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Naturally occurring microbial consortia have been utilized in a variety of bioremediation processes. Recent developments in molecular microbial ecology offer new tools that facilitate molecular analyses of microbial populations at contaminated and bioremediated sites. Information provided by such analyses aids in the evaluation of the effectiveness of bioremediation and the formulation of strategies that might accelerate bioremediation.
Molecular ecological approaches have detected diverse microorganisms that occur in response to pollution and bioremediation; however, most of these organisms have not been isolated, and their physiological traits are poorly understood. One important objective in current bioremediation studies would therefore be an assessment of the physiology and functions of the diverse microbial population at a polluted site. Among the parameters relating to the diversity of the microbial catabolic potential, e.g., substrate specificity, inducer specificity, number of catabolic routes and kinetics of catabolic enzymes, our studies have focused on the kinetic diversity of phenol-degrading bacteria. In one example, a kinetic analysis allowed functionally important phenol-degrading bacteria to be identified in activated sludge; this information could be used to improve the performance of phenol-degrading activated sludge. In an analysis of phenol-degrading bacteria present in trichloroethylene (TCE)-contaminated aquifer soil, the kinetic data could be linked to group-specific monitoring of their phenol-hydroxylase genes. The results have suggested that one group of phenol-degrading bacteria can effectively contribute to TCE bioremediation, while other groups work poorly. Based on this information, we have succeeded in developing a high-performance TCE-degrading bioreactor. We suggest that a careful analysis of the diversity of microbial catabolic potential, particularly of the kinetic traits, may facilitate the development of new bioremediation strategies.
Bioremediation, the process by which hazardous substances are degraded by microorganisms, is at the forefront of a larger group of innovative remediation technologies being applied at hazardous waste sites worldwide. Although the process of bioremediation has been utilized for decades in the field of wastewater engineering, its application to soils and groundwater at hazardous waste sites is fairly new and still undergoing intensive development. This article is intended to provide both an overview of the state of practice of bioremediation in hazardous waste remediation operations, and an inventory of issues to consider when evaluating the use of this technology for a contaminated site. These topics will be the subject matter of a unique Bioremediation Satellite seminar to be broadcast on January 9, 1992. The seminar, a joint venture between the Air and Waste Management Association (A&WMA) and the Hazardous Waste Action Coalition (HWAC), is the first in a series of satellite seminars that will deal with innovative hazardous waste remediation technologies. The intent of these seminars is to design programs which will make hazardous waste practitioners more familiar with innovative remediation technologies so that they will consider using the technologies in future clean-up operations.
This study originated from an accidental event of diesel oil contamination in a loam soil area of 7,000 m2. Approximately a volume of 1,300 m3 of diesel oil was released into the environment. Reclamation of the contaminated soil by on-site bioremediation was selected as the most appropriate treatment method. A major concern was associated with the nature of the local loam soil. Loam has a very low hydraulic conductivity and very quickly becomes impermeable after its contact with water. The bioremediation approach incorporated excavation of the contaminated soil, mixing it with an agent, which increased its permeability. Following this preliminary treatment came the construction of bioreactors as a suitable environment of nutrients, moisture, dissolved oxygen, and enriched culture of microorganisms, which enabled breakdown of the diesel oil. This case study indicated that the target of 99% of diesel oil clean up could be achieved by using the technology of on-site bioremediation. The selected treatment method was found to be technologically and economically feasible. However, some improvement in the application of the basic treatment approach might increase the bioremediation efficiency.
Bioremediation, the exploitation of biological catalysts (mostly microorganisms) for removing pollutants from the environment, requires the integration of huge amounts of data from different sources. We have developed MetaRouter, a system for maintaining heterogeneous information related to bioremediation in a framework that allows its query, administration and mining (application of methods for extracting new knowledge). MetaRouter is an application intended for laboratories working in biodegradation and bioremediation, which need to maintain and consult public and private data, linked internally and with external databases, and to extract new information from it. Among the data-mining features is a program included for locating biodegradative pathways for chemical compounds according to a given set of constraints and requirements. The integration of biodegradation information with the corresponding protein and genome data provides a suitable framework for studying the global properties of the bioremediation network. The system can be accessed and administrated through a web interface. The full-featured system (except administration facilities) is freely available at http://pdg.cnb.uam.es/MetaRouter. Additional material: http://www.pdg.cnb.uam.es/biodeg_net/MetaRouter.
Bacterial community dynamics and biodegradation processes were examined in a highly creosote-contaminated soil undergoing a range of laboratory-based bioremediation treatments. The dynamics of the eubacterial community, the number of heterotrophs and polycyclic aromatic hydrocarbon (PAH) degraders, and the total petroleum hydrocarbon (TPH) and PAH concentrations were monitored during the bioremediation process. TPH and PAHs were significantly degraded in all treatments (72 to 79% and 83 to 87%, respectively), and the biodegradation values were higher when nutrients were not added, especially for benzo(a)anthracene and chrysene. The moisture content and aeration were determined to be the key factors associated with PAH bioremediation. Neither biosurfactant addition, bioaugmentation, nor ferric octate addition led to differences in PAH or TPH biodegradation compared to biodegradation with nutrient treatment. All treatments resulted in a high first-order degradation rate during the first 45 days, which was markedly reduced after 90 days. A sharp increase in the size of the heterotrophic and PAH-degrading microbial populations was observed, which coincided with the highest rates of TPH and PAH biodegradation. At the end of the incubation period, PAH degraders were more prevalent in samples to which nutrients had not been added. Denaturing gradient gel electrophoresis analysis and principal-component analysis confirmed that there was a remarkable shift in the composition of the bacterial community due to both the biodegradation process and the addition of nutrients. At early stages of biodegradation, the alpha-Proteobacteria group (genera Sphingomonas and Azospirillum) was the dominant group in all treatments. At later stages, the gamma-Proteobacteria group (genus Xanthomonas), the alpha-Proteobacteria group (genus Sphingomonas), and the Cytophaga-Flexibacter-Bacteroides group (Bacteroidetes) were the dominant groups in the nonnutrient treatment, while the gamma-Proteobacteria group (genus Xathomonas), the beta-Proteobacteria group (genera Alcaligenes and Achromobacter), and the alpha-Proteobacteria group (genus Sphingomonas) were the dominant groups in the nutrient treatment. This study shows that specific bacterial phylotypes are associated both with different phases of PAH degradation and with nutrient addition in a preadapted PAH-contaminated soil. Our findings also suggest that there are complex interactions between bacterial species and medium conditions that influence the biodegradation capacity of the microbial communities involved in bioremediation processes.
Bioremediation is a promising technology for responding to marine oil spills. A majority of molecules in crude oils and refined products are biodegradable, and they will eventually leave the environment as they are consumed by microbes. Bioremediation aims to stimulate the rate of this process. Successful bioremediation efforts have so far focused on applying fertilizers to aerobic oiled shorelines to at least partially relieve the nitrogen limitation of biodegradation by indigenous microorganisms. Nevertheless, there seems to be room for improving the process by developing better fertilizers, developing surfactants to stimulate degradation, and perhaps using exogenous bacteria. There also is room to extend the application to oiled marshes and other anaerobic sediments, and perhaps to floating slicks. This review covers our present understanding of hydrocarbon degradation in the marine environment, and discusses field trials and field use of bioremediation as an important adjunct to other tools for responding to marine oil spills.
The effect of NH4(+)-N removal in the polluted raw water of water sources by the bioremediation action of the biocontact oxidation process with the elastic packing and micropore aerator was studied in this paper. The research results showed the bioremediation process can reach a removal ratio of 64%-95% for NH4(+)-N of water sources under the condition of ordinary temperature 20 degrees C-27 degrees C, CODMn 7-14 mg/L, NH4(+)-N 0.7-2.0 mg/L in the water sources and the running parameters HRT 1.4 h, gas and water ratio 0.5:1, and DO 7-9 mg/L for the bioremediation process and a removal ratio of 40%-63% for NH4(+)-N of water sources under the condition of low temperature 7 degrees C-12 degrees C, CODMn 6-11 mg/L, NH4(+)-N 1.2-8.0 mg/L in the water sources and the running parameters HRT 1.4 h, gas and water ratio 0.5:1, and DO 8-10 mg/L for the bioremediation process.
In a practical sense, biotechnology is concerned with the production of commercial products generated by biological processes. More formally, biotechnology may be defined as "the application of scientific and engineering principles to the processing of material by biological agents to provide goods and services" (Cantor, 2000). From a historical perspective, biotechnology dates back to the time when yeast was first used for beer or wine fermentation, and bacteria were used to make yogurt. In 1972, the birth of recombinant DNA technology moved biotechnology to new heights and led to the establishment of a new industry. Progress in biotechnology has been truly remarkable. Within four years of the discovery of recombinant DNA technology, genetically modified organisms (GMOs) were making human insulin, interferon, and human growth hormone. Now, recombinant DNA technology and its products--GMOs are widely used in environmental biotechnology (Glick and Pasternak, 1988; Cowan, 2000). Bioremediation is one of the most rapidly growing areas of environmental biotechnology. Use of bioremediation for environmental clean up is popular due to low costs and its public acceptability. Indeed, bioremediation stands to benefit greatly and advance even more rapidly with the adoption of molecular techniques developed originally for other areas of biotechnology. The 1990s was the decade of molecular microbial ecology (time of using molecular techniques in environmental biotechnology). Adoption of these molecular techniques made scientists realize that microbial populations in the natural environments are much more diverse than previously thought using traditional culture methods. Using molecular ecological methods, such as direct DNA isolation from environmental samples, denaturing gradient gel electrophoresis (DGGE), PCR methods, nucleic acid hybridization etc., we can now study microbial consortia relevant to pollutant degradation in the environment. These techniques promise to provide a better understanding and better control of environmental biotechnology processes, thus enabling more cost effective and efficient bioremediation of our toxic waste and contaminated environments.
With composting technology of off-site bioremediation, the bioremediation of soil contaminated by crude oil from Liaohe Oil Field was studied. 4 treatments units were set, each units being 118.5 cm in length, 65.5 cm in width, and 12.5 cm in height. The results showed that when the soil was contaminated with 5.22 g.100 g-1 TPH, the degradation rate of TPH reached 54.2% after 55 days operation by Phanerochaete chrysosporium. The results also indicated that the major factors that effected the TPH bioremediation results were the content of O2 and CO2, the amounts of microorganism that degraded petroleum hydrocarbons, and the changes of pH in contaminated soil. These factors could directly reflect the effect of composting treatment technology, and be used to optimize the operation conditions of composting technology to reach the best result. The treatment engineering adopted periodical aired means, operated very simple, and costed very cheap, whtch provided a practical technology for the bioremediation of petroleum-contaminated soil.
Industrial and environmental biotechnology are going to new paths, resulting in processes with "clean technologies", with the maximum production and the less residues. Technologies of remediation and bioremediation are continuously being improved using genetically modified microorganisms or those naturally occurring, to clean residues and contaminated areas from toxic organics. Bioremediation of soils, water and marine environments has many advantages but at the same time it is a challenge for the researchers and engineers. Consequently, it is extremely important to carry out feasibility study based on pilot-testing before starting a remediation project in order to determine the best conditions for the process. The article presents a brief review of bioremediation including the description of the different methods applied to soil and industrial wastes, and, finally, some experiences of solid-state fermentation in relation to bioremediation.
Effects of bioremediation on microbial communities in soils contaminated with petroleum hydrocarbons are a scientific problem to be solved. Changes in dominate microbial species and the total amount of microorganisms including bacteria and fungi in rhizospheric soils after bioremediation were thus evaluated using field bioremediation experiments. The results showed that there were changed dominant microorganisms including 11 bacterial strains which are mostly Gram positive bacteria and 6 fungal species which were identified. The total amount of microorganisms including bacteria and fungi increased after bioremediation of microbial agents combined with planting maize. On the contrary, fungi in rhizospheric soils were inhibited by adding microbial agents combined with planting soybean.
Selenium (Se) is a contaminant of agricultural irrigation-drainage water in the western United States, and the cause of wildlife deaths and grotesque deformities. Some approaches in reducing the toxic Se concentrations from contaminated sediments and water have been proposed, but most of these tend to be costly or ineffective. Bioremediation through microbial transformations of toxic Se species into nontoxic forms is being considered as an effective remedial alternative. The microbial reduction of toxic oxyanions of Se (SeO(4)(2-) and SeO(3)(2-)) into insoluble Se(0) or methylation of these species to dimethylselenide (DMSe) has been accepted as a potential bioremediation strategy for cleanup of Se-contaminated water and sediments. By conducting a series of laboratory, bench-scale and field studies, we have thoroughly investigated the remedial potential of these approaches. It was observed that microorganisms, particularly Enterobacter cloacea, are very active in reduction of Se oxyanions present in irrigation drainage water, into insoluble Se(0) and, by monitoring various environmental conditions and addition of organic amendments, the process could be stimulated manifold. Similarly, the process of biomethylation of Se in soil sediments and water was found active and highly dependent on specific carbon amendments (pectin and proteins), pH, temperature, moisture, aeration and activators (cofactors). Moreover, Se biomethylation was protein/peptide-limited rather than nitrogen-, amino acid- or carbon-limited. Crude casein and its components were equally stimulatory producing a >50-fold enhancement in DMSe yield. Methionine and methyl cobalamin stimulated DMSe production by Alternaria alternata, indicating that the coenzyme may mediate the transfer of a methyl group to the Se atom. An acute toxicity test involving inhalation of DMSe by rats revealed that DMSe is nontoxic. Experiments were scaled up from laboratory studies to field plots to verify the feasibility of this bioremediation approach. Based upon the promising results of these studies, a biotechnology prototype was developed which could be applicable for cleanup of polluted sediments and water throughout the western United States.
Microbial-mediated attenuation of toxic aromatic pollutants offers great potential for the restoration of contaminated environments in an ecologically acceptable manner. However, incomplete biological information regarding the regulation of growth and metabolism in many microbial communities restricts progress in the site-specific mineralization process. In the postgenomic era, recent advances in MS have allowed enormous progress in proteomics and elucidated many complex biological interactions. These research forefronts are now expanding toward the analysis of low-molecular-weight primary and secondary metabolites analysis, i.e., metabolomics. The advent of 2-DE in conjunction with MS offers a promising approach to address the molecular mechanisms of bioremediation. The two fields of proteomics and metabolomics have thus far worked separately to identify proteins and primary and secondary metabolites during bioremediation. A simultaneous study combining functional proteomics and metabolomics, i.e., proteometabolomics would create a system-wide approach to studying site-specific microorganisms during active mineralization processes. This article deals with advances in environmental proteomics and metabolomics and advocates the simultaneous study of both technologies to implement cell-free bioremediation.
Contamination of ground and surface water puts pressure on the use of pesticides. Pesticide contamination of water can often be linked to point sources rather than to diffuse sources. Examples of such point sources are areas on farms where pesticides are handled and filled into sprayers, and where sprayers are cleaned. To reduce contamination from these point sources, different kinds of bioremediation system are being researched in various member states of the EU. Bioremediation is the use of living organisms, primarily microorganisms, to degrade the environmental contaminants into less toxic forms. The systems available for biocleaning of pesticides vary according to their shape and design. Up till now, three systems have been extensively described and reported: the biobed, the Phytobac and the biofilter. Most of these constructions are excavations or different sizes of container filled with biological material. Typical overall clean-up efficiency exceeds 95%, realising even more than 99% in many cases. This paper provides an overview of the state of the art of these bioremediation systems and discusses their construction, efficiency and drawbacks.
A new flow injection (FI) method for photometric monitoring of cyanate in bioremediation processes using immobilised native cyanase is described. The method is based on the catalytic reaction between cyanate and bicarbonate to produce ammonia and carbon dioxide in the presence of an inducible native cyanase, immobilised in a reactor packed with glass beads. Two degrees of purification of the biocatalyst were used-heated cell-free extract and purified extract of cyanase from Pseudomonas pseudoalcaligenes CECT 5344. The ammonia produced by the enzymatic reaction is finally monitored photometrically at 700 nm using a modification of the conventional Berthelot method. The method furnishes different calibration curves depending on the degree of purification of the cyanase, with linear ranges between 1.23 and 616.50 micromol L(-1) ( r(2)=0.9979, n=7) and between 1.07 and 308.25 micro mol L(-1) ( r(2)= 0.9992, n=7) for the heated cell-free extract and the purified cyanase extract, respectively. No statistically significant differences between the samples were found in the precision study evaluated at two cyanate concentration levels using one-way analysis of variance. A sampling frequency of 15 h(-1) was achieved. The method was used to monitor cyanate consumption in a cyanate bioremediation tank inoculated with Pseudomonas pseudoalcaligenes CECT 5344 strain. The correlation between cyanate degradation and ammonia production was tested using a conventional method. Finally, the method was applied to different samples collected from the bioremediation tank using the standard addition method; recoveries between 85.9 and 97.4% were obtained.
Soils from the Yorktown Naval Base contaminated with trinitrotoluene (TNT) and other explosives were used to prepare eluates before and after bioremediation using microbial growth amendments in the presence (P1 eluates) or absence (P2 eluates) of exogenous white rot fungus. Effectiveness of bioremediation was examined by several immunotoxicity assays-viability/growth of lymphocytes, cytokine production, and expression of the interleukin-2 (IL-2) receptor-using human peripheral blood mononuclear cells exposed to the eluates. Although TNT concentrations decreased in both P1 and P2 eluates relative to untreated baseline soil (BL) eluates, a recovery in lymphocyte growth/viability and IL-2 secretion was seen with P2 but not P1 eluates relative to BL eluates. IL-2 receptor levels were higher in cells exposed to BL and P2 eluates than when exposed to P1 eluates. Interferon-gamma, tumor necrosis factor-beta, and IL-10 levels were highest in BL and P2 eluates and lowest in P1 eluates. Taken together, these results suggest that treatment of the soil with microbial growth amendments in the absence but not the presence of exogenous white rot fungi lead to partial bioremediation as assessed by lymphocyte functions.
A field study was initiated in February 1996 in a remote sandy beach of The Grande Terre (Kerguelen Archipelago, 69 degrees 42 degrees E, 49 degrees 19 degrees S) with the objective of determining the long-term effects of some bioremediation agents on the biodegradation rate and the toxicity of oil residues under severe subantarctic conditions. A series of 10 experimental plots were settled firmly into sediment. Each plot received 2L of Arabian light crude oil and some of them were treated with bioremediation agents: slow release fertilizer Inipol EAP-22 (Elf Atochem) or fish composts. Plots were sampled on a regular basis over a 3-year period. A two-order of magnitude increase of saprophytic and hydrocarbon-utilizing microorganisms occurred during the first month of the experiment in all treated enclosures, but no clear differences appeared between the plots. Very high microbial populations were present during the experiment. Biodegradation within treated spots was faster than within the untreated ones and appeared almost complete after 6 months as indicated by the degradation index of aliphatic hydrocarbons within all plots. The analysis of interstitial water collected below the oily residues presented no toxicity. However, a high toxicity signal, using Microtox solid phase, appeared for all oiled sand samples with a noticeable reduction with time even if the toxicity signal remained present and strong after 311 days of oil exposition. As a conclusion, it is clear that the microbial response was rapid and efficient in spite of the severe weather conditions, and the rate of degradation was improved in presence of bioremediation agents. However, the remaining residues had a relatively high toxicity.