Advances and perspective in bioremediation of polychlorinated biphenyl-contaminated soils.

In recent years, microbial degradation and bioremediation approaches of polychlorinated biphenyls (PCBs) have been studied extensively considering their toxicity, carcinogenicity and persistency potential in the environment. In this direction, different catabolic enzymes have been identified and reported for biodegradation of different PCB congeners along with optimization of biological processes. A genome analysis of PCB-degrading bacteria has led in an improved understanding of their metabolic potential and adaptation to stressful conditions. However, many stones in this area are left unturned. For example, the role and diversity of uncultivable microbes in PCB degradation are still not fully understood. Improved knowledge and understanding on this front will open up new avenues for improved bioremediation technologies which will bring economic, environmental and societal benefits. This article highlights on recent advances in bioremediation of PCBs in soil. It is demonstrated that bioremediation is the most effective and innovative technology which includes biostimulation, bioaugmentation, phytoremediation and rhizoremediation and acts as a model solution for pollution abatement. More recently, transgenic plants and genetically modified microorganisms have proved to be revolutionary in the bioremediation of PCBs. Additionally, other important aspects such as pretreatment using chemical/physical agents for enhanced biodegradation are also addressed. Efforts have been made to identify challenges, research gaps and necessary approaches which in future, can be harnessed for successful use of bioremediation under field conditions. Emphases have been given on the quality/efficiency of bioremediation technology and its related cost which determines its ultimate acceptability.

Microbial population shift caused by sulfamethoxazole in engineered-Soil Aquifer Treatment (e-SAT) system.

The engineered-Soil Aquifer Treatment (e-SAT) system was exploited for the biological degradation of Sulfamethoxazole (SMX) which is known to bio-accumulate in the environment. The fate of SMX in soil column was studied through laboratory simulation for a period of 90 days. About 20 ppm SMX concentration could be removed in four consecutive cycles in e-SAT. To understand the microbial community change and biological degradation of SMX in e-SAT system, metagenomic analysis was performed for the soil samples before (A-EBD) and after SMX exposure (B-EBD) in the e-SAT. Four bacterial phyla were found to be present in both the samples, with sample B-EBD showing increased abundance for Actinobacteria, Bacteroidetes, Firmicutes and decreased Proteobacterial abundance compared to A-EBD. The unclassified bacteria were found to be abundant in B-EBD compared to A-EBD. At class level, classes such as Bacilli, Negativicutes, Deltaproteobacteria, and Bacteroidia emerged in sample B-EBD owing to SMX treatment, while Burkholderiales and Nitrosomonadales appeared to be dominant at order level after SMX treatment. Furthermore, in response to SMX treatment, the family Nitrosomonadaceae appeared to be dominant. Pseudomonas was the most dominating bacterial genus in A-EBD whereas Cupriavidus dominated in sample B-EBD. Additionally, the sulfur oxidizing bacteria were enriched in the B-EBD sample, signifying efficient electron transfer and hence organic molecule degradation in the e-SAT system. Results of this study offer new insights into understanding of microbial community shift during the biodegradation of SMX.

Comparative study on removal of enteric pathogens from domestic wastewater using Typha latifolia and Cyperus rotundus along with different substrates.

A comparative study was carried out to evaluate the efficiency of different substrate materials along with macrophytes Typha latifolia and Cyperus rotundus in treating domestic wastewater intended for reuse in agriculture. The study was conducted over a period of 6 months with different retention times, and observations were taken twice per month. One-way analysis of variance and Tukey's Honest Significant Difference (HSD) tests were used to determine statistical significant differences between experimental columns. Treatment with T. latifolia planted in sand and mix substrate with 4-day retention time remarkably reduced the concentration of all bacterial pathogens. Log reductions observed were approximately 5.01 and 4.82 for total coliform (TC), 4.46 and 3.93 for Escherichia coli, and 5.52 and 5.48 for Shigella, respectively. Moreover, these treatments were also efficient in completely removing fecal coliform (FC) and Salmonella.Maximum parasites were removed by the treatment having sand alone as a substrate containing C. rotundus, but the difference was not significant from those planted with T. latifolia in the same substrate. The results suggest that T. latifolia aids in bacterial pathogens removal, while C. rotundus aids in parasites removal. Thus, wastewater treatment through constructed wetland having mix plantation of these species along with sand can eliminate some of the major enteric pathogens.

The role of sand, marble chips and Typha latifolia in domestic wastewater treatment - a column study on constructed wetlands.

The relative importance of sand, marble chips and wetland plant Typha latifolia is evaluated in constructed wetlands (CWs) for the treatment of domestic wastewater intended for reuse in agriculture. The prototype CWs for the experiments are realized in polyvinyl chloride columns, which are grouped into four treatments, viz. sand (<2 mm) + Typha latifolia (cattail), sand, marble chips (5-20 mm) + cattail and marble chips. The removal percentage of organic and nutritional pollutants from the wastewater is measured at varying hydraulic retention time in the columns. The statistical analysis suggests that the main effects of sand and cattail are found to be significant (p < .05) for the removal of biological oxygen demand and chemical oxygen demand from the wastewater. The presence of cattail significantly (p < .01) contributes to the conversion of total nitrogen in wastewater into [Formula: see text] by fostering the growth of favorable microbes for the nitrification. The removal of [Formula: see text] and turbidity from the wastewater is significantly (p < .01) influenced by sand than the presence of cattail. The maximum [Formula: see text] adsorption capacity of the sand is estimated to be 2.5 mg/g. Marble chips have significantly (p < .01) influenced the removal of [Formula: see text]and its maximum removal capacity is estimated to be 9.3 mg/g. The negative correlation between the filter media biofilm and column hydraulic conductivity is also reported for all the treatments. Thus, the findings of this study elucidate the role of low-cost and easily available filter media and it will guide the environmental practitioners in designing cost-effective CWs for wastewater treatment.

Synergistic growth of Bacillus and Pseudomonas and its degradation potential on pretreated polypropylene.

This study investigated biodegradation of physically pretreated polypropylene (PP) by using two different combinations of microorganisms, namely, Bacillus flexus + Pseudomonas azotoformans(B1) and B. flexus + B. subtilis(B2), for a period of 12 months. The growth rate of (B1) was found to be high throughout the study period, and reached a maximum of 1 × 10(14) colony-forming units (CFU)/mL. At the end of the experiment, the polymers become hydrophilic. Carbonyl indices showed that ultraviolet (UV)-treated polymers started degrading faster than the thermally treated PP. The thermogravimetric analysis also revealed that UV-treated PP exposed to the B. flexus + P. azotoformans combination for 1 year exhibited maximum degradation (22.7%). The gravimetric weight loss method showed 1.95% weight loss followed by 1.45% with B. flexus + B. subtilis. The changes in the carbonyl indices of the polymer through Fourier-transform infrared (FTIR) analysis also support the degradation.

Reclamation of petrol oil contaminated soil by rhamnolipids producing PGPR strains for growing Withania somnifera a medicinal shrub.

Soil contaminated by hydrocarbons, cannot be used for agricultural intents due to their toxic effect to the plants. Surfactants producing by plant growth promotory rhizobacteria (PGPR) can effectively rig the problem of petroleum hydrocarbon contamination and growth promotion on such contaminated soils. In the present study three Pseudomonas strains isolated from contaminated soil identified by 16S rRNA analysis were ascertained for PGPR as well as biosurfactants property. Biosurfactants produced by the strains were further characterized and essayed for rhamnolipids. Inoculation of the strains in petrol hydrocarbon contaminated soil and its interaction with Withania somnifera in presence of petrol oil hydrocarbons depict that the strains helped in growth promotion of Withania somnifera in petrol oil contaminated soil while rhamnolipids helped in lowering the toxicity of petrol oil. The study was found to be beneficial as the growth and antioxidant activity of Withania sominfera was enhanced. Hence the present study signifies that rhamnolipids producing PGPR strains could be a better measure for reclamation of petrol contaminated sites for growing medicinal plants.

Phytoremediation and bioremediation of polychlorinated biphenyls (PCBs): state of knowledge and research perspectives.

This review summarizes the bioremediation and phytoremediation technologies proposed so far to detoxify PCB-contaminated sites. A critical analysis about the potential and limits of the PCB pollution treatment strategies by means of plants, fungi and bacteria are elucidated, including the new insights emerged from recent studies on the rhizosphere potential and on the implementation of simultaneous aerobic and anaerobic biodegradation processes. The review describes the biodegradation and phytoremediation processes and elaborates on the environmental variables affecting contaminant degradation rates, summarizing the amendments recommended to enhance PCB degradation. Additionally, issues connected with PCB toxicology, actual field remediation strategies and economical evaluation are discussed.

Degradation of Di- Through Hepta-Chlorobiphenyls in Clophen Oil Using Microorganisms Isolated from Long Term PCBs Contaminated Soil.

Present work describes microbial degradation of selected polychlorinated biphenyls (PCBs) congeners in Clophen oil which is used as transformer oil and contains high concentration of PCBs. Indigenous PCBs degrading bacteria were isolated from Clophen oil contaminated soil using enrichment culture technique. A 15 days study was carried out to assess the biodegradation potential of two bacterial cultures and their consortium for Clophen oil with a final PCBs concentration of 100 mg kg(-1). The degradation capability of the individual bacterium and the consortium towards the varying range of PCBs congeners (di- through hepta-chlorobiphenyls) was determined using GCMS. Also, dehydrogenase enzyme was estimated to assess the microbial activity. Maximum degradation was observed in treatment containing consortium that resulted in up to 97 % degradation of PCB-44 which is a tetra chlorinated biphenyl whereas, hexa chlorinated biphenyl congener (PCB-153) was degraded up to 90 % by the consortium. This indicates that the degradation capability of microbial consortium was significantly higher than that of individual cultures. Furthermore, the results suggest that for degradation of lower as well as higher chlorinated PCB congeners; a microbial consortium is required rather than individual cultures.

Investigation of polybrominated diphenyl ethers in old consumer products in India.

Polybrominated diphenyl ethers (PBDEs) used extensively over the past 3 decades as flame retardants in most types of polymers, all over the world, have been identified as global pollutants. PBDEs pose various health problems such as thyroid hormone disruption, permanent learning and memory impairment, behavioral changes, hearing deficits, delayed puberty onset, fetal malformations, and possibly cancer. Many measurements of PBDEs in various matrices from Sweden, Holland, Japan, the USA, and elsewhere have been reported, but few measurements are available for India. In this study, a preliminary screening of different congeners of PBDEs has been performed in different old electronic and consumer products with an objective to build capacity in order to analyze PBDEs and BFRs. Six different samples, foam from upholstery, motherboard of a computer, children toy composite sample, old vanishing window blind sample, electrical wire sample, and PVC flooring sample, were collected and analyzed for the presence of the following PBDE congeners: BDE-28, BDE-47, BDE-99, BDE-100, BDE-153, BDE-154, BDE-183, and BDE-209. It was found that three out of six samples were positive for the presence of PBDEs. Three congeners were detected in the samples, i.e., BDE-47, BDE-153, and BDE-209, of which, highest concentration was of BDE-209. Among the samples, motherboard of computer showed the highest concentration of BDE-209 followed by window blind and foam from upholstery. The results of this preliminary investigation indicate that PBDEs are still present in the old consumer products which can be an important additional source of exposure to the population.

Surface-active potential of biosurfactants produced in curd whey by Pseudomonas aeruginosa strain-PP2 and Kocuria turfanesis strain-J at extreme environmental conditions.

Surface-active potential of biosurfactants produced cost-effectively in curd whey by Pseudomonas aeruginosa strain-PP2 and Kocuria turfanesis strain-J were tested using parameters viz. surface tension (ST) reduction, F(CMC) (highest dilution factor to reach critical micelle concentration) and emulsification index (EI-24) of pesticides; monocrotophos and imidacloprid at extreme environmental conditions. Results have shown that ST reduction of biosurfactants was stable at pH 2-11. High F(CMC) of the biosurfactant in the fermented whey at low pH improved emulsification of pesticides. ST marginally increased at 5% and 15% NaCl, resulting in high EI-24 and F(CMC). Over a range of temperatures 30-121 °C, ST remained low with a higher F(CMC) and EI-24 at 60 °C than at 121 and 30 °C. The biosurfactants have shown differences in their surface-active property and have marked specificity to emulsify pesticides in extreme environmental conditions.

Isolation and characterization of dimethyl sulfide (DMS)-degrading bacteria from soil and biofilter treating waste gas containing DMS from the laboratory and pulp and paper industry.

Dimethyl sulfide (DMS) is one of the sulfurous pollutants present in the waste gas generated from the pulp and paper industry. DMS has environmental health implications; therefore, it is necessary to treat the waste gas containing DMS prior to discharge into the environment. A bench-scale biofilter was operated in the laboratory as well as in a pulp and paper industry for the treatment of DMS. Both the biofilters were packed with pre-sterilized wood chips and cow dung/compost of the same origin seeded with biomass developed from garden soil enriched with DMS. The biofilters were operated for the generation of process parameters, and the potential microorganisms isolated from both the biofilters have been purified and characterized for degradation of DMS. Further, these cultures were purified on a basal medium using DMS as a sole carbon source for the growth. Further, the purified cultures were characterized through standard fatty acid methyl esters (FAME)-gas chromatography method, and the isolates were found to be mesophilic, aerobic microbes. These microbes were identified as Bacillus sphaericus-GC subgroup F, Paenibacillus polymyxa, B. sphaericus-GC subgroup F, B. sphaericus-GC subgroup F, and Bacillus megaterium-GC subgroup A, respectively. The potential culture for degradation of DMS was identified as B. sphaericus by 16s rRNA molecular analysis.

Growth responses and metal accumulation capabilities of woody plants during the phytoremediation of tannery sludge.

Five woody plants species (i.e. Terminalia arjuna, Prosopis juliflora, Populus alba, Eucalyptus tereticornis and Dendrocalamus strictus) were selected for phytoremediation and grow on tannery sludge dumps of Common Effluent Treatment Plant (CETP), Unnao (Uttar Pradesh), India. Concentration of toxic metals were observed high in the raw tannery sludge i.e. Fe-1667>Cr-628>Zn-592>Pb-427>Cu-354>Mn-210>Cd-125>Ni-76 mg kg(-1) dw, respectively. Besides, physico-chemical properties of the raw sludge represented the toxic nature to human health and may pose numerous risks to local environment. The growth performances of woody plants were assessed in terms of various growth parameters such as height, diameter at breast height (DBH) and canopy area of plants. All the plant species have the capabilities to accumulate substantial amount of toxic metals in their tissues during the remediation. The ratio of accumulated metals in the plants were found in the order Fe>Cr>Mn>Pb>Zn>Cu>Cd>Ni and significant changes in physico-chemical parameters of tannery sludge were observed after treatment. All the woody plants indicated high bioconcentration factor for different metals in the order Fe>Cr>Mn>Ni>Cd>Pb>Zn>Cu. After one year of phytoremediation, the level of toxic metals were removed from tannery sludge up to Cr (70.22)%, Ni (59.21)%, Cd (58.4)%, Fe (49.75)%, Mn (30.95)%, Zn (22.80)%, Cu (20.46)% and Pb (14.05)%, respectively.

Differential antioxidative enzyme responses of Jatropha curcas L. to chromium stress.

Chromium (Cr) tolerant and accumulation capability of Jatropha curcas L. was tested in Cr spiked soil amended with biosludge and biofertilizer. Plants were cultivated in soils containing 0, 25, 50, 100 and 250 mg kg(-1) of Cr for one year with and without amendment. Plant tissue analysis showed that combined application of biosludge and biofertilizer could significantly reduce Cr uptake and boost the plant biomass, whereas biofertilizer alone did not affect the uptake and plant growth. Antioxidative responses of catalase (CAT), ascorbate peroxidase (APX) and glutathione S-transferase (GST) were increased with increasing Cr concentration in plant. Hyperactivity of the CAT and GST indicated that antioxidant enzymes played an important role in protecting the plant from Cr toxicity. However, APX took a little part in detoxification of H(2)O(2) due to its sensitivity to Cr. Therefore, reduced APX activity was recorded. Reduced glutathione (GSH) activity was recorded in plant grown on/above 100 mg kg(-1) of Cr in soil. The study concludes that J. curcas could grow under chromium stress. Furthermore, the results encouraged that J. curcas is a suitable candidate for the restoration of Cr contaminated soils with the concomitant application of biosludge and biofertilizer.

Carbon sequestration in reclaimed manganese mine land at Gumgaon, India.

Carbon emission is supposed to be the strongest factor for global warming. Removing atmospheric carbon and storing it in the terrestrial biosphere is one of the cost-effective options, to compensate greenhouse gas emission. Millions of acres of abandoned mine land throughout the world, if restored and converted into vegetative land, would solve two major problems of global warming and generation of degraded wasteland. In this study, a manganese spoil dump at Gumgaon, Nagpur in India was reclaimed, using an integrated biotechnological approach (IBA). The physicochemical and microbiological status of the mine land improved after reclamation. Soil organic carbon (SOC) pool increased from 0.104% to 0.69% after 20 years of reclamation in 0-15 cm spoil depth. Soil organic carbon level of reclaimed site was also compared with a native forestland and agricultural land. Forest soil showed highest SOC level of 1.11% followed by reclaimed land and agriculture land of 0.70% and 0.40%, respectively. Soil profile studies of all three sites showed that SOC pool decreased from 0-15, 15-30, and 30-45 cm depths. Although reclaimed land showed less carbon than forestland, it showed better SOC accumulation rate. Reclamation of mine lands by using IBA is an effective method for mitigating CO2 emissions.

In vivo studies to elucidate the role of extracellular polymeric substances from Azotobacter in immobilization of heavy metals.

The role of extracellular polymeric substances (EPS) produced by the heavy metal-resistant strain of Azotobacter spp. in restricting the uptake of cadmium (Cd) and chromium (Cr) by wheat plants cultivated in soils contaminated with the respective heavy metals has been demonstrated. A heavy metal-resistant strain of Azotobacter spp. was isolated and identified. Minimum inhibitory concentrations (MIC) of Cd2+ and CrO4(2-) were determined to be 20 and 10 mg L(-1), respectively. Under in vitro conditions, the EPS produced by the strain could bind 15.17 +/- 0.58 mg g(-1) of Cd2+ and 21.9 +/- 0.08 mg g(-1) of CrO4(2-). Fourier transform infrared spectra of the EPS revealed the presence of functional groups like carboxyl (-COOH) and hydroxyl (-OH), primarily involved in metal ion binding. Under pot culture experiments, the isolated strain of Azotobacter was added to the metal-contaminated soils in the form of free cells and immobilized cells. The total Azotobacter count and plant metal concentrations under different treatments showed a negative coefficient between the Azotobacter population and plant Cd (-0.496) and Cr (-0.455). Thus it could be inferred that Azotobacter spp. is involved in metal ion complexation either through EPS or through cell wall lipopolysaccharides (LPS).

Bioaccumulation and phyto-translocation of arsenic, chromium and zinc by Jatropha curcas L.: impact of dairy sludge and biofertilizer.

The present study was planned to remediate the metalloid and metal contaminated soil by using non-edible and economic plant species Jatropha curcas L. The experiment was conducted on pots to improve the survival rate, metal tolerance and growth response of the plant on soil; having different concentrations of arsenic, chromium and zinc. The soil was amended with dairy sludge and bacterial inoculum (Azotobacter chroococcum) as biofertilizer. The results of the study showed that the bioaccumulation potential was increased with increase in metalloid and metal concentration in soil system. Application of dairy sludge significantly reduces the DTPA-extractable As, Cr and Zn concentration in soil. The application of organic amendment stabilizes the As, Cr and Zn and reduced their uptake in plant tissues.

Assessment of bioaccumulation of heavy metals by different plant species grown on fly ash dump.

A field experiment was conducted on a 10-hectare area on fly ash dump at Khaperkheda Thermal Power Plant, Nagpur, India, where different ecologically and economically important plant species were planted using bioremediation technology. The technology involves the use of organic amendment and selection of suitable plant species along with site-specific nitrogen-fixing strains of biofertilizers. The study was conducted to find out the metal accumulation potential of different plant species. The total heavy metal contents in fly ash were determined and their relative abundance was found in the order of Fe>Mn>Zn>Cu>Ni>Cr>Pb>Cd. Fly ash samples had acidic pH, low electrical conductivity, low level of organic carbon and trace amounts of N and P. Plantation of divergent species was done on fly ash dump using the bioremediation technique. After 3 years of plantation, luxuriant growth of these species was found covering almost the entire fly ash dump. The results of the metal analysis of these species indicated that iron accumulated to the greatest extent in vegetation followed by Mn, Ni, Zn, Cu, Cr and Pb. Cassia siamea was found to accumulate all metals at higher concentrations compared to other species. The experimental study revealed that C. siamea could be used as a hyper-accumulator plant for bioremediation of fly ash dump.

Developmental strategies for sustainable ecosystem on mine spoil dumps: a case of study.

An important goal of ecological rehabilitation is to accelerate natural successional processes to increase biological productivity, soil fertility and biotic control over biogeochemical fluxes within the recovering ecosystems. A new approach called Microbe Assisted Green Technology (MAGT) is an integrated biotechnological approach developed at National Environmental Engineering Research Institute (NEERI) through exhaustive laboratory as well as field studies and serve as a model for land reclamation and development of lush green vegetation on mine overburdens. One year old seedlings of native tree species were planted on 6.3 ha area of manganese mine overburden at Gumgaon under Manganese Ore India Ltd., Maharashtra, India. Continuous efforts resulted in nutrient rich soil with high N, P, K and organic carbon; well developed biodiversity, including bacteria, fungi, higher plants (more than 350 species) and different classes of animals. Planted trees accumulated 698 t ha( - 1) above ground biomass and 143 t ha( - 1) below ground mass. This was achieved in 18 years by MAGT, which otherwise takes hundreds of years.

Bioremediation of multi-metal contaminated soil using biosurfactant - a novel approach.

An unconventional nutrient medium, distillery spent wash (1:3) diluted) was used to produce di-rhamnolipid biosurfactant by Pseudomonas aeruginosa strain BS2. This research further assessed the potential of the biosurfactant as a washing agent for metal removal from multimetal contaminated soil (Cr-940 ppm; Pb-900 ppm; Cd-430 ppm; Ni-880 ppm; Cu-480 ppm). Out of the treatments of contaminated soil with tap water and rhamnolipid biosurfactant, the latter was found to be potent in mobilization of metal and decontamination of contaminated soil. Within 36 hours of leaching study, di-rhamnolipid as compared to tap water facilitated 13 folds higher removal of Cr from the heavy metal spiked soil whereas removal of Pb and Cu was 9-10 and 14 folds higher respectively. Leaching of Cd and Ni was 25 folds higher from the spiked soil. This shows that leaching behavior of biosurfactant was different for different metals. The use of wastewater for production of biosurfactant and its efficient use in metal removal make it a strong applicant for bioremediation.

Restoration of fly ash dump through biological interventions.

Field experiment on 10 ha area of fly ash dump was conducted to restore and revegetate it using biological interventions, which involves use of organic amendment, selection of suitable plant species along with specialized nitrogen fixing strains of biofertilizer. The results of the study indicated that amendment with farm yard manure at 50 t/ha improved the physical properties of fly ash such as maximum water holding capacity from 40.0 to 62.42% while porosity improved from 56.78 to 58.45%. The nitrogen content was increased by 4.5 times due to addition of nitrogen fixing strains of Bradyrhizobium and Azotobacter species, while phosphate content was increased by 10.0 times due to addition of VAM, which helps in phosphate immobilization. Due to biofertilizer inoculation different microbial groups such as Rhizobium, Azotobacter and VAM spores, which were practically absent in fly ash improved to 7.1 x 10(7), 9.2 x 10(7) CFU/g and 35 VAM spores/10 g of fly ash, respectively. Inoculation of biofertilizer and application of FYM helped in reducing the toxicity of heavy metals such as cadmium, copper, nickel and lead which were reduced by 25, 46, 48 and 47%, respectively, due to the increased organic matter content in the fly ash which complexes the heavy metals thereby decreasing the toxicity of metals. Amendment of fly ash with FYM and biofertilizer helped in profuse root development showing 15 times higher growth in Dendrocalamus strictus plant as compared to the control. Thus amendment and biofertilizer application provided better supportive material for anchorage and growth of the plant.