Genotoxic hazard and oxidative stress induced by wastewater irrigated soil with special reference to pesticides and heavy metal pollution

Due to enhancement of industrial growth and urbanization, soil contamination is increasing prominently. Therefore, it is important to examine possible adverse effects of industrial waste. Soil samples were might to be polluted with several heavy-metals and pesticides. Gas chromatographic results showed occurrence of high-level of organochlorine and organophosphate pesticides in studied soil samples. Genotoxicity of soil extracts was assessed using environmental-risk assessment models. Soil samples were extracted in hexane and dichloromethane solvents and were evaluated for genotoxic potential by prokaryotic (Ames test, plasmid nicking assay and E. coli K-12 DNA repair defective mutants) and eukaryotic (Allium cepa root chromosomal aberration and Vigna radiata seed-germination test) bioassays. Strain TA98 was found the most susceptible among soil extracts. The mutagenicity of hexane soil extract from wastewater irrigation was found to be higher than that of DCM samples in terms of mutagenic index, mutagenic potential, and induction factor for Ames strains. The damage in DNA repair defective mutants of hexane extracts were found higher compared to DCM extracts at dose of 20 μl/ml of culture. Survival in polA, lexA and recA mutants were 39%, 47% and 55% while treated with hexane extract. Allium cepa test, mitotic index was decreased in dose-dependent way and various kinds of chromosomal aberrations were found. Vigna radiata seeds germination and other parameters were also affected when treated with wastewater irrigated (WWI) soil. Oxidative stress in V. radiata roots were also showed under CLS microscope. Genotoxicity of WWI soil extract was also confirmed by plasmid nicking test. Our study provides possible explanation for the assessment of potential health and environmental hazards of the industrial region.

Tobacco Waste Liquid-Based Organic Fertilizer Particle for Controlled-Release Fulvic Acid and Immobilization of Heavy Metals in Soil

Every year, a large amount of tobacco waste liquid (TWL) is discharged into the environment, resulting in serious pollution for the environment. In this work, a TWL-based particle (OACT) was fabricated by CaO, attapulgite (ATP), and TWL, and, then, OACT was coated by amino silicon oil (ASO) to form OACT@ASO. Therein, OACT@ASO had high controlled-release ability for fulvic acid (FA), because of the nanonetworks structure for ATP and the high content of FA in TWL. The release ratio (RR) of FA from OACT@ASO reached 94% at 75 h in deionized water, and 23% at 32 d in silica sand. Furthermore, the release mechanism of FA from OACT@ASO was consistent with the First-order law. Additionally, OACT@ASO also possessed high immobilization capacity for Cu(II), Cd(II), and Pb(II) (CCP) in soil. Notably, a pot experiment indicated that OACT@ASO could facilitate the growth of pakchoi seedlings and decrease the absorption of CCP by pakchoi seedlings. Thus, this study provides a new kind of organic fertilizer which could not only release FA, but also immobilize CCP in soil.

Effective bioremediation of tobacco wastewater by microalgae at acidic pH for synergistic biomass and lipid accumulation

Tobacco wastewater is too difficult to decontaminate which poses a significant environmental problem due to the harmful and toxic components. Chlorella pyrenoidosa is a typical microalgal species with potential in removal of organic/inorganic pollutants and proves to be an ideal algal-based system for wastewater treatment. However, the strategy of tobacco related wastewater treatment using microalgae is in urgent need of development. In this study, C. pyrenoidosa was used to evaluate the removal efficiency of artificial tobacco wastewater. Under various solid-to-liquid (g/L) ratios, 1:1 ratio and acidic pH 5.0 were optimal for C. pyrenoidosa to grow with high performance of removal capacity to toxic pollutants (such as COD, NH3-N, nicotine, nitrosamines and heavy metals) with the alleviation of oxidative damage. Algal biomass could reach up to 540.24 mg/L. Furthermore, carbon flux of C. pyrenoidosa was reallocated from carbohydrate and protein biosynthesis to lipogenesis with a high lipid content of 268.60 mg/L at pH 5.0. Overall, this study demonstrates an efficient and sustainable strategy for tobacco wastewater treatment at acidic pH with the production of valuable microalgal products, which provides a promising biorefinery strategy for microalgal-based wastewater bioremediation.

Production and purification of 2-phenylethanol by Saccharomyces cerevisiae using tobacco waste extract as a substrate

2-phenylethanol (2-PE), which is extracted naturally from plant or biotechnology processing, is widely used in the food and cosmetics industries. Due to the high cost of 2-PE production, the valorization of waste carbon to produce 2-PE has gained increasing attention. Here, 2-PE was produced by Saccharomyces cerevisiae using tobacco waste extract (TWE) as the substrate. Considering the toxicity of nicotine and its inhibition of 2-PE, the tolerance of S. cerevisiae was first evaluated. The results suggested that the production of 2-PE by S. cerevisiae in TWEs could be carried out at 2·0 mg ml-1 nicotine concentrations and may be inhibited by 1·0 mg ml-1 2-PE. Thus, the compounds in the TWEs prepared at different temperatures were detected, and the results revealed that the TWEs prepared at 140°C contained 2·18 mg ml-1 of nicotine, had total sugar concentrations of 26·8 mg ml-1 and were suitable for 2-PE production. Due to feedback regulation, the 2-PE production was only 1·11 mg ml-1 , and the remaining glucose concentration remained at 13·78 mg ml-1 , which indicated insufficient glucose utilization. Then, in situ product recovery was further implemented to remove this inhibition; the glucose utilization (the remaining concentration decreased to 3·64 mg ml-1 ) increased, and the 2-PE production increased to 1·65 mg ml-1 . The 2-PE produced in the fermentation broth was first isolated by elution from the resin with 75% ethanol and then by removing the impurities with 2·5% activated charcoal, and pure 2-PE was identified by gas chromatography mass spectrometry. The results of this study suggest that TWE could be an alternative carbon source for 2-PE production. This could provide an outlet tobacco waste as well as reducing the price of natural 2-PE, although more strategies need to be explored to improve the production yield of 2-PE by using TWE.

Mutagenicity and genotoxicity of water boiled in aluminum pots of different duration of use using SOS chromotest and Ames fluctuation test

Boiling water before drinking or using it for cooking is a general practice especially in areas where portable water is not readily available. However, boiling water in an aluminum pot could be a route of entry of heavy metals into humans. This study assessed the genotoxic and mutagenic potential of boiled water samples from aluminum pots of different duration of use using the SOS chromotest on Escherichia coli PQ37 and the Ames fluctuation test on Salmonella typhimurium strains TA98 and TA100, respectively. Three aluminum pots from the same manufacturer but of different years of use (6-year-old, 3-year-old, and new aluminum pots) were used for the experiment. Six selected heavy metals (Cadmium, Copper, Arsenic, Nickel, Lead, and Aluminum) were also analyzed in the samples using an Atomic Absorption Spectrophotometer (AAS Buck, Scientific model 210 VGP). Cadmium, Copper, Arsenic, Nickel, Lead, and Aluminum were present in all the test water samples at concentrations that were higher than the maximum limit allowable by standard regulatory organizations. The concentrations of these metals in the samples also increased as the duration of use of the aluminum pots increased. The results further showed that the water boiled in the three aluminum pots is mutagenic and genotoxic in both Ames fluctuation and SOS chromotests. The 6-year-old aluminum pot induced the highest mutagenicity and genotoxicity followed by the 3-year-old aluminum pot. The metals in the tested samples were believed to be responsible for the observed mutagenicity and genotoxicity in the microbial assays. The findings of this study revealed that cooking with Aluminum pots could lead to the leaching of heavy metals into food, and pose mutagenic and genotoxic risks to consumers.

Mutagenic and ecotoxicological assessment of urban surface runoff flowing to the beaches of Guarujá, State of São Paulo, Brazil

Along the coast of the State of São Paulo, Brazil, urban drainage channels introduce a complex mixture of pollutants into the South Atlantic Ocean, that may cause deleterious effects to the aquatic biota. The objective of this study was to analyse, for the first time, the mutagenicity (Ames Salmonella/microsome test) and ecotoxicity (acute and chronic tests, with Daphnia simillis and Ceriodaphnia dubia, respectively) exerted by the diffuse loads discharged in Guarujá, São Paulo coast, Brazil. Water sampling occurred bimonthly between January and July 2018 (rainy season: January through March; dry season: May through July) at four beaches with different profiles of use and land occupation: Tombo (Blue Flag certification), Enseada (high use by tourists), Perequê (fishing community) and Iporanga (conservation unit). No mutagenic potential was detected in the complex mixtures flowing to the study beaches. However, 30 and 80% of the analyses showed acute and chronic toxicities, respectively, mainly in the Enseada and Perequê channels during the rainy season. To improve the environmental quality of these coastal waters and to reduce the ecological risks posed to the aquatic organisms and public health, several actions are imperative, such as the amelioration of the basic sanitation facilities and land regularisation actions.

In vitro mutagenicity and genotoxicity of raw and simulated leachates from plastic waste dumpsite

Increase in production of different types of plastics has led to increase in the amount of plastic waste generation worldwide. The chemical constituents of these plastic wastes have made their disposal an important economic and environmental health problem globally. This study assessed the mutagenic and genotoxic potential of plastic waste dumpsite raw and simulated leachates using the Ames Salmonella fluctuation test with Salmonella typhimurium strains TA98 and TA100, and the SOS chromotest with Escherichia coli PQ37. Physico-chemical parameters and organic constituents of the leachates were also analyzed. The result of the Ames test showed that the leachates are mutagenic even at low concentration. Also, the TA100 strain was the more responsive strain in terms of mutagenic index in the absence of metabolic activation. The SOS chromotest results complimented the Ames Salmonella fluctuation test results. Nevertheless, the E. coli PQ37 system was slightly more sensitive than the Salmonella assay for detecting mutagens and genotoxins in the tested leachates. Generally, simulated leachate showed a higher mutagenicity and genotoxicity than the raw leachate. Pb, Cd, Cr, Ni, Cu, As, PBDEs, PAHs, PCBs, and Bisphenol A contents analyzed in the leachates were believed to play significant role in the observed mutagenicity and genotoxicity in the microbial assays. These data showed that plastic waste constituents are capable of inducing DNA damage in exposed organisms and might induce similar damage in plants, animals and humans exposed to it, hence, great care should be taken to eliminate indiscriminate disposal of plastics in the environment.

Bacterial cellulose production by Acetobacter xylinum ATCC 23767 using tobacco waste extract as culture medium

In this study, bacterial cellulose (BC) was synthesized by Acetobacter xylinum ATCC 23767 using tobacco waste extract (TWE) as a carbon source. Nicotine was found to be an inhibitory factor for BC synthesis, but it can be removed at pH 9.0 by steam distillation. After removing nicotine, the BC production was 2.27 g/L in TWE prepared with solid-liquid (S-L) ratio at 1:10. To further enhance the BC production, two fermentation stages were performed over 16 days by re-adjusting the pH to 6.5 at 7 days, after the first fermentation stage was completed. Using this two-stage fermentation, the BC production could reach 5.2 g/L. Structural and thermal analysis by FE-SEM, FT-IR, XRD and TGA showed the properties of BC obtained from TWE were similar to that from Hestrin-Schramm (HS) medium. Considering the huge disposal tobacco waste in China, the present study provides an alternative methodology to synthesize BC.

Semi-continuous production of high-activity pectinases by immobilized Rhizopus oryzae using tobacco wastewater as substrate and their utilization in the hydrolysis of pectin-containing lignocellulosic biomass at high solid content

In this study, highly reactive endo- and exo-polygalacturonases (PGs) were produced from the tobacco industry wastewater using immobilized Rhizopus oryzae. Compared with free cells, immobilized cells increased enzyme activity 2.8-fold and reduced production time to 24h by shake-flask production. Moreover, the immobilized cells enabled the semi-continuous production of enzymes through repeated-batch mode for seven consecutive cycles in a scale-up bioreactor. During the first five cycles, the average endo-PG and exo-PG activities reached 307.5 and 242.6U/ml, respectively. The addition of crude enzyme for the hydrolysis of pectin-containing lignocellulosic biomass under high-gravity conditions increased glucose release 4.2-fold (115.4 vs. 29.0g/L), compared with hydrolysis using cellulase alone. This process achieves the efficient production of pectin-degrading enzymes, provides a cost-effective method for tobacco wastewater treatment, and offers the possibility to obtain fermentable sugars with high-titer from pectin-containing lignocellulosic biomass, which has important potential for the commercial production of bio-fuels.