Genotoxicity of sludges, wastewater and effluents from three different industries.

Many surface waters in Europe, Asia and South America have been reported to be contaminated with genotoxic substances. Therefore, it is important to establish strategies for identification of the most critical sources. In this study, we used a battery of four genotoxicity assays namely chromosomal aberration, DNA strand break, DNA laddering and P53 accumulation tests in mononuclear blood cells. Before cleaning of wastewater high levels of genotoxic contamination could be observed. For instance, we observed an increase in chromosomal aberrations from 2.6 +/- 1.1 (aberrant cells in %; control), to 33.6 +/- 6.6 in a petrochemical plant, 29.4 +/- 3.3 in a petroleum refinery and 14.4 +/- 1.8 in a coke plant of steel industry. A good correlation between the four assays was found. The most sensitive and reproducible results were obtained with the chromosomal aberration assay. Interestingly, clear differences in the efficiency of wastewater cleaning in three different treatment plants were observed. The first and second treatment plants in petrochemical industry and coke plant of steel industry completely eliminated genotoxicity of the wastewater. However, the third plant in petroleum refinery could achieve a reduction in genotoxicity but significant genotoxic contaminations were still present. In conclusion, our battery of genotoxicity tests allows the identification of critical sources contributing to contamination of surface waters.

Modulatory effect of distillate of Ocimum sanctum leaf extract (Tulsi) on human lymphocytes against genotoxicants.

OBJECTIVE: To study the modulatory effect of distillate of Ocimum sanctum (traditionally known as Tulsi) leaf extract (DTLE) on genotoxicants. METHODS: In the present investigation, we studied the antigenotoxic and anticlastogenic effect of distillate of Tulsi leaf extract on (i) human polymorphonuclear leukocytes by evaluating the DNA strand break without metabolic activation against mitomycin C (MMC) and hexavalent chromium (Cr+6) and (ii) human peripheral lymphocytes (in vitro) with or without metabolic activation against mitomycin C (MMC), hexavalent chromium (Cr+6) and B[a]P by evaluating chromosomal aberration (CA) and micronucleus assay (MN). Three different doses of DTLE, 50 microL/mL, 100 microL/mL, and 200 microL/mL were selected on the basis of cytotoxicity assay and used for studying DNA strand break, chromosomal aberration and micronucleus emergence. The following positive controls were used for inducing genotoxicity and clastogenicity: MMC (0.29 micromol/L) for DNA strand break, chromosomal aberration and 0.51 micromol/L for micronucleus assay; Potassium dichromate (Cr+6) 600 micromol/L for DNA strand break and 5 micromol/L for chromosomal aberration and micronucleus assay; Benzo[a]pyrene (30 micromol/L) for chromosomal aberration and 40 micromol/L for micronucleus assay. The active ingredients present in the distillate of Tulsi leaf extract were identified by HPLC and LC-MS. RESULTS: Mitomycin C (MMC) and hexavalent chromium (Cr+6) induced statistically significant DNA strand break of respectively 69% and 71% (P<0.001) as revealed by fluorometric analysis of DNA unwinding. Furthermore, the damage could be protected with DTLE (50 microL/mL, 100 microL/mL, and 200 microL/mL) on simultaneous treatment. Chromosomal aberration and micronucleus formation induced by MMC, Cr+6 and B[a]P were significantly protected (P<0.001) by DTLE with and without metabolic activation. CONCLUSION: Distillate of Tulsi leaf extract possesses antioxidants contributed mainly by eugenol, luteolin and apigenin as identified by LC-MS. These active ingredients may have the protective effect against genotoxicants.

Enrichment and isolation of endosulfan degrading and detoxifying bacteria.

In the present study, degradation of endosulfan by a mixed culture isolated from a pesticide-contaminated soil was studied in batch experiments. After two weeks of incubation, the mixed culture was able to degrade 73% and 81% of alpha and beta endosulfan respectively. Endodiol was identified by GC/MS as degradation intermediate. The toxicity studies of endosulfan before and after degradation were carried out using micronucleus assay on human polymorphonuclear cells. The findings suggested that the metabolism of endosulfan isomers by the mixed culture was accompanied by significant reduction in the toxicity. Studies were also carried out to quantify the degradation potential of the individual species in the mixed bacterial culture. Two cultures identified by 16S rRNA as Stenotrophomonas maltophilia and Rhodococcus erythropolis were found to be responsible for majority of the degradation by the mixed culture. S. maltophilia showed better degradation efficiency compared to that by R. erythropolis. This is the first report of endosulfan degradation using the above-mentioned organisms.

Decolorisation and detoxification of Direct Blue-15 by a bacterial consortium.

Studies were carried out on decolorisation and biotransformation of the dye Direct Blue-15 into 3,3'-dimethoxybenzidine (O'-dianisidine) and a sulphonated derivative by a five-member bacterial consortium. Chromatographic studies revealed further complete biodegradation of 3,3'-dimethoxybenzidine coupled with release of ammonia, but the recalcitrant sulphonated derivative persisted. The microorganisms identified in the mixed consortium by 16S rDNA sequence analysis were Alcaligenes faecalis, Sphingomonas sp. EBD, Bacillus subtilis, Bacillus thuringiensis and Enterobacter cancerogenus. The cytotoxicity data showed a significant reduction in the toxicity (P<0.001) of the degraded dye as evidenced from the number of viable human polymorphonuclear leukocyte cells present.

Decolorisation, biodegradation and detoxification of benzidine based azo dye.

The present study deals with the decolorisation, biodegradation and detoxification of Direct Black-38, a benzidine based azo dye, by a mixed microbial culture isolated from an aerobic bioreactor treating textile wastewater. The studies revealed a biotransformation of Direct Black-38 into benzidine and 4-aminobiphenyl followed by complete decolorisation and biodegradation of these toxic intermediates. From cytotoxicity studies, it was concluded that detoxification of the dye took place after degradation of the toxic intermediates by the culture.