Enzymatic technologies for remediation of hydrophobic organic pollutants in soil

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.

Advanced biotechnology strategies for detoxification of persistent organic pollutants and toxic elements in soil

This paper aims to comprehensively examine and present the current state of persistent organic pollutants (POPs) and toxic elements (TEs) in soil. Additionally, it seeks to assess the viability of employing advanced biotechnology, specifically phytoremediation with potent microbial formulations, as a means of detoxifying POPs and TEs. In the context of the "global treaty," which is known as the Stockholm Convention, we analyzed the 3D chemical structures of POPs and its prospects for living organisms which have not been reviewed up to date. The obstacles associated with the phytoremediation strategy in biotechnology, including issues like slow plant growth and limited efficiency in contaminant uptake, have also been discussed and demonstrated. While biotechnology is recognized as a promising method for detoxifying persistent organic pollutants (POPs) and facilitating the restoration of contaminated and degraded lands, its full potential in the field is constrained by various factors. Recent advances in biotechnology, such as microbial enzymes, designer plants, composting, and nanobiotechnology techniques, have opened up new avenues for mitigating persistent organic pollutants (POPs) and toxic elements (TEs). The insights gained from this review can contribute to the development of innovative, practical, and economically viable approaches for remediating and restoring soils contaminated with persistent organic pollutants (POPs) and toxic elements (TEs). The ultimate aim is to reduce the risks to both human and environmental health.

Bioremediation of Automotive Residual Oil-Contaminated Soils by Biostimulation with Enzymes, Surfactant, and Vermicompost

Contamination of soils by automotive residual oil represents a global environmental problem. Bioremediation is the technology most suitable to remove this contaminant from the medium. Therefore, this work aimed to evaluate the effectiveness of bioremediation of automotive residual oil-contaminated soils by biostimulation with enzymes, surfactant, and vermicompost. The bioremediation efficiency was examined using a factorial design of 24 to determine the effect of the time, pH and temperature conditions, biostimulation with enzyme-vermicompost, and biostimulation with enzyme-surfactant. Enzymes obtained from Ricinus communis L. seeds, commercial vermicompost, and Triton X-100 were used. Results showed that the highest removal efficiency (99.9%) was achieved at 49 days, with a pH of 4.5, temperature of 37 °C, and using biostimulation with enzyme-vermicompost (3% w/v-5% w/w). The addition of surfactant was not significant in increasing the removal efficiency. Therefore, the results provide adequate conditions to bioremediate automotive residual oil-contaminated soils by biostimulation using enzymes supported with vermicompost.

Fungal bioproducts for petroleum hydrocarbons and toxic metals remediation: recent advances and emerging technologies

Petroleum hydrocarbons and toxic metals are sources of environmental contamination and are harmful to all ecosystems. Fungi have metabolic and morphological plasticity that turn them into potential prototypes for technological development in biological remediation of these contaminants due to their ability to interact with a specific contaminant and/or produced metabolites. Although fungal bioinoculants producing enzymes, biosurfactants, polymers, pigments and organic acids have potential to be protagonists in mycoremediation of hydrocarbons and toxic metals, they can still be only adjuvants together with bacteria, microalgae, plants or animals in such processes. However, the sudden accelerated development of emerging technologies related to the use of potential fungal bioproducts such as bioinoculants, enzymes and biosurfactants in the remediation of these contaminants, has boosted fungal bioprocesses to achieve higher performance and possible real application. In this review, we explore scientific and technological advances in bioprocesses related to the production and/or application of these potential fungal bioproducts when used in remediation of hydrocarbons and toxic metals from an integral perspective of biotechnological process development. In turn, it sheds light to overcome existing technological limitations or enable new experimental designs in the remediation of these and other emerging contaminants.

Bioremediation of Endocrine Disrupting Chemicals- Advancements and Challenges

Endocrine Disrupting Chemicals (EDCs), major group of recalcitrant compounds, poses a serious threat to the health and future of millions of human beings, and other flora and fauna for years to come. A close analysis of various xenobiotics undermines the fact that EDC is structurally diverse chemical compounds generated as a part of anthropogenic advancements as well as part of their degradation. Regardless of such structural diversity, EDC is common in their ultimate drastic effect of impeding the proper functioning of the endocrinal system, basic physiologic systems, resulting in deregulated growth, malformations, and cancerous outcomes in animals as well as humans. The current review outlines an overview of various EDCs, their toxic effects on the ecosystem and its inhabitants. Conventional remediation methods such as physico-chemical methods and enzymatic approaches have been put into action as some form of mitigation measures. However, the last decade has seen the hunt for newer technologies and methodologies at an accelerated pace. Genetically engineered microbial degradation, gene editing strategies, metabolic and protein engineering, and in-silico predictive approaches - modern day's additions to our armamentarium in combating the EDCs are addressed. These additions have greater acceptance socially with lesser dissonance owing to reduced toxic by-products, lower health trepidations, better degradation, and ultimately the prevention of bioaccumulation. The positive impact of such new approaches on controlling the menace of EDCs has been outlaid. This review will shed light on sources of EDCs, their impact, significance, and the different remediation and bioremediation approaches, with a special emphasis on the recent trends and perspectives in using sustainable approaches for bioremediation of EDCs. Strict regulations to prevent the release of estrogenic chemicals to the ecosystem, adoption of combinatorial methods to remove EDC and prevalent use of bioremediation techniques should be followed in all future endeavors to combat EDC pollution. Moreover, the proper development, growth and functioning of future living forms relies on their non-exposure to EDCs, thus remediation of such chemicals present even in nano-concentrations should be addressed gravely.

Role of microbes in bioaccumulation of heavy metals in municipal solid waste: Impacts on plant and human being

The presence of heavy metals in municipal solid waste (MSW) is considered as prevalent global pollutants that cause serious risks to the environment and living organisms. Due to industrial and anthropogenic activities, the accumulation of heavy metals in the environmental matrices is increasing alarmingly. MSW causes several adverse environmental impacts, including greenhouse gas (GHG) emissions, river plastic accumulation, and other environmental pollution. Indigenous microorganisms (Pseudomonas, Flavobacterium, Bacillus, Nitrosomonas, etc.) with the help of new pathways and metabolic channels can offer the potential approaches for the treatment of pollutants. Microorganisms, that exhibit the ability of bioaccumulation and sequestration of metal ions in their intracellular spaces, can be utilized further for the cellular processes like enzyme signaling, catalysis, stabilizing charges on biomolecules, etc. Microbiological techniques for the treatment and remediation of heavy metals provide a new prospects for MSW management. This review provides the key insights on profiling of heavy metals in MSW, tolerance of microorganisms, and application of indigenous microorganisms in bioremediation. The literatures revealed that indigenous microbes can be exploited as potential agents for bioremediation.

Petroleum-contaminated soil: environmental occurrence and remediation strategies

Soil is an environmental matrix that carries life for all living things. With the rise of human activities and the acceleration of population, the soil has been exposed in part to pollution by the discharge of various xenobiotics and persistent pollutants into it. The disposal of toxic substances such as polycyclic aromatic hydrocarbons (PAHs) alters soil properties, affects microbial biodiversity, and damages objects. Considering the mutagenicity, carcinogenicity, and toxicity of petroleum hydrocarbons, the restoration and clean-up of PAH-polluted sites represents an important technological and environmental challenge for sustainable growth and development. Though several treatment methods to remediate PAH-polluted soils exist, interesting bacteria, fungi, and their enzymes receive considerable attention. The aim of the present review is to discuss PAHs' impact on soil properties. Also, this review illustrates physicochemical and biological remediation strategies for treating PAH-contaminated soil. The degradation pathways and contributing factors of microbial PAH-degradation are elucidated. This review also assesses the use of conventional microbial remediation compared to the application of genetically engineered microorganisms (GEM) that can provide a cost-effective and eco-friendly PAH-bioremediation strategy.

Tyrosinase-functionalized polyhydroxyalkanoate bio-beads as a novel biocatalyst for degradation of bisphenol analogues

Bisphenol compounds are emerging contaminants of high concerns with known endocrine-disrupting effects. Biocatalysis provides a green chemistry alternative for advanced treatment in water reclamation. This study createda novel biocatalyst through genetically immobilizing the Bacillus megaterium tyrosinase enzyme (BmTyr) on the surface ofself-assembled polyhydroxyalkanoate (PHA) biopolymer beads (termed PHA-BmTyr) by using synthetic biology techniques and demonstrated one-pot in vivo production of the biocatalyst for effective degradation and detoxification of various bisphenol analogues for the first time. The degradation pathway of bisphenols was determined to be mediated by the monophenolase and diphenolase activity of BmTyr. Notably, biocatalytic bisphenol degradation by PHA-BmTyr could substantially reduce or eliminate estrogenic activity of the contaminants, and the degradation products had remarkably lower acute and chronic toxicity than their parent compounds. Furthermore, the PHA-BmTyr biocatalyst had high reusability for multiple bisphenol degradation reaction cycles and showed excellent stability that retained 100% and 86.6% of the initial activity when stored at 4 °C and room temperature, respectively for 30 days. Also, the PHA-BmTyr biocatalyst could efficiently degrade bisphenol analogues in real wastewater effluent matrix. This study provides a promising approach to develop innovative biocatalysis technologies for sustainable water reclamation.

Green remediation potential of immobilized oxidoreductases to treat halo-organic pollutants persist in wastewater and soil matrices - A way forward

The alarming presence of hazardous halo-organic pollutants in wastewater and soils generated by industrial growth, pharmaceutical and agricultural activities is a major environmental concern that has drawn the attention of scientists. Unfortunately, the application of conventional technologies within hazardous materials remediation processes has radically failed due to their high cost and ineffectiveness. Consequently, the design of innovative and sustainable techniques to remove halo-organic contaminants from wastewater and soils is crucial. Altogether, these aspects have led to the search for safe and efficient alternatives for the treatment of contaminated matrices. In fact, over the last decades, the efficacy of immobilized oxidoreductases has been explored to achieve the removal of halo-organic pollutants from diverse tainted media. Several reports have indicated that these enzymatic constructs possess unique properties, such as high removal rates, improved stability, and excellent reusability, making them promising candidates for green remediation processes. Hence, in this current review, we present an insight of green remediation approaches based on the use of immobilized constructs of phenoloxidases (e.g., laccase and tyrosinase) and peroxidases (e.g., horseradish peroxidase, chloroperoxidase, and manganese peroxidase) for sustainable decontamination of wastewater and soil matrices from halo-organic pollutants, including 2,4-dichlorophenol, 4-chlorophenol, diclofenac, 2-chlorophenol, 2,4,6-trichlorophenol, among others.

Overview of a bioremediation tool: organophosphorus hydrolase and its significant application in the food, environmental, and therapy fields

In the past decades, the organophosphorus compounds had been widely used in the environment and food industries as pesticides. Owing to the life-threatening and long-lasting problems of organophosphorus insecticide (OPs), an effective detection and removal of OPs have garnered growing attention both in the scientific and practical fields in recent years. Bacterial organophosphorus hydrolases (OPHs) have been extensively studied due to their high specific activity against OPs. OPH could efficiently hydrolyze a broad range of substrates both including the OP pesticides and some nerve agents, suggesting a great potential for the remediation of OPs. In this review, the microbial identification, molecular modification, and practical application of OPHs were comprehensively discussed.Key points• Microbial OPH is a significant bioremediation tool against OPs.• Identification and molecular modification of OPH was discussed in detail.• The applications of OPH in food, environmental, and therapy fields are presented.

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.

Elucidating fungal Rigidoporus species FMD21 lignin-modifying enzyme genes and 2,3,7,8-tetrachlorodibenzo-p-dioxin degradation by laccase isozymes

White-rot fungus Rigidoporus sp. FMD21 is a lignin-modifying enzyme producing fungus that can degrade dioxin. Extracellular enzymes from FMD21 include laccase and manganese peroxidase which are promising enzymes for myco-remediation because of their wide substrate specificity and mild catalysis conditions. The FMD21 genome was sequenced using Ion Torrent technology and consists of 38.98 Mbps with a GC content of 47.4 %. Gene prediction using Augustus with Basidiomycota reference setting resulted in 8245 genes. Functional gene annotations were carried out by using several programs and databases. We focused on laccase and ligninolytic peroxidase genes, which are most likely involved in the degradation of aromatic pollutants. The genome of FMD21 contains 12 predicted laccase genes (10 out of 12 predicted as full length) and 13 putative ligninolytic peroxidases which were annotated as MnP or versatile peroxidases. Four predicted laccases showed a higher than 65 % binding chance to 2,3,7,8-TCDD with the highest at 72 % in in silico docking analysis. Heterologous expressed laccases showed activity towards three tested substrates included ABTS, guaiacol and 2,6-DMP. ABTS displayed two-stage oxidation which differed from natural FMD21 laccases. 2,3,7,8-TCDD was degraded by 50 % after two weeks of enzymatic treatment by three out of five laccase isozymes which were natural laccases secreted by FMD21. In this study, we provide direct evidence for the 2,3,7,8-TCDD biodegradation capability of fungal laccases.

Recent environmental applications of and development prospects for immobilized laccase: a review

Laccases have enormous potential as promising 'green' biocatalysts in environmental applications including wastewater treatment and polluted soil bioremediation. The catalytic oxidation reaction they perform uses only molecular oxygen without other cofactors, and the only product after the reaction is water. The immobilization of laccase offers several improvements such as protected activity and enhanced stability over free laccase. In addition, the reusability of immobilized laccase is adistinct advantage for future applications. This review covers the sources of and progress in laccase research, and discusses the different methodologies of laccase immobilization that have emerged in the recent 5-10 years, as well as its applications to environmental fields, and evaluates these emerging technologies. Abbreviations: (2,4,6-TCP): 2,4,6-trichlorophenol; (2,4-DCP): 2,4-dichlorophenol; (ABTS), 2,2-azinobis (3-ethylbenzothiazoline-6-sulfonic acid); (ACE), acetaminophen; (BC-AS), almond shell; (BC-PM), pig manure; (BC-PW), pine wood; (BPA), bisphenol A; (BPA), bisphenol A; (BPF), bisphenol F; (BPS), bisphenol S; (C₆₀), fullerene; (Ca-AIL), calcium-alginate immobilized laccase; (CBZ), carbamazepine; (CETY), cetirizine; (CHT-PGMA-PEI-Cu (II) NPs), Cu (II)-chelated chitosan nanoparticles; (CLEAs), cross-linked enzyme aggregates; (CMMC), carbon-based mesoporous magnetic composites; (COD), chemical oxygen demand; (CPH), ciprofloxacin hydrochloride; (CS), chitosan; (CTC), chlortetracycline; (Cu-AIL), copper-alginate immobilized laccase; (DBR K-4BL), Drimarene brilliant red K-4BL; (DCF), diclofenac; (E1),estrone; (E2), 17 β-estradiol; (EDC), 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride; (EDCs), endocrine disrupting chemicals; (EE2), 17α-ethinylestradiol; (EFMs), electrospun fibrous membranes; (FL), free laccase; (fsMP), fumed silica microparticles; (GA-CBs), GLU-crosslinked chitosan beads; (GA-CBs), glutaraldehyde-crosslinked chitosan beads; (GA-Zr-MOF), graphene aerogel-zirconium-metal organic framework; (GLU), glutaraldehyde; (GO), graphene oxide; (HMCs), hollow mesoporous carbon spheres; (HPEI/PES), hyperbranched polyethyleneimine/polyether sulfone; (IC), indigo carmine; (IL), immobilized laccase; (k_cat), catalytic constant; (K_m), Michealis constant; (M-CLEAs), Magnetic cross-linked enzyme aggregates; (MMSNPs-CPTS-IDA-Cu²⁺), Cu²⁺-chelated magnetic mesoporous silica nanoparticles; (MSS), magnetic mesoporous silica spheres; (MWNTs), multi-walled carbon nanotubes; (MWNTs), multi-walled carbon nanotubes; (NHS), N-hydroxy succinimide; (O-MWNTs), oxidized-MWNTs; (P(AAm-NIPA)), poly(acrylamide-N-isopropylacrylamide); (p(GMA)), poly(glycidyl methacrylate); (p(HEMA)), poly(hydroxyethyl methacrylate); (p(HEMA-g-GMA)-NH₂, poly(glycidyl methacrylate) brush grafted poly(hydroxyethyl methacrylate); (PA6/CHIT), polyamide 6/chitosan; (PAC), powdered active carbon; (PAHs), polycyclic aromatic hydrocarbons; (PAM-CTS), chitosan grafted polyacrylamide hydrogel; (PAN/MMT/GO), polyacrylonitrile/montmorillonite/graphene oxide; (PAN/PVdF), polyacrylonitrile/polyvinylidene fluoride; (PEG), poly ethylene glycol; (PEI), Poly(ethyleneimine); (poly(4-VP)), poly(4-vinyl pyridine); (poly(GMA-MAA)), poly(glycidyl methacrylate-methacrylic acid); (PVA), polyvinyl alcohol; (RBBR), Remazol Brilliant Blue R; (SDE), simulated dye effluent; (semi-IPNs), semi-interpenetrating polymer networks; (TC), tetracycline; (TCH), tetracycline hydrochloride; (TCS), triclosan; (Vmax), maximum activity; (Zr-MOF, MMU), micro-mesoporous Zr-metal organic framework.

Biochemical characterization of NADH:FMN oxidoreductase HcbA3 from Nocardioides sp. PD653 in catalyzing aerobic HCB dechlorination

Nocardioides sp. PD653 genes hcbA1, hcbA2, and hcbA3 encode enzymes that catalyze the oxidative dehalogenation of hexachlorobenzene (HCB), which is one of the most recalcitrant persistent organic pollutants (POPs). In this study, HcbA1, HcbA2, and HcbA3 were heterologously expressed and characterized. Among the flavin species tested, HcbA3 showed the highest affinity for FMN with a K _d value of 0.75±0.17 µM. Kinetic assays revealed that HcbA3 followed a ping-pong bi-bi mechanism for the reduction of flavins. The K _m for NADH and FMN was 51.66±11.58 µM and 4.43±0.69 µM, respectively. For both NADH and FMN, the V _max and k _cat were 2.21±0.86 µM and 66.74±5.91 sec^-1, respectively. We also successfully reconstituted the oxidative dehalogenase reaction in vitro, which consisted of HcbA1, HcbA3, FMN, and NADH, suggesting that HcbA3 may be the partner reductase component for HcbA1 in Nocardioides sp. PD653.

The crucial role of bacterial laccases in the bioremediation of petroleum hydrocarbons

Laccases (EC 1.10.3.2) are a class of metallo-oxidases found in a variety of fungi, plants, and bacteria as well as in certain insects. They can oxidize a wide variety of organic compounds and can be widely applied in many fields, especially in the field of biodegradation and detoxification of environmental pollutants. The practical efficacy of laccases depends on their ability to capture the target substance as well as their catalytic activity, which is related to their catalytic center, substrate selectivity, and substrate tolerance. Over the past few decades, many laccases have been identified in plants and fungi. Concurrently, bacterial laccases have received increasing attention because of their high thermostability and high tolerance to organic compounds. The aim of this review is to summarize the role of bacterial laccases in the bioremediation of petroleum hydrocarbons and to outline the correlation between the molecular structure of the mononuclear T1 Cu center of bacterial laccases and their substrate preference.

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.

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.

Peroxidases from an invasive Mesquite species for management and restoration of fertility of phenolic-contaminated soil

Phenolics drive the global economy, but they also pose threats to soil health and plant growth. Enzymes like peroxidase have the potential to remove the phenolic contaminants from the wastewater; however, their role in restoring soil health and improving plant growth has not yet been ascertained. We fractionated efficient peroxidases (MPx) from leaves of an invasive species of Mesquite, Prosopis juliflora, and demonstrated its superiority over horseradish peroxidase (HRP) in remediating phenol, 3-chlorophenol (3-CP), and a mixture of chlorophenols (CP-M), from contaminated soil. MPx removes phenolics over a broader range of pH (2.0-9.0) as compared with HRP (pH: 7.0-8.0). In soil, replacing H₂O₂ with CaO₂ further increases the phenolic removal efficiency of MPx (≥90% of phenol, ≥ 70% of 3-CP, and ≥90% of CP-M). MPx maintains ~4-fold higher phenolic removal efficiency than purified HRP even in soils with extremely high contaminant concentration (2 g phenolics/kg of soil), which is desirable for environmental applications of enzymes for remediation. MPx treatment restores soil biological processes as evident by key enzymes of soil fertility viz. Acid- and alkaline-phosphatases, urease, and soil dehydrogenase, and improves potential biochemical fertility index of soil contaminated with phenolics. MPx treatment also assists the Vigna mungo test plant to overcome toxicant stress and grow healthy in contaminated soils. Optimization of MPx for application in the field environment would help both in the restoration of phenolic-contaminated soils and the management of invasive Mesquite.

Overview of bioremediation with technology assessment and emphasis on fungal bioremediation of oil contaminated soils

Environmental contamination is a problem that requires sustainable solutions. Bioremediation technologies have been developed in the last decades and are increasingly used to mitigate environmental accidents and systematic contaminations. A review of bioremediation technologies, based on published article and patent documents, is presented for different types of contaminated matrices, bioremediation agents and contaminants. The worldwide database of the European Patent Office was searched using radicals of keyword as well as the International Patent Classification (IPC) to identify patents in our areas of concern. Technological domains, annual filing volume, legal status, assignee countries and development collaborations are presented and examples are discussed. The total number of patents is compared with the total number of articles. A SWOT analysis for bioremediation technologies is presented. The technologies for water (53%), soils (36%), and sludges (11%) are growing yearly at nearly constant rates. The bioremediation agents are predominantly bacteria (57%), enzymes (19%), fungi (13%), algae (6%), plants (4%) and protozoa. The major contaminants are oils (38%), followed by metals (21%), organic waste (21%), polymers (10%), food (5%), cellulose (5%) and biodiesel. Most of the patents are generally originated from China and United States of America. The soils bioremediation technology of oil is centered on bacteria usage (about two thirds of the articles and patents), being fungi a technology with critical mass and high growth potential. A recent trend in oil bioremediation of soils is the combination of bioremediation agents (fungi and bacteria) in the same process, thus making the process more robust to environment changes.

Degradation and defluorination of 6:2 fluorotelomer sulfonamidoalkyl betaine and 6:2 fluorotelomer sulfonate by Gordonia sp. strain NB4-1Y under sulfur-limiting conditions

6:2 fluorotelomer sulfonamidoalkyl betaine (6:2 FTAB) is a major component of aqueous film-forming foams (AFFFs) used for firefighting and is frequently detected, along with one of its suspected transformation products, 6:2 fluorotelomer sulfonate (6:2 FTSA), in terrestrial and aquatic ecosystems impacted by AFFF usage. Biochemical processes underlying bacterial biodegradation of these compounds remain poorly understood due to a lack of pure culture studies. Here, we characterized the water-soluble and volatile breakdown products of 6:2 FTSA and 6:2 FTAB produced using Gordonia sp. strain NB4-1Y cultures over seven days under sulfur-limited conditions. After 168 h, 99.9% of 60 μM 6:2 FTSA was degraded into ten major breakdown products, with a mol% recovery of 88.2, while 70.4% of 60 μM 6:2 FTAB was degraded into ten major breakdown products, with a mol% recovery of 84.7. NB4-1Y uses two pathways for 6:2 FTSA metabolism, with 55 mol% of breakdown products assigned to a major pathway and <1.0 mol% assigned to a minor pathway. This work indicates that rapid transformation of 6:2 FTSA and 6:2 FTAB can be achieved under controlled conditions and improves the bacterial metabolism of these compounds.

Oxidoreductases for the remediation of organic pollutants in water - a critical review

Water contamination by various recalcitrant organic aromatic compounds is an emerging environmental issue that is increasingly attracting the attention of environmental scientists. A great majority of these recalcitrant pollutants are industrial wastes, textile dyes, pharmaceuticals, hormones, and personal care products that are discharged into wastewater. Not surprisingly, various chemical, physical, and biological strategies have been proposed and developed to remove and/or degrade these pollutants from contaminated water bodies. Biological approaches, specifically using oxidoreductase enzymes (such as peroxidases and laccases) for pollutant degradation are a relatively new and a promising research area that has potential advantages over other methods due to their higher efficiency and the ease of handling. This review focuses on the application of different classes of oxidoreductase enzymes to degrade various classes of organic pollutants. In addition to classifying these enzymes based on structural differences, the major factors that can affect their remediation ability, such as the class of peroxidases employed, pH, molecular structure of the pollutant, temperature, and the presence of redox mediators are also examined and discussed. Interestingly, a literature survey combined with our unpublished data suggests that "peroxidases" are a very heterogeneous and diverse family of enzymes and have different pH profiles, temperature optima, thermal stabilities, requirements for redox mediators, and substrate specificities as well as varying detoxification abilities. Additionally, remediation of real-life polluted samples by oxidoreductases is also highlighted as well as a critical look at current challenges and future perspectives.

Bulk isolation of basidiospores from wild mushrooms by electrostatic attraction with low risk of microbial contaminations

The basidiospores of most Agaricomycetes are ballistospores. They are propelled off from their basidia at maturity when Buller's drop develops at high humidity at the hilar spore appendix and fuses with a liquid film formed on the adaxial side of the spore. Spores are catapulted into the free air space between hymenia and fall then out of the mushroom's cap by gravity. Here we show for 66 different species that ballistospores from mushrooms can be attracted against gravity to electrostatic charged plastic surfaces. Charges on basidiospores can influence this effect. We used this feature to selectively collect basidiospores in sterile plastic Petri-dish lids from mushrooms which were positioned upside-down onto wet paper tissues for spore release into the air. Bulks of 10⁴ to >10⁷ spores were obtained overnight in the plastic lids above the reversed fruiting bodies, between 10⁴ and 10⁶ spores already after 2-4 h incubation. In plating tests on agar medium, we rarely observed in the harvested spore solutions contaminations by other fungi (mostly none to up to in 10% of samples in different test series) and infrequently by bacteria (in between 0 and 22% of samples of test series) which could mostly be suppressed by bactericides. We thus show that it is possible to obtain clean basidiospore samples from wild mushrooms. The technique of spore collection through electrostatic attraction in plastic lids is applicable to fresh lamellate and poroid fruiting bodies from the wild, to short-lived deliquescent mushrooms, to older and dehydrating fleshy fruiting bodies, even to animal-infested mushrooms and also to dry specimens of long-lasting tough species such as Schizophyllum commune.

Optimization of the Use of His₆-OPH-Based Enzymatic Biocatalysts for the Destruction of Chlorpyrifos in Soil

Applying enzymatic biocatalysts based on hexahistidine-containing organophosphorus hydrolase (His₆-OPH) is suggested for the decomposition of chlorpyrifos, which is actively used in agriculture in many countries. The application conditions were optimized and the following techniques was suggested to ensure the highest efficiency of the enzyme: first, the soil is alkalinized with hydrated calcitic lime Ca(OH)₂, then the enzyme is introduced into the soil at a concentration of 1000 U/kg soil. Non-equilibrium low temperature plasma (NELTP)-modified zeolite is used for immobilization of the relatively inexpensive polyelectrolyte complexes containing the enzyme His₆-OPH and a polyanionic polymer: poly-l-glutamic acid (PLE₅₀) or poly-l-aspartic acid (PLD₅₀). The soil’s humidity is then increased up to 60–80%, the top layer (10–30 cm) of soil is thoroughly stirred, and then exposed for 48–72 h. The suggested approach ensures 100% destruction of the pesticide within 72 h in soils containing as much as 100 mg/kg of chlorpyrifos. It was concluded that using this type of His₆-OPH-based enzyme chemical can be the best approach for soils with relatively low humus concentrations, such as sandy and loam-sandy chestnut soils, as well as types of soil with increased alkalinity (pH 8.0–8.4). Such soils are often encountered in desert, desert-steppe, foothills, and subtropical regions where chlorpyrifos is actively used.

Comparison of landfarming amendments to improve bioremediation of petroleum hydrocarbons in Niger Delta soils

Large scale landfarming experiments, using an extensive range of treatments, were conducted in the Niger-Delta, Nigeria to study the degradation of oil in contaminated soils. In this work the effect of nutrient addition, biosurfactant, Eisenia fetida (earthworm) enzyme extract, bulking and sorption agents and soil neutralization were tested. It was found that these treatments were successful in removing up to 53% of the total petroleum hydrocarbon in the soil within 16 weeks. A comparison between treatments demonstrated that most were no more effective than agricultural fertilizer addition alone. One strategy that did show better performance was a combination of nutrients, biochar and biosurfactant, which was found to remove 23% more Total Petroleum Hydrocarbons (TPH) than fertilizer alone. However, when performance normalized costs were considered, this treatment became less attractive as a remedial option. Based on this same analysis it was concluded that fertilizer only was the most cost effective treatment. As a consequence, it is recommended that fertilizer is used to enhance the landfarming of hydrocarbon contaminated soils in the Niger Delta. The attenuation rates of both bulk TPH and Total Petroleum Hydrocarbon Criteria Working Group (TPHCWG) fractions are also provided. These values represent one of the first large scale and scientifically tested datasets for treatment of contaminated soil in the Niger Delta region. An inverse correlation between attenuation rates and hydrocarbon molecular weight was observed with heavy fractions showing much slower degradation rates than lighter fractions. Despite this difference, the bioremediation process resulted in significant removal of all TPH compounds independent of carbon number.

Biotechnological Advances for Restoring Degraded Land for Sustainable Development

Global land resources are under severe threat due to pollution and unsustainable land use practices. Restoring degraded land is imperative for regaining ecosystem services, such as biodiversity maintenance and nutrient and water cycling, and to meet the food, feed, fuel, and fibre requirements of present and future generations. While bioremediation is acknowledged as a promising technology for restoring polluted and degraded lands, its field potential is limited for various reasons. However, recent biotechnological advancements, including producing efficient microbial consortia, applying enzymes with higher degrees of specificity, and designing plants with specific microbial partners, are opening new prospects in remediation technology. This review provides insights into such promising ways to harness biotechnology as ecofriendly methods for remediation and restoration.