Decolorization of reactive dyes by mixed cultures isolated from textile effluent under anaerobic conditions

In the present study mixed cultures that could grew in the molasses media were isolated from textile dye effluent and its decolorization activity was studied in a batch system under anaerobic conditions, in order to determine the optimal conditions required for the highest decolorization activity. The optimum pH value for decolorization was determined as 8 for all the dyes tested. In the experiment with pH 8 dye decolorizations by mixed cultures were investigated at about 96.2–1031.3 mg l⁻¹ initial dye concentrations. The highest dye removal rates of mixed cultures were 94.9% for Reactive Red RB, 91.0% for Reactive Black B and 63.6% for Remazol Blue at 953.2, 864.9 and 1031.3 mg l⁻¹ initial dye concentrations respectively within 24 h incubation period. When the Reactive Red RB was used, approximately 82–98% total color removal was obtained at between 96.2 and 953.2 mg l⁻¹ initial dye concentrations after 12 h of incubation at 35 °C. These results show that our enriched mixed cultures have the potential to serve as an excellent biomass for the use in reactive dye removal from wastewaters under anaerobic conditions.     

Decolourization of recalcitrant dyes with a laccase from Streptomyces coelicolor under alkaline conditions

Colored wastewater from textile industries is a consequence of dye manufacturing processes. Two percent of dyes that are produced are discharged directly in aqueous effluent and more than 10% are subsequently lost during the textile coloration process. It is not surprising that these compounds have become a major environmental concern. In that context, we have evaluated the potential use of Streptomyces coelicolor laccase for decolourization of various dyes with and without a mediator. Results showed that in all cases the combination of laccase and the mediator acetosyringone was able to rapidly decolourize, to various degrees, all the dyes tested. In 10 min, decolourization was achieved at 94% for acid blue 74, 91% for direct sky blue 6b and 65% for reactive black 5. Furthermore, decolourization was achieved at 21% for reactive blue 19 and at 39% for the direct dye Congo red in 60 min. These results demonstrate the potential use of this laccase in combination with acetosyringone, a natural mediator, for dye decolourization.     

Newly isolated Bacillus clausii GMBAE 42: an alkaline protease producer capable to grow under higly alkaline conditions

AIMS: The isolation and identification of new Bacillus sp. capable of growing under highly alkaline conditions as alkaline protease producers. METHODS AND RESULTS: A Bacillus strain capable of growing under highly alkaline conditions was isolated from compost. The strain is a Gram-positive, spore-forming, motile, aerobic, catalase- and oxidase-positive, alkaliphilic bacterium and designated as GMBAE 42. Good growth of the strain was observed at pH 10. The strain was identified as Bacillus clausii according to the physiological properties, cellular fatty acid composition, G + C content of genomic DNA and 16S rRNA gene sequence analyses. The result of 16S rRNA sequence analyses placed this bacterium in a cluster with B. clausii. The G + C content of the genomic DNA of the isolate GMBAE 42 was found to be 49 mol%. The crude extracellular alkaline protease produced by the isolate showed maximal activity at pH 11.0 and 60 degrees C. CONCLUSIONS: The results suggest that isolated strain GMBAE 42 is a new type of B. clausii capable of growing at pH 10.0 and produce extracellular alkaline protease very active at pH 11.0. SIGNIFICANCE AND IMPACT OF THE STUDY: Isolated strain could be used in commercial alkaline protease production and its enzyme can be considered as a candidate as an additive for commercial detergents.     

Biosorption of anionic textile dyes by nonviable biomass of fungi and yeast

The nonviable biomass of Aspergillus niger, Aspergillus japonica, Rhizopus nigricans, Rhizopus arrhizus, and Saccharomyces cerevisiae were screened for biosorption of textile dyes. The selected anionic reactive dyes were C.I. Reactive Black 8, C.I. Reactive Brown 9, C.I. Reactive Green 19, C.I. Reactive Blue 38, and C.I. Reactive Blue 3. Experiments were conducted at initial dye concentration of 50, 100, 150 and 200mg/L. The effect of initial dye concentration, dose of biosorbent loading, temperature, and pH on adsorption kinetics was studied. S. cerevisiae and R. nigricans were good biosorbents at initial dye concentration of 50mg/L, 1g% (w/v) biomass loading and 29+/-1 degrees C. R. nigricans adsorbed 90-96% dye in 15min, at 20 degrees C and pH 6.0. The data showed an optimal fit to the Langmuir and Freundlich isotherms. The maximum uptake capacity (Q(o)) for the selected dyes was in the range 112-204mg/g biomass.     

Improving the decolorization for textile dyes of a metagenome-derived alkaline laccase by directed evolution

To obtain better performing laccases for textile dyes decolorization, random mutagenesis of Lac591, a metagenome-derived alkaline laccase, was carried out. After three rounds of error-prone PCR and high-throughput screening by assaying enzymatic activity toward the phenolic substrate 2,6-dimethoxyphenol (2,6-DMP), a mutant (Lac3T93) with remarkably improved enzymatic activity was obtained. Sequence analysis revealed that four amino acid substitutions (N40S, V55A, F62L, and E316V) were accumulated in the Lac3T93. Compared to the wild-type enzyme, the specific activity of Lac3T93 toward 2,6-DMP was increased to 4.8-fold (61.22 U/mg), and its optimal temperature and pH were changed to 60°C and 8.0 from 55°C and 7.5 of the wild-type enzyme, respectively. Furthermore, the degradation ability of Lac3T93 for textile dyes was investigated, and the new variant represented improved decolorization percentage for four industrial dyes with complex phenyl structure (Basic Blue 3, Methylene Blue, Bromophenol Blue, and Crystal Violet) and higher decolorization efficiency for Indigo Carmine than that of the parent enzyme. Furthermore, the decolorization percentage of Lac3T93 for five dyes in the absence of hydroxybenzotrizole (HBT) is clearly higher than those of the wild-type enzyme with 1 mM HBT, and HBT can further improve its decolorization ability.     

Effects of arbuscular mycorrhizal fungi alkaline phosphatase activities on Hippophae rhamnoides drought-resistance under water stress conditions

The effects of arbuscular mycorrhizal fungi alkaline phosphatase (ALP) activities on the drought-resistance of Hippophae rhamnoides under water stress have been studied using histochemical techniques. The result shows in the mycorrhizae that total hyphae and functional hyphae form the base for the active hyphae, and amounts follow the order total hyphae>functional hyphae>active hyphae. Active hyphae play an important role in the biomass accumulation of the hosts; the hyphae with phosphatase activity (ALP) have a positive and strong effect on H. rhamnoides growth and its drought-resistance, and the rise of ALP is related to an increase in the fresh weight of the host trees, and a reduction of wilting. The direct participation of ALP in the P nutrient exchange host trees can improve the nutrient and water conditions, and raise their drought-resistance. Received: 17 August 1998 / Accepted: 18 March 1999     

Degradation of synthetic reactive azo dyes and treatment of textile wastewater by a fungi consortium reactor

In this paper, two microbial cultures with high decolorization efficiencies of reactive dyes were obtained and were proved to be dominant with fungi consortium in which 21 fungal strains were isolated and 8 of them showed significant decolorization effect to reactive red M-3BE. A 4.5 l continuous biofilm reactor was established using the mixed cultures to investigate the decolorization performance and the system stability under the conditions of simulated and real textile wastewater as influents. The optimal nutrient feed to this bioreactor was 0.5 g l⁻¹ glucose and 0.1 g l⁻¹ (NH₄)₂SO₄ when 30 mg l⁻¹ reactive black 5 was used as initial dye concentrations. Dye mineralization rates of 50–75% and color removal efficiencies of 70–80% were obtained at 12 h hydraulic retention time (HRT) in this case. Higher glucose concentrations in the influents could significantly improve color removal, but was not helpful for dye mineralization. Besides reactive black 5, the bioreactor could effectively decolorize reactive red M-3BE, acid red 249 and real textile wastewater with efficiency of 65%, 94% and 89%, respectively. In addition, the microbial community on the biofilm was monitored in the whole running process. The results indicated fungi as a dominant population in the decolorization system with the ratio of fungi to bacteria 6.8:1 to 51.8:1 under all the tested influent conditions. Analysis of molecular biological detection indicated that yeasts of genus Candida occupied 70% in the fungal clone library based on 26S rRNA gene sequences.     

Isolation of microorganisms capable of degrading isoquinoline under aerobic conditions

Isoquinoline-degrading microbial cultures were isolated from oil- and creosote-contaminated soils. The establishment of initial enrichment cultures required the use of emulsified isoquinoline. Once growth on isoquinoline was established, isoquinoline emulsification was no longer required for utilization of isoquinoline as the sole source of carbon and nitrogen by these cultures. An isoquinoline-degrading Acinetobacter strain was isolated from one of the enrichment cultures. The degradation of isoquinoline was accompanied by the accumulation of a red cell-associated pigment and of 1-hydroxyisoquinoline, which was further degraded to unknown intermediary ring-cleavage products and carbon dioxide.     

Microbial thiocyanate utilization under highly alkaline conditions

Three kinds of alkaliphilic bacteria able to utilize thiocyanate (CNS-) at pH 10 were found in highly alkaline soda lake sediments and soda soils. The first group included obligate heterotrophs that utilized thiocyanate as a nitrogen source while growing at pH 10 with acetate as carbon and energy sources. Most of the heterotrophic strains were able to oxidize sulfide and thiosulfate to tetrathionate. The second group included obligately autotrophic sulfur-oxidizing alkaliphiles which utilized thiocyanate nitrogen during growth with thiosulfate as the energy source. Genetic analysis demonstrated that both the heterotrophic and autotrophic alkaliphiles that utilized thiocyanate as a nitrogen source were related to the previously described sulfur-oxidizing alkaliphiles belonging to the gamma subdivision of the division Proteobacteria (the Halomonas group for the heterotrophs and the genus Thioalkalivibrio for autotrophs). The third group included obligately autotrophic sulfur-oxidizing alkaliphilic bacteria able to utilize thiocyanate as a sole source of energy. These bacteria could be enriched on mineral medium with thiocyanate at pH 10. Growth with thiocyanate was usually much slower than growth with thiosulfate, although the biomass yield on thiocyanate was higher. Of the four strains isolated, the three vibrio-shaped strains were genetically closely related to the previously described sulfur-oxidizing alkaliphiles belonging to the genus Thioalkalivibrio. The rod-shaped isolate differed from the other isolates by its ability to accumulate large amounts of elemental sulfur inside its cells and by its ability to oxidize carbon disulfide. Despite its low DNA homology with and substantial phenotypic differences from the vibrio-shaped strains, this isolate also belonged to the genus Thioalkalivibrio according to a phylogenetic analysis. The heterotrophic and autotrophic alkaliphiles that grew with thiocyanate as an N source possessed a relatively high level of cyanase activity which converted cyanate (CNO-) to ammonia and CO2. On the other hand, cyanase activity either was absent or was present at very low levels in the autotrophic strains grown on thiocyanate as the sole energy and N source. As a result, large amounts of cyanate were found to accumulate in the media during utilization of thiocyanate at pH 10 in batch and thiocyanate-limited continuous cultures. This is a first direct proof of a "cyanate pathway" in pure cultures of thiocyanate-degrading bacteria. Since it is relatively stable under alkaline conditions, cyanate is likely to play a role as an N buffer that keeps the alkaliphilic bacteria safe from inhibition by free ammonia, which otherwise would reach toxic levels during dissimilatory degradation of thiocyanate.     

Mg induced Ca deficiency under alkaline conditions

Little is known about Mg induced Ca deficiency in alkaline conditions, and the relationship between Mg induced Ca deficiency and Na induced Ca deficiency. Dilute nutrient solutions (dominated by Mg) were used to investigate the effect of Ca activity ratio (CAR) on the growth of mungbeans (Vigna radiata (L.) Wilczek cv. Emerald). At pH 9.0, root growth was reduced below a critical CAR of 0.050 (corresponding to 90% relative root length). Root growth was found to be limited more in Mg solutions than had been previously observed for Na solutions. Using a CAR equation modified with plasma membrane binding constants (to incorporate the differing antagonistic effects of Mg and Na), new critical CAR values were calculated for both Na (0.56) and Mg (0.44) dominated solutions. This modified CAR equation permits the calculation of CAR irrespective of the dominant salt present.     

Decolourisation of model and industrial dyes by mitosporic fungi in different culture conditions

Six mitosporic fungi belonging to five species (Aspergillus flavus var. flavus, Aspergillus ochraceus, Cladosporium cladosporioides, Penicillium glabrum and Penicillium verrucosum) were selected from a screening on 258 fungal strains as the most promising for their ability to remove 2 model dyes in solid conditions. Hence they were tested in liquid conditions for their ability to decolourise 3 model dyes and 9 industrial dyes widely used in the textile industry. The influence of the culture medium, particularly its carbon:nitrogen ratio, on biomass development and decolourisation capacity was considered. All the strains were able to grow in the dyed media and displayed various degrees of decolourisation according to the dye and culture medium. The decolourisation was due to biosorption phenomena. Aspergillus ochraceus performed the highest decolourisation yield being able to remove all dyes over 90%. This strain was also found very effective, both in the living and inactivated form, against simulated effluents that mimicked the recalcitrance of real wastewaters being composed of ten different dyes at high concentration (1,000 ppm), in saline solution.     

Microbial decolorization of reactive azo dyes under aerobic conditions

Summary Kodam et al. reported a 100% decolorization of the sulfonated azo dyes Reactive Red 2, Reactive Red 141, Reactive Orange 4, Reactive Orange 7 and Reactive Violet 5 by an unidentified bacterium, KMK 48. High effectiveness was attained within 36 h of incubation at room temperature and neutral pH. Optimum decolorization took place strictly under aerobic conditions, which is contrary to other well-documented reports. Thus, this microorganism seems to be potentially effective for bioremediation of textile-dyeing industry effluents.     

Isolation of bacteria producing siderophores under alkaline conditions

Summary The isolation of bacteria producing siderophores under alkaline conditions is reported. Enrichment cultures initiated with samples from a number of alkaline environmental sources yielded 80 isolates. From this group selections were made on the basis of growth at high pH and the gallium-binding capacity of the siderophores. It was found that some isolates grew well and high concentrations of siderophore were detected whereas others grew well in the presence of much lower concentrations of siderophore. The effect of iron, gallium and aluminium on growth and siderophore production in batch culture was investigated for six isolates. The presence of iron greatly decreased the siderophore concentration in these cultures, whereas the response to added gallium or aluminium was dependent upon the isolate. Offsprint requests to: D. J. Gascoyne     

Isolation of microorganisms capable of degrading isoquinoline under aerobic conditions.

Isoquinoline-degrading microbial cultures were isolated from oil- and creosote-contaminated soils. The establishment of initial enrichment cultures required the use of emulsified isoquinoline. Once growth on isoquinoline was established, isoquinoline emulsification was no longer required for utilization of isoquinoline as the sole source of carbon and nitrogen by these cultures. An isoquinoline-degrading Acinetobacter strain was isolated from one of the enrichment cultures. The degradation of isoquinoline was accompanied by the accumulation of a red cell-associated pigment and of 1-hydroxyisoquinoline, which was further degraded to unknown intermediary ring-cleavage products and carbon dioxide.     

Microbial decolourisation and degradation of textile dyes

Dyes and dyestuffs find use in a wide range of industries but are of primary importance to textile manufacturing. Wastewater from the textile industry can contain a variety of polluting substances including dyes. Increasingly, environmental legislation is being imposed to control the release of dyes, in particular azo-based compounds, into the environment. The ability of microorganisms to decolourise and metabolise dyes has long been known, and the use of bioremediation based technologies for treating textile wastewater has attracted interest. Within this review, we investigate the mechanisms by which diverse categories of microorganisms, such as the white-rot fungi and anaerobic bacterial consortia, bring about the degradation of dyestuffs.     

Binding of textile azo dyes byMyrothecium verrucaria

Summary A strain ofMyrothecium verrucaria that showed a high capacity for rapid decolorization of textile dye solutions was isolated from soil. As much as 70%, 86%, and 95% of Orange II, 10B (blue) and RS (red) dyes (color index no. 15510, 20470, 23635), respectively, were adsorbed from solutions of approximately 0.2 g dye per liter in 5 h by approximately 4.5 g dry weight of cells per liter of dye solution. Intact cells showed a higher adsorption capacity than disrupted cells for Orange II and RS but not for 10B. Dye bound to cells was recoverable by extraction with methanol and methanol-treated cells were able to be recycled, albeit with a slightly diminished dye-binding capacity. The Tween detergents were shown to reduce dye adsorption. Dyes strongly bound to the fungal biomass required sonication in dH₂O or in Triton X-100 or extraction with methanol for their removal. These results suggest that hydrophobic/hydrophilic interactions are important in dye binding.     

Mechanism for the depolymerization of cellulose under alkaline conditions

The mechanism for the hydroxyl-radical-induced depolymerization of cellulose under alkaline conditions in air was investigated using density functional theory at the B3LYP/6-31+G(d,p) level as well as electron transfer theory. The pathway for the depolymerization of cellulose was obtained theoretically and H abstraction from the C(3) atom of the pyran ring during the cleavage of the glucosidic bond was found to be the rate-limiting step due to its high energy barrier (16.81 kcal/mol) and low reaction rate constant (4.623?×?10⁴ mol L^?1 s^?1). Calculations of the electron transfer between O₂ and the saccharide radical performed with the HARLEM software package revealed that following the H abstraction, the oxygen molecule approaches C(2) on the saccharide radical and obtains an electron from the radical, even though no bond forms between the oxygen molecule and the radical. The rate constant for electron transfer could be as high as 1.572?×?10¹¹ s^?1. Furthermore, an enol intermediate is obtained during the final stage of the depolymerization.     

Selection of Pseudomonas for industrial textile dyes decolourization

Pigment is the first contaminant to be recognised in bodies of water and wastewater. Besides the aesthetic problem, dyes obstruct light and reduce oxygen mass transfer. This paper describes the selection of Pseudomonas strains with the ability to remove colour from textile industrial dyes. Four Pseudomonas species were tested against 14 commercial industrial dyes. Pseudomonas cepacia exhibited no growth at all on plates containing dyes (1 g l^?1), whereas Pseudomonas aeruginosa, Pseudomonas oleovorans and Pseudomonas putida exhibited considerable growth. Decolourization in a liquid culture revealed that P. oleovorans is more viable for decolourizing textile dyes, as it achieved over 80% colour removal for two of the 14 dyes studied; it also proved to be more tolerant to high dye concentrations.