Evaluation of support materials for the surface immobilization and decoloration of amaranth by Trametes versicolor

Biodegradation and metabolic pathway of anthraquinone dyes by Trametes hirsuta D7 immobilized in light expanded clay aggregate and cytotoxicity assessment

Biodegradation and metabolic pathways of three anthraquinone dyes, Reactive Blue 4 (RB4), Remazol Brilliant Blue - R (RBBR), and Acid Blue 129 (AB129) by Trametes hirsuta D7 fungus immobilized in light expanded clay aggregate (LECA) were investigated. Morphological characteristics observed with scanning electron microscope (SEM) showed successful immobilization of the fungus in LECA. Based on UV absorbance measurement, immobilized T. hirsuta D7 effectively degraded 90%, 95%, and 96% of RB4, RBBR and AB129, respectively. Metabolites were identified with high-resolution mass spectrometry (HRMS) and degradation pathway of the dyes by T. hirsuta D7 was proposed. Toxicity assay on human dermal fibroblast (HDF) showed that anthraquinone dyes exhibits significant toxicity of 35%, 40%, and 34% reduction of cell viability by RB4, RBBR, and AB129, respectively. Fungal treatment resulted in an abatement of the toxicity and cell viability was increased up to 94%. The data clearly showed the effectiveness of immobilized T. hirsuta D7 in LECA on detoxification of anthraquinone dyes. This study provides potential and fundamental understanding of wastewater treatment using the newly isolated fungus T. hirsuta D7.

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.

Kinetic characterization, thermo-stability and Reactive Red 195A dye detoxifying properties of manganese peroxidase-coupled gelatin hydrogel

An indigenous and industrially important manganese peroxidase (MnP) was isolated from solid-state bio-processing of wheat bran by white-rot fungal strain Ganoderma lucidum IBL-05 under pre-optimized growth conditions. Crude MnP extract was partially purified (2.34-fold) to apparent homogeneity by ammonium sulphate precipitation and dialysis. The homogeneous enzyme preparation was encapsulated on gelatin matrix using glutaraldehyde as a cross-linking agent. Optimal conditions for highest immobilization (82.5%) were: gelatin 20% (w/v), glutaraldehyde 0.25% (v/v) and 2 h activation time using 0.6 mg/mL of protein concentration. Gelatin-encapsulated MnP presented its maximum activity at pH 6.0 and 60 °C. Thermo-stability was considerably improved after immobilization. The optimally active MnP fraction was tested against MnSO₄ as a substrate to calculate kinetic parameters. More than 90% decolorization of Sandal-fix Red C₄BLN (Reactive Red 195A) dye was achieved with immobilized MnP in 5 h. It also preserved more than 50% of its original activity after the sixth reusability cycle. The water quality parameters (pH, chemical oxygen demand, total organic carbon) and cytotoxicity (brine shrimp and Daphnia magna) studies revealed the non-toxic nature of the bio-treated dye sample. A lower K_m, higher V_max, greater acidic and thermal-resistant up to 60 °C were the improved catalytic features of immobilized MnP suggesting its suitability for a variety of biotechnological applications.

Decolorization of the metal textile dye Lanaset Grey G by immobilized white-rot fungi

In this paper we studied the ability of four Tunisian-isolated fungi (i.e. Coriolopsis gallica, Bjerkandera adusta, Trametes versicolor and Trametes trogii) immobilized into Ca-alginate beads to decolorize the metal textile dye Lanaset Grey G (LG). The effect of different operational conditions, such as initial dye concentration, temperature, pH, beads/medium ratio and agitation, on dye decolorization by the immobilized fungi was investigated. Maximal decolorization percentages of 88.7%, 89.3%, 82.1% and 81.3% for C. gallica, B. adusta, T. versicolor and T. trogii were attained, respectively, when operating at an initial LG concentration of 150 mg/L, pH values of 5.0-6.0, temperatures of 40-45 °C and a beads/medium ratio of 20% (w/v) in static conditions after 72 h of incubation. Subsequently, the re-usability of the immobilized fungi was evaluated. After three decolorization cycles, the decolorization percentage of free cell cultures dropped to values below 36%, while decolorization percentages of about 75%, 70%, 60% and 68% were obtained by the immobilized cultures of C. gallica, B. adusta, T. versicolor and T. trogii, respectively.

The use of the fungus Dichomitus squalens for degradation in rotating biological contactor conditions

Biodegradation potential of Dichomitus squalens in biofilm cultures and rotating biological contactor (RBC) was investigated. The fungus formed thick biofilms on inert and lignocellulosic supports and exhibited stable activities of laccase and manganese peroxidase to reach 40-62 and 25-32% decolorization of anthraquinone Remazol Brilliant Blue R and heterocyclic phthalocyanine dyes, respectively. The decolorization ceased when glucose concentration dropped to 1 mmol l(-1). In RBC reactor, respective decolorizations of Remazol Brilliant Blue R and heterocyclic Methylene Blue and Azure B dyes (50 mg l(-1)) attained 99%, 93%, and 59% within 7, 40 and 200 h. The fungus exhibited tolerance to coliform and non-coliform bacteria on rich organic media, the inhibition occurred only on media containing tryptone and NaCl. The degradation efficiency in RBC reactor, capability to decolorize a wide range of dye structures and tolerance to bacterial stress make D. squalens an organism applicable to remediation of textile wastewaters.

Pentachlorophenol sorption in nylon fiber and removal by immobilized Rhizopus oryzae ENHE

This study describes pentachlophenol (PCP) sorption in nylon fiber in which Rhizopus oryzae ENHE was immobilized to remove the chemical compound. The experimental sorption data were analyzed using the Langmuir, Freundlich, and Redlich-Peterson isotherm models using non-linear error functions to fit the experimental data to the three models. Results showed that the isotherm obtained from the data fitted the three models used. However, the g parameter from Redlich-Peterson model showed that the isotherm obtained approaches the Freundlich model. This support reached the sorption equilibrium concentration at 3mg PCPg(-1)nylon. To study PCP removal capability by R. oryzae ENHE and to eliminate the error caused by PCP sorbed by the nylon fiber during its quantification, nylon fiber at PCP equilibrium sorption concentration was used to immobilize R. oryzae ENHE. It was found that this fungus grew within nylon fiber cubes in presence or not of PCP, even when PCP caused growth inhibition. Maximum biomass accumulated into nylon cubes without PCP was of 32 mg biomass g(-1)nylon and into nylon cubes at PCP equilibrium concentration was of 18 mg g(-1)nylon. The results showed that R. oryzae ENHE immobilized into nylon fiber removed 88.6% and 92% of PCP in cultures with 12.5 and 25 mg PCPL(-1), as initial concentration, respectively. This is the first work to report that a zygomycete, such as R. oryzae ENHE, immobilized into nylon fiber kept its potential to remove PCP.

Decolouration of azo dyes by Phanerochaete chrysosporium immobilised into alginate beads

BACKGROUND, AIM AND SCOPE

Because of high discharged volumes and effluent composition, wastewater from the textile industry can be considered as the most polluting amongst all industrial sectors, thus greatly requiring appropriate treatment technologies. Although some abiotic methods for the reduction of several dyes exist, these require highly expensive catalysts and reagents. Biotechnological approaches were proven to be potentially effective in the treatment of this pollution source in an eco-efficient manner. The white-rot fungi are, so far, the most efficient microorganisms in degrading synthetic dyes. This white-rot fungi's property is due to the production of extracellular lignin-modifying enzymes, which are able to degrade a wide range of xenobiotic compounds because of their low substrate specificity. In this paper, we studied the ability of the white-rot fungus Phanerochaete chrysosporium immobilised into Ca-alginate beads to decolourise different recalcitrant azo dyes such as Direct Violet 51 (DV), Reactive Black 5 (RB), Ponceau Xylidine (PX) and Bismark Brown R (BB) in successive batch cultures. To the best of our knowledge, this is the first study on the immobilisation of P. chrysosporium into Ca-alginate beads for its application in dye decolouration.

MATERIALS AND METHODS

P. chrysosporium was immobilised into Ca-alginate beads using a method of gel recoating to minimise cellular leaking. The immobilised fungus was transferred to 250-ml Erlenmeyer flasks containing 50 ml of growth medium and incubated on an orbital shaker at 150 rpm and 30 degrees C for 7 days. The ratio of beads/medium used was 10% (w/v). The dyes were added into the culture flasks when MnP production started (50 U l(-1)), which corresponded with the seventh cultivation day. MnP activity and dye decolouration were measured spectrophotometrically.

RESULTS

The dyes DV, RB and PX were almost totally decolourised at the end of each batch during the course of three successive batches. However, the dye BB was more resistant to decolouration and it was not completely decolourised (86.7% in 144 h). Further, the beads were kept in sterilised calcium chloride (2 g l(-1)) for 3 weeks at 4 degrees C. After these three storage weeks, the immobilised P. chrysosporium was again efficiently reused for azo dye decolouration during two successive batches, decolouration being more effective even for BB. Also, the in vitro decolouration of the aforementioned azo dyes by crude MnP from P. chrysosporium was performed. The decolouration levels obtained were lower than those attained with the whole cultures especially for RB and BB dyes, in spite of the fact that dye concentrations used were considerable lower.

DISCUSSION

The good performance of the immobilisation system was likely due to the gel re-coating method utilised to prepare the alginate beads which not only maintained the beads integrity but also avoided cellular leaking. The lower decolouration percentages obtained by the enzyme indicates that the mycelial biomass may supply other intracellular or mycelial-bound enzymes, or other compounds that favour dye decolouration.

CONCLUSIONS

Immobilised P. chrysosporium efficiently decolourised different types of azo dyes. In this decolouration process, the MnP secreted by the fungus played the main role whilst adsorption was found to be negligible except for the dye BB.

RECOMMENDATIONS AND PERSPECTIVES

Efforts should be made to scale up and apply fungal decolouration techniques to real industrial dye-containing wastewater. Further, detailed characterisation of the intermediates and metabolites produced during biodegradation must be done to ensure the safety of the decolourised wastewater.

Dye removal by immobilised fungi

Dyes are widely used within the food, pharmaceutical, cosmetic, printing, textile and leather industries. This has resulted in the discharge of highly coloured effluents that affect water transparency and gas solubility in water bodies. Furthermore, they pose a problem because of their carcinogenicity and toxicity. Therefore, removal of such dyes before discharging them into natural water streams is essential. For this, appropriate treatment technologies are required. The treatment of recalcitrant and toxic dyes with traditional technologies is not always effective or may not be environmentally friendly. This has impelled the search for alternative technologies such as biodegradation with fungi. In particular, ligninolytic fungi and their non-specific oxidative enzymes have been reported to be responsible for the decolouration of different synthetic dyes. Thus, the use of such fungi is becoming a promising alternative to replace or complement the current technologies for dye removal. Processes using immobilised growing cells seem to be more promising than those with free cells, since the immobilisation allows using the microbial cells repeatedly and continuously. This paper reviews the application of fungal immobilisation to dye removal.

Bioaccumulation versus adsorption of reactive dye by immobilized growing Aspergillus fumigatus beads

The removal of reactive brilliant blue KN-R using growing Aspergillus fumigatus (abbr. A. fumigatus) immobilized on carboxymethylcellulose (CMC) beads with respect to initial dye concentration was investigated. Bioaccumulation was the dominant mechanism of the dye removal. According to the UV-vis spectra and the results of three sets of experiments, it could be concluded that the bioaccumulation using immobilized growing A. fumigatus beads was achieved by metabolism-dependent accumulation and metabolism-independent adsorption (15-23% proportion of overall dye removal), which included biosorption by mycelia entrapped in them and adsorption on immobilization matrix. The transmission electron microscope (TEM) images showed the intracellular structures of mycelia and the toxicity of dye. It was found that the fungus had a considerable tolerance to reactive brilliant blue KN-R at initial dye concentrations of <114.7 mg/l. Though at high initial dye concentrations the growth of mycelia was inhibited significantly by the dye molecules in the growth medium, the bioaccumulation capacity was not markedly affected and the maximum bioaccumulation capacity was 190.5+/-2.0 mg/g at an initial dye concentration of 374.4 mg/l. The bioaccumulation rates were not constant over the contact time.

Decolorization and detoxication of reactive industrial dyes by immobilized fungi Trametes pubescens and Pleurotus ostreatus

Trametes pubescens and Pleurotus ostreatus, immobilized on polyurethane foam cubes in bioreactors, were used to decolorize three industrial and model dyes at concentrations of 200, 1000 and 2000 ppm. Five sequential cycles were run for each dye and fungus. The activity of laccase, Mn-dependent and independent peroxidases, lignin peroxidase, and aryl-alcohol oxidase were daily monitored during the cycles and the toxicity of media containing 1000 and 2000 ppm of each dye was assessed by the Lemna minor (duckweed) ecotoxicity test. Both fungi were able to efficiently decolorize all dyes even at the highest concentration, and the duckweed test showed a significant reduction (p < or = 0.05) of the toxicity after the decolorization treatment. T. pubescens enzyme activities varied greatly and no clear correlation between decolorization and enzyme activity was observed, while P. ostreatus showed constantly a high laccase activity during decolorization cycles. T. pubescens showed better decolorization and detoxication capability (compared to the better known P. ostreatus). As wide differences in enzyme activity of the individual strains were observed, the strong decolorization obtained with the two fungi suggested that different dye decolorization mechanisms might be involved.

[Stereum hirsutum (Wild) Pers. action in dye degradation]

Stereum hirsutum, a white rot fungus, has a good growth in solid state fermentation. This was carried on with wheat bran, soy bran and a mixture of both. Mycelia grown on soy bran showed the highest decolorization activity on Ponceau 2R (xylidine), indigo carmine and malachite green. Optimal relationship between decolorization and detoxification of malachite green was 30 g of fresh weight (mycelia plus substrate) in 500 ml malachite green solution, 42 U/l of laccase was measured in this solution. Decolorization was carried on without the addition either of nutrients or mediators. Conditions for maximal decolorization did not agree with those for maximal ligninolytic enzyme production, but effectiveness of laccase activity on decolorization was evidenced by electrophoretic analysis, that allowed laccase identification and its decolorization activity in gels stained with indigo carmine and malachite green, with ABTS as mediator. Detoxification was assayed using the sensible fungus Phanerochaete chrysosporium.

Laccase production at reactor scale by filamentous fungi

Laccases have received much attention from researchers during the past decades due to their broad substrate specificity and to the fact that they use molecular oxygen as the final electron acceptor instead of hydrogen peroxide as used by peroxidases. This makes laccases highly interesting for a wide variety of processes, such as textile dye decolouration, pulp bleaching, effluent detoxification, biosensors and bioremediation. The successful application of laccases to the above-mentioned processes requires the production of large quantities of enzyme at low cost. Filamentous fungi are able to produce laccases in high amounts, however, an efficient production system at bioreactor scale is still lacking. This is mainly due to the fact that laccase production by wild-type strains of filamentous fungi is linked to secondary metabolism, which implies that the following drawbacks must be overcome: uncontrolled fungal growth, the formation of polysaccharides around mycelia and the secretion of certain compounds (i.e. proteases) that inactivate laccases. This review summarizes the current status of laccase production by wild-type strains of filamentous fungi at the bioreactor scale.

Production of dye-decolorizing peroxidase (rDyP) from complex substrates by repeated-batch and fed-batch cultures of recombinant Aspergillus oryzae

We examined production levels of dye-decolorizing peroxidase (rDyP) by recombinant Aspergillus oryzae using wheat bran and rice bran powders in repeated-batch and fed-batch cultures. Similar average rDyP productivities were observed in repeated-batch cultures using wheat bran powder and rice bran powder. Average rDyP productivities in fed-batch cultures were slightly lower than those in repeated-batch cultures. The rDyP production was affected by the addition of K(2)HPO(4) in the repeated-batch and fed-batch cultures using wheat bran powder. All average rDyP productivities in this study were significantly higher than those for any other peroxidases previously reported.

Growth and laccase production kinetics of Trametes versicolor in a stirred tank reactor

White rot fungi are a promising option to treat recalcitrant organic molecules, such as lignin, polycyclic aromatic hydrocarbons, and textile dyes, because of the lignin-modifying enzymes (LMEs) they secrete. Because knowledge of the kinetic parameters is important to better design and operate bioreactors to cultivate these fungi for degradation and/or to produce LME(s), these parameters were determined using Trametes versicolor ATCC 20869 (ATCC, American Type Culture Collection) in a magnetic stir bar reactor. A complete set of kinetic data has not been previously published for this culture. Higher than previously reported growth rates with high laccase production of up to 1,385 U l(-1) occurred during growth without [Formula: see text] or glucose limitation. The maximum specific growth rate averaged 0.94 +/- 0.23 day(-1), whereas the maximum specific substrate consumption rates for glucose and ammonium were 3.37 +/- 1.16 and 0.15 +/- 0.04 day(-1), respectively. The maximum specific oxygen consumption rate was 1.63 +/- 0.36 day(-1).

Amaranth decoloration by Trametes versicolor in a rotating biological contacting reactor

Sequential batch and continuous operation of a rotating biological contacting (RBC) reactor and the effects of dissolved oxygen on the decoloration of amaranth by Trametes versicolor were evaluated. Amaranth belongs to the group of azo dyes which are potential carcinogens and/or mutagens that can be transformed into toxic aryl amines under anaerobic conditions. Cultivation of T. versicolor in a stirred tank reactor was found to be unsuitable for amaranth decoloration due to significant biomass fouling and increase in medium viscosity. Assuming that decoloration follows first-order kinetics, amaranth was decolorized more rapidly when T. versicolor was immobilized on jute twine in a RBC reactor operated either in a sequential batch (k=0.25 h(-1)) or in a continuous (0.051 h(-1)) mode compared to a stirred tank reactor (0.015 h(-1)). Oxygen was found to be essential for decoloration with the highest decoloration rates occurring at oxygen saturation. Although longer retention times resulted in more decoloration when the RBC was operated in the continuous mode (about 33% amaranth decoloration), sequential batch operation gave better results (>95%) under similar nutrient conditions. Our data indicate that the fastest decoloration should occur in the RBC using nitrogen-free Kirk's medium with 1 g/l glucose in sequential batch operation at rotational speeds and/or aeration rates which maintain oxygen saturation in the liquid phase.

Decoloration of textile dyes by alginate-immobilized Trametes versicolor

Alginate-immobilized Trametes versicolor decolorized Amaranth at similar rates in repeated batch culture when the dye was present in either (i) modified Kirk's medium containing 0.22 gl(-1) ammonium tartrate, (ii) the same buffer, thiamine, trace elements and glucose concentrations as in the modified Kirk's medium, or (iii) glucose alone at either 1, 5 or 10 gl(-1). With glucose alone (0.5 gl(-1)), Amaranth, Reactive Black 5, Reactive Blue 19 and Direct Black 22 had first-order decoloration rate constants of 0.56, 0.76, 0.52, and 0.15 h(-1), respectively. Mixtures of these dyes were also completely decolorized. After four successive decolorations, beads were kept in storage solutions for 48 d at 6 degrees C. CaCl2 (1g l(-1)) was the best storage solution as the beads were easier to handle and had the fastest decoloration rates after storage. Decoloration rates were faster with lower viscosity (less than 2000 cps) alginates and with softer beads which had a lower resistance to compression. Fungal colonization of the beads resulted in higher biomass concentrations with a corresponding higher decoloration rate but the beads became larger, had a lower resistance to compression and a higher percentage of bead breakage in a stirred tank reactor. Biomass, recovered from beads in which there was no growth, could be dispersed while the biomass from colonized beads formed a hollow, spherical shell due to growth on and near the bead surface and no growth in the bead interior. If alginate-immobilized T. versicolor is to be used in a stirred tank reactor, a high biomass loading during the immobilization phase and no fungal growth in the beads is recommended to have high decoloration rates and low bead breakage.

Decolourisation of reactive textile dyes Drimarene Blue X3LR and Remazol Brilliant Blue R by Funalia trogii ATCC 200800

Decolourisation of reactive dyes Drimarene Blue X3LR and Remazol Brilliant Blue R by white rot fungi Funalia trogii was studied under static conditions. The effect of various conditions such as mycelial age, initial dye and glucose concentrations on decolourisation were also investigated. Decolourisation activity of F. trogii was compared with Phanerochaete chrysosporium known as test microorganism. It was found that 7-day-old cultures were more effective than 5-day-old cultures of F. trogii for decolourisation of these dyes. Decolourisations by F. trogii of both dyes were increased with glucose concentration decreasing. In contrast, decolourisations by P. chrysosporium were decreased. F. trogii decolourised 92-98% of both dyes within 4-10 h. However, P. chrysosporium partiallydecolourised (11-20%) these dyes during 10 days incubation period under the same conditions.

Role of white rot fungusFunalia trogii in detoxification of textile dyes

Toxic and genotoxic effects of the textile dyes on organisms suggest the need for remediation of dyes before discharging them into the environment. For this reason, the ability of Funalia trogii pellets to detoxify textile dyes was investigated and evaluated. Although, textile dyes are toxic substances for many microorganisms, the pellets were able to decolorize and detoxify the azo dyes used. Astrazon Blue and Red dyes inhibit growth of F. trogii and S. aureus on solid medium in a concentration dependent manner. The toxicity of these dyes on a fungus, F. trogii and a bacterium, S. aureus was significantly decreased after pretreatment with fungal pellets.

Removal of synthetic dyes from wastewaters: a review

The more recent methods for the removal of synthetic dyes from waters and wastewater are complied. The various methods of removal such as adsorption on various sorbents, chemical decomposition by oxidation, photodegradation, and microbiological decoloration, employing activated sludge, pure cultures and microbe consortiums are described. The advantages and disadvantages of the various methods are discussed and their efficacies are compared.