transformed by the four fungi, disappearing 24 h after its addition to the liquid cultures. However, a 2-week incubation period was required to transform 100 μM B(a)P up to 75% by P. eryngii and P. pulmonarius. Whereas the fungi were able to begin degradation of the two pollutants with high transformation rates, their complete degradation (mineralization) rates were very low. Mineralization of B(a)P in liquid cultures was only observed with P. eryngii and P. pulmonarius, although the four Pleurotus species studied were able to mineralize this compound in solid state fermentation (SSF). The ligninolytic enzymes laccase and versatile peroxidase (VP), together with aryl-alcohol oxidase (AAO) providing extracellular H₂O₂, were found in liquid cultures. Except AAO, these enzymes were also detected in SSF experiments. In order to investigate the role of ligninolytic enzymes in the process, their action on both pollutants (50 μM) was studied in vitro in the absence and presence of redox mediators. As observed with the fungal cultures, 2,4-DCP was oxidized faster than B(a)P by both laccase (60% transformation after 6 h) and VP (100% transformation after 1 h). Moreover, laccase oxidation was strongly increased (up to 90% transformation after 3 h), by the presence of the mediators 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) or 1-hydroxybenzotriazole (HBT). In the case of B(a)P, the presence of ABTS or HBT was strictly required for oxidation by laccase (25% transformation after 8 h). Degradation of B(a)P was also observed in reactions with VP (40% transformation after 6 h). The results obtained suggest that Pleurotus species can be used in applications focused to the degradation of aromatic pollutants using wheat straw as a growth substrate, and provide the first evidence on the direct transformation of recalcitrant aromatic pollutants by VP.     

The Production of Ligninolytic Enzymes by Marine-Derived Basidiomycetes and Their Biotechnological Potential in the Biodegradation of Recalcitrant Pollutants and the Treatment of Textile Effluents

Filamentous fungi derived from marine environments are well known as a potential genetic resource for various biotechnological applications. Although terrestrial fungi have been reported to be highly efficient in the remediation of xenobiotic pollutants, fungi isolated from the marine environment may possess biological advantages over terrestrial fungi because of their adaptations to high salinity and pH extremes. The present study describes the production of ligninolytic enzymes under saline and non-saline conditions and the decolorization of Remazol Brilliant Blue R (RBBR) dye by three basidiomycetes recovered from marine sponges (Tinctoporellus sp. CBMAI 1061, Marasmiellus sp. CBMAI 1062, and Peniophora sp. CBMAI 1063). Ligninolytic enzymes were primarily produced by these fungi in a salt-free malt extract and malt extract formulated with artificial seawater (saline condition). CuSO₄ and wheat bran were the best inducers of lignin peroxidase and manganese peroxidase activity. RBBR was decolorized up to 100% by the three fungi, and Tinctoporellus sp. CBMAI 1061 was the most efficient. Our results revealed the biotechnological potential of marine-derived basidiomycetes for dye decolorization and the treatment of colored effluent as well as for the degradation of other organopollutants by ligninolytic enzymes in non-saline and saline conditions that resemble the marine environment.     

碳氮源对复合木质素降解菌木质素降解能力及相关酶活的影响

白腐真菌所具有的降解木质素能力源于其所产生的酶系统,碳源和氮源是其降解木质素和产酶的一个极为重要的影响因素。通过室内小麦秸秆固态发酵试验,研究了不同的碳、氮源对两株侧耳属真菌Tf1（P.pulmonarius）和JG1（P.cornucopiae）产酶活力、木质素降解和粗蛋白含量的影响。结果表明,Lip和MnP是参与复合木质素降解菌Tf1＋JG1降解小麦秸秆重要的木质素降解酶。以葡萄糖为碳源,酒石酸铵为氮源能显著提高复合木质素降解菌对木质素的降解能力,发酵9 d后小麦秸秆的失重率为14.87%,木质素含量为8.68%,木质素降解率为22.95%;粗蛋白含量为7.28%,比未发酵麦秸提高了36.84%（P〈0.05）;Lip和MnP活力分别为629.11 U.g-1和622.22 U.g-1。     

Degradation of selected polycyclic aromatic hydrocarbons in coastal sediments: Importance of microbes and polychaete worms

Rates of degradation of polycyclic aromatic hydrocarbons (PAH) were examined after addition of crude oil enriched with anthracene, fluoranthene, benz(a)anthracene, and benzo(a)pyrene to coastal sediments in a laboratory (20°) flowing seawater system. Three types of sediment (fine sand, medium sand, and marsh sediment) with and without the benthic polychaete worm, Capitella capitata, were used. After extraction from the sediment, PAH concentrations were measured by liquid chromatography with fluorescent detection. Microbial degradation was studied by incubating sediments with radioactive PAH and measuring subsequent production of ¹⁴C0₂. Concentrations of the four PAH decreased significantly with time in fine and medium sized sands. PAH levels also decreased in marsh sediment but trends were not significant (P < 0.05). C. capitata stimulated PAH degradation. Microbial degradation was more rapid in upper surfaces than in lower layers of the sediments.     

Effect of environmental C/N ratio on activities of lignin-degrading enzymes produced by Phanerochaete chrysosporium

Lignin-degrading enzymes secreted by white rot fungi play an important role in the degradation of lignin and persistent organic pollutants(POPs).In this study,effect of environmental C/N ratio on the activities of lignin-degrading enzymes,lignin peroxide(Li P)and manganese peroxidase(Mn P),produced by Phanerochaete chrysosporium,a white rot fungus,was investigated.Glucose was used as C source,and ammonium tartrate of different concentrations was used as N source to provide different C/N ratios.Relationships between Li P and Mn P activities and environmental C/N ratio were explored.The results showed that the higher the N source concentration,the faster the mycelium pellets aged.The faster the mycelium dry weight increased,the higher the Li P and Mn P activities.A high C/N ratio was a necessary condition for the secretion of Li P or Mn P.In addition,mycelium dry weight essentially affected enzyme activities.In the 122 C/N ratio and 50 C/N ratio treatments,mycelium dry weight essentially affected Mn P activity and both Li P and Mn P activities,respectively.     

Role of Biochar and Fungi on PAH Sorption to Soil Rich in Organic Matter

The use of biochar (BC) has been suggested for remediation of contaminated soils. This study aims to investigate the role of microorganisms in sorption of PAH to BC-amended soils. Fungi, especially the wood and litter-degrading fungi, have shown the ability for humification and to degrade recalcitrant molecules, and are thus suitable model organisms. Haplic Arenosol with high organic matter content was chosen to highlight the importance of soil organic matter (SOM) in PAH sorption, possibly to form non-extractable residue. Basidiomycetous fungi Agrocybe praecox and Phanerochaete velutina grown on pine bark were inoculated in organic matter (OM)-rich Haplic Arenosol and OM-poor sandy loam with either BC or chemically activated BC (ABC) and ¹⁴C-labelled pyrene for 60 days. Fungi did not mineralize pyrene, but increased sorption up to 47–56% in BC-amended Haplic Arenosol in comparison with controls (13–25%) without a fungus irrespective of the presence of an adsorbent. In OM-poor sandy loam, only 9–12% of pyrene was sorbed to amended soil in the presence of fungus and adsorbent. The results suggest that BC and fungal amendment increased sorption of pyrene, especially to Haplic Arenosol more than by either BC or fungi alone.     

Batch Culture Enrichment of Indiginous Soil Microorganisms Capable of Catabolizing Creosote Components

Batch enrichment cultures for creosote catabolizing microorganisms was carried out using a creosote-contaminated soil as the inoculum. The flasks were separately spiked with phenol, o-cresol, m-cresol, p-cresol, naphthalene, anthracene, phenanthrene, pyrrole, fluorene, pyrene, fluoranthene, chrysene,benzo(a)pyrene and creosote (a complex mixture of about 400 compounds) in concentrations of 50, 100, 500, 1000, 5000, 10 000, 15 000, 20 000, 25 000 and 30 000 mg L^-1. The flasks were incubated on a rotary shaker in the dark at 30 °C. Samples for analysis were taken from the flasks every three days for three weeks. Counts of microorganisms were observed to be highest in most cases in 5000 mg L^-1 cultures. The pH values were observed to fluctuate between 5 and8 but this did not seem to affect the growth of the organisms except at 50 and 100 mg L^-1 in the phenolics and some polycyclic aromatic hydrocarbons (PAHs) were the decreases correlated with decreases in cell counts. The isolates in the first week were mainly of one morphological type in most cultures. In subsequent weeks, the populations became mixed. The higher molecular mass PAHs at higher concentration continued to support only a few types of organisms. Isolates included bacteria, actinomycetes and fungi. The phenolics and naphthalene were more readily removed (up to 100%) from the cultures. Other hydrocarbons removal were between 45 and 83% with the higher molecular mass compounds being most recalcitrant. The decreases in creosote concentration was similar to those in the phenolic compounds and the lower molecular mass compounds up to a concentration of 10 000mg L^-1. Decreases in creosote concentration started to decrease from a concentration of 15 000 mg L^-1 upward. Subsequent subculturing was observed to enhance the degradative capabilities of the isolates and the further removal of the higher molecular mass compounds. However, this enhanced degradation was much lower in creosote cultures than in the other cultures.     

Effect of Anthracene and Pyrene on Dehydrogenases Activity in Soils Exposed and Unexposed to PAHs

The effect of anthracene and pyrene on dehydrogenases activitywas compared between freshly spiked soils and soils previouslyexposed to PAHs. Four different soils (two soils from anunpolluted rural area and two soils from highly pollutedindustrial areas) were spiked with anthracene and pyrene atthe levels of 1, 10, 100 and 400 mg Σ2PAH per kg of soil (laboratory experiments). The soil samples were moisted to60% of water holding capacity and incubated in the dark at 18-20 °C. Dehydrogenase activity was determined after 7 and30 days. The results indicate that long-term exposure of soilfrom an industrial area to high level of PAHs (Σ13PAH = 40 mg kg^-1) caused the acclimatisation of soilmicroorganisms and lowered their sensitivity to these compounds.After the longer incubation period (30 days vs. 7 days)the soil microorganisms in the uncontaminated rural samples showed an increase in their tolerance to the freshly introduced PAH compounds; in the industrial soils the effect was less pronounced. However, this apparent adaptation of soil microorganisms may be also partly explained by the dissipation and/or ageing processes of anthracene and pyrene during incubation.     

Independent roles of ectomycorrhizal and saprotrophic communities in soil organic matter decomposition

The relative roles of ectomycorrhizal (ECM) and saprotrophic communities in controlling the decomposition of soil organic matter remain unclear. We tested the hypothesis that ECM community structure and activity influences the breakdown of nutrient-rich biopolymers in soils, while saprotrophic communities primarily regulate the breakdown of carbon-rich biopolymers. To test this hypothesis, we used high-throughput techniques to measure ECM and saprotrophic community structure, soil resource availability, and extracellular enzyme activity in whole soils and on ECM root tips in a coastal pine forest. We found that ECM and saprotroph richness did not show spatial structure and did not co-vary with any soil resource. However, species richness of ECM fungi explained variation in the activity of enzymes targeting recalcitrant N sources (protease and peroxidase) in bulk soil. Activity of carbohydrate- and organic P- targeting enzymes (e.g. cellobiohydrolase, β-glucosidase, α-glucosidase, hemicellulases, N-acetyl-glucosaminidase, and acid phosphatase) was correlated with saprotroph community structure and soil resource abundance (total soil C, N, and moisture), both of which varied along the soil profile. These observations suggest independent roles of ECM fungi and saprotrophic fungi in the cycling of N-rich, C-rich, and P-rich molecules through soil organic matter. Enzymatic activity on ECM root tips taken from the same soil cores used for bulk enzyme analysis did not correlate with the activity of any enzyme measured in the bulk soil, suggesting that ECM contributions to larger-scale soil C and nutrient cycling may occur primarily via extramatrical hyphae outside the rhizosphere.     

Influence of Nitrogen Addition and Plant Root Parameters on Phytoremediation of Pyrene-contaminated Soil

Phytoremediation is a method in which plants, soil microorganisms, amendments, and agronomic techniques interact to enhance contaminant degradation. We hypothesized that bermudagrass (Cynodon dactylon L) and an appropriate amount of N fertilizer would improve remediation of pyrene-contaminated Captina silt loam soil. The soil was contaminated with 0 or 1,000 mg pyrene/kg of soil and amended with urea at pyrene-C:urea-N (C:N) ratios of 4.5:1, 9:1, 18:1, or unamended (36:1). Either zero, one, two, or three bermudagrass sprigs were planted per pot and ?33 kPa moisture potential was maintained. Pyrene concentrations, inorganic-N levels, shoot and root parameters, and pyrene degrader microbial numbers were measured following a 100-day greenhouse study. At a C:N ratio of 4.5:1, the presence of plants increased pyrene biodegradation from 31% for the no plant treatment to a mean of 62% for the one, two, and three plant treatments. With no plants and C:N ratios of 4.5:1, 9:1, 18:1, and 36:1, the mean pyrene biodegradation was 31, 52, 77, and 88%, respectively, indicating that increased inorganic-N concentration in the soil reduced pyrene degradation in the treatments without plants. Additionally, none of the one, two, or three plant treatments at any of the C:N ratios were different with a mean pyrene degradation value of 69% after 100 days. Pyrene resulted in reduced shoot and root biomass, root length, and root surface area, but increased root diameter. The pyrene degrading microbial numbers were approximately 10,000-fold higher in the pyrene-contaminated soil compared to the control. At the highest N rate, bermudagrass increased pyrene degradation compared to the no plant treatment, however, in the unvegetated treatment pyrene degradation was reduced with added N.     

Dissipation of polycyclic aromatic hydrocarbons (PAHs) in soil microcosms amended with mushroom cultivation substrate

The potential of mushroom cultivation substrate (MCS) in bioremediation was examined in polycyclic aromatic hydrocarbon (PAH)-contaminated soil. After a 60-day incubation, 32.9% dissipation of the 15 studied PAHs was observed in MCS-amended microcosms, with anthracene, benzo(a)pyrene and benzo(a)anthracene being the most degradable PAHs. MCS significantly increased the abundance and changed the community compositions of bacteria, fungi and aromatic hydrocarbon degraders. Two species belonging to the Sordariomycetes of the Ascomycota were enriched in all MCS-treated soil samples, and coupled with the unique changes in the PAH profile, this implies the involvement of laccase-like enzymes. Limited improvement was observed after adding Pleurotus ostreatus, possibly because of its poor colonization of the soil. In addition, alfalfa appeared to antagonize the bioremediation effects of MCS. The results of this study suggest that MCS can be a cost-effective and green biostimulation agent, thereby providing support for the development of MCS-based biostimulation of PAH-contaminated soil.     

Evolution of Chemistry along the Bagmati Drainage Network in Kathmandu Valley

Two fungal strains producing ligninolytic enzymes and having the potential to decolorize distillery effluent were isolated from the soil of a distillery effluent contaminated site. DNA was isolated from the pure cultures of these fungi and polymerase chain reaction (PCR) amplification of their internal transcribed spacer (ITS) region of nuclear ribosomal DNA was carried out. Further, the DNA was sequenced and the comparison of generated sequence with database led to their identification as Penicillium pinophilum TERI DB1 and Alternaria gaisen TERI DB6 respectively. These two isolates along with one isolate of Pleurotus florida EM 1303 were assessed for their ligninolytic enzyme activity in culture filtrate as well as after solid state fermentation on two substrates wheat straw and corncob powder. Ergosterol was measured to assess the growth of fungi on solid media. Both P. pinophilum TERI DB1 and A. gaisen TERI DB6 were found to produce laccase, manganese-dependent peroxidases (MnP) and lignin peroxidases (LiP). The immobilized fungal biomass was then used for decolorization of the post biomethanated wastewater from the distillery. Reduction in color up to the magnitude of 86, 50 and 47% was observed with P. florida, P. pinophilum and A. gaisen respectively.     

Modifications of degradation-resistant soil organic matter by soil saprobic microfungi

Modifications of humic (HA) and fulvic (FA) acids in their solutions and in sterile soil by microfungal species and two well-known HA degraders were studied by measurement of total oxidizable carbon (OC), absorbances, enzyme activities and CO₂ release. The effect of glucose on FA and HA, and also minerals on FA utilization was also observed. Microfungi affected HA more than FA. Common microfungal species decolorized HA and decreased their molecular size (evaluated in terms of A₄/A₆ ratio). Some of them decreased aromaticity of HA and FA as the only carbon sources. They did not affect OC, although released CO₂ from FA. Under higher availability of mineral nutrients, the FA aromaticity increased and FA decolorization decreased. The molecular size of HA decreased in the presence of glucose. In the FA medium complemented by minerals, the known basidiomycete HA degrader, Trametes versicolor, decreased the amount of aromatic compounds in contrast to microfungal species Alternaria alternata, Clonostachys rosea, Exophiala cf. salmonis, Fusarium coeruleum, F. redolens, Penicillium canescens, Phoma sp. and another basidiomycete Phanerochaete chrysosporium. No microfungal species exhibited lignin peroxidase activity. On the other hand, activities of manganese peroxidase (MnP) were recorded for all species incubated in FA. Carbon dioxide produced from soil inoculated by microfungi negatively correlated with the decolorization, aromaticity and OC of/in FA reisolated from the soil. The results support the hypothesis that soil microfungi can attack both HA and FA and can represent an important factor in their transformations in arable soils. The enzyme involved in FA modifications is probably fungal MnP. We enriched a group of known HA and FA degraders and showed some abilities of a few frequent soil microfungal species. This can be one of the first but important step towards learning the functioning of carbon release from the big reservoir represented by humic substances in arable soils.     

Interaction between earthworms and arbuscular mycorrhizal fungi on the degradation of oxytetracycline in soils

The interactive impact of earthworms (Eisenia fetida) and arbuscular mycorrhizal fungi (Rhizophagus intraradices, AM fungi) on the degradation of oxytetracycline (OTC) in soils was studied under greenhouse conditions. Treatments included maize plants inoculated vs. not inoculated with AM fungi and treated with or without earthworms at low (1 mg kg⁻¹ soil DM) or high (100 mg kg⁻¹ soil DM) OTC rates. The root colonization rate, the hyphal density of mycorrhizae, the residual OTC concentration in soils, catalase, dehydrogenase, urease, soil microbial biomass C, Shannon–Wiener index (H) for microbial communities from T-RFLP profiles were measured at harvest. The results indicated that earthworms and AM fungi would individually or interactively enhance OTC decomposition and significantly decreased the residual OTC concentration at both high and low OTC rates. Both earthworms and AM fungi could promote the degradation of OTC by increasing soil microbial biomass C at both high and low OTC rates. The effect of soil enzyme activity and soil microbial diversity on OTC decomposition was different between high and low OTC rates. Hyphomicrobium and Bacillus cereus were dominant bacteria, and Thielavia and Chaetomium were dominant phyla of fungi at all occasions. Earthworm activity stimulated the growth of Hyphomicrobium and Thielavia, while AM fungi may stimulate B. cereus, Thielavia and Chaetomium, resulting in greater OTC decomposition. The interaction between earthworms and AM fungi in affecting the degradation of OTC may be attributed to different mechanisms, depending on soil microbial biomass, function (enzyme activity) and communities (the abundance of Hyphomicrobium, B. cereus, Thielavia and Chaetomium) in the soil.