Lignin modifying enzymes of Coriolopsis polyzona and their role in olive oil mill wastewaters decolourisation

A novel laccase from Trametes polyzona with high performance in the decolorization of textile dyes

Laccases are multicopper oxidases able to oxidize several phenolic compounds and find application in numerous industrial applications. Among laccase producers, white-rot fungi represent a valuable source of multiple isoforms and isoenzymes of these multicopper oxidases. Here we describe the identification, biochemical characterization, and application of laccase 2 from Trametes polyzona (TP-Lac2), a basidiomycete fungus emerged among others that have been screened by plate assay. This enzyme has an optimal temperature of 50 °C and in acidic conditions it is able to oxidize both phenolic and non-phenolic compounds. The ability of TP-Lac2 to decolorize textile dyes was tested in the presence of natural and synthetic mediators at 30 °C and 50 °C. Our results indicate that TP-Lac2 most efficiently decolorizes (decolorization rate > 75%) malachite green oxalate, orange G, amido black10B and bromocresol purple in the presence of acetosyringone and 2,2'-azinobis (3-ethylbenzthiazoline-6-sulfonate)-ABTS. Overall, the laccase mediator system consisting of TP-Lac2 and the natural mediator acetosyringone has potential as an environmentally friendly alternative for wastewater treatment in the textile industry.

Dephenolization of palm oil mill effluent by oil palm fiber-immobilized Trametes hirsuta AK04 in temporary immersion bioreactor for the enhancement of biogas production

The dephenolization of palm oil mill effluent (POME) with oil palm fiber-immobilized Trametes hirsuta AK 04 was conducted in a temporary immersion bioreactor to reduce the inhibitory effects of phenolics in anaerobic digestion. Longer immersion times provided greater removal of phenolics due to a higher release of manganese peroxidase. The most effective dephenolization was observed at 6 h immersed and 2 h non-immersed time (immersion ratio 6/8) with maximum removal of 85% from 1277 mg L^-1 of phenolics in 4 days. The immobilized fungus maintained its high activity during multiple repeated batch treatments. The pretreated POME of 2 h showed higher methane yields compared with the untreated POME substrate. The methane yields increased with increasing pretreatment time and dephenolization levels. The results suggested that an increased abundance of methanogens was associated with the detoxification of phenolics. The fungal biomass contained crude protein, amino acids, and essential phenolics, which can be used as animal feed supplements.

Optimization of mycoremediation treatment for the chemical oxygen demand (COD) and ammonia nitrogen (AN) removal from domestic effluent using wild-Serbian Ganoderma lucidum (WSGL)

The fungi-based technology, wild-Serbian Ganoderma lucidum (WSGL) as myco-alternative to existing conventional microbial-based wastewater treatment is introduced in this study as a potential alternative treatment. The mycoremediation is highly persistent for its capability to oxidatively breakdown pollutant substrates and widely researched for its medicinal properties. Utilizing the nonhazardous properties and high degradation performance of WSGL, this research aims to optimize mycoremediation treatment design for chemical oxygen demand (COD) and ammonia nitrogen (AN) removal in domestic wastewater based on proposed Model 1 (temperature and treatment time) and Model 2 (volume of pellet and treatment time) via response surface methodology (RSM). Combined process variables were temperature (0C) (Model 1) and the volume of mycelial pellets (%) (Model 2) against treatment time (hour). Response variables for these two sets of central composite design (CCD) were the removal efficiencies of COD (%) and AN (%). The regression line fitted well with the data with R2 values of 0.9840 (Model 1-COD), 0.9477 (Model 1-AN), 0.9988 (Model 2-COD), and 0.9990 (Model 2-AN). The lack of fit test gives the highest value of sum of squares equal to 9494.91 (Model 1-COD), 9701.68 (Model 1-AN), 23786.55 (Model 2-COD), and 13357.02 (Model 2-AN), with probability F values less than 0.05 showing significant models. The optimized temperature for Model 1 was at 25 °C within 24 h of treatment time with 95.1% COD and 96.3% AN removals. The optimized condition (temperature) in Model 1 was further studied in Model 2. The optimized volume of pellet for Model 2 was 0.25% in 24-h treatment time with 76.0% COD and 78.4% AN removals. Overall, the ascended sequence of high volume of pellet considered in Model 2 will slow down the degradation process. The best fit volume of pellet with maximum degradation of COD and AN is equivalent to 0.1% at 25 °C in 24 h. The high performance achieved demonstrates that the mycoremediation of G. lucidum is highly potential as part of the wastewater treatment system in treating domestic wastewater of high organic loadings.

Enhanced Production of Ligninolytic Enzymes by a Mushroom Stereum ostrea

The white rot fungi Stereum ostrea displayed a wide diversity in their response to supplemented inducers, surfactants, and copper sulphate in solid state fermentation. Among the inducers tested, 0.02% veratryl alcohol increased the ligninolytic enzyme production to a significant extent. The addition of copper sulphate at 300 μM concentration has a positive effect on laccase production increasing its activity by 2 times compared to control. Among the surfactants, Tween 20, Tween 80, and Triton X 100, tested in the studies, Tween 80 stimulated the production of ligninolytic enzymes. Biosorption of dyes was carried out by using two lignocellulosic wastes, rice bran and wheat bran, in 50 ppm of remazol brilliant blue and remazol brilliant violet 5R dyes. These dye adsorbed lignocelluloses were then utilized for the production of ligninolytic enzymes in solid state mode. The two dye adsorbed lignocelluloses enhanced the production of laccase and manganese peroxidase but not lignin peroxidase.

Hybrid microfluidic fuel cell based on Laccase/C and AuAg/C electrodes

A hybrid glucose microfluidic fuel cell composed of an enzymatic cathode (Laccase/ABTS/C) and an inorganic anode (AuAg/C) was developed and tested. The enzymatic cathode was prepared by adsorption of 2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and Laccase on Vulcan XC-72, which act as a redox mediator, enzymatic catalyst and support, respectively. The Laccase/ABTS/C composite was characterised by Fourier Transform Infrared (FTIR) Spectroscopy, streaming current measurements (Zeta potential) and cyclic voltammetry. The AuAg/C anode catalyst was characterised by Transmission electron microscopy (TEM) and cyclic voltammetry. The hybrid microfluidic fuel cell exhibited excellent performance with a maximum power density value (i.e., 0.45 mW cm(-2)) that is the highest reported to date. The cell also exhibited acceptable stability over the course of several days. In addition, a Mexican endemic Laccase was used as the biocathode electrode and evaluated in the hybrid microfluidic fuel cell generating 0.5 mW cm(-2) of maximum power density.

Comparative examination of the olive mill wastewater biodegradation process by various wood-rot macrofungi

Olive mill wastewater (OMW) constitutes a major cause of environmental pollution in olive-oil producing regions. Sixty wood-rot macrofungi assigned in 43 species were evaluated for their efficacy to colonize solidified OMW media at initially established optimal growth temperatures. Subsequently eight strains of the following species were qualified: Abortiporus biennis, Ganoderma carnosum, Hapalopilus croceus, Hericium erinaceus, Irpex lacteus, Phanerochaete chrysosporium, Pleurotus djamor, and P. pulmonarius. Fungal growth in OMW (25%v/v in water) resulted in marked reduction of total phenolic content, which was significantly correlated with the effluent's decolorization. A. biennis was the best performing strain (it decreased phenolics by 92% and color by 64%) followed by P. djamor and I. lacteus. Increase of plant seeds germination was less pronounced evidencing that phenolics are only partly responsible for OMW's phytotoxicity. Laccase production was highly correlated with all three biodegradation parameters for H. croceus, Ph. chrysosporium, and Pleurotus spp., and so were manganese-independent and manganese dependent peroxidases for A. biennis and I. lacteus. Monitoring of enzymes with respect to biomass production indicated that Pleurotus spp., H. croceus, and Ph. chrysosporium shared common patterns for all three activities. Moreover, generation of enzymes at the early biodegradation stages enhanced the efficiency of OMW treatment.

Fungal laccases and their applications in bioremediation

Laccases are blue multicopper oxidases, which catalyze the monoelectronic oxidation of a broad spectrum of substrates, for example, ortho- and para-diphenols, polyphenols, aminophenols, and aromatic or aliphatic amines, coupled with a full, four-electron reduction of O₂ to H₂O. Hence, they are capable of degrading lignin and are present abundantly in many white-rot fungi. Laccases decolorize and detoxify the industrial effluents and help in wastewater treatment. They act on both phenolic and nonphenolic lignin-related compounds as well as highly recalcitrant environmental pollutants, and they can be effectively used in paper and pulp industries, textile industries, xenobiotic degradation, and bioremediation and act as biosensors. Recently, laccase has been applied to nanobiotechnology, which is an increasing research field, and catalyzes electron transfer reactions without additional cofactors. Several techniques have been developed for the immobilization of biomolecule such as micropatterning, self-assembled monolayer, and layer-by-layer techniques, which immobilize laccase and preserve their enzymatic activity. In this review, we describe the fungal source of laccases and their application in environment protection.

Laccase production by Coriolopsis caperata RCK2011: optimization under solid state fermentation by Taguchi DOE methodology

Laccase production by Coriolopsis caperata RCK2011 under solid state fermentation was optimized following Taguchi design of experiment. An orthogonal array layout of L18 (2(1) × 3(7)) was constructed using Qualitek-4 software with eight most influensive factors on laccase production. At individual level pH contributed higher influence, whereas, corn steep liquor (CSL) accounted for more than 50% of the severity index with biotin and KH2PO4 at the interactive level. The optimum conditions derived were; temperature 30°C, pH 5.0, wheat bran 5.0 g, inoculum size 0.5 ml (fungal cell mass = 0.015 g dry wt.), biotin 0.5% w/v, KH2PO4 0.013% w/v, CSL 0.1% v/v and 0.5 mM xylidine as an inducer. The validation experiments using optimized conditions confirmed an improvement in enzyme production by 58.01%. The laccase production to the level of 1623.55 Ugds(-1) indicates that the fungus C. caperata RCK2011 has the commercial potential for laccase.

Purification and characterization of the extracellular laccase produced by Trametes polyzona WR710-1 under solid-state fermentation

Laccase from Trametes polyzona WR710-1 was produced under solid-state fermentation using the peel from the Tangerine orange (Citrus reticulata Blanco) as substrate, and purified to homogeneity. This laccase was found to be a monomeric protein with a molecular mass of about 71 kDa estimated by SDS-PAGE. The optimum pH was 2.0 for ABTS, 4.0 for L-DOPA, guaiacol, and catechol, and 5.0 for 2,6-DMP. The K(m) value of the enzyme for the substrate ABTS was 0.15 mM, its corresponding V(max) value was 1.84 mM min(-1), and the k(cat)/K(m) value was about 3960 s(-1)  mM(-1). The enzyme activity was stable between pH 6.0 and 8.0, at temperatures of up to 40 °C. The laccase was inhibited by more than 50% in the presence of 20 mM NaCl, by 95% at 5 mM of Fe(2+), and it was completely inhibited by 0.1 mM NaN(3). The N-terminal amino acid sequence of this laccase is AVTPVADLQISNAGISPDTF, which is highly similar to those of laccases from other white-rot basidiomycetes.

Biodegradation and detoxification of olive mill wastewater by selected strains of the mushroom genera Ganoderma and Pleurotus

Thirty-nine white-rot fungi belonging to nine species of Agaricomycotina (Basidiomycota) were initially screened for their ability to decrease olive-mill wastewater (OMW) phenolics. Four strains of Ganoderma australe, Ganoderma carnosum, Pleurotus eryngii and Pleurotus ostreatus, were selected and further examined for key-aspects of the OMW biodegradation process. Fungal growth in OMW-containing batch cultures resulted in significant decolorization (by 40-46% and 60-65% for Ganoderma and Pleurotus spp. respectively) and reduction of phenolics (by 64-67% and 74-81% for Ganoderma and Pleurotus spp. respectively). COD decrease was less pronounced (12-29%). Cress-seeds germination increased by 30-40% when OMW was treated by Pleurotus strains. Toxicity expressed as inhibition of Aliivibrio fischeri luminescence was reduced in fungal-treated OMW samples by approximately 5-15 times compared to the control. As regards the pertinent enzyme activities, laccase and Mn-independent peroxidase were detected for Ganoderma spp. during the entire incubation period. In contrast, Pleurotus spp. did not exhibit any enzyme activities at early growth stages; instead, high laccase (five times greater than those of Ganoderma spp.) and Mn peroxidases activities were determined at the end of treatment. OMW decolorization by Ganoderma strains was strongly correlated to the reduction of phenolics, whereas P. eryngii laccase activity was correlated with the effluent's decolorization.

Degradation of phenols in olive oil mill wastewater by biological, enzymatic, and photo-Fenton oxidation

BACKGROUND, AIM, AND SCOPE

Olive oil mill wastewater (OOMW) environmental impacts minimization have been attempted by developing more effective processes, but no chemical or biological treatments were found to be totally effective to mitigate their impact on receiving systems. This work is the first that reports simultaneously the efficiency of three different approaches: biological treatment by two fungal species (Trametes versicolor or Pleurotus sajor caju), enzymatic treatment by laccase, and chemical treatment by photo-Fenton oxidation on phenols removal.

MATERIALS AND METHODS

Those treatments were performed on OOMW with or without phenol supplement (p-coumaric, vanillin, guaiacol, vanillic acid, or tyrosol). OOMW samples resulted from treatments were extracted for phenols using liquid-liquid extraction and analyzed by gas chromatography coupled to mass spectrometry.

RESULTS

Treatment with T. versicolor or P. sajor caju were able to remove between 22% and 74% and between 8% and 76% of phenols, respectively. Treatment by laccase was able to reduce 4% to 70% of phenols whereas treatment by photo-Fenton oxidation was responsible for 100% phenols reduction.

DISCUSSION

Range of phenol degradation was equivalent between T. versicolor, P. sajor caju and laccase for p-coumaric, guaiacol, caffeic acid, and tyrosol in supplemented OOMW, which enhances this enzyme role in the biological treatment promoted by these two species.

CONCLUSIONS

Phenols were removed more efficiently by photo-Fenton treatment than by biological or enzymatic treatments.

RECOMMENDATIONS AND PERSPECTIVES

Use of fungi, laccase, or photo-Fenton presents great potential for removing phenols from OOMW. This should be further assessed by increasing the application scale and the reactor configurations effect on the performance, besides a toxicity evaluation of treated wastewater in comparison to raw wastewater.

Toxicity and organic content characterization of olive oil mill wastewater undergoing a sequential treatment with fungi and photo-Fenton oxidation

Olive oil mill wastewater (OOMW) is responsible for serious environmental problems. In this study, the efficiency of two treatments involving fungi and photo-Fenton oxidation, sequentially applied to OOMW was analyzed for organic compounds degradation and toxicity mitigation. The treatment with fungi (especially Pleurotus sajor caju) of diluted OOMW samples promoted a reduction of their acute toxicity to Daphnia longispina. Although this fungi species have not induced significant color reduction it was responsible for 72,91 and 77% reductions in chemical oxygen demand (COD), total phenolic and organic compound contents. After biological treatment, photo-Fenton oxidation seemed to be an interesting solution, especially for color reduction. However, the OOMWs remained highly toxic after photo-Fenton oxidation. Considering the second sequence of treatments, namely photo-Fenton oxidation followed by biological treatment, the former revealed, once more, a great potential because it can be applied to non-diluted OOMW, with significant reductions in COD (53-76%), total phenolic content (81-92%) and organic compounds content (100%). Despite fungal species still have demonstrated a high capacity for bioaccumulation of organic compounds, resulting from photo-Fenton oxidation, the biological treatment did not cause substantial benefits in terms of COD, total phenolic content and toxicity reduction.

Reduced toxicity of olive mill waste waters by oxidative coupling with biomimetic catalysis

Large quantities of environmentally toxic olive mill waste waters (OMWW) result from olive oil production worldwide. A synthetic water-soluble meso-tetra(2,6-dichloro-3-sulfonatophenyl)porphyrinate of iron(III) chloride (FePha) was used as biomimetic catalystto oxidatively couple toxic phenols in OMWW fractions obtained by micro-, ultra-, and nanofiltration, and reverse osmosis. The occurrence of oxidative coupling in different OMWW size-fractions was assessed by high performance size exclusion chromatography (HPSEC), before and after conformational disruption with acetic acid, and measurements of proton spin-lattice relaxation time in the rotating frame (T1(rho)H) through 13C-CPMAS-NMR spectroscopy. The concurrent reduction in toxicity of OMWW size-fractions brought about by the FePha treatment was monitored by an algal bioassay. HPSEC chromatograms of OMWW samples subjected to catalyzed coupling showed apparent weight-average molecular weight (Mwa) values varying from 18 to 185% larger than for control. Moreover, when such FePha-treated fractions were added to acetic acid prior to HPSEC, the Mwa values still ranged from 14 to 162% larger than for control fractions similarly treated with acetic acid. This evidence of polymerization among toxic phenols was confirmed by T1(rho)(H) values which were significantly enhanced by the FePha treatment, thereby indicating an increased conformational rigidity of OMWW materials. These molecular changes were reflected in a significantly reduced toxicity exerted on microalgae by the OMWW size-fractions subjected to catalyzed oxidative couplings. Our results suggest that OMWW can be effectively treated with a biomimetic catalyst to induce oxidative phenol polymerization and reduce their toxicity before amendments to soils or other disposal means.