In situ textile wastewater treatment in high rate transpiration system furrows planted with aquatic macrophytes and floating phytobeds

Plants are known to remediate dyes, metals and emerging contaminants from wastewaters. Vetiveria zizanioides, a perennial bunchgrass showed removal of Remazol Red (RR, 100 mg/L) up to 93% within 40 h. Root and shoot tissues of V. zizanioides revealed induction in dye degrading enzymes viz. lignin peroxidase by 2.28 and 1.43, veratryl alcohol oxidase 2.72 and 1.60, laccase 6.15 and 3.55, and azo reductase 2.17 and 2.65-fold, respectively, during RR decolorization. Substantial increase was observed in the contents of chlorophyll a, chlorophyll b, and carotenoids in the plant leaves during treatment. Anatomical studies of roots, HPLC and GC-MS analysis of metabolites, and phytotoxicity assessment confirmed phytotransformation of RR into nontoxic metabolites. Floating phytobed with V. zizanioides treated textile wastewater (400 L) effectively and reduced ADMI, COD, BOD, TDS, and TSS by 74, 74, 81, 66 and 47%, respectively within 72 h. In-situ treatment of textile wastewater for 5 days in constructed furrows planted with semiaquatic plants, V. zizanioides, Ipomoea aquatica and its consortium-VI decreased ADMI by 68, 61 and 76%, COD by 75, 74 and 79%, BOD by 73, 71 and 84%, TDS by 77, 75 and 83%, and TSS by 34, 31 and 51%, respectively. This treatment was also useful to remove arsenic, cadmium, chromium and lead from wastewater. Overall observation suggests wise strategy to use this plantation in the furrows of high rate transpiration system and phytobeds in deep water for textile wastewater treatment.

Combined effects of sulfamethazine and sulfamethoxazole on a freshwater microalga, Scenedesmus obliquus: toxicity, biodegradation, and metabolic fate

This study investigated the environmental effects of two common emerging contaminants, sulfamethazine (SMZ) and sulfamethoxazole (SMX), and their mixture using a green microalga, Scenedesmus obliquus. The calculated EC₅₀ values of SMZ, SMX, and their mixture (11:1 wt/wt) after 96 h were 1.23, 0.12, and 0.89 mg L^-1, respectively. The toxicity of the mixture could be better predicted using a concentration addition model than an independent action model. The risk quotients of SMZ, SMX, and their mixture were >1 during the experiment, indicating their high potential risks on aquatic microorganisms. Despite their toxicity, S. obliquus exhibited 17.3% and 29.3% removal of 0.1 mg L^-1 and 0.2 mg L^-1 after 11 days of cultivation. The changes of SMZ and SMX removal were observed when combined, which showed a significantly improved removal of SMZ (up to 3.4 folds) with addition of SMX (0.2 mg L^-1). The metabolic pathways of SMZ and SMX were proposed according to mass spectroscopic analysis, which showed six metabolites of SMX and seven intermediates of SMZ, formed as a result of ring cleavage, hydroxylation, methylation, nitrosation, and deamination.

Toxicity of sulfamethazine and sulfamethoxazole and their removal by a green microalga, Scenedesmus obliquus

A comprehensive ecotoxicological evaluation of a sulfamethazine (SMZ) and sulfamethoxazole (SMX) mixture was conducted using an indicator microalga, Scenedesmus obliquus. The toxicological effects of this mixture were studied using microalgal growth patterns, biochemical characteristics (total chlorophyll, carotenoid, carbohydrate, fatty acid methyl ester), and elemental and Fourier-transform infrared spectroscopy analyses. The 96-h half maximal effective concentration (EC₅₀) of the SMZ and SMX mixture was calculated to be 0.15 mg L^-1 according to the dose-response curves obtained. The chlorophyll content decreased with elevated SMZ and SMX concentrations, while the carotenoid content initially increased and then decreased as concentration raised. The unsaturated fatty acid methyl esters (FAMEs) content was enhanced with higher SMZ and SMX concentrations, while that of saturated FAMEs simultaneously decreased due to SMZ and SMX stress. Elemental analyses showed an improved percentage of nitrogen and sulfur in the microalgal biomass as SMZ and SMX concentrations increased. The microalga S. obliquus was shown to biodegrade the chemicals tested and removed 31.4-62.3% of the 0.025-0.25 mg SMZ L^-1 and 27.7-46.8% of the 0.025-0.25 mg SMX L^-1 in the mixture after 12 days of cultivation. The greater biodegradation observed at higher SMZ and SMX concentrations indicates that microalgal degradation of SMZ and SMX could act as an efficient adaptive mechanism to antibiotics.

Mineralization and Detoxification of the Carcinogenic Azo Dye Congo Red and Real Textile Effluent by a Polyurethane Foam Immobilized Microbial Consortium in an Upflow Column Bioreactor

A microbial consortium that is able to grow in wheat bran (WB) medium and decolorize the carcinogenic azo dye Congo red (CR) was developed. The microbial consortium was immobilized on polyurethane foam (PUF). Batch studies with the PUF-immobilized microbial consortium showed complete removal of CR dye (100 mg·L-1) within 12 h at pH 7.5 and temperature 30 ± 0.2 °C under microaerophilic conditions. Additionally, 92% American Dye Manufactureing Institute (ADMI) removal for real textile effluent (RTE, 50%) was also observed within 20 h under the same conditions. An upflow column reactor containing PUF-immobilized microbial consortium achieved 99% CR dye (100 mg·L-1) and 92% ADMI removal of RTE (50%) at 35 and 20 mL·h-l flow rates, respectively. Consequent reduction in TOC (83 and 79%), COD (85 and 83%) and BOD (79 and 78%) of CR dye and RTE were also observed, which suggested mineralization. The decolorization process was traced to be enzymatic as treated samples showed significant induction of oxidoreductive enzymes. The proposed biodegradation pathway of the dye revealed the formation of lower molecular weight compounds. Toxicity studies with a plant bioassay and acute tests indicated that the PUF-immobilized microbial consortium favors detoxification of the dye and textile effluents.

Biodegradation and detoxification of textile azo dyes by bacterial consortium under sequential microaerophilic/aerobic processes

Release of textile azo dyes to the environment is an issue of health concern while the use of microorganisms has proved to be the best option for remediation. Thus, in the present study, a bacterial consortium consisting of Providencia rettgeri strain HSL1 and Pseudomonas sp. SUK1 has been investigated for degradation and detoxification of structurally different azo dyes. The consortium showed 98-99 % decolorization of all the selected azo dyes viz. Reactive Black 5 (RB 5), Reactive Orange 16 (RO 16), Disperse Red 78 (DR 78) and Direct Red 81 (DR 81) within 12 to 30 h at 100 mg L^-1 concentration at 30 ± 0.2 °C under microaerophilic, sequential aerobic/microaerophilic and microaerophilic/aerobic processes. However, decolorization under microaerophilic conditions viz. RB 5 (0.26 mM), RO 16 (0.18 mM), DR 78 (0.20 mM) and DR 81 (0.23 mM) and sequential aerobic/microaerophilic processes viz. RB 5 (0.08 mM), RO 16 (0.06 mM), DR 78 (0.07 mM) and DR 81 (0.09 mM) resulted into the formation of aromatic amines. In distinction, sequential microaerophilic/ aerobic process doesn’t show the formation of amines. Additionally, 62-72 % reduction in total organic carbon content was observed in all the dyes decolorized broths under sequential microaerophilic/aerobic processes suggesting the efficacy of method in mineralization of dyes. Notable induction within the levels of azoreductase and NADH-DCIP reductase (97 and 229 % for RB 5, 55 and 160 % for RO 16, 63 and 196 % for DR 78, 108 and 258 % for DR 81) observed under sequential microaerophilic/aerobic processes suggested their critical involvements in the initial breakdown of azo bonds, whereas, a slight increase in the levels of laccase and veratryl alcohol oxidase confirmed subsequent oxidation of formed amines. Also, the acute toxicity assay with Daphnia magna revealed the nontoxic nature of the dye-degraded metabolites under sequential microaerophilic/aerobic processes. As biodegradation under sequential microaerophilic/aerobic process completely detoxified all the selected textile azo dyes, further efforts should be made to implement such methods for large scale dye wastewater treatment technologies.

Identification and characterization of inhibitors of Haemophilus influenzae acetohydroxyacid synthase

Acetohydroxyacid synthase (AHAS), a potential target for antimicrobial agents, catalyzes the first common step in the biosynthesis of branched-chain amino acids. The gene coding for the AHAS catalytic subunit from Haemophilus influenzae (Hi) was cloned, overexpressed in Escherichia coli, and purified. To identify new inhibitory scaffolds, we used a high-throughput screen to test 221 small diverse chemical compounds against Hi-AHAS. Compounds were selected for their ability to inhibit AHAS in vitro. The screen identified 3 compounds, each representing a structural class, as Hi-AHAS inhibitors with an IC(50) in the low micromolar range (4.4-14.6 μM). The chemical scaffolds of the three compounds were oxa-1-thia-4-aza-cyclopenta[b]naphthalene (KHG25229), phenyl-2,3-dihydro-isothiazole (KHG25386), and phenyl-pyrrolidine-3-carboxylic acid phenylamide (KHG25056). Further, molecular docking of the two most potent chemicals, KHG25229 and KHG25386, in Hi-AHAS yielded binding energies of -10.41 and -9.21 kcal/mol, respectively. The binding modes were consistent with inhibition mechanisms, as both chemicals oriented outside the active site. As the need for novel antibiotic classes to combat drug resistant bacteria increases, screening compounds that act against Hi-AHAS may assist in the identification of potential new anti-Hi drugs.

Decolorization of Textile Dyes and Degradation of Mono-Azo Dye Amaranth by Acinetobacter calcoaceticus NCIM 2890

Acinetobacter calcoaceticus NCIM 2890 (A. caloaceticus) was found to decolorize 20 different textile dyes of various classes. Decolorization of an azo dye amaranth was observed effectively (91%) at static anoxic condition, whereas agitated culture grew well but showed less decolorization (68%) within 48 h of incubation. Induction of intracellular and extracellular lignin peroxidase, intracellular laccase, dichlorophenol indophenol (DCIP) reductase and riboflavin reductase represented their involvement in the biodegradation of amaranth. The products obtained after degradation of Amaranth were characterized as naphthalene sulfamide, hydroxyl naphthalene diazonium and naphthalene diazonium. The germination and growth of Sorghum vulgare and Phaseolus mungo seeds, and the growth of E. coli and Bacillus substilis were not inhibited by the metabolic products of the dye.

Degradation analysis of Reactive Red 198 by hairy roots of Tagetes patula L. (Marigold)

Tagetes patula L. (Marigold) hairy roots were selected among few hairy root cultures from other plants tested for the decolorization of Reactive Red 198. Hairy roots of Tagetes were able to remove dye concentrations up to 110 mg L(-l) and could be successively used at least for five consecutive decolorization cycles. The hairy roots of Tagetes decolorized six different dyes, viz. Golden Yellow HER, Methyl Orange, Orange M2RL, Navy Blue HE2R, Reactive Red M5B and Reactive Red 198. Significant induction of the activity of biotransformation enzymes indicated their crucial role in the dye metabolism. UV-vis spectroscopy, HPLC and FTIR spectroscopy analyses confirmed the degradation of Reactive Red 198. A possible pathway for the biodegradation of Reactive Red 198 has been proposed with the help of GC-MS and metabolites identified as 2-aminonaphthol, p-aminovinylsulfone ethyl disulfate and 1-aminotriazine, 3-pyridine sulfonic acid. The phytotoxicity study demonstrated the non-toxic nature of the extracted metabolites. The use of such hairy root cultures with a high ability for bioremediation of dyes is discussed.

Biodegradation of kerosene by Aspergillus ochraceus NCIM-1146

The filamentous fungus Aspergillus ochraceus NCIM-1146 was found to degrade kerosene, when previously grown mycelium (96 h) was incubated in the broth containing kerosene. Higher levels of NADPH-DCIP reductase, aminopyrine N-demethylase and kerosene biodegradation activities were found to be present after the growth in potato dextrose broth for 96 h, when compared with the activities at different time intervals during the growth phase. NADPH was the preferred cofactor for enzyme activity, which was inhibited by CO, indicating cytochrome P450 mediated reactions. A significant increase in all the enzyme activities was observed when mycelium incubated for 18 h in mineral salts medium, containing cholesterol, camphor, naphthalene, 1,2-dimethoxybenzene, phenobarbital, n-hexane, kerosene or saffola oil as inducers. Acetaldehyde produced by alcohol dehydrogenase could be used as an indicator for the kerosene biodegradation.

Biotransformation enzymes inCunninghamella blakesleeana (NCIM-687)

Presence of higher enzyme levels of aminopyrine N-demethylase, aniline hydroxylase and 11-beta hydroxylase activities were observed in Cunninghamella blakesleeana grown in potato-dextrose medium for 96 h. The enzyme activity preferred NADPH as a cofactor and showed inhibition with CO, indicating cytochrome P450 mediated reactions. A significant increase in aniline hydroxylase enzyme activity was observed when mycelia incubated in incubation medium containing different inducers (viz. camphor, cholesterol, naphthalene, veratrole, phenobarbital, n -hexadecane and ethyl alcohol) when compared with mycelia incubated in same way but in absence of inducers. Cunninghamella blakesleeana (NCIM 687) have shown the ability to degrade cholesterol, camphor and naphthalene when 96 h grown mycelia incubated in incubation medium containing these organic compounds.

Inhibition of human term placental and fetal liver glutathione-S-transferases by fatty acids and fatty acid esters

Glutathione-S-transferase (GST) activity from human term placenta and human fetal liver towards 1-chloro-2,4-dinitrobenzene as the second substrate was significantly inhibited by the saturated fatty acids, stearic (SA) and palmitic (PA) acids and fatty acid esters, ascorbyl stearate (Asc-S) and ascorbyl palmitate (Asc-P). The nature of inhibition of human placental GST was competitive towards CDNB with Ki values of 3.1, 10.0, 13.5 and 18.5 microM for Asc-S, Asc-P, PA and SA, respectively. The inhibitory effect of Asc-S on human term placental GST was reversible. I50 values for Asc-S, Asc-P, SA and PA were 15, 45, 83 and 78 microM, respectively, for partially purified human fetal liver GSTs and 21, 6, 88 and 117 microM, respectively, for partially pure rat liver GSTs. The evidence suggests that Asc-S, Asc-P, SA and PA are potent inhibitors especially of the pi-class of GST.

Inhibition of hepatic glutathione-S-transferases by fatty acids and fatty acid esters

Micromolar concentrations of polyunsaturated fatty acids and ascorbate esters of saturated fatty acids were found to cause a marked inhibition of rat and mouse hepatic glutathione-S-transferase (GST) activity towards 1-chloro-2,4-dinitrobenzene. Arachidonic acid was approximately 25 times more potent in inhibiting rat GST than palmitic acid which was the least effective. Both linoleic and arachidonic acids did not inhibit rat liver GST when ethacrynic acid was used as substrate while the reverse was true with 1,2-dichoro-4-nitrobenzene. In contrast, all the chemicals tested inhibited rat liver GST activity towards 4-nitropyridine N-oxide, indicating isozyme specificity.