DOI 10.1515/reveh-2014-0035 Rev Environ Health 2014; 29(1-2): 33–35
Rajendra Prasad*
New approaches and insights into bioremediation of hazardous waste Abstract: An overview of the bioremediation session in 15th International Conference of the Pacific Basin Consortium for Environment and Health is presented. Brief summaries of the presentations made in the session covering topics dealing with remediation aspects using latest concepts of metagenomics, magnetic nano-composites and air pollution modeling with reference to PCBs have been described.
treatment, known as bioremediation, turned out to be typically more economical than other known and possible methods. Because bioremediation is based on natural attenuation, the public considers it more acceptable than other technologies. Bioremediation has thus become an enormous scientific and commercial field. Many aerobic bacteria, viz., Pseudomonas, Alcaligenes, Sphingomonas, Rhodococcus, and Mycobacterium, have been recognized and successfully used for their abilities to degrade Keywords: bioremediation; magnetic nanocomposites; many toxic pesticides, hydrocarbons, alkanes, and polyaromatic compounds. Many of these bacteria have been metagenomics; uncultured microbes. found to use the contaminant as the sole source of carbon and energy. Anaerobic bacteria have rarely been used *Corresponding author: Rajendra Prasad, Technology-Patent.Com, for decontamination except for bioremediation of polySession Chair, Hazardous Waste, 15th International Conference of chlorinated biphenyls (PCBs) and dechlorination of the the Pacific Basin Consortium for Environment and Health, Honolulu, solvent trichloroethylene and chloroform. Hawai’i, USA, E-mail: [email protected] Before the advent of metagenomics, the most common bioremediation processes depended on microorganisms that could be isolated from contaminated soils and culSession overview tured in the laboratory. Metagenomics has now emerged The spectacular progress made in recent times in molec- as a powerful tool to analyze microbial communities ular biologic techniques with uncultured microbes in regardless of the ability of member organisms to be culnature (dubbed as metagenomics), with nanocompos- tured in the laboratory. It involves genomic analysis of ites, particularly magnetic nanocomposites having strong microbial DNA extracted directly from communities in affinity with target contaminants and easily recoverable, environmental samples. Thus, metagenomics offers to and with air-pollution modeling, whose ability to show unlock the massive uncultured microbial diversity present trends of plumes opened up new avenues for understand- in the environment to provide new molecules for theraing the fate of contaminants and developing technologies peutic and biotechnological applications. Not surprisfor the cleanup of contaminated environments with effi- ingly, therefore, attempts have begun to use the ability of metagenomics in bioremediation of recalcitrant contamicient ‘green’ solutions. A number of thermostable enzymes and novel bio- nants persistent in soil. A presentation made by Siddavattam (2) elucidated molecules from contaminated soil samples have been the role of a novel small RNA, sRNA46, in the minerreported in recent literature to efficiently biodegrade polluting chemicals using metagenomic techniques. An alization of organophosphates and nitrophenols using increased understanding of how microbial communities metagenomics techniques. The expression of a novel cope with pollutants and their degradation pathways can esterase, encoded by orf243, found as part of the organo lead to the design of more efficient and customized biore- phosphate degradation (opd) island of Sphingobium fuliginis ATCC 27551 (previously known as Flavobactemediation applications. Between the early 1990s and the mid-2000s, much rium sp. ATCC 27551), induced the expression of a novel of the scientific effort for developing technologies for small RNA gene, srna46, in Escherichia coli MG 1655. remediation of soil contamination was broadly based, in sRNA46 inhibited the translation of the Lpd protein, the nearly equal measure, on four major approaches, viz., key subunit required for the synthesis of functional pyruphysical, chemical and physicochemical, thermal, and vate dehydrogenase and α-keto glutarate dehydrogenase. biologic treatment (1). Of all these approaches, biological In the absence of these two key enzymes, a shift was
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34 Prasad: New approaches and insights into bioremediation noted in pathways contributing to carbon catabolism. In the Orf243-induced E. coli cells, in place of glycolysis and TCA cycle, the glyoxylate and methyl isocitrate TCA cycle super pathway was found to be operational. Interestingly, the phenyl propionate (hca) and hydroxy phenyl propionate (mhp) degradation operons, induced in the presence of this novel esterase, played a key role in the conversion of p-nitrophenol into succinate and acetyl co-A. Because they are also the catabolic intermediates of glyoxylate and methyl isocitrate TCA cycle super pathway, p-nitrophenol appears to have assimilated into the carbon skeleton of E. coli. The esterase-dependent induction of hca and mhp operons appears to be independent of carbon catabolite repression. Chakraborty and Sabine (3) presented an empirical study modeling the emission sources and concentration of PCBs1 in the air as well as soil samples from seven prominent cities in India during 2006–2012. To assess the possible source areas for PCBs in India, the authors used the National Oceanic and Atmospheric Administration’s HYSPLIT model system. The high concentration of PCB congeners in the air and the observed trends of their variation have been attributed to the re-emission of PCBs from the primary source areas to higher ambient temperature in the cities under study. Assuming that the concentrations in air and terrestrial surfaces are in equilibrium at all times, the authors also presented estimates of surface concentrations of PCBs calculated from those observed in the air in each city. Based on the available estimates, the authors also calculated the toxicity and neurotoxic equivalences for PCBs in air and soil from Indian cities to determine the possible risk to human health. The estimates found were at alarming levels as compared with World Health Organization standards. This study thus indicates the need for immediate measures to control activities contributing to the point source of PCB release in Indian cities.
1 PCBs are typically produced by the chlorination of biphenyl, whereby the aromatic hydrogen atoms are substituted by chlorine atoms; depending on the overall chlorine substitution, as many as 209 substituted products are formed and are known as congeners. PCBs have been widely used in the past in many parts of the world in industrial transformers and capacitors, electrical devices of all kinds, fluorescent light fixture ballasts, insulation materials, adhesives tapes, etc. until toxic effect of PCB exposure were observed. PCBs can cause skin and eye disorders and are known as endocrine disruptors. They are also carcinogens and have neurotoxic effects. Numerous PCB congeners are routinely formed in minor quantities during the combustion of solid fuels like coal and wood. The largescale industrial use of PCBs is now regulated through environmental laws in many countries.
A case study on the remediation of a mercury-contaminated2 site in India was presented by Chakrabarti et al. (4). Mercury was released from a glass thermometer factory (1984–2001) in an ecologically sensitive area located at an elevation of 2180 m and occupying an area of approximately 87,250 m2. The manufacturing area had 36 exhaust fans to facilitate air change and maintain the workplace occupational safety standard for air, which is 0.05 mg/nm3 of mercury. The expelled air containing mercury vapors from the manufacturing area settled down on surrounding soils and trees close to the manufacturing area, causing contamination of soil and biomass adjacent to the manufacturing area. The whole site is underlain by shallow impermeable archaeon bedrock, mainly granite and charnockite. The soil profile is very thin, predominantly sandy in the upper part of the site and grading down into densely vegetated peaty soil. A risk-based remediation approach for the decontamination of mercury in the soil was followed by measuring the concentrations of mercury in lichen, bark, soil, water, and fish samples. The distribution of mercury in soil, sediments, barks, lichen, and water samples suggested that the major risk for human exposure is through mercurycontaminated soil because the concentration of mercury in the rest of the environmental media was not significant from a risk point of view. It was estimated that of 7358 MT of mercury-contaminated soil, nearly half had a mercury concentration between 10 and 25 mg/kg. Thus, the remaining soil having a mercury concentration > 25 mg/kg was considered suitable for remediation. After a detailed literature survey of available technologies for mercury remediation, a combination of soil washing and thermal retorting was chosen as a feasible technological option. Magnetic nanocomposites emerged as a hot topic some years ago in the context of homogenous catalysis when a number of industrially important conversions made nanocomposites possible, which were not feasible through other catalysts. Soon, these began to find applications in environmental remediation for removal of heavy metals (Cr, As, Pd, and Hg) from polluted waters. This session also saw a presentation by Newsome et al. (5) on the synthesis and applications of magnetic nanocomposites for removal of PBCs from drinking water.
2 Mercury in all forms is highly toxic, and its release in the environment causes health problems. It can remain in the atmosphere for up to 1 year and hence can be widely dispersed and transported thousands of miles from the source of the emissions. Mercury poisoning can result from both acute and chronic exposures.
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Prasad: New approaches and insights into bioremediation 35
In this work, magnetic nanocomposite microparticles (MNMs) were produced using iron oxide nanoparticles incorporated into a polyphenolic-based polymer matrix with high affinity for organic pollutants. This platform allows for the specific binding of chlorinated organics from contaminated drinking water sources, the rapid magnetic separation of bound organics, and the thermal destabilization of the polymer matrix for contaminant release and material regeneration. Quercetin multiacrylate (QMA), an acrylated form of the nutrient polyphenol with known affinity for chlorinated organics, was cross-linked with polyethylene glycol diacrylate using a free radical polymerization in the presence of magnetic iron nanoparticles, and the magnetic nanocomposite was subsequently cryomilled to form the MNMs. Particles were characterized using transmission electron microscopy, dynamic light scattering, Fourier transform infrared spectroscopy, and thermal gravimetric analysis.
Pollutant-binding studies were performed using model chlorinated organic pollutants, PCBs (specifically PCB 126), to determine binding affinity and capacity as well as optimal binding kinetics, and this was quantified using liquid chromatography – mass spectrometry/mass spectrometry (LC-MS/MS). MNMs were demonstrated to effectively bind PCBs with the addition of QMA, resulting in greater affinity. An alternating magnetic field was used to heat and destabilize the binding in the polymer matrix, leading to PCB release from the particles, and the percentage of uptake and release was determined. Repeated PCB binding/release was performed to determine MNM stability and reusability. This work provides a rapid, nontoxic platform for pollutant removal from contaminated water sources.
Received January 21, 2014; accepted January 21, 2014
References 1. Prasad R. Review of soil remediation technologies through patent analysis. Presented at: 13th International Conference of the Pacific Basin Consortium for Environment and Health, Perth, Australia, 20–22 Nov 2009. 2. Siddavattam D. Role of a novel small RNA, sRNA46 in mineralization of organophosphates and nitrophenols. Presented at: 15th International Conference of the Pacific Basin Consortium for Environment and Health, Honolulu, Hawai’i, USA, 24–27 Sept 2013. 3. Chakraborty P, Sabine E. Modeling the emission sources for polychlorinated biphenyls in India: implications for human health risk assessment. Paper presented at: 15th International
Conference of the Pacific Basin Consortium for Environment and Health, Honolulu, Hawai’i, USA, 24–27 Sept 2013. 4. Chakrabarti T, Vaidya AN, Patil MP, Prasad R. Remediation of mercury contaminated soil – a case study. Paper presented at: 15th International Conference of the Pacific Basin Consortium for Environment and Health, Honolulu, Hawai’i, USA, 24–27 Sept 2013. 5. Newsome BJ, Hennig B, Dziubla R, Hilt JZ. Magnetic nanocomposite microparticles for on/off binding of persistent organic pollutants from water sources. Paper presented at: 15th International Conference of the Pacific Basin Consortium for Environment and Health, Honolulu, Hawai’i, USA, 24–27 Sept 2013.
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Rajendra Prasad*
New approaches and insights into bioremediation of hazardous waste Abstract: An overview of the bioremediation session in 15th International Conference of the Pacific Basin Consortium for Environment and Health is presented. Brief summaries of the presentations made in the session covering topics dealing with remediation aspects using latest concepts of metagenomics, magnetic nano-composites and air pollution modeling with reference to PCBs have been described.
treatment, known as bioremediation, turned out to be typically more economical than other known and possible methods. Because bioremediation is based on natural attenuation, the public considers it more acceptable than other technologies. Bioremediation has thus become an enormous scientific and commercial field. Many aerobic bacteria, viz., Pseudomonas, Alcaligenes, Sphingomonas, Rhodococcus, and Mycobacterium, have been recognized and successfully used for their abilities to degrade Keywords: bioremediation; magnetic nanocomposites; many toxic pesticides, hydrocarbons, alkanes, and polyaromatic compounds. Many of these bacteria have been metagenomics; uncultured microbes. found to use the contaminant as the sole source of carbon and energy. Anaerobic bacteria have rarely been used *Corresponding author: Rajendra Prasad, Technology-Patent.Com, for decontamination except for bioremediation of polySession Chair, Hazardous Waste, 15th International Conference of chlorinated biphenyls (PCBs) and dechlorination of the the Pacific Basin Consortium for Environment and Health, Honolulu, solvent trichloroethylene and chloroform. Hawai’i, USA, E-mail: [email protected] Before the advent of metagenomics, the most common bioremediation processes depended on microorganisms that could be isolated from contaminated soils and culSession overview tured in the laboratory. Metagenomics has now emerged The spectacular progress made in recent times in molec- as a powerful tool to analyze microbial communities ular biologic techniques with uncultured microbes in regardless of the ability of member organisms to be culnature (dubbed as metagenomics), with nanocompos- tured in the laboratory. It involves genomic analysis of ites, particularly magnetic nanocomposites having strong microbial DNA extracted directly from communities in affinity with target contaminants and easily recoverable, environmental samples. Thus, metagenomics offers to and with air-pollution modeling, whose ability to show unlock the massive uncultured microbial diversity present trends of plumes opened up new avenues for understand- in the environment to provide new molecules for theraing the fate of contaminants and developing technologies peutic and biotechnological applications. Not surprisfor the cleanup of contaminated environments with effi- ingly, therefore, attempts have begun to use the ability of metagenomics in bioremediation of recalcitrant contamicient ‘green’ solutions. A number of thermostable enzymes and novel bio- nants persistent in soil. A presentation made by Siddavattam (2) elucidated molecules from contaminated soil samples have been the role of a novel small RNA, sRNA46, in the minerreported in recent literature to efficiently biodegrade polluting chemicals using metagenomic techniques. An alization of organophosphates and nitrophenols using increased understanding of how microbial communities metagenomics techniques. The expression of a novel cope with pollutants and their degradation pathways can esterase, encoded by orf243, found as part of the organo lead to the design of more efficient and customized biore- phosphate degradation (opd) island of Sphingobium fuliginis ATCC 27551 (previously known as Flavobactemediation applications. Between the early 1990s and the mid-2000s, much rium sp. ATCC 27551), induced the expression of a novel of the scientific effort for developing technologies for small RNA gene, srna46, in Escherichia coli MG 1655. remediation of soil contamination was broadly based, in sRNA46 inhibited the translation of the Lpd protein, the nearly equal measure, on four major approaches, viz., key subunit required for the synthesis of functional pyruphysical, chemical and physicochemical, thermal, and vate dehydrogenase and α-keto glutarate dehydrogenase. biologic treatment (1). Of all these approaches, biological In the absence of these two key enzymes, a shift was
Brought to you by | University of California Authenticated Download Date | 6/5/15 4:31 PM
34 Prasad: New approaches and insights into bioremediation noted in pathways contributing to carbon catabolism. In the Orf243-induced E. coli cells, in place of glycolysis and TCA cycle, the glyoxylate and methyl isocitrate TCA cycle super pathway was found to be operational. Interestingly, the phenyl propionate (hca) and hydroxy phenyl propionate (mhp) degradation operons, induced in the presence of this novel esterase, played a key role in the conversion of p-nitrophenol into succinate and acetyl co-A. Because they are also the catabolic intermediates of glyoxylate and methyl isocitrate TCA cycle super pathway, p-nitrophenol appears to have assimilated into the carbon skeleton of E. coli. The esterase-dependent induction of hca and mhp operons appears to be independent of carbon catabolite repression. Chakraborty and Sabine (3) presented an empirical study modeling the emission sources and concentration of PCBs1 in the air as well as soil samples from seven prominent cities in India during 2006–2012. To assess the possible source areas for PCBs in India, the authors used the National Oceanic and Atmospheric Administration’s HYSPLIT model system. The high concentration of PCB congeners in the air and the observed trends of their variation have been attributed to the re-emission of PCBs from the primary source areas to higher ambient temperature in the cities under study. Assuming that the concentrations in air and terrestrial surfaces are in equilibrium at all times, the authors also presented estimates of surface concentrations of PCBs calculated from those observed in the air in each city. Based on the available estimates, the authors also calculated the toxicity and neurotoxic equivalences for PCBs in air and soil from Indian cities to determine the possible risk to human health. The estimates found were at alarming levels as compared with World Health Organization standards. This study thus indicates the need for immediate measures to control activities contributing to the point source of PCB release in Indian cities.
1 PCBs are typically produced by the chlorination of biphenyl, whereby the aromatic hydrogen atoms are substituted by chlorine atoms; depending on the overall chlorine substitution, as many as 209 substituted products are formed and are known as congeners. PCBs have been widely used in the past in many parts of the world in industrial transformers and capacitors, electrical devices of all kinds, fluorescent light fixture ballasts, insulation materials, adhesives tapes, etc. until toxic effect of PCB exposure were observed. PCBs can cause skin and eye disorders and are known as endocrine disruptors. They are also carcinogens and have neurotoxic effects. Numerous PCB congeners are routinely formed in minor quantities during the combustion of solid fuels like coal and wood. The largescale industrial use of PCBs is now regulated through environmental laws in many countries.
A case study on the remediation of a mercury-contaminated2 site in India was presented by Chakrabarti et al. (4). Mercury was released from a glass thermometer factory (1984–2001) in an ecologically sensitive area located at an elevation of 2180 m and occupying an area of approximately 87,250 m2. The manufacturing area had 36 exhaust fans to facilitate air change and maintain the workplace occupational safety standard for air, which is 0.05 mg/nm3 of mercury. The expelled air containing mercury vapors from the manufacturing area settled down on surrounding soils and trees close to the manufacturing area, causing contamination of soil and biomass adjacent to the manufacturing area. The whole site is underlain by shallow impermeable archaeon bedrock, mainly granite and charnockite. The soil profile is very thin, predominantly sandy in the upper part of the site and grading down into densely vegetated peaty soil. A risk-based remediation approach for the decontamination of mercury in the soil was followed by measuring the concentrations of mercury in lichen, bark, soil, water, and fish samples. The distribution of mercury in soil, sediments, barks, lichen, and water samples suggested that the major risk for human exposure is through mercurycontaminated soil because the concentration of mercury in the rest of the environmental media was not significant from a risk point of view. It was estimated that of 7358 MT of mercury-contaminated soil, nearly half had a mercury concentration between 10 and 25 mg/kg. Thus, the remaining soil having a mercury concentration > 25 mg/kg was considered suitable for remediation. After a detailed literature survey of available technologies for mercury remediation, a combination of soil washing and thermal retorting was chosen as a feasible technological option. Magnetic nanocomposites emerged as a hot topic some years ago in the context of homogenous catalysis when a number of industrially important conversions made nanocomposites possible, which were not feasible through other catalysts. Soon, these began to find applications in environmental remediation for removal of heavy metals (Cr, As, Pd, and Hg) from polluted waters. This session also saw a presentation by Newsome et al. (5) on the synthesis and applications of magnetic nanocomposites for removal of PBCs from drinking water.
2 Mercury in all forms is highly toxic, and its release in the environment causes health problems. It can remain in the atmosphere for up to 1 year and hence can be widely dispersed and transported thousands of miles from the source of the emissions. Mercury poisoning can result from both acute and chronic exposures.
Brought to you by | University of California Authenticated Download Date | 6/5/15 4:31 PM
Prasad: New approaches and insights into bioremediation 35
In this work, magnetic nanocomposite microparticles (MNMs) were produced using iron oxide nanoparticles incorporated into a polyphenolic-based polymer matrix with high affinity for organic pollutants. This platform allows for the specific binding of chlorinated organics from contaminated drinking water sources, the rapid magnetic separation of bound organics, and the thermal destabilization of the polymer matrix for contaminant release and material regeneration. Quercetin multiacrylate (QMA), an acrylated form of the nutrient polyphenol with known affinity for chlorinated organics, was cross-linked with polyethylene glycol diacrylate using a free radical polymerization in the presence of magnetic iron nanoparticles, and the magnetic nanocomposite was subsequently cryomilled to form the MNMs. Particles were characterized using transmission electron microscopy, dynamic light scattering, Fourier transform infrared spectroscopy, and thermal gravimetric analysis.
Pollutant-binding studies were performed using model chlorinated organic pollutants, PCBs (specifically PCB 126), to determine binding affinity and capacity as well as optimal binding kinetics, and this was quantified using liquid chromatography – mass spectrometry/mass spectrometry (LC-MS/MS). MNMs were demonstrated to effectively bind PCBs with the addition of QMA, resulting in greater affinity. An alternating magnetic field was used to heat and destabilize the binding in the polymer matrix, leading to PCB release from the particles, and the percentage of uptake and release was determined. Repeated PCB binding/release was performed to determine MNM stability and reusability. This work provides a rapid, nontoxic platform for pollutant removal from contaminated water sources.
Received January 21, 2014; accepted January 21, 2014
References 1. Prasad R. Review of soil remediation technologies through patent analysis. Presented at: 13th International Conference of the Pacific Basin Consortium for Environment and Health, Perth, Australia, 20–22 Nov 2009. 2. Siddavattam D. Role of a novel small RNA, sRNA46 in mineralization of organophosphates and nitrophenols. Presented at: 15th International Conference of the Pacific Basin Consortium for Environment and Health, Honolulu, Hawai’i, USA, 24–27 Sept 2013. 3. Chakraborty P, Sabine E. Modeling the emission sources for polychlorinated biphenyls in India: implications for human health risk assessment. Paper presented at: 15th International
Conference of the Pacific Basin Consortium for Environment and Health, Honolulu, Hawai’i, USA, 24–27 Sept 2013. 4. Chakrabarti T, Vaidya AN, Patil MP, Prasad R. Remediation of mercury contaminated soil – a case study. Paper presented at: 15th International Conference of the Pacific Basin Consortium for Environment and Health, Honolulu, Hawai’i, USA, 24–27 Sept 2013. 5. Newsome BJ, Hennig B, Dziubla R, Hilt JZ. Magnetic nanocomposite microparticles for on/off binding of persistent organic pollutants from water sources. Paper presented at: 15th International Conference of the Pacific Basin Consortium for Environment and Health, Honolulu, Hawai’i, USA, 24–27 Sept 2013.
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