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Impact of present and future regulations on bioremediation.

Innovative treatment technologies are in increasing demand to clean up the nation's existing environmental contamination. There also are mounting pressures for industry to minimize the production or generation of hazardous pollutants. Bioremediation is a viable, cost-effective treatment option for both field remediation and treatment in enclosed systems. The use of innovative treatment technologies is largely regulatory driven. Over the last two decades, at least a dozen Federal environmental statutes have been enacted and hundreds of regulations implemented to control releases of pollutants into the air, water and on land. These statutes not only have created markets for the use of treatment technologies, they also may regulate some aspect of the application of that technology. Regarding bioremediation, four statutes should be reviewed to determine if compliance is necessary before employing microorganisms in the field or in enclosed systems. This paper summarizes the Federal statutes (i.e., the Toxic Substances Control Act (TSCA); the Resource Conservation and Recovery Act (RCRA); the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA); and the Federal Plant Pest Act (FPPA], and regulations that may impact the bioremediation industry; outlines potential markets for bioremediation that are being driven by regulations; and highlights, within the regulatory framework, promising applications for the bioremediation of hazardous wastes.

Biotechnology

Bioprospecting Chromobacterium violaceum for bioremediation: an alternative to environmental lead pollution.

Lead pollution is a major environmental concern, but current decontamination technologies remain limited due to high costs. Therefore, alternative biotechnological processes have been successfully developed and applied due to their reduced cost and lower aggressiveness in the environment. The remarkable adaptive versatility of Chromobacterium violaceum in metal-contaminated environments makes this bacterium a promising candidate for Pb bioremediation. Therefore, the reference strain C. violaceum ATCC 12,472 and the environmental isolate C. violaceum SCV1, the first strain of this species isolated from a Brazilian area with natural Pb occurrence, were evaluated for Pb resistance under different Pb concentrations and exposure times. Pb biosorption was assessed by scanning electron microscopy, while strain-specific protein profiles were characterized using tandem mass spectrometry-based proteomic analysis. The results obtained revealed the potential of C. violaceum to perform lead bioremediation. Scanning electron microscopy analysis confirmed the biosorption of lead by C. violaceum strains. C. violaceum SCV1 was able to remove up to 40% more lead concentration when compared to ATCC 12,472 which suggested adaptation through natural selection process of C. violaceum SCV1. Proteome analysis revealed 1531 proteins, of which several are candidates for lead bioremediation. This is the first study on the resistance proteomics of C. violaceum against lead. The acclimatization of the bacteria linked to the identification of several proteins related to: biosorption; efflux and ionic uptake (bioaccumulation); biomolecule transport; and biomethylation, point out to this organism as a potential lead bioremediation agent.

Chromobacterium

Water a major source of endocrine-disrupting chemicals: An overview on the occurrence, implications on human health and bioremediation strategies.

Endocrine disrupting chemicals (EDCs) are toxic compounds that occur naturally or are the output of anthropogenic activities that negatively impact both humans and wildlife. A number of diseases are associated with these disruptors, including reproductive disorders, cardiovascular disorders, kidney disease, neurological disorders, autoimmune disorders, and cancer. Due to their integral role in pharmaceuticals and cosmetics, packaging companies, agro-industries, pesticides, and plasticizers, the scientific awareness on natural and artificial EDCs are increasing. As these xenobiotic compounds tend to bioaccumulate in body tissues and may also persist longer in the environment, the concentrations of these organic compounds may increase far from their original point of concentrations. Water remains as the major sources of how humans and animals are exposed to EDCs. However, these toxic compounds cannot be completely biodegraded nor bioremediated from the aqueous medium with conventional treatment strategies thereby requiring much more efficient strategies to combat EDC contamination. Recently, genetically engineered microorganism, genome editing, and the knowledge of protein and metabolic engineering has revolutionized the field of bioremediation thereby helping to breakdown EDCs effectively. This review shed lights on understanding the importance of aquatic mediums as a source of EDCs exposure. Furthermore, the review sheds light on the consequences of these EDCs on human health as well as highlights the importance of different remediation and bioremediation approaches. Particular attention is paid to the recent trends and perspectives in order to attain sustainable approaches to the bioremediation of EDCs. Additionally, rigorous restrictions to preclude the discharge of estrogenic chemicals into the environment should be followed in efforts to combat EDC pollution.

Animals

Innovative technologies for contaminated site remediation: focus on bioremediation.

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.

Biodegradation, Environmental

Bioremediation potential of lead and cadmium tolerant bacteria isolated from industrial (tannery) effluents.

Heavy metal pollution from tannery industries presents significant environmental and public health concerns due to the toxicity and persistence of metals such as Pb2+ and Cd2+. This study aimed to isolate and characterize indigenous Pb2+ and Cd2+-tolerant bacteria from tannery effluents and contaminated soils of highly polluted areas in Dhaka for potential bioremediation applications. A total of 72 Pb2+-tolerant and 52 Cd2+-tolerant bacterial isolates were obtained using metal-supplemented LB agar. The minimum inhibitory concentrations (MICs) recorded were 4000 ppm for Pb2+ and 250 ppm for Cd2+. Quantitative analysis demonstrated removal efficiencies of 93.91% for Pb2+ and 89.66% for Cd2+. All isolates exhibited plant growth-promoting traits, including phosphate solubilization, ammonia production, indole-3-acetic acid (IAA) production, and cellulase activity. Most isolates were antibiotic-sensitive, though some showed multidrug resistance, emphasizing the need for biosafety evaluation. The most promising isolates were partially identified as Enterobacter spp. and K. pneumoniae. Protein expression profiling by SDS-PAGE revealed metal-responsive proteins ranging from 25 to 75 kDa under selective Pb2+ and Cd2+ stress. Genomic and proteomic analyses further indicated the involvement of efflux pump-associated genes in metal resistance, where cusR was identified as a common resistance gene among the dominant strains. Overall, these findings suggest that the indigenous K. pneumoniae possesses strong potential for Pb2+ and Cd2+ removal, along with plant growth-promoting capabilities, making them promising candidate for bioremediation and phytoremediation strategies.

Antibiogram

Bench scale studies of the soil aeration process for bioremediation of petroleum hydrocarbons.

An alternative to traditional hydrocarbon bioremediation is to pump air through unsaturated soils to create aerobic conditions and induce biodegradation. This study examines the effects of moisture and nutrient augmentation on biodegradation of petroleum hydrocarbons in aerated soils. Findings indicate that forced aeration, coupled with additions of nutrients and moisture, stimulate hydrocarbon-degrading microorganisms and present a feasible approach to bioremediation management.

Bacteria

Cooperative anaerobic catabolism of chlorinated organic compounds: implications for sustainable bioremediation.

Biodegradation research historically followed a reductionist approach focused on axenic (pure) cultures capable of catabolizing the specific contaminant(s) of interest. While this approach has substantially advanced our understanding of the microbiology, physiology, biochemistry, and genetics of contaminant degradation under laboratory conditions, it does not capture the complexity of natural and engineered environments. During in situ bioremediation, microbiomes are exposed to mixtures of contaminants, and microbial interactions profoundly influence contaminant transformation and fate. In anoxic environments, degradation of chlorinated compounds is often sustained by metabolic cooperation among taxonomically and physiologically distinct microorganisms. Through the exchange of metabolites such as hydrogen, formate, acetate, and other nutrients, microbial populations establish interdependent networks that overcome thermodynamic and physiological constraints, enabling self-sustaining systems of contaminant transformations that would be inefficient or impossible with individual organisms. We highlight examples of microbial interactions that underpin anaerobic catabolism of chlorinated contaminants, including systems resulting in self-sustained anaerobic bioremediation.

Biodegradation, Environmental

Genomic Insights Into the Multimetal Resilience and Biofilm-Templated Nanorod Biosynthesis of Stenotrophomonas bentonitica BII-R7: Bioremediation and Green Nanotechnology Implications.

While microbial metal reduction is widely documented, the genomic determinants that govern the morphological transition from disordered phases to structured nanocrystals remain elusive. Here, we present an integrative study of Stenotrophomonas bentonitica BII-R7, a strain exhibiting exceptional metal resistance and the unique capacity to synthesize crystalline trigonal selenium (t-Se) nanorods. Comparative pangenomic analysis of 38 Stenotrophomonas strains revealed that BII-R7 possesses a notably large accessory genome of 2311 exclusive singletons. We identify a specialized genomic toolkit, absent in all related strains, comprising key metal resistance determinants (e.g., copB, copF, and czcA) alongside extracellular remodelling enzymes (Wzyligase and GH92-glycosyl hydrolase). This unique repertoire confers BII-R7 with significantly higher Cu and Ni tolerance compared to related Stenotrophomonas species, which we hypothesize is fundamental for maintaining metabolic activity in polymetallic environments. RT-qPCR and functional assays confirm that these singletons are not only upregulated under metal stress (e.g., czcA: 42.2-fold) but are also consistent with a critical role in maintaining biofilm resilience. Crucially, we propose a mechanistic model where this unique genetic repertoire governs the assembly of a compositionally distinctive Extracellular Polymeric Substance (EPS). Using a three-state (biofilm, planktonic, EPS-depleted) experiment, we provide direct phenotypic evidence that an intact EPS matrix is required for the efficient transition from amorphous nanospheres to highly ordered crystalline nanorods, and we propose that it acts as a molecular template directing the anisotropic growth of selenium. By bridging genomics and bionanotechnology, this work positions BII-R7 as a promising candidate for sustainable green synthesis and bioremediation, while defining the targeted gene-knockout and complementation experiments now required to establish direct causal roles for the candidate determinants.

Stenotrophomonas

Integration of domestic wastewater and native Tetradesmus obliquus for bioremediation and production of biomass rich in protein and polyunsaturated fatty acids.

The large-scale deployment of microalgae-based bioprocesses is often limited by high freshwater and nutrient demands. Domestic wastewater represents a sustainable alternative, enabling simultaneous pollutant removal and biomass production. In this study, a native strain of Tetradesmus obliquus, isolated in southern Brazil, was cultivated in raw domestic wastewater (RDW) and primary-treated domestic wastewater (TDW) at three initial inoculum densities (10%, 20%, and 30% v/v) for 14 days. Tetradesmus obliquus in TDW inoculated at 10% (v/v) removed 62.46% of ammonium and 98.56% of phosphate, simultaneously exhibiting the highest specific growth rate (0.16 d⁻1) and the highest biomass productivity (42.54 mg L⁻1 d⁻1). Iron and manganese concentrations decreased significantly with a native strain in TDW, indicating effective removal of them under the evaluated conditions. RDW was associated with higher carbohydrate accumulation (32.68%) and pigment production, whereas TDW was associated with higher protein content (45.83%) and a lipid fraction with a high relative proportion of polyunsaturated fatty acids (72.70-78.90%), primarily represented by α-linolenic and linoleic acids. The combined assessment of wastewater condition and initial inoculum density revealed distinct effects on the cultivation system. These aspects influence the biochemical composition of biomass, initial inoculum density, nutrient removal, specific growth rate, and biomass productivity. Thus, the present study supports the potential to integrate domestic wastewater treatment with the cultivation of a native Tetradesmus obliquus strain and indicates that, under the evaluated conditions, both the wastewater treatment conditions and the initial inoculum density influenced bioremediation performance and the biochemical composition of biomass.

Biochemical composition

Bioremediation of groundwater pollution.

Significant progress has been made in the past year towards an understanding of the microbial processes in subsurface environments that may allow natural microbial populations to be employed for bioremediation of groundwater pollution. Among the highlights were: the discovery of several previously unknown xenobiotic-degrading abilities in groundwater microorganisms; progress in using the unique abilities of methanotrophs to oxidize halogenated solvents; and characterizations of microbial populations from subsurface soils.

Biodegradation, Environmental

Bioremediation of chemical spills.

It is evident from the data collected to date that substantial progress was made in the remediation of the site prior to the shutdown of the bioreclamation system. Extrapolation of the data suggests that completion of the project was imminent. Further remediation at the site, including the possibility of expanding the original area treated with in situ bioreclamation, is pending further definition of the new sources of contamination. The success of the two projects described here demonstrates the efficacy and potential of enhanced bioreclamation in remediating contamination problems both in soils and in groundwater.

Alkalies

Towards microplastic bioremediation: Fungal degradation of pristine and pretreated high-density polyethylene and polystyrene.

Microplastic (MP) contamination has become a significant ecological issue because of its enduring existence in the ecosystem and its possible negative impacts. Therefore, using degrading strategies to eliminate these stubborn polymers has been a subject of scientific research. However, the currently used degradation methods are relatively inefficient. Given the pervasiveness of High-Density Polyethylene (HDPE) and Polystyrene (PS) and their resistance to biodegradability, disposal strategies are critical and must be addressed. This manuscript examines the biodegradation of pristine and UV-treated HDPE and PS MPs by Aspergillus flavus species in minimal growth media over 70 days. The maximum weight loss observed at 70 days for pristine HDPE and PS in sole carbon source (SCS) media was (29.33 ± 0.28) % and (17.67 ± 0.35) %, respectively. Whereas, for UV-treated HDPE and PS MPs, the % weight reduction was (33 ± 0.21) % and (25 ± 0.19) %, respectively. UV-treated MPs exhibited greater weight reduction, as UV induced oxygenated functional groups enhance polymer susceptibility to enzymes, thereby promoting biodegradation. HDPE MPs typically show a higher proportion of particles in the lower size range compared to PS MPs. This assertion was based on the weight loss, particle size distribution, and SEM analysis. Furthermore, chemical changes were evaluated using Fourier transform Infrared Spectroscopy (FTIR) analysis, which also displayed chemical oxidation occurring during biodegradation. Liquid Chromatography-Mass Spectrometry (LC-MS) results indicate that UV pretreatment enhances biodegradability by promoting chain scission. These findings further suggest that this fungus's natural and ubiquitous occurrence in terrestrial and marine environments may actively contribute to MP biodegradation while requiring few nutrients.

Microplastics