Biodegradation Of Malachite Green Research Articles

Dye degradation by early colonizing marine bacteria from the Arabian Sea, India.

Malachite green dye belongs to the triphenylmethane group and is a common environmental pollutant that threatens non-target organisms. We report the potential of the early colonizing marine bacterium Pseudomonas sp. ESPS40 isolated from the Arabian Sea, India, to decolorize malachite green (MG). The bacterium ESPS40 exhibited a higher ability for MG degradation (86-88%) at varying NaCl concentrations (1-3%). The highest MG degradation (~ 88%) was observed at 1% NaCl. Thebacterialstrain ESPS40 showed degradation up to 800mg L-1 MG. Further, enzyme activities such as tyrosinase (63.48-526.52 U L-1) and laccase (3.62-28.20 U L-1) were also analyzed with varying concentrations (100mg L-1-1000mg L-1) of MG during the degradation process. The dye degradation was confirmed by Fourier transform infrared spectroscopy (FTIR) and high-performance liquid chromatography (HPLC). The outcome of the present study demonstrated Pseudomonas sp. ESPS40 as a potential strain for the efficient degradation of MG at higher concentrations. Thus, Pseudomonas sp. ESPS40 can be utilized as a potential candidate for the biodegradation of MG in wastewater treatment.

Microbial Degradation, Spectral analysis and Toxicological Assessment of Malachite Green Dye by Streptomyces exfoliatus.

Malachite green (MG) dye is a common environmental pollutant that threatens human health and the integrity of the Earth’s ecosystem. The aim of this study was to investigate the potential biodegradation of MG dye by actinomycetes species isolated from planted soil near an industrial water effluent in Cairo, Egypt. The Streptomyces isolate St 45 was selected according to its high efficiency for laccase production. It was identified as S. exfoliatus based on phenotype and 16S rRNA molecular analysis and was deposited in the NCBI GenBank with the gene accession number OL720220. Its growth kinetics were studied during an incubation time of 144 h, during which the growth rate was 0.4232 (µ/h), the duplication time (td) was 1.64 d, and multiplication rate (MR) was 0.61 h, with an MG decolorization value of 96% after 120 h of incubation at 25 °C. Eleven physical and nutritional factors (mannitol, frying oil waste, MgSO4, NH4NO3, NH4Cl, dye concentration, pH, agitation, temperature, inoculum size, and incubation time) were screened for significance in the biodegradation of MG by S. exfoliatus using PBD. Out of the eleven factors screened in PBD, five (dye concentration, frying oil waste, MgSO4, inoculum size, and pH) were shown to be significant in the decolorization process. Central composite design (CCD) was applied to optimize the biodegradation of MG. Maximum decolorization was attained using the following optimal conditions: food oil waste, 7.5 mL/L; MgSO4, 0.35 g/L; dye concentration, 0.04 g/L; pH, 4.0; and inoculum size, 12.5%. The products from the degradation of MG by S. exfoliatus were characterized using high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS). The results revealed the presence of several compounds, including leuco-malachite green, di(tert-butyl)(2-phenylethoxy) silane, 1,3-benzenedicarboxylic acid, bis(2-ethylhexyl) ester, 1,4-benzenedicarboxylic acid, bis(2-ethylhexyl) ester, 1,2-benzenedicarboxylic acid, di-n-octyl phthalate, and 1,2-benzenedicarboxylic acid, dioctyl ester. Moreover, the phytotoxicity, microbial toxicity, and cytotoxicity tests confirmed that the byproducts of MG degradation were not toxic to plants, microbes, or human cells. The results of this work implicate S. exfoliatus as a novel strain for MG biodegradation in different environments.

Engineering globins for efficient biodegradation of malachite green: two case studies of myoglobin and neuroglobin.

Malachite green (MG)-contaminated wastewater resulting from industrialization causes a global problem because of its toxicity and widespread usage. Compared with traditional physical and chemical approaches, biodegradation provides a new route for the degradation of MG. As promising candidates for native enzymes, artificial enzymes have received tremendous attention for potential applications due to unlimited possibilities based on precise design. In this study, we rationally engineered artificial enzymes based on myoglobin (Mb) and neuroglobin (Ngb). We introduced an aspartic acid (H64D mutation) in the heme pocket of Mb. A distal histidine (F43H mutation) was further introduced into H64D Mb to obtain a double mutant of F43H/H64D Mb. Moreover, we used A15C/H64D Ngb as designed recently for comparison studies. The H64D Mb, F43H/H64D Mb, and A15C/H64D Ngb were found to catalyze MG degradation efficiently, with activities much higher than those of native enzymes, such as dye-decolorizing peroxidase and laccase (83–205-fold). The crystal structure of H64D Mb was solved and the interactions of MG and H64D Mb and A15C/H64D Ngb were investigated by using both experimental and molecular docking studies. The biodegradation products of MG were also revealed by ESI-MS analysis. Therefore, these artificial enzymes have potential applications in the biodegradation of MG in textile industries and fisheries.

Biodegradation of Malachite Green by Extracellular Laccase Producing Bacillus thuringiensis RUN1

A bacteria strain Bacillus thuringiensis RUN1identifiedby 16s RNA gene phylogenetic analysiswas used to decolorize malachite green, a triphenylmethane dye in a simulated wastewater. The ability of the organism to produce extracellular laccase and degrade the dye were also investigated. Results showed that the organism decolorized (84.67 ± 1.19 %) malachite green at 40 mgl-1 within 6 h; and the decolorization was associated to laccase production by the organism experimentally. Laccase activity increased as the decolorization process progressed, with the highest activity value of 0.1043 ± 0.02 U/min/ mg protein recorded after 24 h of incubation using ABTS as substrate. In addition, FTIR analysis showed that the strain actually degraded the dye. It was therefore concluded that this strain of Bacillus thuringiensis will be relevant in the biotreatment of industrial effluent containing malachite green and in the production of laccase, an industrially important enzyme.

Decolourization of malachite green dye by endolichenic fungi from the lichen Usnea sp.: A novel study on their dye removal potential

ObjectiveThis novel study explored the potential of two endolichenic fungi, Pseudopestalotiopsis theae (PT, accession number MG881833) and Astrocystis bambusae (AB, accession number MH370741) in decolorizing Malachite Green (MG). MethodsTheir efficacy in dye decolorization was compared to non-endolichenic fungus Trichoderma asperellum (TA, accession number KP792512). Decolorization test was performed using MG (100 ppm) for 14 days (absorbance at 617 nm) to determine decolorization efficiency (DE, %). The pellet was collected for FTIR analysis (4000 to 700 cm−1, 50-scan speed) while the supernatant was analysed with UV-spectral analysis (300–800 nm) to detect for biodegradation. ResultsP. theae demonstrated the highest decolorization efficiency (DE%) at 89.22%, followed by T. asperellum (76.19%) and A. bambusae (67.69%). Common functional groups (i.e., OH, COOH, NH, CH, CO, CH) were detected in all isolates and their roles in biosorption were evident by the shifts in peaks and peak intensity. Biodegradation of MG was concluded based on UV-spectra peaks at 617 nm, which were significantly reduced (or absent). ConclusionThis study is the first to reveal that endolichenic fungi P. theae and A. bambusae are capable of decolorizing the toxic dye malachite green.

Heterologous expression of bacterial CotA-laccase, characterization and its application for biodegradation of malachite green

Malachite green (MG) is used as fungicide/parasiticide in aquaculture, its persistence is detrimental as it exhibits carcinogenic effects to aquatic organisms. Bacterial laccase evaluated as the best enzyme at extreme condition for aquatic MG removal. Study aims to increase laccase concentration, CotA-laccase from Bacillus subtilis was cloned and overexpressed in Escherichia coli. Optimal catalysis for purified CotA-laccase were at pH 5.0, 60 °C, and 1 mM of (2,2-azino-di-[3-ethylbenzothiazoline-sulphonate-(6)]) with Km and Kcat 0.087 mM and 37.64 S-1 respectively. MG biodegradation by CotA-laccase in clam and tilapia pond wastewaters and cytotoxic effect of biodegraded products in grouper fin-1 cells were determined. MG degradation by CotA-laccase was equally efficient, exhibiting upto 90–94% decolorization at freshwater and saline conditions and treated solution was non-toxic to GF-1 cells. Thus, recombinant-CotA-laccase could be an environmentally-friendly enzyme for aquaculture to remove MG, thereby effective to reduce its accumulation in aquatic organisms and ensuring safe aquaculture products.

ITRAQ-facilitated proteomic analysis of Bacillus cereus via degradation of malachite green

The wide use of malachite green (MG) as a dye has caused substantial concern owing to its toxicity. Bacillus cereus can against the toxic effect of MG and efficiently decolourise it. However, detailed information regarding its underlying adaptation and degradation mechanisms based on proteomic data is scarce. In this study, the isobaric tags for relative and absolute quantitation (iTRAQ)-facilitated quantitative method was applied to analyse the molecular mechanisms by which B. cereus degrades MG. Based on this analysis, 209 upregulated proteins and 198 downregulated proteins were identified with a false discovery rate of 1% or less during MG biodegradation. Gene ontology and KEGG analysis determined that the differentially expressed proteins were enriched in metabolic processes, catalytic activity, antioxidant activity, and responses to stimuli. Furthermore, real-time qPCR was utilised to further confirm the regulated proteins involved in benzoate degradation. The proteins BCE_4076 (Acetyl-CoA acetyltransferase), BCE_5143 (Acetyl-CoA acetyltransferase), BCE_5144 (3-hydroxyacyl-CoA dehydrogenase), BCE_4651 (Enoyl-CoA hydratase), and BCE_5474 (3-hydroxyacyl-CoA dehydrogenase) involved in the benzoate degradation pathway may play an important role in the biodegradation of MG by B. cereus. The results of this study not only provide a comprehensive view of proteomic changes in B. cereus upon MG loading but also shed light on the mechanism underlying MG biodegradation by B. cereus.

Synthetic dyes degradation using lignolytic enzymes produced from Halopiger aswanensis strain ABC_IITR by Solid State Fermentation

The present work focuses on studying the degradation of industrial synthetic dyes, which poses serious health hazards and a drastic impact on the environment. Currently available enzymatic processes have higher production and operational costs. However, most enzymes are active at acidic pH, which limits its application in textile dye degradation. This problem can be overcome by lignolytic enzymes obtained from halo-alkaliphile through Solid State Fermentation (SSF) using wheat bran (agro-byproduct) as a substrate. The major lignolytic enzymes studied were Lignin Peroxidase (LiP), Manganese Peroxidase (MnP), and laccase. The results demonstrated the highest activity of 215.4 ± 1.57 of LiP, 36.8 ± 2.38 of MnP, and 8.34 ± 0.21 IU/gds of laccase. Crude enzymes were used to treat synthetic dyes (mainly azo dyes), and their potential for its degradation was confirmed by spectrophotometric, GC-MS, and HPLC analysis. The highest decolorization of 82–93% of Malachite Green (MG) was achieved in LiP and MnP mediated reaction system within 2 hours. The laccase reaction system showed degradation of 53.87% of methyl orange without adding any redox mediator. After obtaining these results, the crude LiP and MnP in the reaction system were further subjected to decolorization at a higher MG concentration of 100–600 mg/L without a redox mediator. As a result, both LiP and MnP decolorized MG by 72–89%. Further, GC-MS analysis of MG biodegradation products confirmed the formation of less toxic low molecular weight products such as benzaldehyde and methanone.

Biodegradation of Malachite Green by White-Rot Fungus, Pleurotus Pulminarious

Wide spectrum of the industrial applications of Malachite green dyes and its lethal effect on the living organisms become major source of concerns as this causes damage to tissues, hindered growth and development system, developmental abnormalities, and mutagenic/carcinogenic potentials. This study evaluated the degradation of malachite green by laccase producing Pleurotus pulminarious. The pH, Total Protein, and laccase activities were used to monitor the progress of the degradation. The laccase activity and protein contents increased as the biodegradation process progressed with the highest Laccase activities and extracellular protein values of 0.2867±0.00 and 14.872±0.43 respectively at pH 3.9 and decreased progressively with increase in pH. Metabolites obtained after decolorizations were analyzed with GC-MS and FTIR studies and confirmed the biodegradation of dye. GC-MS analysis identified metabolites that were produced after the degradation of MG. This study demonstrated complete degradation of MG into low molecular weight compounds such as 3-Benzylhexahydropyrrolo[1,2-a] pyrazine-1,4-dione,3-Isobutylhexahydropyrrolo [1,2-a] pyrazine-1,4-dione, 3-Aminoacetophenone, N,4,4-Trimethylcyclohexanamine, 2,3,4-Trimethylhexane. It was concluded that the organism posses multifunction of having medicinal values, production of industrially important laccase, and for the treatment of industrial effluent containing malachite green.

Microbial degradation, spectral analysis and toxicological assessment of malachite green by Streptomyces chrestomyceticus S20.

Malachite green (MG), a triphenylmethane dye is extensively used for coloring silk, aquaculture and textile industries, it has also has been reported toxic to life forms. This study aimed to investigate the biodegradation potential of MG by actinobacteria. The potent actinobacterial strain S20 used in this study was isolated from forest soil (Sabarimala, Kerala, India) and identified as Streptomyces chrestomyceticus based on phenotype and molecular features. Strain S20 degraded MG up to 59.65 ± 0.68% was studied in MSM medium and MG (300mgl-1) and degradation was increased (90-99%) by additions of 1% glucose and yeast extract into the medium at pH 7. The treated metabolites from MG by S20 characterized by FT-IR and GC-MS. The results showed MG has been degraded into nontoxic compounds evaluated by (1) phytotoxic assay on Vigna radiata, (2) microbial toxicity on Staphylococcus aureus, Bacillus subtilis, Micrococcus luteus, Streptococcus sp. and Escherichia coli, (3) cytotoxicity assay in a human cell line (MCF 7). The toxicity studies demonstrated that the byproducts from MG degradation by S. chrestomyceticus S20 were no toxic to plants and microbes and less toxic to human cells as compared to the parent MG. Perhaps this is the first work reported on biodegradation of MG by S. chrestomyceticus which could be a potential candidate for the removal of MG from various environments.

Biodegradation of malachite green by a newly isolated Bacillus vietnamensis sp. MSB17 from continental slope of the Eastern Arabian Sea: Enzyme analysis, degradation pathway and toxicity studies

A marine bacterial isolate, Bacillus vietnamensis sp. MSB17 from the sediments collected from the continental slope of the eastern Arabian Sea exhibited good Malachite Green (MG) decolorization ability in mineral medium supplemented with glucose and yeast extract under static conditions. The complete decolorization of dye (50 mg/L) was attained within 4 h of incubation. The activities of enzymes such as tyrosinase (0.62 IU/ml), laccase (12.02 U/ml), and manganese peroxidase (6.23 U/ml) were observed during dye degradation. UV-VIS, FT-IR, and GC-MS analysis of dye samples extracted with ethyl acetate confirmed the biodegradation of MG into methanone, [4-(dimethylamino) phenyl] phenyl- and 2, 6-bis (1, 1-dimethylethyl) phenol. The metabolites obtained from B. vietnamensis sp. MSB17 mediated MG degradation did not exhibit any microbial toxicity and phytotoxicity. The present study indicated the efficiency of Bacillus vietnamensis sp. MSB17 to effectively degrade MG, revealing its potential to be further utilized for bioremediation purposes.

The Malachite Green Biodegradation in Bioreactors on Various pH Domains

In the experimental study was studied the malachite green colorant biodegradation in biological sludge with biological activity. The biodegradability tests were carried out in laboratory bioreactors, on aqueous solutions of green malachite contacted with microorganisms in which the dominant species is Paramecium caudatum, in a pH range between 8 and 12, temperatures in the ranges 25-350C, using pH neutralizing substances and biomass growth promoters. The colorant initial concentrations and those obtained after biological degradation depending on the contact time, at certain pH values, were established through UV-Vis spectrometry. The studies have shown the measure of possible biological degradation of some organic substances with extended uses, with largely aromatic structure, resistance to biodegradation of microorganisms, commonly used in wastewater treatment plants.

Efficient biodegradation of malachite green by a newly isolated Klebsiella pneumoniae strain WA‐1

AbstractBiodegradation by microorganisms is a potential treatment technique of malachite green (MG) in aquaculture environments. In this study, a bacterium with high MG decolorization and biodegradation ability was isolated through enrichment culture and color‐decoloration circle method, and was identified as Klebsiella pneumoniae WA‐1 after molecular and biochemical identification. The MG biodegradation characteristics and the factors affecting the MG biodegradation ability of this strain were studied using KBH4 reduction‐high performance liquid chromatography with fluorescence detector (HPLC‐FLD) method. K. pneumoniae WA‐1 could efficiently biodegrade MG in aqueous solution without any nutrients that over 94.0% MG was biodegraded by this strain at 1–20 mg/L within 0.5 hr and 100% MG were biodegraded at 1–10 mg/L within 12 hr. Fairly stable MG biodegradation performance was observed in complex environments, including various pH, temperature, salinity, and metal ions, especially at low MG concentration. Furthermore, the presence of NaCl, Mn2+, Mg2+, or Cu2+ could enhance the MG biodegradation ability of this strain. These results indicate that K. pneumoniae WA‐1 could be used as a potential MG degradation agent in complex aquaculture environments.

Biodegradation of Malachite Green in Milkfish Pond Sediments

Malachite green (MG) is usually applied as a biocide in aquaculture worldwide. The microbial degradation of MG and changes in the microbial community composition of milkfish (Chanos chanos) culture pond sediments were assessed in this study. Three MG-degrading bacteria strains—M6, M10, and M12—were isolated, identified, and characterized. Strains M6, M10, and M12 are closely related to Zhouia amylolytica, Tenacibaculum mesophilum, and Enterobacter cloacae, respectively. The bacterial strains M10 and M12 showed good ability to degrade MG in the sediment. The MG degradation rate was increased after adding MG three more times. The microbial community in the sediment changes with different treatments. The bacterial strains M10 and M12 provide a potential solution for the treatment of sediment of saline aquaculture ponds with MG contamination.

Biodegradation and detoxification of malachite green by a newly isolated bioluminescent bacterium Photobacterium leiognathi strain MS under RSM optimized culture conditions

Abstract The isolated bioluminescent bacterium was identified as Photobacterium leiognathi strain MS using 16 S rRNA sequence analysis and subjected to malachite green (MG) dye degradation. The Box-Behnken based response surface methodology (RSM) was employed in optimizing medium conditions exhibiting maximum growth at pH 8.0, temperature 30 °C, NaCl 3.5%, and peptone 6.5%. Photobacterium leiognathi strain MS was capable of tolerating high concentration of MG (1.0 gL-1) with 92.50% decolorization potency within 24 h. UV-Vis, FTIR, and LC-MS QTOF analyses confirmed biodegradation of MG into several metabolites as well as its catabolism pathway. A significant increase in the activity of laccase was obtained which revealed its major involvement in the degradation of MG dye. Moreover, phytotoxicity and cytotoxicity analyses illustrated that the metabolites generated were less toxic than the parental compound.

New nano-biomaterials for the removal of malachite green from aqueous solution via a response surface methodology

The development of new biomaterials for the remove of organic contaminants from wastewater has attracted much attention over the few past years. One of the most cost-effective approaches is to produce new high value biomaterials from low value solid agricultural biowastes. In this work, sugarcane bagasse and agricultural waste rich in reducing sugars, acted as both a green bioreductant for graphene oxide (GO) and a sustainable supporter for the immobilization of Burkholderia cepacia. Therefore, this new biomaterial which contained both reduced graphene oxide (RGO) and Burkholderia cepacia, was cable of initial adsorption of malachite green (MG) and its subsequent biodegradation. After 60 h, immobilized Burkholderia cepacia degraded more MG (98.5%) than a cell cultured Burkholderia cepacia (87.7%) alone. Raman spectroscopy confirmed that GO was successfully reduced by bagasse and that consequently a composite (B-RGO) was prepared. SEM indicated that Burkholderia cepacia was well immobilized and kinetics studies showed that the adsorption of MG onto the developed composite fitted a pseudo-second order kinetics model (R2 > 0.99). Biodegradation of MG, was confirmed by the detection of appropriate degradation products such as N, N-dimethylaniline and 4-(Dimethylamino) benzophenone using GC-MS, UV and FT-IR, and via best fit first-order biodegration kinetics. Furthermore, a response surface methodology (RSM) was applied to the removal process by varying four independent parameters using a Box-Behnken design (BBD). Optimum MG removal (99.3%) was achieved at 31.5 °C, with an initial MG concentration of 114.5 mg L−1, initial pH of 5.85, and an adsorbent dosage of 0.11 g L −1. The excellent removal efficiency indicated that agricultural waste derived reduced graphene oxide bio-adsorbents have significant potential for the removal of dyes such as MG from industrial wastewaters.

Degradation of malachite green dye by Tenacibaculum sp. HMG1 isolated from Pacific deep-sea sediments

A deep-sea bacterium from the Pacific Ocean identified as Tenacibaculum sp. HMG1 was found to have strong malachite green (MG) degradation activity. The MG tolerance and decolorizing activities of strain HMG1 were confirmed by bacterial growth and high-performance liquid chromatography (HPLC) analyses. Strain HMG1 was capable of removing 98.8% of the MG in cultures within 12 h and was able to grow vigorously at 20 mg/L MG. A peroxidase gene detected in the genome of strain HMG1 was found to be involved in the MG biodegradation process. The corresponding recombinant peroxidase (rPOD) demonstrated high degradative activity at 1 000 mg/L MG. Based on the common candidate intermediates, strain HMG1 was inferred to have one primary MG degradation pathway containing rPOD. In addition, five other candidate intermediates of the rPOD-MG degradative process were detected. The optimal conditions for MG degradation were determined and showed that strain HMG1 and the rPOD enzyme could maintain high bioactivity at a low temperature (20°C), variable pH values (6.0–9.0), higher salinities (100 mmol/L) and other factors, such as multiple metal ions, H2O2 and EDTA. MG-tolerant strain Tenacibaculum sp. HMG1 and its peroxidase have prospective applications as environmental amendments for MG degradation during coastal remediation.

Efficient degradation of Malachite Green by Aeromonas sp. strain DH-6

Microbial decolorization has been investigated extensively. Various microbes have been studied for their dye removing capability; however, microbial decolorizer with a strong environmental adaptability and wide substrate spectrum is of great potential for its possible practical application. Therefore, in this study, Aeromonas sp. DH-6, a wide dye spectrum decolorizer, was investigated in terms of its use for Malachite Green (MG) remediation. Results indicated that most of carbon sources have no effect on decolorization, while the nitrogen sources of beef extract and yeast extract could enhance MG decolorization significantly. Among the tested metal ions, Cu 2+ , Fe 2+ , and Zn 2+ could significantly inhibit decolorization. Moreover, the strain showed a very stable and efficient decolorization performance in the pH of 5.0-10.0 and at 20-40 o C. Besides, it could almost completely decolorize MG at concentrations ≤ 1000 mg/L within 36 h. Based on UV-visible, GC-MS, and FTIR analysis, biodegradation of MG by the strain DH-6 was confirmed and data showed that MG was decomposed into 4-(Dimethylamino)benzophenone and other metabolites containing –C=O, –NH, and –OH groups. Enzyme analysis showed that tyrosinase, laccase, LiP, NADH-DCIP reductase, and MG reductase might be involved in MG degradation by the strain DH-6. Overall, the results demonstrated that the strain DH-6 will have an effective use as an alternative in MG bioremediation.

Enhanced biodegradation and detoxification of malachite green by Trichoderma asperellum laccase: Degradation pathway and product analysis

The central composite design (CCD)-based response surface methodology (RSM) was engaged in optimizing the biodegradation process of malachite green (MG), a potentially toxic dye, by a laccase identified from Trichoderma asperellum with various parameters viz., enzyme concentration, dye concentration, reacting pH and incubation time. The maximal degradation of MG was obtained to be 97.18% under the optimum conditions with the enzyme concentration of 1.50 U/mL, the dye concentration of 122.66 mg/L, pH of 6.75and the incubation time of 98.58 min. The kinetics investigation of MG degradation was studied at various concentrations of MG, and the values of Km and Vmax were determined as 87.50 mg/L and 1.28 mg/L/min, respectively. Through the UV-Visible spectroscopy, FTIR, HPLC and GC-MS/MS analysis, the metabolites during the biodegradation of MG were identified to include Michler's ketone,4-(dimethylamino)benzophenone, 4-aminobenzophenone and 4-(dimethylamino)benzaldehyde, indicating that the hydroxylation, oxidation, deamination and demethylation processes were all involved in this laccase-mediated MG degradation without the formation of leuco-malachite green derivatives. The genotoxicity studies using the Allium cepa assay have further confirmed that the metabolites are less minimally toxic than the untreated MG. Therefore, this T. asperellum laccase-mediated dye degradation possesses the potentially promising biotreatment process.

Biological Decolorization and Degradation of Malachite Green by Pseudomonas sp. YB2: Process Optimization and Biodegradation Pathway.

A novel strain Pseudomonas sp. YB2, which was isolated from activated sludge, was studied for biological decolorization and degradation of malachite green (MG). The results show that this aerobic strain is an aerobic bacterium, which has relatively high salt tolerance and high antibiotic resistance. The optimal performance condition for both bacterial growth and decolorization of MG was at 25-35°C and pH 5.0-7.0. It could efficiently decolorize 90.40% MG at a high concentration up to 1500mg/L in 24h, and concentrations of MG lower than 1000mg/L could be completely decolorized in 12h. The intermediate products of MG were detected using gas chromatography-mass spectrometer, including leucomalachite green, 4,4'-bis(dimethylamino) benzophenone, 4-(dimethylamino) benzophenone, phenol, dimethylaniline. The possible degradation pathways of MG by strain YB2 were proposed. This strain might be potentially useful for biodegradation of MG in real environments.