Ligninolytic enzymes of selected white rot fungi cultivated on wheat straw

Advanced biological sequential treatment of mature landfill leachate using aerobic activated sludge SBR and fungal bioreactor

This study utilized Penicillium spp. to treat mature landfill leachate (MLL) in a continuous bioreactor and batch experimental tests under non-sterile conditions. MLL characteristics such as chemical oxygen demand (COD), soluble COD (sCOD), total carbon (TC), total organic carbon (TOC), and color removal efficiency were determined. The lignocellulosic enzymatic activity of laccase (Lac), lignin-peroxidase (LiP), and manganese-peroxidase (MnP) was also determined. The batch experimental test was carried out with raw and pretreated MLL containing the initial NH4 +-N concentrations of 0, 105, 352, and 914 mg/L. A maximum COD reduction of 41% and maximum enzymatic activity of 193, 37, and 25 U/L for Lac, LiP and MnP was recorded for the MLL containing 352 mg/L NH4 +-N. The continuous bioreactor exhibited maximum values of 52, 54, 60, 58, and 75 percentage of COD, sCOD, TC, TOC, and color removal efficiency with MLL containing 352 mg/L NH4 +-N that was pretreated at HRT 120 h, while the maximum detected lignocellulosic enzymatic activities were 149, 27, and 16 U/L for Lac, LiP, and MnP, respectively. A total of 64% COD reduction was achieved from the raw MLL considering 12% COD and 100% NH4 +-N reduction in the aerobic activated sludge sequencing batch reactor pretreatment process. The steady and higher removal efficiency of the bioreactor over the entire study period is promising for further exploration to enhance removal of refractory contaminants from the MLL.

Fungal treatment of mature landfill leachate utilizing woodchips and wheat-straw as co-substrates

Mature landfill leachate (MLL) tend to be highly contaminated due to the presence of refractory contaminants such as humic-fulvic substances, xenobiotic compounds, and heavy metals. This study investigated the treatment efficiency of MLL by deploying Cladosporium sp., Trichoderma asperellum, and Tyromyces chioneus fungal strains. Chemical oxygen demand (COD) and soluble COD (sCOD) removal efficiencies were assessed along with the evaluation of lignocellulosic enzymatic activities of laccase (Lac), lignin-peroxidase (LiP), and manganese-peroxidase (MnP). Glucose, woodchips, and wheat straw were utilized as co-substrates. Higher percentage of COD and sCOD reduction efficiencies and lignocellulosic enzymatic activities were found for woodchips than glucose and wheat-straw. The highest sCOD removal rates were 44%, 38% and 59% by Cladosporium sp., T. asperellum, and T. chioneus, respectively. Overall, Lac activity was significantly higher than LiP and MnP activity for all three species. Tyromyces chioneus was the most effective strain among the three selected fungi in terms of COD and sCOD reduction efficiencies and high enzymatic activities of 165, 14 and 20 U/L were detected for Lac, LiP, and MnP, respectively. Tyromyces chioneus is a potentially effective fungal strain for the enhanced bioremediation of MLL and its further investigation is recommended to explore the removal of recalcitrant contaminants from problematic wastewater.

Stability of fungal biomass continuously fed with tannic acid in a non-sterile moving-packed bed reactor

A number of bacteria and fungi are known to degrade tannins. In this study, the efficiency of the white-rot fungus, Bjerkandera adusta MUT 2295, was evaluated for the treatment of a synthetic solution prepared with tannic acid. Tests were performed in continuously fed, bench-scale, packed-bed reactors, operated under non-sterile conditions with biomass immobilized within PolyUrethane Foam cubes (PUFs). The main parameters monitored to evaluate the process efficiency were: soluble Chemical Oxygen Demand (sCOD), Total Organic Carbon (TOC) removal, and activities. of Tannase and Lignin Peroxidase. At the end of the process, additional parameters were evaluated, including the increase of fungal dry weight and the presence of ergosterol. The reactor was operative for 210 days, with maximum sCOD and TOC removal of 81% and 73%, respectively. The reduction of sCOD and TOC were positively correlated with the detection of Tannase and Lignin Peroxidase (LiP) activities. Increases in biomass within the PUF cubes was associated with increases in ergosterol concentrations. This study proved that the fungal-based system tested was efficient for the degradation of tannic acid over a period of time, and under non-sterile conditions.

Effect of lignocellulosic enzymes on the treatment of mature landfill leachate

The inherent necessity to remediate refractory contaminants from the toxic problematic wastewater like mature landfill leachate (MLL) has become a global challenge. This study investigated the effect of a potentially sustainable technological approach, i.e. lignocellulosic enzymatic activities (lignin-peroxidase, manganese-peroxidase and laccase), produced from six selected fungi on the removal efficiency of chemical oxygen demand (COD) and soluble COD (sCOD) from the MLL. The COD/sCOD removal percentage was significantly increased with higher enzymatic activities. Tyromyces chioneus was revealed to be the first ever fungi that produced significant amount of all three enzymes. Penicillium sp. and Tyromyces chioneus were the most effective strains, which removed 66% and 59% of COD, and 64% and 57% of sCOD, respectively. The maximum lignin-peroxidase, manganese-peroxidase and laccase enzymatic activities were 19.3 and 26.9 U/L by Tyromyces chioneus, and 249.8 U/L by Penicillium sp, respectively. It was concluded that lignocellulosic biomass could be a sustainable and advanced biological treatment option to remove refractory components from MLL.

Diversity of fungi in creosote-treated crosstie wastes and their resistance to polycyclic aromatic hydrocarbons

This study was conducted to generate information regarding the diversity of fungi inhabiting creosote-treated wood in a storage yard for crosstie wastes in Gwangmyeong, Korea. Additionally, the resistance to polycyclic aromatic hydrocarbons (PAHs) of indigenous fungi that mainly occupy creosote-treated wood was evaluated. We isolated fungi from the surface and inner area of crosstie wastes and identified them using a combination of traditional methods and molecular techniques. Overall, 179 isolates including 47 different species were isolated from 240 sampling sites. The identified fungal species included 23 ascomycetes, 19 basidiomycetes, and 5 zygomycetes. Three species, Alternaria alternata, Irpex lacteus, and Rhizomucor variabilis, were the most frequently isolated ascomycetes, basidiomycetes, and zygomycetes, respectively. The results of this study showed that there was a large difference in the fungal diversity between the surface and the inner area. Additionally, zygomycetes and ascomycetes were found to have a greater tolerance to PAHs than basidiomycetes. However, two basidiomycetes, Heterobasidion annosum and Schizophyllum commune, showed very high resistance to PAHs, even in response to the highest concentration (1,000 ppm), which indicates that these species may play a role in the degradation of PAHs.

Modification of wheat straw lignin by solid state fermentation with white-rot fungi

The potential of crude enzyme extracts, obtained from solid state cultivation of four white-rot fungi (Trametes versicolor, Bjerkandera adusta, Ganoderma applanatum and Phlebia rufa), was exploited to modify wheat straw cell wall. At different fermentation times, manganese-dependent peroxidase (MnP), lignin peroxidase (LiP), laccase, carboxymethylcellulase (CMCase), avicelase, xylanase and feruloyl esterase activities were screened and the content of lignin as well as hydroxycinnamic acids in fermented straw were determined. All fungi secreted feruloyl esterase while LiP was only detected in crude extracts from B. adusta. Since no significant differences (P>0.05) were observed in remaining lignin content of fermented straw, LiP activity was not a limiting factor of enzymatic lignin removal process. The levels of esterified hydroxycinnamic acids degradation were considerably higher than previous reports with lignocellulosic biomass. The data show that P. rufa, may be considered for more specific studies as higher ferulic and p-coumaric acids degradation was observed for earlier incubation times.

Mycelium growth and degradation of creosote-treated wood by basydiomycetes

Tolerance of wood decay fungi of the genera Agrocybe, Armillaria, Auricularia, Daedalea, Pleurotus, Trametes to the presence of various amounts of creosote-treated wood (CTW) in the growth medium was compared. In the case of the most tolerant strain, Pleurotus ostreatus SMR 684, extracellular laccase and peroxidase specific activities were monitored during growth in the presence of CTW. Degradation of various creosote-constituting polycyclic aromatic hydrocarbons by this strain was evaluated by GC-MS and the ecotoxicity of treated and untreated CTW was compared by Microtox test.

Isolation and purification of pyranose 2-oxidase from Phanerochaete chrysosporium and characterization of gene structure and regulation

Pyranose 2-oxidase (POX) was recovered from Phanerochaete chrysosporium BKM-F-1767 solid substrate culture using mild extraction conditions and was purified. (13)C-nuclear magnetic resonance confirmed production of d-arabino-hexos-2-ulose (glucosone) from d-glucose with the oxidase. Peptide fingerprints generated by liquid chromatography-tandem mass spectrometry of tryptic digests and analysis of the corresponding cDNA revealed a structurally unusual sequence for the P. chrysosporium POX. Relatively high levels of pox transcript were detected under carbon-starved culture conditions but not under nutrient sufficiency. This regulation pattern is similar to that observed for lignin peroxidases, manganese peroxidases, and glyoxal oxidase of P. chrysosporium, supporting evidence that POX has a role in lignocellulose degradation.

Decolorization and bioremediation of molasses wastewater by white-rot fungi in a semi-solid-state condition

Molasses wastewater (vinasse; the by-product of distillation of fermented sugar) was decolorized and its chemical oxygen demand (COD) was reduced in static cultivation using the fungi Coriolus versicolor, Funalia trogii, Phanerochaete chrysosporium and Pleurotus pulmonarius ('Pleurotus sajorcaju'). The effect of cotton stalk on decolorizing and COD removing capability of four fungi was determined. In the entire concentration range tested (10-30%), wastewater was effectively decolorized by C. versicolor and F. trogii. Cotton stalk addition stimulated the decolorization activity of all fungi. The utilization of cotton stalk represents several advantages due to its function as an attachment place and as a source of nutrients; its use also reduces process costs.

Decolorization of RBBR by plant cells and correlation with the transformation of PCBs

An extracellular H2O2-requiring Remazol Brilliant Blue R (RBBR) decolorizing enzyme activity was detected after cultivation of cells of various plant species both in liquid medium and when growing on agar plates containing RBBR. Level of the enzyme activity was compared with the ability to metabolize polychlorinated biphenyls (PCBs). The ability to decolorize RBBR was tested in the presence and absence of PCBs. The cultures with high PCB-transforming activity proved to exhibit RBBR oxidase much more resistant towards the influence of PCBs. In addition low activities of lignin peroxidase (LiP) and manganese dependent peroxidase (MnP) were detected in medium and in plant cells. No correlation of MnP and LiP activities with PCB degradation could be found. The RBBR decolorization could be used as a rough screening method for plant cultures able to metabolize PCBs.

Industrial and agricultural wastes as substrates for laccase production by white-rot fungi

White-rot fungi, Coriolus versicolor and Funalia trogii, produced laccase on media with diluted olive-oil mill wastewater and vinasse. Addition of spent cotton stalks enhanced the laccase activity with a maximum after 12 d of cultivation.

Effect of spent cotton stalks on color removal and chemical oxygen demand lowering in olive oil mill wastewater by white rot fungi

Wastewater from olive oil mill was decolorized (and its chemical oxygen demand reduced in static cultivation) using the fungi Coriolus versicolor, Funalia trogii, Phanerochaete chrysosporium and Pleurotus sajor-caju. The effect of cotton stalk on decolorizing and COD removing capability was demonstrated. P. chrysosporium (in 20% medium with cotton stalk) reduced the COD by 48% and color by 58%, F. trogii (in 30% medium with cotton stalk)) by 51 and 55%, respectively.

Degradation of 2,4-dichlorophenol and pentachlorophenol by two brown rot fungi

Wheat straw cultures of the brown rot fungi Gloeophyllum striatum and G. trabeum degraded 2,4-dichlorophenol and pentachorophenol. Up to 54% and 27% 14CO2, respectively, were liberated from uniformly 14C-labeled substrates within 6 weeks. Under identical conditions Trametes versicolor, a typical white rot species employed as reference, evolved up to 42% and 43% 14CO2 and expressed high activities of laccase, manganese peroxidase, and manganese-independent peroxidase. No such activity could be detected in straw or liquid cultures of Gloeophyllum. Moreover, G. striatum degraded both chlorophenols most efficiently under non-cometabolic conditions, i.e. on a defined mineral medium lacking sources of carbon, nitrogen and phosphate.

Production of manganese peroxidase and organic acids and mineralization of 14C-labelled lignin (14C-DHP) during solid-state fermentation of wheat straw with the white rot fungus nematoloma frowardii

The basidiomycetous fungus Nematoloma frowardii produced manganese peroxidase (MnP) as the predominant ligninolytic enzyme during solid-state fermentation (SSF) of wheat straw. The purified enzyme had a molecular mass of 50 kDa and an isoelectric point of 3.2. In addition to MnP, low levels of laccase and lignin peroxidase were detected. Synthetic 14C-ring-labelled lignin (14C-DHP) was efficiently degraded during SSF. Approximately 75% of the initial radioactivity was released as 14CO2, while only 6% was associated with the residual straw material, including the well-developed fungal biomass. On the basis of this finding we concluded that at least partial extracellular mineralization of lignin may have occurred. This conclusion was supported by the fact that we detected high levels of organic acids in the fermented straw (the maximum concentrations in the water phases of the straw cultures were 45 mM malate, 3.5 mM fumarate, and 10 mM oxalate), which rendered MnP effective and therefore made partial direct mineralization of lignin possible. Experiments performed in a cell-free system, which simulated the conditions in the straw cultures, revealed that MnP in fact converted part of the 14C-DHP to 14CO2 (which accounted for up to 8% of the initial radioactivity added) and 14C-labelled water-soluble products (which accounted for 43% of the initial radioactivity) in the presence of natural levels of organic acids (30 mM malate, 5 mM fumarate).

Involvement of an extracellular H2O2-dependent ligninolytic activity of the white rot fungus Pleurotus ostreatus in the decolorization of Remazol brilliant blue R

During solid-state fermentation of wheat straw, a natural lignocellulosic substrate, the white rot fungus Pleurotus ostreatus produced an extracellular H2O2-requiring Remazol brilliant blue R (RBBR)-decolorizing enzymatic activity along with manganese peroxidase, manganese-independent peroxidase, and phenol oxidase activities. The presence of RBBR was not essential for the production of RBBR-decolorizing enzymatic activity by P. ostreatus, because this activity was also produced in the absence of RBBR. This RBBR-decolorizing enzymatic activity in crude enzyme preparations of 14- and 20-day-old cultures exhibited an apparent Km for RBBR of 31 and 52 microM, respectively. The RBBR-decolorizing enzyme activity was maximal in the pH range 3.5 to 4.0. This activity was independent of manganese, and veratryl alcohol had no influence on it. Manganese peroxidase of P. ostreatus did not decolorize RBBR. This H2O2-dependent RBBR-decolorizing enzymatic activity behaved like an oxygenase possessing a catalytic metal center, perhaps heme, because it was inhibited by Na2S2O5, NaCN, NaN3, and depletion of dissolved oxygen. Na2S2O5 brought an early end to the reaction without interfering with the initial reaction rate of RBBR oxygenase. The activity was also inhibited by cysteine. Concentrations of H2O2 higher than 154 microM were observed to be inhibitory as well. Decolorization of RBBR by P. ostreatus is an oxidative process.