Emerging technologies in bioremediation: constraints and opportunities

Insights Into the Efficiency and Health Impacts of Emerging Microplastic Bioremediation Approaches

The pollution caused by microplastics (MPs) is a global environmental and health concern. These plastic particles disrupt food chains and pose health risks to organisms, including humans. From a total of 827 studies, synthetic textiles (35%) and tires (28%) are the primary sources of MPs, with fibers being the most common shape (60%). MPs were detected in feces (44% of studies), lungs (35%), and blood (17%), indicating widespread contamination and potential health impacts. Bioremediation is a promising and sustainable method for mitigating MP pollution, as it uses microorganisms and plants to break down or convert MPs into less hazardous substances. However, it is important to understand and address the potential unintended consequences of bioremediation methods on the environment and human health. This scoping literature review examines the efficiency of currently emerging approaches for microplastic bioremediation, their strengths and weaknesses, and their potential impacts on the environment and human health. Highly effective methods such as mycoremediation, soil microbes for enhanced biodegradation, and phytoextraction were identified, but they pose high toxicity risks. Moderately effective methods include plant-assisted remediation, rhizosphere degradation, phytodegradation, and biodegradation, with effectiveness rates between 50% and 65% and moderate toxicity risks.

Bioremediation of Polycyclic Aromatic Hydrocarbons by Means of Bacteria and Bacterial Enzymes

Polycyclic aromatic hydrocarbons (PAHs) are widespread, persistent, and toxic environmental pollutants. Many anthropogenic and some natural factors contribute to the spread and accumulation of PAHs in aquatic and soil systems. The effective and environmentally friendly remediation of these chemical compounds is an important and challenging problem that has kept scientists busy over the last few decades. This review briefly summarizes data on the main sources of PAHs, their toxicity to living organisms, and physical and chemical approaches to the remediation of PAHs. The basic idea behind existing approaches to the bioremediation of PAHs is outlined with an emphasis on a detailed description of the use of bacterial strains as individual isolates, consortia, or cell-free enzymatic agents.

Cyberlindnera fabianii, an Uncommon Yeast Responsible for Gluten Bread Spoilage

A single strain of yeast was isolated from industrial gluten bread (GB) purchased from a local supermarket. This strain is responsible for spoilage consisting of white powdery and filamentous colonies due to the fragmentation of hyphae into short lengths (dust-type spots), similar to the spoilage produced by chalk yeasts such as Hyphopichia burtonii, Wickerhamomyces anomalus and Saccharomycopsis fibuligera. The isolated strains were identified initially by traditional methods as Wickerhamomyces anomalus, but with genomic analysis, they were definitively identified as Cyberlindnera fabianii, a rare ascomycetous opportunistic yeast species with low virulence attributes, uncommonly implicated in bread spoilage. However, these results demonstrate that this strain is phenotypically similar to Wi. anomalus. Cy. fabianii grew in GB because of its physicochemical characteristics which included pH 5.34, Aw 0.97 and a moisture of about 50.36. This spoilage was also confirmed by the presence of various compounds typical of yeasts, derived from sugar fermentation and amino acid degradation. These compounds included alcohols (ethanol, 1-propanol, isobutyl alcohol, isoamyl alcohol and n-amyl alcohol), organic acids (acetic and pentanoic acids) and esters (Ethylacetate, n-propil acetate, Ethylbutirrate, Isoamylacetate and Ethylpentanoate), identified in higher concentrations in the spoiled samples than in the unspoiled samples. The concentration of acetic acid was lower only in the spoiled samples, but this effect may be due to the consumption of this compound to produce acetate esters, which predominate in the spoiled samples.

Novel enzymes for biodegradation of polycyclic aromatic hydrocarbons identified by metagenomics and functional analysis in short-term soil microcosm experiments

Polycyclic aromatic hydrocarbons (PAHs) are highly toxic, carcinogenic substances. On soils contaminated with PAHs, crop cultivation, animal husbandry and even the survival of microflora in the soil are greatly perturbed, depending on the degree of contamination. Most microorganisms cannot tolerate PAH-contaminated soils, however, some microbial strains can adapt to these harsh conditions and survive on contaminated soils. Analysis of the metagenomes of contaminated environmental samples may lead to discovery of PAH-degrading enzymes suitable for green biotechnology methodologies ranging from biocatalysis to pollution control. In the present study, our goal was to apply a metagenomic data search to identify efficient novel enzymes in remediation of PAH-contaminated soils. The metagenomic hits were further analyzed using a set of bioinformatics tools to select protein sequences predicted to encode well-folded soluble enzymes. Three novel enzymes (two dioxygenases and one peroxidase) were cloned and used in soil remediation microcosms experiments. The experimental design of the present study aimed at evaluating the effectiveness of the novel enzymes on short-term PAH degradation in the soil microcosmos model. The novel enzymes were found to be efficient for degradation of naphthalene and phenanthrene. Adding the inorganic oxidant CaO2 further increased the degrading potential of the novel enzymes for anthracene and pyrene. We conclude that metagenome mining paired with bioinformatic predictions, structural modelling and functional assays constitutes a powerful approach towards novel enzymes for soil remediation.

Microbial assisted multifaceted amelioration processes of heavy-metal remediation: a clean perspective toward sustainable and greener future

Rapidly increasing heavy metal waste has adversely affected the environment and the Earth's health. The lack of appropriate remediation technologies has worsened the issue globally, especially in developing countries. Heavy-metals contaminants have severely impacted the environment and led to devastating conditions owing to their abundance and reactivity. As they are nondegradable, the potential risk increases even at a low concentration. However, heavy-metal remediation has increased with the up-gradation of technologies and integration of new approaches. Also, of all the treatment methodologies, microbial-assisted multifaceted approach for ameliorating heavy metals is a promising strategy for propagating the idea of a green and sustainable environment with minimal waste aggregation. Microbial remediation combined with different biotechniques could aid in unraveling new methods for eradicating heavy metals. Thus, the present review focuses on various microbial remediation approaches and their affecting factors, enabling recapitulation of the interplay between heavy-metals ions and microorganisms. Additionally, heavy-metals remediation mechanisms adapted by microorganisms, the role of genetically modified (GM) microorganisms, life cycle assessment (LCA), techno-economic assessment (TEA) limitations, and prospects of microbial-assisted amelioration of heavy-metals have been elaborated in the current review with focus toward "sustainable and greener future."

Recent advances in eco-friendly technology for decontamination of pulp and paper mill industrial effluent: a review

The economic development of a country directly depends upon industries. But this economic development should not be at the cost of our natural environment. A substantial amount of water is spent during paper production, creating water scarcity and generating wastewater. Therefore, the Pollution Control Board classifies this industry into red category. Water is used in different papermaking stages such as debarking, pulping or bleaching, washing, and finishing. The wastewater thus generated contains lignin and xenobiotic compounds such as resin acids, chlorinated lignin, phenols, furans, dioxins, chlorophenols, adsorbable organic halogens (AOX), extractable organic halogens (EOCs), polychlorinated biphenyls, plasticizers, and polychlorinated dibenzodioxins. Nowadays, several microorganisms are used in the detoxification of these hazardous effluents. Researchers have found that microbial degradation is the most promising treatment method to remove high biological oxygen demand (BOD) and chemical oxygen demand (COD) from wastewater. Microorganisms also remove AOX toxicity, chlorinated compounds, suspended solids, color, lignin, derivatives, etc. from the pulp and paper mill effluents. But in the current scenario, mill effluents are known to deteriorate the environment and therefore it is highly desirable to deploy advanced technologies for effluent treatment. This review summarizes the eco-friendly advanced treatment technologies for effluents generated from pulp and paper mills.

Phytoremediation as an Effective Remedy for Removing Trace Elements from Ecosystems

The pollution of soil by trace elements is a global problem. Conventional methods of soil remediation are often inapplicable, so it is necessary to search intensively for innovative and environment-friendly techniques for cleaning up ecosystems, such as phytoremediation. Basic research methods, their strengths and weaknesses, and the effects of microorganisms on metallophytes and plant endophytes resistant to trace elements (TEs) were summarised and described in this manuscript. Prospectively, bio-combined phytoremediation with microorganisms appears to be an ideal, economically viable and environmentally sound solution. The novelty of the work is the description of the potential of "green roofs" to contribute to the capture and accumulation of many metal-bearing and suspended dust and other toxic compounds resulting from anthropopressure. Attention was drawn to the great potential of using phytoremediation on less contaminated soils located along traffic routes and urban parks and green spaces. It also focused on the supportive treatments for phytoremediation using genetic engineering, sorbents, phytohormones, microbiota, microalgae or nanoparticles and highlighted the important role of energy crops in phytoremediation. Perceptions of phytoremediation on different continents are also presented, and new international perspectives are presented. Further development of phytoremediation requires much more funding and increased interdisciplinary research in this direction.

Removal of lindane in liquid culture using soil bacteria and toxicity assessment in human skin fibroblast and HCT116 cell lines

The development of effective measures for the remediation of lindane contaminated sites is the need of the hour. In this study, a potent lindane degrading bacteria, identified as Rhodococcus rhodochrous NITDBS9 was isolated from an agricultural field of Odisha that could utilize up to 87% of 100 mg L^-1 lindane when grown under liquid culture conditions in mineral salt media in 10 days. The bacteria could produce biofilm in lindane-containing media. Rhodococcus rhodochrous NITDBS9 was further characterized for its plant growth-promoting properties and it was found that the bacteria showed abilities for phytohormone, ammonia and biosurfactant production, etc. This could be beneficial for the bioremediation and improvement of crop production in contaminated sites. Ecotoxicity studies carried out for lindane, and its degradation products in mung bean and mustard seeds showed a reduction in toxicity of lindane after treatment with NITDBS9. NITDBS9 was used with a previously isolated potent lindane degrading strain Paracoccus sp. NITDBR1 in a dual mixed culture for the enhanced removal of lindane in the liquid system i.e. up to 93% in 10 days. Cytotoxicity studies were conducted with lindane before and after treatment with the single and dual mixed cultures on human skin fibroblast and HCT116 cell lines. They revealed a significant reduction in toxicity of lindane after it was bioremediated with the single and dual mixed cultures. Therefore, our proposed strategy could be efficiently used for the detoxification of the lindane-contaminated system, and further work should be done to study the use of these cultures in the contaminated soil system.

Novel fungal organophosphorus hydrolases in acidic media: an application to apples decontamination

Organophosphorus pesticides bring significant improvements in agriculture, but their toxicity causes environmental and health negative impacts. The aim of this work was the development of robust biocatalysts to be applied in bioremediation. Four fungi were evaluated as hydrolase sources capable of degrading organophosphorus pesticides: Aspergillus niger, Fusarium sp., Penicillium chrysogenum, and Penicillium nalgiovense. The hydrolysis rates of methyl paraoxon obtained under acidic conditions were in the range of 10 to 21 mg L^-1 d^-1, which is remarkable since most similar biocatalysts are active under alkaline conditions. Penicillium chrysogenum activity was outstanding, and it was selected to prepare, characterize, and study the applications of its enzymatic extract. It was used to evaluate the bioremediation of apple surfaces at pH 2 in the presence of SDS, achieving complete methyl paraoxon degradation under proposed conditions. These results indicate that this biocatalyst could complement industrialized fruit washing processes for the elimination of organophosphorus pesticides.

An Overview of Emerging Cyanide Bioremediation Methods

Cyanide compounds are hazardous compounds which are extremely toxic to living organisms, especially free cyanide in the form of hydrogen cyanide gas (HCN) and cyanide ion (CN−). These cyanide compounds are metabolic inhibitors since they can tightly bind to the metals of metalloenzymes. Anthropogenic sources contribute significantly to CN− contamination in the environment, more specifically to surface and underground waters. The treatment processes, such as chemical and physical treatment processes, have been implemented. However, these processes have drawbacks since they generate additional contaminants which further exacerbates the environmental pollution. The biological treatment techniques are mostly overlooked as an alternative to the conventional physical and chemical methods. However, the recent research has focused substantially on this method, with different reactor configurations that were proposed. However, minimal attention was given to the emerging technologies that sought to accelerate the treatment with a subsequent resource recovery from the process. Hence, this review focuses on the recent emerging tools that can be used to accelerate cyanide biodegradation. These tools include, amongst others, electro-bioremediation, anaerobic biodegradation and the use of microbial fuel cell technology. These processes were demonstrated to have the possibility of producing value-added products, such as biogas, co-factors of neurotransmitters and electricity from the treatment process.

Recent Strategies for Bioremediation of Emerging Pollutants: A Review for a Green and Sustainable Environment

Environmental pollution brought on by xenobiotics and other related recalcitrant compounds have recently been identified as a major risk to both human health and the natural environment. Due to their toxicity and non-biodegradability, a wide range of pollutants, such as heavy metals, polychlorinated biphenyls, plastics, and various agrochemicals are present in the environment. Bioremediation is an effective cleaning technique for removing toxic waste from polluted environments that is gaining popularity. Various microorganisms, including aerobes and anaerobes, are used in bioremediation to treat contaminated sites. Microorganisms play a major role in bioremediation, given that it is a process in which hazardous wastes and pollutants are eliminated, degraded, detoxified, and immobilized. Pollutants are degraded and converted to less toxic forms, which is a primary goal of bioremediation. Ex situ or in situ bioremediation can be used, depending on a variety of factors, such as cost, pollutant types, and concentration. As a result, a suitable bioremediation method has been chosen. This review focuses on the most recent developments in bioremediation techniques, how microorganisms break down different pollutants, and what the future holds for bioremediation in order to reduce the amount of pollution in the world.

Recent advancements in hydrocarbon bioremediation and future challenges: a review

Petrochemicals are important hydrocarbons, which are one of the major concerns when accidently escaped into the environment. On one hand, these cause soil and fresh water pollution on land due to their seepage and leakage from automobile and petrochemical industries. On the other hand, oil spills occur during the transport of crude oil or refined petroleum products in the oceans around the world. These hydrocarbon and petrochemical spills have not only posed a hazard to the environment and marine life, but also linked to numerous ailments like cancers and neural disorders. Therefore, it is very important to remove or degrade these pollutants before their hazardous effects deteriorate the environment. There are varieties of mechanical and chemical methods for removing hydrocarbons from polluted areas, but they are all ineffective and expensive. Bioremediation techniques provide an economical and eco-friendly mechanism for removing petrochemical and hydrocarbon residues from the affected sites. Bioremediation refers to the complete mineralization or transformation of complex organic pollutants into the simplest compounds by biological agents such as bacteria, fungi, etc. Many indigenous microbes present in nature are capable of detoxification of various hydrocarbons and their contaminants. This review presents an updated overview of recent advancements in various technologies used in the degradation and bioremediation of petroleum hydrocarbons, providing useful insights to manage such problems in an eco-friendly manner.

Soil initial bacterial diversity and nutrient availability determine the rate of xenobiotic biodegradation

Understanding the relative importance of soil microbial diversity, plants and nutrient management is crucial to implement an effective bioremediation approach to xenobiotics-contaminated soils. To date, knowledge on the interactive effects of soil microbiome, plant and nutrient supply on influencing biodegradation potential of soils remains limited. In this study, we evaluated the individual and interactive effects of soil initial bacterial diversity, nutrient amendments (organic and inorganic) and plant presence on the biodegradation rate of pyrene, a polycyclic aromatic hydrocarbon. Initial bacterial diversity had a strong positive impact on soil biodegradation potential, with soil harbouring higher bacterial diversity showing ~ 2 times higher degradation rates than soils with lower bacterial diversity. Both organic and inorganic nutrient amendments consistently improved the degradation rate in lower diversity soils and had negative (inorganic) to neutral (organic) effect in higher diversity soils. Interestingly, plant presence/type did not show any significant effect on the degradation rate in most of the treatments. Structural equation modelling demonstrated that initial bacterial diversity had a prominent role in driving pyrene biodegradation rates. We provide novel evidence that suggests that soil initial microbial diversity, and nutrient amendments should be explicitly considered in the design and employment of bioremediation management strategies for restoring natural habitats disturbed by organic pollutants.

Recent Developments in Microbe-Plant-Based Bioremediation for Tackling Heavy Metal-Polluted Soils

Soil contamination with heavy metals (HMs) is a serious concern for the developing world due to its non-biodegradability and significant potential to damage the ecosystem and associated services. Rapid industrialization and activities such as mining, manufacturing, and construction are generating a huge quantity of toxic waste which causes environmental hazards. There are various traditional physicochemical techniques such as electro-remediation, immobilization, stabilization, and chemical reduction to clean the contaminants from the soil. However, these methods require high energy, trained manpower, and hazardous chemicals make these techniques costly and non-environment friendly. Bioremediation, which includes microorganism-based, plant-based, microorganism-plant associated, and other innovative methods, is employed to restore the contaminated soils. This review covers some new aspects and dimensions of bioremediation of heavy metal-polluted soils. The bioremediation potential of bacteria and fungi individually and in association with plants has been reviewed and critically examined. It is reported that microbes such as Pseudomonas spp., Bacillus spp., and Aspergillus spp., have high metal tolerance, and bioremediation potential up to 98% both individually and when associated with plants such as Trifolium repens, Helianthus annuus, and Vallisneria denseserrulata. The mechanism of microbe's detoxification of metals depends upon various aspects which include the internal structure, cell surface properties of microorganisms, and the surrounding environmental conditions have been covered. Further, factors affecting the bioremediation efficiency and their possible solution, along with challenges and future prospects, are also discussed.

Evaluation of the sequential coupling of a bacterial treatment with a physicochemical process for the remediation of wastewater containing Cr and organic pollutants

A restoration strategy was developed for the treatment of two artificial liquid systems (Minimal Medium, MM, and Water Carbon Nitrogen, WCN) contaminated with Cr(VI), lindane (γ-HCH), phenanthrene (Phe), and reactive black 5 (RB5), through the use of an actinobacteria consortium, coupled with a physicochemical treatment using a column filled with nano-scale zero valent iron particles immobilized on dried Macrocystis pyrifera algae biomass. The Sequential Treatment A (ST_A: physicochemical followed by biological method) removed the three organic compounds with different effectiveness; however, it was very ineffective for Cr(VI) removal. The Sequential Treatment B (ST_B: biological followed by the physicochemical method) removed the four compounds with variable efficiencies. The removal of γ-HCH, Phe, and RB5 in both effluents did not present significant differences, regardless of the sequential treatment used. The highest removal of Cr(VI) and total Cr was observed in MM and WCN, respectively. Ecotoxicity tests (L. sativa) of the effluents treated with both methodological couplings demonstrated that the toxicity of WCN only decreased at the end of ST_A, while that of MM decreased at all stages of both sequential treatments. Therefore, MM would be more appropriate to perform both treatments.

A compartmentalized microsystem helps understanding the uptake of benzo[a]pyrene by fungi during soil bioremediation processes

Hydrophobic organic soil contaminants such as polycyclic aromatic hydrocarbons (PAH) are poorly mobile in the aqueous phase and tend to sorb to the soil matrix, resulting in low bioavailability. Some filamentous fungi are efficient in degrading this kind of pollutants. However, the mechanism of mobilization of hydrophobic compounds by non-motile microorganisms such as filamentous fungi needs investigations to improve pollutant bioavailability and bioremediation efficiency. Usual homogeneous media for microbial growth in the lab are poorly suited to model the soil, which is a compartmentalized and heterogeneous habitat. A microfluidic device was designed to implement a compartmentalization of the fungal inoculum and the source of the pollutant benzo[a]pyrene (BaP) as a deposit of solid crystals in order to gain a further insight into the mechanisms involved in the access to the contaminant and its uptake in soils. Thus in this device, two chambers are connected by an array of parallel microchannels that are wide enough to allow individual hyphae to grow through them. Macro-cultures of Talaromyces helicus in direct contact with BaP have shown its uptake and intracellular storage in lipid bodies despite the low propensity of BaP to cross aqueous phases as shown by simulation. Observations of T. helicus in the microfluidic device through laser scanning confocal microscopy indicate preferential uptake of BaP at a close range and through contact with the cell wall. However faint staining of some hyphae before contact with the deposit also suggests an extracellular transport phenomenon. Macro-culture filtrates analyses have shown that T. helicus releases extracellular non-lipidic surface-active compounds able to lower the surface tension of culture filtrates to 49.4 mN/m. Thus, these results highlight the significance of active mechanisms to reach hydrophobic contaminants before their uptake by filamentous fungi in compartmentalized micro-environments and the potential to improve them through biostimulation approaches for soil mycoremediation.

Dark septate endophytes (DSE): potential bioremedial promoters of oil derivatives

Oil spills are a global environmental problem. One of the management tools used to solve this problem is phytoremediation, a process that uses the capacity of plants and microorganisms to metabolize the components of the oil. The aims of the present study were to isolate, identify and characterize the fungi obtained from plants growing in an oil-contaminated area and evaluate their growth response and emulsifying and degrading capacity in two petroleum derivatives (kerosene and lube oil). Four dark septate endophytes (DSE) strains were isolated and identified: Exserohilum pedicellatum, Ophiosphaerella sp., and two Alternaria alternata strains. E. pedicellatum was found in an oil-contaminated environment for the first time. All strains were grown in kerosene, although some showed inhibition, whereas in lube oil, all showed growth induction. Ophiosphaerella sp. showed "drops" in kerosene, but the four strains showed surfactant capacity in lube oil. Ophiosphaerella sp. showed the highest emulsifying activity index but both A. alternata strains presented the highest lube oil degradation, which was directly related to the weight of the fungal biomass. There was not relationship between emulsifying capacity and oil degradation. However, these fungi show technological potential for application in phytoremediation processes.

Recent Advances in Enzymes for the Bioremediation of Pollutants

Nowadays, pollution of the environment is a huge problem for humans and other organisms' health. Conventional methods of pollutant removal like membrane filtration or ion exchange are not efficient enough to lower the number of pollutants to standard levels. Biological methods, because of their higher efficiency and biocompatibility, are preferred for the remediation of pollutants. These cost-effective and environment-friendly methods of reducing pollutants are called bioremediation. In bioremediation methods, enzymes play the most crucial role. Enzymes can remedy different types of organic and inorganic pollutants, including PAHs, azo dyes, polymers, organocyanides, lead, chromium, and mercury. Different enzymes isolated from various species have been used for the bioremediation of pollutants. Discovering new enzymes and new subtypes with specific physicochemical characteristics would be a promising way to find more efficient and cost-effective tools for the remediation of pollutants.

New insights into the degradation of synthetic pollutants in contaminated environments

The environment is contaminated by synthetic contaminants owing to their extensive applications globally. Hence, the removal of synthetic pollutants (SPs) from the environment has received widespread attention. Different remediation technologies have been investigated for their abilities to eliminate SPs from the ecosystem; these include photocatalysis, sonochemical techniques, nanoremediation, and bioremediation. SPs, which can be organic or inorganic, can be degraded by microbial metabolism at contaminated sites. Owing to their diverse metabolisms, microbes can adapt to a wide variety of environments. Several microbial strains have been reported for their bioremediation potential concerning synthetic chemical compounds. The selection of potential strains for large-scale removal of organic pollutants is an important research priority. Additionally, novel microbial consortia have been found to be capable of efficient degradation owing to their combined and co-metabolic activities. Microbial engineering is one of the most prominent and promising techniques for providing new opportunities to develop proficient microorganisms for various biological processes; here, we have targeted the SP-degrading mechanisms of microorganisms. This review provides an in-depth discussion of microbial engineering techniques that are used to enhance the removal of both organic and inorganic pollutants from different contaminated environments and under different conditions. The degradation of these pollutants is investigated using abiotic and biotic approaches; interestingly, biotic approaches based on microbial methods are preferable owing to their high potential for pollutant removal and cost-effectiveness.

Epiphytic Microbial Diversity of Vitis vinifera Fructosphere: Present Status and Potential Applications

Vineyard provides an apt environment for growth of different types of microorganisms. The microbial domain is greatly affected by changing climatic conditions, geographical region, water activity, agricultural practices, presence of different pathogens and various pests. Grapevine microbial diversity is also affected by different stages of plant growth. Epiphytic berry microflora is specifically influenced by developmental phases and plays an important role in winemaking which is studied extensively. However, very little information is available about microbial community associated with table grape berries, which are consumed as fresh fruits. Moreover, our knowledge about the important role played by these microbes is precise and their scope might be larger than what is existing in the public domain. A systematic study on effect of developmental stages of table grape berries on microbial diversity would provide new insights for exploring the applicability of these microbes in plant growth, crop protection and bioremediation. In this review, we propose an effort to relate the developmental stages of grape berry with microbial consortium present and at the same time discuss the possible applications of these microbes in plant protection and biodegradation.

Synergistic effects of compost, cow bile and bacterial culture on bioremediation of hydrocarbon-contaminated drill mud waste

Bioremediation has gained global prominence as an effective method for treating hydrocarbon-contaminated drill mud waste (HCDW). However, the problem of low nutrient content, bioavailability and microbial presence remain largely unresolved. In this study, the synergistic effects of compost, cow bile and bacterial culture on the degradation rate of HCDW was investigated. A homogenized HCDW sample (80 kg) obtained from 25 different drill mud tanks was divided into 20 portions (4 kg each) and each adjusted to 1.4% nitrogen content + 20 ml cow bile (i.e., basic treatment). Pure cultures of Brevibacterium casei (Bc) and Bacillus zhangzhouensi (Bz) and their mixture (BcBz) were subsequently added to 12 of the amended HCDW (basic) to undergo a 6-week incubation. A portion of the unamended HCDW (2 kg) was used as control. Initial pH, electrical conductivity and surface tension values of the HCDW were 8.83, 2.34 mS/cm and 36.5 mN/m, respectively. Corresponding values for total petroleum hydrocarbon (TPH), total nitrogen and total plate count bacteria were 165 g/kg, 0.04% and 4.4 × 10² cfu/ml. The treatments led to a substantial reduction in TPH (p < 0.05) while the control had no significant effect (p > 0.05). TPH reduction after the experimental period occurred in the order: basic + BcBz (99.7%) > basic + Bz (99.5%) > basic + Bc (99.2%) > basic (95.2%) > control (0.06%). Multiple regression analysis revealed significant effect of total plate count, pH, CN ratio and electrical conductivity (R² = 0.87, p = 0.05) on the degradation of TPH in the HCDW. The study demonstrates strong interactive effects of compost, cow bile and bacteria culture on the remediation of HCDW, which can be applied to boost the efficiency of the bioremediation technique.

Dehalogenase-producing halophiles and their potential role in bioremediation

This review aims to briefly describe the potential role of dehalogenase-producing halophilic bacteria in decontamination of organohalide pollutants. Hypersaline habitats pose challenges to life because of low water activity (water content) and is considered as the largest and ultimate sink for pollutants due to naturally and anthropogenic activities in which a substantial amount of ecological contaminants are organohalides. Several such environments appear to host and support substantial diversity of extremely halophilic and halotolerant bacteria as well as halophilic archaea. Biodegradation of several toxic inorganic and organic compounds in both aerobic and anaerobic conditions are carried out by halophilic microbes. Therefore, remediation of polluted marine/hypersaline environments are the main scorching issues in the field of biotechnology. Although many microbial species are reported as effective pollutants degrader, but little has been isolated from marine/hypersaline environments. Therefore, more novel microbial species with dehalogenase-producing ability are still desired.

Development of biocatalysts immobilized on coal ash-derived Ni-zeolite for facilitating 4-chlorophenol degradation

A new type of biocatalyst was developed to facilitate the biochemical decomposition of 4-chlorophenol (4-CP) in this study. Oxydoreductases that catalyze the initial steps of 4-CP biodegradation were immobilized on a synthetic inorganic enzyme support. Type-X zeolite, a high-surface area support, was synthesized from coal fly ash, on which nickel ions were plated by impregnation (Ni-zeolite), followed by the effective immobilization (77.5% immobilization yield) of recombinant monooxygenase (CphC-I), dioxygenase (CphA-I), and flavin reductase (Fre) isolated from Pseudarthrobacter chlorophenolicus A6 and Escherichia coli K-12, respectively. The retained catalytic activity of the enzymes immobilized on Ni-zeolite was as high as 64% of the value for the corresponding free enzymes. The Michaelis-Menten kinetic parameters v_max and K_M of the immobilized enzymes were determined to be 0.20 mM·min^-1 and 0.44 mM, respectively. These results are expected to provide useful information with respect to the development of novel enzymatic treatments for phenolic hydrocarbon contaminants.

Alternative Strategies for Microbial Remediation of Pollutants via Synthetic Biology

Continuous contamination of the environment with xenobiotics and related recalcitrant compounds has emerged as a serious pollution threat. Bioremediation is the key to eliminating persistent contaminants from the environment. Traditional bioremediation processes show limitations, therefore it is necessary to discover new bioremediation technologies for better results. In this review we provide an outlook of alternative strategies for bioremediation via synthetic biology, including exploring the prerequisites for analysis of research data for developing synthetic biological models of microbial bioremediation. Moreover, cell coordination in synthetic microbial community, cell signaling, and quorum sensing as engineered for enhanced bioremediation strategies are described, along with promising gene editing tools for obtaining the host with target gene sequences responsible for the degradation of recalcitrant compounds. The synthetic genetic circuit and two-component regulatory system (TCRS)-based microbial biosensors for detection and bioremediation are also briefly explained. These developments are expected to increase the efficiency of bioremediation strategies for best results.

Microbial and plant-assisted heavy metal remediation in aquatic ecosystems: a comprehensive review

Heavy metal (HM) pollution in aquatic ecosystems has an adverse effect on both aquatic life forms as well as terrestrial living beings, including humans. Since HMs are recalcitrant, they accumulate in the environment and are subsequently biomagnified through the food chain. Conventional physical and chemical methods used to remove the HMs from aquatic habitats are usually expensive, slow, non-environment friendly, and mostly inefficient. On the contrary, phytoremediation and microbe-assisted remediation technologies have attracted immense attention in recent years and offer a better solution to the problem. These newly emerged remediation technologies are eco-friendly, efficient and cost-effective. Both phytoremediation and microbe-assisted remediation technologies adopt different mechanisms for HM bioremediation in aquatic ecosystems. Recent advancement of molecular tools has contributed significantly to better understand the mechanisms of metal adsorption, translocation, sequestration, and tolerance in plants and microbes. Albeit immense possibilities to use such bioremediation as a successful environmental clean-up technology, it is yet to be successfully implemented in the field conditions. This review article comprehensively discusses HM accumulation in Indian aquatic environments. Furthermore, it describes the effect of HMs accumulation in the aquatic environment and the role of phytoremediation as well as microbe-assisted remediation in mitigation of the HM toxicity. Finally, the review concludes with a note on the challenges, opportunities and future directions for bioremediation in the aquatic ecosystems.

Efficient removal of 2,4-dinitrophenol from synthetic wastewater and contaminated soil samples using free and immobilized laccases

Among hazardous pollutants, 2,4-Dinitrophenol (2,4-DNP) is considered highly toxic and possesses a remarkable resistance to degradation. Therefore, investigation of the possible mechanisms for removal of such pollutants is important. Laccase enzyme can decompose phenolics despite the fact that its application has been limited due to lack of possibility to reuse it. Immobilization can overcome this problem. In this paper, laccase complexes with montmorillonite K10 and zeolite were used to decompose 2,4-DNP with concentrations of 1.5 mg l^-1 and 50 mg kg^-1 in synthetic wastewater and soil, respectively. The maximum removal of pollutant from wastewater in samples containing laccase-zeolite and laccase-montmorillonite complexes were 99 and 93.3%, respectively, which occurred at 4 h incubation compared with 6 h for free laccase. The maximum removal of pollutant from soil was observed for all treatments after 16 h of incubation. The maximum removal for samples containing free laccase, laccase-zeolite, and laccase-montmorillonite complexes were 98.5%, 98.6%, and 90.4%, respectively. Control sample also showed maximum removal of 35.8%. In general, application of laccase-zeolite complexes in aqueous environment, and these complexes and free laccases in soil was found very effective in degradation of 2,4-DNP. Hence, the use of laccase, especially immobilized laccases, for removal of 2,4-DNP from environment is promising.

Evaluation of the effectiveness of a bioremediation process in experimental soils polluted with chromium and lindane

Bioremediation using actinobacterium consortia proved to be a promising alternative for the purification of co-contaminated environments. In this sense, the quadruple consortium composed of Streptomyces sp. M7, MC1, A5, and Amycolatopsis tucumanensis AB0 has been able to remove significant levels of Cr(VI) and lindane from anthropogenically contaminated soils. However, the effectiveness of the bioremediation process could not be evaluated only by analytical monitoring, which is complex mainly due to the characteristics of the matrix, producing non-quantitative analyte recoveries, or interferences in the detection stage and quantification. However, the effectiveness of the bioremediation process cannot be evaluated only through analytical monitoring, which is complex due mainly to the characteristics of the matrix, to the recoveries of non-quantitative analytes or to interferences in the detection and quantification stage. For this reason, it is essential to have tools of ecological relevance to assess the biological impact of pollutants on the environment. In this context, the objective of this work was to establish the appropriate bioassays to evaluate the effectiveness of a bioremediation process of co-contaminated soils. For this, five model species were studied: four plant species (Lactuca sativa, Raphanus sativus, Lycopersicon esculentum, and Zea mays) and one animal species (Eisenia fetida). On plant species, the biomarkers evaluated were inhibition of germination (IG) and the length of hypocotyls/steam and radicles/roots of the seedling. While on E. fetida, mortality (M), weight lost, coelomocyte concentration and cell viability were tested. These bioindicators and the battery of biomarkers quantified in them showed a different level of sensitivity, from maximum to minimum: E. fetida > L. esculentum > L. sativa > R. sativus ≫>Z. mays. Therefore, E. fetida and L. esculentum and their respective biomarkers were selected to evaluate the effectiveness of the bioremediation process due to the capability of assessing the effect on the flora and the fauna of the soil, respectively. The joint application of these bioindicators in a field scale bioremediation process is a feasible tool to demonstrate the recovery of the quality and health of the soil.

Biodegradation of naphthalene, BTEX, and aliphatic hydrocarbons by Paraburkholderia aromaticivorans BN5 isolated from petroleum-contaminated soil

To isolate bacteria responsible for the biodegradation of naphthalene, BTEX (benzene, toluene, ethylbenzene, and o-, m-, and p-xylene), and aliphatic hydrocarbons in petroleum-contaminated soil, three enrichment cultures were established using soil extract as the medium supplemented with naphthalene, BTEX, or n-hexadecane. Community analyses showed that Paraburkholderia species were predominant in naphthalene and BTEX, but relatively minor in n-hexadecane. Paraburkholderia aromaticivorans BN5 was able to degrade naphthalene and all BTEX compounds, but not n-hexadecane. The genome of strain BN5 harbors genes encoding 29 monooxygenases including two alkane 1-monooxygenases and 54 dioxygenases, indicating that strain BN5 has versatile metabolic capabilities, for diverse organic compounds: the ability of strain BN5 to degrade short chain aliphatic hydrocarbons was verified experimentally. The biodegradation pathways of naphthalene and BTEX compounds were bioinformatically predicted and verified experimentally through the analysis of their metabolic intermediates. Some genomic features including the encoding of the biodegradation genes on a plasmid and the low sequence homologies of biodegradation-related genes suggest that biodegradation potentials of strain BN5 may have been acquired via horizontal gene transfers and/or gene duplication, resulting in enhanced ecological fitness by enabling strain BN5 to degrade all compounds including naphthalene, BTEX, and short aliphatic hydrocarbons in contaminated soil.

Characterization of free and immobilized laccase from Cyberlindnera fabianii and application in degradation of bisphenol A

Recovery difficulty and inactivation of laccases are major challenges that hamper their application in biotechnology. In this study, laccase was purified from Cyberlindnera fabianii using ion-exchange and gel filtration chromatography with homogeneity confirmed by sodium dodecyl sulphate polyacrylamide gel electrophoresis. Purified laccase of 52 kDa was immobilized on calcium and copper alginate beads by entrapment method. Free and immobilized enzymes were characterized, and efficiency of bisphenol A (BPA) degradation was determined. pH optima for free and immobilized laccases were 5.0 and 6.0, respectively. Ca and Cu alginate immobilized laccase (Ca-AIL and Cu-AIL) had optimum activity at 60 °C and 50 °C, respectively while free laccase (FL) was at 40 °C. K_m and V_max of FL, Ca-AIL and Cu-AIL were 0.032 mM and 15 mM/min, 0.078 mM and 6.98 mM/min, and 0.091 mM and 5.61 mM/min, respectively. Remarkably, immobilized laccases had higher operational stability than FL over 21 d at 4°C. Reusability of immobilized laccase was effective for 3 cycles with residual activity above 70%. Notably, Ca-AIL and Cu-AIL exhibited 71% and 65.5% BPA degradation efficiency on 14 d. Results reveal good kinetic parameters, improved thermal stability and enhanced reusability of immobilized laccase from C. fabianii with potentials for various industrial applications and bioremediation.

The accumulation of metals, PAHs and alkyl PAHs in the roots of Echinacea purpurea

We examined the accumulation of polycyclic aromatic hydrocarbons (PAHs), alkyl PAHs, and toxic metals in soils by the roots of Echinacea purpurea (L.) Moench, in a 20-week greenhouse study and a 2-year field study. In the greenhouse study, inoculation by arbuscular mycorrhizal fungus (AMF), Rhizoglomus intraradices (N.C. Schenck & G.S. Sm.). increased the first order accumulation rates (k₁) for PAHs by 10-fold, though had no effect on the bioaccumulation rates of toxic metals. In the greenhouse study, PAHs concentrations in soil increased over time with AMF inoculation, suggesting AMF promote ‘solvent depletion’ in soils by enhancing absorption of minerals and carbon by roots, concentrating the more hydrophobic PAHs in the residual soil. Under field conditions, contaminant concentrations in soils remained unchanged over the 2-year duration of the study. Despite this, all contaminants in E. purpurea roots increased significantly, as a result of a long term extraction of contaminants by plants from soil and a reduction in soil volume as a result of plant growth. First order accumulation rates by roots were inversely correlated to log K_ow for the PAHs and alkyl PAHs, indicating that accumulation is inversely related to the compound’s hydrophobicity. This study is the first to our knowledge to assess the accumulation of alkyl PAHs by roots, with implications for soil bioremediation by plants because alkyl PAHs are a major source of petrogenic contamination in soils.

Construction and Evaluation of a Korean Native Microbial Consortium for the Bioremediation of Diesel Fuel-Contaminated Soil in Korea

A native microbial consortium for the bioremediation of soil contaminated with diesel fuel in Korea was constructed and its biodegradation ability was assessed. Microbial strains isolated from Korean terrestrial environments, with the potential to biodegrade aliphatic hydrocarbons, PAHs, and resins, were investigated and among them, eventually seven microbial strains, Acinetobacter oleivorans DR1, Corynebacterium sp. KSS-2, Pseudomonas sp. AS1, Pseudomonas sp. Neph5, Rhodococcus sp. KOS-1, Micrococcus sp. KSS-8, and Yarrowia sp. KSS-1 were selected for the construction of a microbial consortium based on their biodegradation ability, hydrophobicity, and emulsifying activity. Laboratory- and bulk-scale biodegradation tests showed that in diesel fuel-contaminated soil supplemented with nutrients (nitrogen and phosphorus), the microbial consortium clearly improved the biodegradation of total petroleum hydrocarbons, and all microbial strains constituting the microbial consortium, except for Yarrowia survived and grew well, which suggests that the microbial consortium can be used for the bioremediation of diesel fuel-contaminated soil in Korea.

Assessment of genetic diversity and bioremediation potential of pseudomonads isolated from pesticide-contaminated artichoke farm soils

A total of 68 dimethoate and pentachlorophenol-tolerant rhizobacteria, isolated from a pesticide-contaminated agricultural soil, have been identified and typed by means of 16S-23S rRNA internal transcribed spacers analysis (ITS-PCR), 16S rRNA gene sequencing and by repetitive extragenic palindromic (BOX-PCR). The majority of bacterial isolates (84.31%) belonged to Proteobacteria (with a predominance of Gammaproteobacteria, 72.54%), while the remaining isolates were affiliated with Firmicutes (9.80%), Bacteroidetes (1.96%) and Actinobacteria (3.92%). The pesticide-tolerant bacterial isolates belonged to 11 genera, namely Pseudomonas, Bacillus, Acinetobacter, Flavobacterium, Comamonas, Achromobacter, Rhodococcus, Ochrobactrum, Aquamicrobium, Bordetella and Microbacterium. Within the well-represented genus Pseudomonas (n = 36), the most common species was Pseudomonas putida (n = 32). The efficacy of the selected strain, Pseudomonas putida S148, was further investigated for biodegradation of pentachlorophenol (PCP) in minimal medium, when used as a sole carbon and energy source. At an initial concentration of 100 mg/L, P. putida S148 degraded 91% of PCP after 7 days. GC-MS analyses revealed the formation of tetrachlorohydroquinone, tri- and di-chlorophenols as biodechlorination products in PCP remediation experiments. The toxicity estimation showed that 50% lethal concentration (LC50) and 50% growth inhibition concentration (IGC50) obtained values for the major identified compounds (2,3,4,6 tetrachlorophenol, 2,3,5,6 tetrachlorophenol and tetrachlorohydroquinone) were higher than those estimated for the PCP indicating that the metabolites are less toxic than the original compound for those specific organisms. S148 strain could be added to pesticide-contaminated agricultural soils as a bacterial inoculant for its potential to improve soil quality.

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.

Contemporary enzyme based technologies for bioremediation: A review

The persistent disposal of xenobiotic compounds like insecticides, pesticides, fertilizers, plastics and other hydrocarbon containing substances is the major source of environmental pollution which needs to be eliminated. Many contemporary remediation methods such as physical, chemical and biological are currently being used, but they are not sufficient to clean the environment. The enzyme based bioremediation is an easy, quick, eco-friendly and socially acceptable approach used for the bioremediation of these recalcitrant xenobiotic compounds from the natural environment. Several microbial enzymes with bioremediation capability have been isolated and characterized from different natural sources, but less production of such enzymes is a limiting their further exploitation. The genetic engineering approach has the potential to get large amount of recombinant enzymes. Along with this, enzyme immobilization techniques can boost the half-life, stability and activity of enzymes at a significant level. Recently, nanozymes may offer the potential bioremediation ability towards a broad range of pollutants. In the present review, we have described a brief overview of the microbial enzymes, different enzymes techniques (genetic engineering and immobilization of enzymes) and nanozymes involved in bioremediation of toxic, carcinogenic and hazardous environmental pollutants.

Microbial and Plant-Assisted Bioremediation of Heavy Metal Polluted Environments: A Review

Environmental pollution from hazardous waste materials, organic pollutants and heavy metals, has adversely affected the natural ecosystem to the detriment of man. These pollutants arise from anthropogenic sources as well as natural disasters such as hurricanes and volcanic eruptions. Toxic metals could accumulate in agricultural soils and get into the food chain, thereby becoming a major threat to food security. Conventional and physical methods are expensive and not effective in areas with low metal toxicity. Bioremediation is therefore an eco-friendly and efficient method of reclaiming environments contaminated with heavy metals by making use of the inherent biological mechanisms of microorganisms and plants to eradicate hazardous contaminants. This review discusses the toxic effects of heavy metal pollution and the mechanisms used by microbes and plants for environmental remediation. It also emphasized the importance of modern biotechnological techniques and approaches in improving the ability of microbial enzymes to effectively degrade heavy metals at a faster rate, highlighting recent advances in microbial bioremediation and phytoremediation for the removal of heavy metals from the environment as well as future prospects and limitations. However, strict adherence to biosafety regulations must be followed in the use of biotechnological methods to ensure safety of the environment.

Phytase production by Aspergillus niger NCIM 563 for a novel application to degrade organophosphorus pesticides

The production of phytase using Aspergillus niger NCIM 563 under submerged fermentation conditions was studied using protein rich chickpea flour as substrate. Employing a hybrid statistical media optimization strategy of Plackett-Burman and Box-Behnken experimental designs in shake-flasks gave an increased phytase activity from an initial 66 IU/mL in 216 h to 160 IU/mL in a reduced time of 132 h. Productivity, thus increased by 3.97 times from 7.3 to 29 IU/mL/day. Using the optimized media, the production was successfully scaled-up further and improved up to 164 IU/mL in 96 h by studies carried out employing 2 and 10-L fermenters. The enzyme supernatant was recovered using centrifugal separation of biomass and the stability of the produced phytase was tested for animal feed applications under gastric conditions. In vitro degradation studies of water soluble monocrotophos, methyl parathion and water insoluble chlorpyrifos, pesticides used extensively in agriculture was carried out. It was observed by HPLC analysis that phytase could degrade 72% of chlorpyrifos at pH 7.0, 35 °C. Comparable results were obtained with monocrotophos and methyl parathion. With chlorpyrifos at higher temperature 50 °C as much as 91% degradation could be obtained. The degradation of chlorpyrifos was further validated by spraying phytase on harvested green chilli (Capsicum annuum L) under normal conditions of pH 7.0, 35 °C and the degradation products obtained analyzed by LCMS. Thus, the present study brings out a potentially novel application of phytase for biodegradation of organophosphorus pesticides.

Nano- and micromotors for cleaning polluted waters: focused review on pollutant removal mechanisms

Nano- and micromotors are machines designed to self-propel and-in the process of propelling themselves-perform specialized tasks like cleaning polluted waters. These motors offer distinct advantages over conventionally static decontamination methods, owing to their ability to move around and self-mix-which heightens the interaction between their active sites and target pollutants-thus improving their speed and efficiency, which could potentially decrease treatment times and costs. In the last decade, considerable research efforts have been expended on exploring various mechanisms by which these motors can self-propel and remove pollutants, proving that the removal of oil droplets, heavy metals, and organic compounds using these synthetic motors is possible. This review highlights recent progress in the design of these nano- and micromotors for cleaning polluted waters, and gives an overview of their structure, fabrication, and propulsion methods, with a special focus on the mechanisms by which they remove pollutants-namely, either by adsorption or by degradation. A fundamental understanding of these removal mechanisms, with their attendant advantages and disadvantages, can help researchers fine-tune motor design in the future so that technical issues can be resolved before they are scaled-up for a wide variety of environmental applications.

Isolation and Molecular Characterization of Novel Chlorpyrifos and 3,5,6-trichloro-2-pyridinol-degrading Bacteria from Sugarcane Farm Soils

Chlorpyrifos (CP) is one of the most widely used organophosphate pesticides in agriculture worldwide, but its extensive use has led to the contamination of various soil and water systems. Microbial bioremediation is considered to be one of the most viable options for the removal of CP from the environment; however, little is known about the soil bacterial diversity that degrade CP. Sequential soil and liquid culture enrichments enabled the isolation of bacterial CP degraders with sequence homologies to Xanthomonas sp., Pseudomonas sp., and Rhizobium sp. The efficacy of the three isolated strains: Xanthomonas sp. 4R3-M1, Pseudomonas sp. 4H1-M3, and Rhizobium sp. 4H1-M1 was further investigated for biodegradation of CP and its primary metabolic product, 3,5,6-trichloro-2-pyridinol (TCP). The results indicate that all three bacterial strains almost completely metabolized CP (10 mg/L) and TCP, occurring as a metabolic degradation product, in mineral salt media as a sole source of carbon and nitrogen. The isolated bacterial strains Xanthomonas sp. 4R3-M1 and Pseudomonas sp. 4H1-M3 could also degrade TCP (10 mg/L) as a sole carbon and nitrogen source, when provided externally. Thus, these bacterial strains may be effective in practical application of bioremediation of both CP and TCP.

Effect of Medicago sativa L. and compost on organic and inorganic pollutant removal from a mixed contaminated soil and risk assessment using ecotoxicological tests

Several Gentle Remediation Options (GRO), e.g., plant-based options (phytoremediation), singly and combined with soil amendments, can be simultaneously efficient for degrading organic pollutants and either stabilizing or extracting trace elements (TEs). Here, a 5-month greenhouse trial was performed to test the efficiency of Medicago sativa L., singly and combined with a compost addition (30% w/w), to treat soils contaminated by petroleum hydrocarbons (PHC), Co and Pb collected at an auto scrap yard. After 5 months, total soil Pb significantly decreased in the compost-amended soil planted with M. sativa, but not total soil Co. Compost incorporation into the soil promoted PHC degradation, M. sativa growth and survival, and shoot Pb concentrations [3.8 mg kg(-1) dry weight (DW)]. Residual risk assessment after the phytoremediation trial showed a positive effect of compost amendment on plant growth and earthworm development. The O2 uptake by soil microorganisms was lower in the compost-amended soil, suggesting a decrease in microbial activity. This study underlined the benefits of the phytoremediation option based on M. sativa cultivation and compost amendment for remediating PHC- and Pb-contaminated soils.

In-Situ Remediation Approaches for the Management of Contaminated Sites: A Comprehensive Overview

Though several in-situ treatment methods exist to remediate polluted sites, selecting an appropriate site-specific remediation technology is challenging and is critical for successful clean up of polluted sites. Hence, a comprehensive overview of all the available remediation technologies to date is necessary to choose the right technology for an anticipated pollutant. This review has critically evaluated the (i) technological profile of existing in-situ remediation approaches for priority and emerging pollutants, (ii) recent innovative technologies for on-site pollutant remediation, and (iii) current challenges as well as future prospects for developing innovative approaches to enhance the efficacy of remediation at contaminated sites.

Soil biodiversity and human health

Soil biodiversity is increasingly recognized as providing benefits to human health because it can suppress disease-causing soil organisms and provide clean air, water and food. Poor land-management practices and environmental change are, however, affecting belowground communities globally, and the resulting declines in soil biodiversity reduce and impair these benefits. Importantly, current research indicates that soil biodiversity can be maintained and partially restored if managed sustainably. Promoting the ecological complexity and robustness of soil biodiversity through improved management practices represents an underutilized resource with the ability to improve human health.

Distribution and chemical forms of copper in the root cells of castor seedlings and their tolerance to copper phytotoxicity in hydroponic culture

The subcellular localization and chemical forms of copper in castor (Ricinus communis L.) seedlings grown in hydroponic nutrient solution were identified by chemical extraction, transmission electron microscopy, and Fourier transform infrared spectroscopy. The wild castor seeds were harvested from an abandoned copper mine in Tonglu Mountain, Daye City of Hubei Province, China. The results revealed that (1) the seedlings grew naturally in MS liquid medium with 40.00 mg kg(-1) CuSO4, in which the seedling growth rate and biomass index were 0.14 and 1.23, respectively, which were the highest values among all the treatments. The copper content in castor seedlings increased along with elevated CuSO4 concentration in the medium, reaching a maximum value of 16 570.12 mg kg(-1)(DW) when exposed to 60.00 mg L(-1) CuSO4, where 91.31% of the copper was accumulated in roots. (2) The copper existed in various chemical forms in the roots of the castor seedlings. Copper of 67.66% was extracted from the components of cell walls, such as exchangeable acidic polar compounds, cellulose and lignin, protein and pectin, and less concentrated in cell cytoplasm and nuclei. (3) Furthermore, the root cell walls were thickened when the castor seedlings exposed to CuSO4, with a large amount of high-density electron bodies, attached to the thickened cell walls. In the cell walls, most copper was bound to the carboxyl (-COOH) and hydroxyl (-OH) groups of acidic polar compounds, cellulose, hemicellulose, and polysaccharides. The conclusion showed that castor exhibited a strong tolerance to copper, the copper were accumulated mainly in the root cell, the root cell walls of castor were the major location of patience and detoxification in copper stress.

Bibliometric analysis of phytotechnologies for remediation: global scenario of research and applications

Phytoremediation is often a low cost alternative to conventional remediation. To assess trends, a bibliometric approach using data from SciVerse Scopus, SciVerseHub, and GoogleTM Trends was used. Globally there is a linear increase in publications containing the word phytoremediation as a percent of all published papers in SciVerse Hub, with China, India, and the Philippines concentrating relatively more research in phytoremediation. Furthermore there was an inverse correlation between a country's Human Development Index (HDI) and a country's phytoremediation research output as a percent of total research. Results show a focus on phytoremediation in countries with low HDI values. This suggests that academic experts are available for advancing phytoremediation applications in countries where the majority of the effected population do not have the education, finances, and political leverage to obtain expensive conventional remediation efforts on their land. Phytoremediation can combine expert advice with affected parties commitment and labor to help mitigate the harms of polluted landscapes.

"NiCo Buster": engineering E. coli for fast and efficient capture of cobalt and nickel

BACKGROUND

Metal contamination is widespread and results from natural geogenic and constantly increasing anthropogenic sources (mainly mining and extraction activities, electroplating, battery and steel manufacturing or metal finishing). Consequently, there is a growing need for methods to detoxify polluted ecosystems. Industrial wastewater, surface water and ground water need to be decontaminated to alleviate the contamination of soils and sediments and, ultimately, the human food chain. In nuclear power plants, radioactive metals are produced; these metals need to be removed from effluents before they are released into the environment, not only for pollution prevention but also for waste minimization. Many physicochemical methods have been developed for metal removal from aqueous solutions, including chemical coagulation, adsorption, extraction, ion exchange and membrane separation; however, these methods are generally not metal selective. Bacteria, because they contain metal transporters, provide a potentially competitive alternative to the current use of expensive and high-volume ion-exchange resins.

RESULTS

The feasibility of using bacterial biofilters as efficient tools for nickel and cobalt ions specific remediation was investigated. Among the factors susceptible to genetic modification in Escherichia coli, specific efflux and sequestration systems were engineered to improve its metal sequestration abilities. Genomic suppression of the RcnA nickel (Ni) and cobalt (Co) efflux system was combined with the plasmid-controlled expression of a genetically improved version of a specific metallic transporter, NiCoT, which originates from Novosphingobium aromaticivorans. The resulting strain exhibited enhanced nickel (II) and cobalt (II) uptake, with a maximum metal ion accumulation of 6 mg/g bacterial dry weight during 10 min of treatment. A synthetic adherence operon was successfully introduced into the plasmid carrying the improved NiCoT transporter, conferring the ability to form thick biofilm structures, especially when exposed to nickel and cobalt metallic compounds.

CONCLUSIONS

This study demonstrates the efficient use of genetic engineering to increase metal sequestration and biofilm formation by E. coli. This method allows Co and Ni contaminants to be sequestered while spatially confining the bacteria to an abiotic support. Biofiltration of nickel (II) and cobalt (II) by immobilized cells is therefore a promising option for treating these contaminants at an industrial scale.

Dual-enzyme natural motors incorporating decontamination and propulsion capabilities

Self-propelled dual-enzyme natural motors display attractive decontamination and propulsion capabilities. The movement of the biocatalytic tissue motors through the contaminated sample leads to a greatly improved remediation efficiency.

Harnessing plant-microbe interactions for enhancing farm productivity

Declining soil fertility and farm productivity is a major global concern in order to achieve food security for a burgeoning world population. It is reported that improving soil health alone can increase productivity by 10-15% and in combination with efficient plant traits, farm productivity can be increased up to 50-60%. In this article we explore the emerging microbial and bioengineering technologies, which can be employed to achieve the transformational increase in farm productivity and can simultaneously enhance environmental outcomes i.e., low green house gas (GHG) emissions. We argue that metagenomics, meta-transcriptomics and metabolomics have potential to provide fundamental knowledge on plant-microbes interactions necessary for new innovations to increase farm productivity. Further, these approaches provide tools to identify and select novel microbial/gene resources which can be harnessed in transgenic and designer plant technologies for enhanced resource use efficiencies.