Gamma irradiation-induced degradation and mineralization of methocarbamol in aqueous solution.

Gamma irradiation degradation of the extensively used muscle relaxant in the world methocarbamol (MET) was studied. MET aqueous solutions were irradiated by gamma rays emitted by a Cobalt 60 source at doses of 1-4 kGy. Our findings demonstrated that gamma irradiation degraded more than 98.5% of MET. Absorption spectra analysis revealed that when increased irradiation dose, the absorption bands declined with complete disappearance at 4 kGy dose. Additionally, the most radiolytic degradation rate was recorded at neutral pH, marked by Total Organic Carbon (TOC) removal rate of 98% reflecting the total mineralization of MET at 4 kGy. In-depth spectrophotometric analyses advocated a pseudo-first-order type of MET degradation kinetics. The obtained apparent rate constant value was kapp, MET = (0.02167 ± 0.0006) min-1. Gas chromatography-mass spectrometry (GC-MS) allowed the detection of 3-(o-methoxyphenoxy)-1,2 propanediol,2-methoxyphenol, 1,2,3 propanetriol, 1,2-dihydroxybenzene and 1,2,4 benzentriol identified as by-products generated during radiolytic degradation. Finally, an outline of the degradation mechanism was suggested according to the obtained by-products.

Extremophilic Bacterium Halomonas desertis G11 as a Cell Factory for Poly-3-Hydroxybutyrate-co-3-Hydroxyvalerate Copolymer's Production.

Microbial polyhydroxyalkanoates (PHA) are biodegradable and biocompatible bio-based polyesters, which are used in various applications including packaging, medical and coating materials. In this study, an extremophilic hydrocarbonoclastic bacterium, previously isolated from saline sediment in the Tunisian desert, has been investigated for PHA production. The accumulation of intracellular PHA granules in Halomonas desertis G11 was detected by Nile blue A staining of the colonies. To achieve maximum PHA yield by the strain G11, the culture conditions were optimized through response surface methodology (RSM) employing a Box-Behnken Design (BBD) with three independent variables, namely, substrate concentration (1-5%), inoculum size (1-5%) and incubation time (5-15 days). Under optimized conditions, G11 strain produced 1.5 g/L (68% of DCW) of PHA using glycerol as a substrate. Application of NMR (1H and 13C) and FTIR spectroscopies showed that H. desertis accumulated PHA is a poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV). The genome analysis revealed the presence of typical structural genes involved in PHBV metabolism including phaA, phaB, phaC, phaP, phaZ, and phaR, coding for acetyl-CoA acetyltransferase, acetoacetyl-CoA reductase, class I polyhydroxyalkanoates synthases, phasin, polyhydroxyalkanoates depolymerase and polyhydroxyalkanoates synthesis repressor, respectively. Glycerol can be metabolized to 1) acetyl-CoA through the glycolysis pathway and subsequently converted to the 3HB monomer, and 2) to propionyl-CoA via the threonine biosynthetic pathway and subsequently converted to the 3HV monomer. In silico analysis of PhaC1 from H. desertis G11 indicated that this enzyme belongs to Class I PHA synthase family with a "lipase box"-like sequence (SYCVG). All these characteristics make the extremophilic bacterium H. desertis G11 a promising cell factory for the conversion of bio-renewable glycerol to high-value PHBV.

Kinetic and mechanism investigation on the gamma irradiation induced degradation of quizalofop-p-ethyl.

An efficient gamma radiolytic decomposition of one of the extensively used herbicides in the world quizalofo-p-ethyl (QPE) was explored under different experimental conditions. Aqueous solutions of QPE were irradiated by gamma rays emitted by a Cobalt 60 source. QPE aqueous solutions were irradiated at doses of 0.5-3 kGy with 26.31 Gy min-1 dose rate. Obtained results indicated that removal efficiency of 98.5% and 73% of QPE were obtained, respectively, in absence and in presence of dissolved oxygen. Change of absorption spectra, pH effect and Total Organic Carbon (TOC) were carried out and studied. It was found that all absorption bands decreased with increasing irradiation dose and disappear totally after 3 kGy applied dose. Three pH conditions (pH = 10, pH = 6.2 and pH = 3) were applied in radiolytic degradation of QPE showing that the best removal efficiency has been found for neutral pH. Interestingly, the % TOC removal reaches 98% at 3 kGy indicated practically total mineralization. Furthermore, spectrophotometric analyses argued in favour of a pseudo-first-order kinetic of QPE degradation. The resulting apparent rate constant value is approximately kapp = (0.012 ± 0.001) min-1. Finally, several by-products such as 6-chloroquinoxalin -2-ol, 2-(4-hydroxy-phenyoxy) propionate, 1,4-hydroquinone, quinone, 4-chlorobenzene-1,2diol and 1,2,4-benzenetriol were identified by gas chromatography-mass spectrometry (GC/MS) evidencing that radiation process starting with the fragmentation of the molecule involving the hydroxyl radical, which is generated by the radiolysis of water. Based on the identification intermediates, a degradation mechanistic schema of QPE has been proposed.

Effect of Gamma Irradiation on Enhanced Biological Activities of Exopolysaccharide from Halomonas desertis G11: Biochemical and Genomic Insights.

In this work, a native exopolysaccharide (nEPS) produced by Halomonas desertis G11 isolated from a Tunisian extreme environment was modified by gamma irradiation. Characterization as well as the antioxidant and antitumor activities of nEPS and its gamma-irradiated derivatives (iEPSs) were comparatively evaluated. In vitro and in vivo antioxidant potentials were determined by using different methods and through different antioxidant enzymes. The antitumor activity was checked against a human colon cancer cell line. Analyses of the complete genome sequence were carried out to identify genes implicated in the production of nEPS. Thus, the genomic biosynthesis pathway and the export mechanism of nEPS were proposed. Analyses of irradiation data showed that iEPSs acquired new functional groups, lower molecular weights, and gained significantly (p < 0.05) higher antioxidant and antitumor abilities compared with nEPS. These findings provide a basis for using iEPSs as novel pharmaceutical agents for human therapies.

Genomic characterization of a polyvalent hydrocarbonoclastic bacterium Pseudomonas sp. strain BUN14.

Bioremediation offers a viable alternative for the reduction of contaminants from the environment, particularly petroleum and its recalcitrant derivatives. In this study, the ability of a strain of Pseudomonas BUN14 to degrade crude oil, pristane and dioxin compounds, and to produce biosurfactants, was investigated. BUN14 is a halotolerant strain isolated from polluted sediment recovered from the refinery harbor on the Bizerte coast, north Tunisia and capable of producing surfactants. The strain BUN14 was assembled into 22 contigs of 4,898,053 bp with a mean GC content of 62.4%. Whole genome phylogeny and comparative genome analyses showed that strain BUN14 could be affiliated with two validly described Pseudomonas Type Strains, P. kunmingensis DSM 25974T and P. chloritidismutans AW-1T. The current study, however, revealed that the two Type Strains are probably conspecific and, given the priority of the latter, we proposed that P. kunmingensis DSM 25974 is a heteronym of P. chloritidismutans AW-1T. Using GC-FID analysis, we determined that BUN14 was able to use a range of hydrocarbons (crude oil, pristane, dibenzofuran, dibenzothiophene, naphthalene) as a sole carbon source. Genome analysis of BUN14 revealed the presence of a large repertoire of proteins (154) related to xenobiotic biodegradation and metabolism. Thus, 44 proteins were linked to the pathways for complete degradation of benzoate and naphthalene. The annotation of conserved functional domains led to the detection of putative genes encoding enzymes of the rhamnolipid biosynthesis pathway. Overall, the polyvalent hydrocarbon degradation capacity of BUN14 makes it a promising candidate for application in the bioremediation of polluted saline environments.

Decolorization of textile azo dye Novacron Red using bacterial monoculture and consortium: Response surface methodology optimization.

The present study was intended toward the optimization of a textile dye Novacron Red decolorization by single and mixed culture of Bacillus strains namely, B. firmus, B. filamentosus and B. subterraneus. Optimization of dye decolorization using Bacillus monocultures was conducted using central composite design. The maximum dye decolorization achieved under optimized conditions for B. firmus, B. filamentosus and B. subterraneus was 89.24%, 88.28% and 88.45%, respectively. The effect of various consortia of selected Bacillus strains on dye removal was evaluated by applying a mixture design. The best dye (100 mg/L) decolorization yield (84%) was achieved using the consortium of B. filamentosus and B. subetrraneus.The Fourier Transform Infrared Spectroscopy analyses confirmed biodegradation potential of the two Bacillus strains. The results highlighted the potential of mono- and co-cultures of Bacillus strains for application in textile wastewater treatment. PRACTITIONER POINTS: Novel dye-decolorizing Bacillus strains were isolated from marine sediment. Optimization of decolorization was conducted using response surface methodology. Efficient decolorization of textile dye by Bacillus strains on mono- and co-cultures. The efficiency of the consortium B. filamentosus and B. subetrraneus on dye removal.

New Plant Growth-Promoting, Chromium-Detoxifying Microbacterium Species Isolated From a Tannery Wastewater: Performance and Genomic Insights.

Hexavalent chromium [Cr(VI)], widely generated by tannery activities, is considered among the most toxic substances and causes a serious damage for the environment and for human health. Interestingly, some microorganisms have a potential of bioremediation of chromium-contaminated wastewaters and soils through the reduction of Cr(VI) (soluble and harmful form) into Cr(III) (stable and non-toxic form). Here, we present the full genome sequence of a novel heavy-metal-resistant, plant growth-promoting bacterium (PGPB), Microbacterium metallidurans TL13, which was isolated from a Tunisian leather industry. The strain TL13 was resistant to many heavy metals, such as chromium, copper, nickel, cobalt, and arsenic. The 50% TL13 growth inhibitory concentration (IC50) values of HgCl2, CoCl2, K2Cr2O7, CuSO4, NiCl2, FeSO4, and Na2HAsO4 are 368, 445, 676, 1,590, 1,680, 4,403, and 7,007 mg/L, respectively, with the following toxicity order: HgCl2 > CoCl2 > K2Cr2O7 > CuSO4 > NiCl2 > FeSO4 > Na2HAsO4. This new strain was also able to promote the growth of the hybrid tomato (Elika F1) under chromium metal stress. Its whole genome sequence length was estimated to be 3,587,460 bp (3,393 coding sequences) with a G + C content of 70.7%. Functional annotation of the genome of TL13 revealed the presence of open reading frames (ORFs) involved in adaptation to metal stress, such as the chromate transport protein, cobalt-zinc-cadmium resistance protein, copper resistance protein, copper responsive transcriptional regulator, multidrug resistance transporters, arsenical resistance operon repressor, arsenate reductase, arsenic resistance protein, mercuric resistance operon regulatory protein, mercuric ion reductase, and organomercurial lyase. Moreover, genes for the production of glutathione peroxidase, catalase, superoxide dismutase, and thioredoxin reductase, which confer a higher tolerance to oxidative/metal stresses, were identified in TL13 genome. In addition, genes for heat shock tolerance, cold shock tolerance, glycine-betaine production, mineral phosphate solubilization, ammonia assimilation, siderophores, exopolysaccharides, polyketides, and lytic enzymes (cellulase, chitinase, and proteases) production that enable bacteria to survive biotic/abiotic stress and to promote plant growth and health were also revealed. Based on genome analysis and experimental approaches, strain TL13 appears to have evolved from various metabolic strategies and could play a role in ensuring sustainable environmental and agricultural systems.

Allochthonous and Autochthonous Halothermotolerant Bioanodes From Hypersaline Sediment and Textile Wastewater: A Promising Microbial Electrochemical Process for Energy Recovery Coupled With Real Textile Wastewater Treatment.

The textile and clothing industry is the first manufacture sector in Tunisia in terms of employment and number of enterprises. It generates large volumes of textile dyeing wastewater (TDWW) containing high concentrations of saline, alkaline, and recalcitrant pollutants that could fuel tenacious and resilient electrochemically active microorganisms in bioanodes of bioelectrochemical systems. In this study, a designed hybrid bacterial halothermotolerant bioanode incorporating indigenous and exogenous bacteria from both hypersaline sediment of Chott El Djerid (HSCE) and TDWW is proposed for simultaneous treatment of real TDWW and anodic current generation under high salinity. For the proposed halothermotolerant bioanodes, electrical current production, chemical oxygen demand (COD) removal efficiency, and bacterial community dynamics were monitored. All the experiments of halothermotolerant bioanode formation have been conducted on 6 cm2 carbon felt electrodes polarized at -0.1 V/SCE and inoculated with 80% of TDWW and 20% of HSCE for 17 days at 45°C. A reproducible current production of about 12.5 ± 0.2 A/m2 and a total of 91 ± 3% of COD removal efficiency were experimentally validated. Metagenomic analysis demonstrated significant differences in bacterial diversity mainly at species level between anodic biofilms incorporating allochthonous and autochthonous bacteria and anodic biofilm containing only autochthonous bacteria as a control. Therefore, we concluded that these results provide for the first time a new noteworthy alternative for achieving treatment and recover energy, in the form of a high electric current, from real saline TDWW.

Unravelling the characteristics of a heteropolysaccharide-protein from an Haloarchaeal strain with flocculation effectiveness in heavy metals and dyes removal.

The production, characterization and potential application in heavy metals and dyes removal of a novel heteropolysaccharide-protein named, gpHb, produced by an Haloarchaeal strain Halogeometricum borinquense strain A52 were investigated. The highest gpHb yield of 13.96 ± 0.32 g/L was produced under optimized conditions by response surface methodology. We focused on the characteristics and flocculation performance of gpHb. An important attribute of protein with 16 protein types identified that occupied a total content of 50.2% in the gpHb. Additionally, carbohydrate that occupied 30.4% of the total bioflocculant content consisted of three monosaccharides. Fourier transform-infrared spectroscopy indicated the presence of carboxyl, hydroxyl, amine, amide, and sulphate groups. To further study flocculation activities, factors such as bioflocculant dosage, temperature, pH, salinity and cations addition were tested. In comparison to the chemical flocculant polyaluminium chloride, gpHb maintain high activity at large range of salinity and its flocculation activity was higher on both sides of pH 7. Addition of trivalent cation mainly Fe3+ enhances the flocculating rate indicating that the bioflocculant is negatively charged. Its practical applicability was established for heavy metals and dyes removal from saline aqueous solutions. The highest removal efficiency was observed with Cr3+ (91.4%) and Ni2+ (89.60%) and with basic blue 3 (83.8%) and basic red (78.6%). The excellent flocculation activity of gpHb under saline condition suggests its potential industrial utility for treatment of textile and tannery wastewaters.

Radiation-inducible radioprotective exopolysaccharides of Bacillus siamensis CV5 from irradiated roots of Cistanche violacea to decrease free radical damage produced by ionizing radiation.

Purpose: To assess exopolysaccharides (EPS) of Bacillus siamensis CV5, isolated from irradiated roots of Cistanche violacea, for their induction by ionizing radiation (IR) and their antioxidant and radioprotective power.Materials and methods: Isolated bacteria from the roots of C. violacea were screened for EPS production. The most EPS-producing bacterium was selected and the response surface methodology (RSM) was applied to elucidate the IR dose effects on EPS production. Gamma irradiation effects on the morphology and functional groups of EPS were studied using microscopy and Fourier transform infra-red (FT-IR). The radioprotective potential of EPS on the survival of B. siamensis CV5 following IR was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Free radicals scavenging potentialities (FRSP) of non-irradiated and irradiated EPS were evaluated through 2, 2--diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid (ABTS) and ferric reducing ability of plasma (FRAP) assays.Results: Twenty strains, isolated from irradiated roots of C. violacea, were screened for their EPS production. IR-resistant B. siamensis CV5 was the most EPS-producing strain. Its purified EPS contained rhamnose, fructose, mannose and glucose. RSM indicated that EPS of CV5 (CV5-EPS) are radiation inducible. Micrographs of CV5-EPS suggested an increase in the total area and a decrease in the Feret's statistical diameter following exposure to IR. FT-IR spectra of these EPS revealed an increase of various functional groups. The MTT survival assay demonstrated a positive correlation between the added quantity of CV5-EPS and the viability of irradiated CV5 (p < .01). DPPH, ABTS and FRAP assays indicated that the antioxidant activities of CV5-EPS increased significantly with the irradiation dose (p < .01).Conclusions: CV5-EPS were demonstrated as radiation-inducible and radioprotective biomolecules. This radioprotective potential of CV5-EPS could be associated with their antioxidant activities. In the future, irradiated EPS could be tested as a gel in cancer radiotherapy for minimizing the damage caused by rays to surrounding healthy tissues.

Understanding the cumulative effects of salinity, temperature and inoculation size for the design of optimal halothermotolerant bioanodes from hypersaline sediments.

The main objective of this study was to understand the interaction between salinity, temperature and inoculum size and how it could lead to the formation of efficient halothermotolerant bioanodes from the Hypersaline Sediment of Chott El Djerid (HSCE). Sixteen experiments on bioanode formation were designed using a Box-Behnken matrix and response surface methodology to understand synchronous interactions. All bioanode formations were conducted on 6 cm2 carbon felt electrodes polarized at -0.1 V/SCE and fed with lactate (5 g/L) at pH 7.0. Optimum levels for salinity, temperature and inoculum size were predicted by NemrodW software as 165 g/L, 45 °C and 20%, respectively, under which conditions maximum current production of 6.98 ±â€¯0.06 A/m2 was experimentally validated. Metagenomic analysis of selected biofilms indicated a relative abundance of the two phyla Proteobacteria (from 85.96 to 89.47%) and Firmicutes (from 61.90 to 68.27%). At species level, enrichment of Psychrobacter aquaticus, Halanaerobium praevalens, Psychrobacter alimentaris, and Marinobacter hydrocarbonoclasticus on carbon-based electrodes was correlated with high current production, high salinity and high temperature. Members of the halothermophilic bacteria pool from HSCE, individually or in consortia, are candidates for designing halothermotolerant bioanodes applicable in the bioelectrochemical treatment of industrial wastewater at high salinity and temperature.

Genome analysis provides insights into crude oil degradation and biosurfactant production by extremely halotolerant Halomonas desertis G11 isolated from Chott El-Djerid salt-lake in Tunisian desert.

Here, we report the genomic features and the bioremediation potential of Halomonas desertis G11, a new halophilic species which uses crude oil as a carbon and energy source and displays intrinsic resistance to salt stress conditions (optimum growth at 10% NaCl). G11 genome (3.96 Mb) had a mean GC content of 57.82%, 3622 coding sequences, 480 subsystems and 64 RNA genes. Annotation predicted 38 genes involved in osmotic stress including the biosynthesis of osmoprotectants glycine-betaine, ectoine and osmoregulated periplasmic glucans. Genome analysis revealed also the versatility of the strain for emulsifying crude oil and metabolizing hydrocarbons. The ability of G11 to degrade crude oil components and to secrete a glycolipid biosurfactant with satisfying properties was experimentally confirmed and validated. Our results help to explain the exceptional capacity of G11 to survive at extreme desertic conditions, and highlight the metabolic features of this organism that has biotechnological and ecological potentialities.

Pseudomonas rhizophila S211, a New Plant Growth-Promoting Rhizobacterium with Potential in Pesticide-Bioremediation.

A number of Pseudomonas strains function as inoculants for biocontrol, biofertilization, and phytostimulation, avoiding the use of pesticides and chemical fertilizers. Here, we present a new metabolically versatile plant growth-promoting rhizobacterium, Pseudomonas rhizophila S211, isolated from a pesticide contaminated artichoke field that shows biofertilization, biocontrol and bioremediation potentialities. The S211 genome was sequenced, annotated and key genomic elements related to plant growth promotion and biosurfactant (BS) synthesis were elucidated. S211 genome comprises 5,948,515 bp with 60.4% G+C content, 5306 coding genes and 215 RNA genes. The genome sequence analysis confirmed the presence of genes involved in plant-growth promoting and remediation activities such as the synthesis of ACC deaminase, putative dioxygenases, auxin, pyroverdin, exopolysaccharide levan and rhamnolipid BS. BS production by P. rhizophila S211 grown on olive mill wastewater based media was effectively optimized using a central-composite experimental design and response surface methodology (RSM). The optimum conditions for maximum BS production yield (720.80 ± 55.90 mg/L) were: 0.5% (v/v) inoculum size, 15% (v/v) olive oil mill wastewater (OMWW) and 40°C incubation temperature at pH 6.0 for 8 days incubation period. Biochemical and structural characterization of S211 BS by chromatography and spectroscopy studies suggested the glycolipid nature of the BS. P. rhizophila rhamnolipid was stable over a wide range of temperature (40-90°C), pH (6-10), and salt concentration (up to 300 mM NaCl). Due to its low-cost production, emulsification activities and high performance in solubilization enhancement of chemical pesticides, the indigenous BS-producing PGPR S211 could be used as a promising agent for environmental bioremediation of pesticide-contaminated agricultural soils.

A novel thermally stable heteropolysaccharide-based bioflocculant from hydrocarbonoclastic strain Kocuria rosea BU22S and its application in dye removal.

A new bioflocculant named pKr produced by hydrocarbonoclastic strain Kocuria rosea BU22S (KC152976) was investigated. Gas chromatography-flame ionization detector (GC-FID) analysis confirmed the high potential of the strain BU22S in the degradation of n-alkanes. Plackett-Burman experimental design and response surface methodology were carried out to optimize pKr production. Glucose, peptone and incubation time were found to be the most significant factors affecting bioflocculant production. Maximum pKr production was about 4.72 ± 0.02 g/L achieved with 15.61 g/L glucose, 6.45 g/L peptone and 3 days incubation time. Chemical analysis of pKr indicated that it contained 71.62% polysaccharides, 16.36% uronic acid and 2.83% proteins. Thin layer chromatography analysis showed that polysaccharides fraction consisted of galactose and xylose. Fourier transform infrared analysis revealed the presence of many functional groups, hydroxyl, carboxyl, methoxyl, acetyl and amide that likely contribute to flocculation. K. rosea pKr showed high flocculant potential using kaolin clay at different pH (2-11), temperature (0-100°C) and cation concentrations. The bioflocculant was particularly effective in flocculating soluble anionic dyes, Reactive Blue 4 and Acid Yellow, with a decolorization efficiency of 76.4% and 72.6%, respectively. The outstanding flocculating performances suggest that pKr could be useful for bioremediation applications.

Diversity, ecological distribution and biotechnological potential of Actinobacteria inhabiting seamounts and non-seamounts in the Tyrrhenian Sea.

In the present study, the ecological distribution of marine Actinobacteria isolated from seamount and non-seamount stations in the Tyrrhenian Sea was investigated. A collection of 110 isolates was analyzed by Automated Ribosomal Intergenic Spacer Analysis (ARISA) and 16S rRNA gene sequencing of representatives for each ARISA haplotype (n=49). Phylogenetic analysis of 16S rRNA sequences showed a wide diversity of marine isolates and clustered the strains into 11 different genera, Janibacter, Rhodococcus, Arthrobacter, Kocuria, Dietzia, Curtobacterium, Micrococcus, Citricoccus, Brevibacterium, Brachybacterium and Nocardioides. Interestingly, Janibacter limosus was the most encountered species particularly in seamounts stations, suggesting that it represents an endemic species of this particular ecosystem. The application of BOX-PCR fingerprinting on J. limosus sub-collection (n=22), allowed their separation into seven distinct BOX-genotypes suggesting a high intraspecific microdiversity among the collection. Furthermore, by screening the biotechnological potential of selected actinobacterial strains, J. limosus was shown to exhibit the most important biosurfactant activity. Our overall data indicates that Janibacter is a major and active component of seamounts in the Tyrrhenian Sea adapted to low nutrient ecological niche.

Pseudomonas extremorientalis BU118: a new salt-tolerant laccase-secreting bacterium with biotechnological potential in textile azo dye decolourization.

The present investigation focused on screening of a new potent strain for laccase production and optimizing the process parameters to achieve the maximum enzymatic decolourization of textile azo dye Congo red. Seven hydrocarbonoclastic bacterial strains were selected as positive in laccase production in solid medium using 2,6 dimethoxyphenol as an enzyme activity indicator. The best enzyme producer Pseudomonas extremorientalis BU118 showed a maximum laccase activity of about 7000 U/L of wheat bran under solid-state conditions. The influence of different concentrations of dye, enzyme, salt and various incubation times on Congo red decolourization was studied using response surface methodology to find the optimum conditions required for maximum decolourization by P. extremorientalis laccase. The enzyme exhibited a remarkable colour removal capability over a wide range of dye and salt concentrations. The above results show the potential use of this bacterial laccase in the biological treatment of the textile effluent.