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Arsenic (As) hyperaccumulator Pteris ferns are renowned for their capacity to accumulate As and have been used to remediate As-contaminated environmental. However, there is less information on how ...

Microorganisms form strong communities known as biofilms, which are ubiquitous in both natural and artificial environments and lead to problems such as health hazards and energy loss. The most effective solution against biofouling is to prevent the initial adhesion of the microbial cells to the material surface. This paper reports the fabrication of slippery liquid-infused porous surfaces (SLIPSs) through a simple method and the antibiofouling properties of these surfaces against microorganisms. The principle of these surfaces is inspired by Nepenthes, which are pitcher plants. SLIPSs can be easily and inexpensively generated through the breath figure method and ultrasonic processing. The developed silicon oil-infused substrate exhibited a low fall angle and antifouling characteristics. The results suggest that the proposed simple method can be used to successfully generate an antibiofouling substrate. A microstructured film was fabricated using the breath figure method, and a slippery surface was achieved by infusing silicone oil onto the film. Among the obtained samples, oil-supported pincushion films (oPCF) most efficiently prevented water droplets and microorganisms from adhering to the surfaces. In addition, the adhesion of E. coli and B. subtilis to oPCF was reduced to 7.1 and 13% of that pertaining to PTFE, respectively. These results suggest that our efficient antifouling substrate can ensure human health and environmental safety without the use of any toxic compounds.

Microbial consortia-mediated biodegradation of 1,4-dioxane (1,4-D), an emerging water contaminant, is always a superior choice over axenic cultures. Thus, better understanding of the functions of coexisting microbes and their interspecies interactions within the consortia is crucial for predicting biodegradation efficiency and designing efficient 1,4-D-degrading microbial consortia. This study evaluated how microbial community compositions and interspecies interactions govern the microbial consortia-mediated 1,4-D biodegradation by investigating the biodegradability and microbial community dynamics of both enriched (N112) and synthetic (SCDs and SCDNs) microbial consortia in the absence or presence of additional organic compound (AOC). In the absence of AOC, N112 exhibited 100% 1,4-D biodegradation efficiency at a rate of 12.5 mg/L/d, whereas the co-occurrence of AOC resulted in substrate-dependent biodegradation inhibition and thereby reduced the biodegradation efficiency and activity (2.0-10.0 mg/L/d). The coexistence and negative influence of certain low-abundant non-degraders on both 1,4-D-degraders and key non-degraders in N112 was identified as the prime cause behind such biodegradation inhibition. Comparing with N112, SCDN-1 composed of 1,4-D-degraders and key non-degraders significantly improved the 1,4-D biodegradation efficiency in the presence of AOC, confirming the absence of negative influence of low-abundant non-degraders and cooperative interactions between 1,4-D-degraders and key non-degraders in SCDN-1. On the contrary, both two-species and three-species SCDs comprised of only 1,4-D-degraders resulted in lower 1,4-D biodegradation efficiency as compared to SCDN-1 under all treatment conditions, while max. 91% 1,4-D biodegradation occurred by SCDs in the absence of AOC. These results were attributed to the negative interaction among 1,4-D-degraders and the absence of complementary roles of key non-degraders in SCDs. The findings improve our understanding of how interspecies interactions can regulate the intrinsic abilities and functions of coexisting microbes during biodegradation in complex environments and provide valuable guidelines for designing highly efficient and robust microbial consortia for practical bioremediation of 1,4-D like emerging organic contaminants.

Arsenic (As) is a toxic semi-metallic element that is ubiquitous in the environment and poses serious human health risks. Phytoextraction by Pteris vittata is considered a low-cost and environmentally friendly approach to treat As-contaminated soil. P. vittata mainly absorbs arsenate thus the bioavailability of As to P. vittata depends on the chemical form of As. Microbial redox of As contributes to the biogeochemical cycling of As, and rhizobacterium-assisted phytoextraction by P. vittata was proposed. In this study, this microbe-assisted phytoextraction was applied to two fields, and the effectiveness of phytoextraction was evaluated. The results revealed that P. vittata was able to grow in temperate and subarctic climate zones. The biomass was influenced by the weather, and the As concentration in plants was dependent on the As content in the soil. The ratio of arsenite oxidase genes (aioA-like genes) to 16S rRNA genes was employed to evaluate the effect of As phytoextraction, and the results exhibited that the ratio was related to the As concentration in P. vittata. Our results showed that arsenite oxidation in the rhizosphere might not be achieved by single-strain inoculation, while this study provided empirical evidence that the rhizospheric aioA-like genes could be an indicator for evaluating the effectiveness of As phytoextraction.

Arsenic (As) is a toxic semi-metallic element that is ubiquitous in the environment and poses serious human health risks. Phytoextraction by

Using plants as bioremediation agents are rising worldwide as an environmentally friendly tool to remove contaminants such as heavy metals. Arabidopsis halleri ssp. gemmifera is able to hyperaccumulate Cd/Zn, however, the commonality between Cd/Zn accumulation pathways are still vague. This study focused on HMA4 and IRT3 as indicators and investigated their transcription in A. halleri ssp. gemmifera under Cd/Zn treatments. In addition to the known Cd/Zn xylem loading functions in roots, HMA4 showed a potential role in Cd/Zn redistribution or metal efflux from the vascular bundle in leaves due to increased transcription by 3-fold after 7 d under all treatments. On the other hand, IRT3 as a Zn homeostasis gene was expressed continuously in both roots and leaves under single Cd or Zn treatment. However, IRT3 transcription in leaves plunged to 50-fold lower under combined Cd and Zn treatment. The result indicated an increase of intracellular free Zn ion, implying a new unreported mechanism of Zn homeostasis in leaves under the presence of both metals. Furthermore, no competition between Cd/Zn uptake and accumulation suggested the existence of independent transport system for Cd and Zn in A. halleri ssp. gemmifera, which is differed from what have been reported until now.

In this study, the phytoremediation potential of tropical and subtropical arsenic (As) hyperaccumulating fern Pteris vittata in an As contaminated farmland field near an abandoned goldmine was investigated. The tested field is located in a subarctic area of northeast Japan. This study was aimed at decreasing the risk of As in the soil (water-soluble As) with nurturing the soil and respecting the plant life cycle for the sustainable phytoremediation for 8 years. The field was tilled and planted with new seedlings of the fern every spring and the grown fern was harvested every autumn. The biomass and As concentration in fronds, rhizomes and roots of the fern were analyzed separately after harvesting each year. The biomass of the fronds of P. vittata was significantly affected by the yearly change of the weather condition, but As concentration in fronds was kept at 100-150 mg/kg dry weight. The accumulated As in P. vittata was higher than that of As-hyperaccumulator fern Pteris cretica, the native fern in the field trial area. Harvested biomass of P. vittata per plant was also higher than that of P. cretica. More than 43.5 g As/154 m

Pteris vittata is an arsenic (As) hyperaccumulator plant that accumulates a large amount of As into fronds and rhizomes (around 16,000 mg/kg in both after 16 weeks hydroponic cultivation with 30 mg/L arsenate). However, the sequence of long-distance transport of As in this hyperaccumulator plant is unclear. In this study, we used a positron-emitting tracer imaging system (PETIS) for the first time to obtain noninvasive serial images of As behavior in living plants with positron-emitting 74As-labeled tracer. We found that As kept accumulating in rhizomes as in fronds of P. vittata, whereas As was retained in roots of a non-accumulator plant Arabidopsis thaliana. Autoradiograph results of As distribution in P. vittata showed that with low As exposure, As was predominantly accumulated in young fronds and the midrib and rachis of mature fronds. Under high As exposure, As accumulation shifted from young fronds to mature fronds, especially in the margin of pinna, which resulted in necrotic symptoms, turning the marginal color to gray and then brown. Our results indicated that the function of rhizomes in P. vittata was As accumulation and the regulation of As translocation to the mature fronds to protect the young fronds under high As exposure.

Grasses are advantageous in the removal of polycyclic aromatic hydrocarbons (PAHs) in soil because of their fibrous root, high tolerance to environmental stress, and low nutritional requirements. In this study, a pot experiment was conducted to test the ability of four grasses to remove PAHs in the soil, and to investigate the corresponding bacterial community shift in the rhizosphere of each. Sudangrass achieved the maximum removal of PAHs at 98% dissipation rate after 20 days. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and next-generation sequencing revealed that sudangrass specially enriched the growth of a known PAHs degrader, Sphingomonadales, regardless of the presence or absence of PAHs in the soil. Moreover, the gene copy numbers of PAHs catabolic genes, PAH-RHDα and nidA, as measured by real time-PCR (RT-PCR) were highest in the soil planted with sudangrass. Overall, this study suggested that sudangrass further enhanced the dissipation of PAHs by enriching Sphingomonadales in its rhizosphere.

Selected cathodes, including carbon paper (C) and plates of titanium (Ti), iron (Fe), copper (Cu) and aluminum (Al), combined with a Ti/PbO2 anode (a lead dioxide electrodeposited on titanium plate) were employed for studying quick nitrate removal from neutral water in this work. Cathode materials, current densities and the presence of chloride ions (Cl−) in water were investigated as to the effects on nitrate removal. Nitrate and two main reduction products, i.e. nitrite and ammonia, were measured using ion chromatography. The results showed that the nitrate removal efficiency decreased in the order of cathode materials: C > Ti ≈ Fe > Cu > Al. The optimum removal was achieved to be 47.7% for a 50 mg-N/L nitrate solution by using carbon paper cathode and Ti/PbO2 anode after 120-min electrolysis with a current density of 40 mA/cm2. The subsequent experimental results showed that the current density of 20 mA/cm2 is also high enough for achieving a considerable nitrate removal. Moreover, the presence of Cl− in water was proven to have no significant effect on nitrate removal but be able to promote the destruction of nitrite and ammonia ions, resulting in the virtual decrease in nitrate and total nitrogen. By a designed experiment, the nitrate removal pathway was confirmed to include a reciprocating reduction (of nitrate) and oxidation (of nitrite and ammonia), both of which can lead to the removal of nitrate as well as total nitrogen from nitrate-containing wastewater by generation of nitrogen. cathodes and anodes may play different roles.

Biodegradation is found to be a promising, cost-effective and eco-friendly option for the treatment of industrial wastewater contaminated by 1,4-dioxane (1,4-D), a highly stable synthetic chemical and probable human carcinogen. This study aimed to isolate, identify, and characterize metabolic 1,4-D-degrading bacteria from a stable 1,4-D-degrading microbial consortium. Three bacterial strains (designated as strains TS28, TS32, and TS43) capable of degrading 1,4-D as a sole carbon and energy source were isolated and identified as Gram-positive Pseudonocardia sp. (TS28) and Gram-negative Dokdonella sp. (TS32) and Afipia sp. (TS43). This study, for the first time, confirmed that the genus Dokdonella is involved in the biodegradation of 1,4-D. The results reveal that all of the isolated strains possess inducible 1,4-D-degrading enzymes and also confirm the presence of a gene encoding tetrahydrofuran/dioxane monooxygenase (thmA/dxmA) belonging to group 5 soluble di-iron monooxygenases (SDIMOs) in both genomic and plasmid DNA of each of the strains, which is possibly responsible for the initial oxidation of 1,4-D. Moreover, the isolated strains showed a broad substrate range and are capable of degrading 1,4-D in the presence of additional substrates, including easy-to-degrade compounds, 1,4-D biodegradation intermediates, structural analogs, and co-contaminants of 1,4-D. This indicates the potential of the isolated strains, especially strain TS32, in removing 1,4-D from contaminated industrial wastewater containing additional organic load. Additionally, the results will help to improve our understanding of how multiple 1,4-D-degraders stably co-exist and interact in the consortium, relying on a single carbon source (1,4-D) in order to develop an efficient biological 1,4-D treatment system.

Bioremediation is one of the promising environment-friendly approaches to eliminate oil contamination. However, heavy oil is known to degrade slowly due to its hydrophobicity. Therefore, microorganisms capable of producing biosurfactants are gaining substantial interest because of their potential to alter hydrocarbon properties and thereby speed up the degradation process. In this study, six bacterial consortia were obtained from the oil-spilled beach areas in Miyagi, Japan, and all of which exhibited high potential in degrading heavy oil measured by gas chromatography with flame ionization detector (GC-FID). The polymerase chain reaction&mdash, denaturing gradient gel electrophoresis (PCR-DGGE) and next-generation sequencing (NGS) revealed that the diverse microbial community in each consortium changed with subculture and became stable with a few effective microorganisms after 15 generations. The total petroleum hydrocarbons (TPH) degradation ability of the consortia obtained from a former gas station (C1: 81%) and oil refinery company (C6: 79%) was higher than that of the consortia obtained from wastewater treatment plant (WWTP) (C3: 67%, and C5: 73%), indicating that bacteria present in C1 and C6 were historically exposed to petroleum hydrocarbons. Moreover, it was intriguing that the consortium C4, also obtained from WWTP, exhibited high TPH degradation ability (77%). The NGS results revealed that two bacteria, Achromobacter sp. and Ochrobactrum sp., occupied more than 99% of the consortium C4, while no Pseudomonas sp. was found in C4, though this bacterium was observed in other consortia and is also known to be a potential candidate for TPH degradation as reported by previous studies. In addition, the consortium C4 showed high biosurfactant-producing ability among the studied consortia. To date, no study has reported the TPH degradation by the combination of Achromobacter sp. and Ochrobactrum sp., therefore, the consortium C4 provided an excellent opportunity to study the interaction of and biosurfactant production by these two bacteria during TPH degradation.

Phytoremediation is a promising inexpensive method of detoxifying arsenic (As) contaminated soils using plants and associated soil microorganisms. The potential of Pteris vittata to hyperaccumulate As contamination has been investigated widely. Since As(V) is efficiently taken up by P. vittata than As(III), As speciation by associated rhizobacteria could offer enormous possibility to enhance As phytoremediation. Specifically, increased rhizobacteria mediated As(III) to As(V) conversion appeared to be a crucial step in As mobilization and translocation. In this study, Pseudomonasvancouverensis strain m318 with the potential to improve As phytoremediation was inoculated to P. vittata in a field trial for three years to evaluate its long-term efficacy and stability for enhancing As phytoextraction. The biomass, As concentration, and As accumulation of ferns showed to be increased by inoculation treatment. Although this trend occasionally declined which may be accounted to lower As concentration in soil and amount of precipitation during experiments, the potential of inoculation was observed in increased enrichment coefficients. Further, the arsenite oxidase (aioA-like) genes in the rhizosphere were detected to evaluate the influence of inoculation on As phytoremediation. The findings of this study suggested the potential application of rhizosphere regulation to improve phytoremediation technologies for As contaminated soils. However, the conditions which set the efficacy of this method could be further optimized.

The increasing contamination of the environment with microplastic requires efficient methods for the separation and detection of these plastic particles. In this work, we present a protocol that uses Fenton oxidation to remove biological material, centrifugation to separate microplastics from soil, and Nile Red staining, fluorescence microscopy, and image processing to detect and quantify of microplastic. The main component of this work was the separation process using centrifugation. All the main polymers used in this work, polyethylene, polypropylene, polystyrene, poly (vinyl chloride), and poly (ethylene terephthalate), were efficiently recovered at more than 94 wt% from heat-altered soil using CaCl2 solution with a density of 1.4 g ml−1. The hydrophilicity of the polymer had a greater effect on the recovery than density. The protocol was then tested on agricultural soil sampled near a contaminated site. The number of microplastic particles was quantified, and the weight of microplastic in the soil was estimated. The highest contamination was observed near the hotspot at a distance of 1 m with 75✕103 particles kg−1, corresponding to a weight between 20 and 6 mg kg−1. The number of particles decreased logarithmically to 30✕103 particles kg−1 or 5 to 2 mg kg−1.

The main threats to the environment from heavy metals are associated with arsenic (As), lead (Pb) and cadmium (Cd). In this study, the potential of Pteris multifida for removing As, Pb and Cd from hydroponic solution and pot soil was evaluated for the first time. Short-term (5 day) experiments were conducted to assess phytofiltration efficiency of temperate zone fern P. multifida and to compare it with mostly studied tropical zone fern P. vittata. Within 5 days, P. multifida accumulated 33% of As(III), whereas P. vittata could not accumulate that most toxic arsenic species As(III) at all. Long-term hydroponic results showed that 90% of Pb, 50% of As and 36% of Cd were removed by P. multifida. Concentration of As in the frond (22 mg/kg dw) was comparatively higher than other parts of plant and significantly higher concentration of Cd and Pb were stored in root and rhizome. Pot soil experiment of P multifida confirmed the comparative uptake and translocation of As(V), Pb and Cd from soil. Therefore, from the assessment of heavy metal accumulation capacity, translocation and healthy survival for long time, P. multifida was identified as an excellent species for the treatment of multi-metal contaminated water and soil.

The depletion of rare metals is an issue of major concern since rare metals are limited in the abundance but essential for high technology industry. However, the present rare metal recovery technical by chemical methods has high environmental impact, poor selectivity, and is too expensive to be practical. To resolve these problems, this study aimed to create a rare metal recover system using yeast, and molybdenum was selected as the first target. A molybdenum binding protein, ModE, which was derived from Escherichia coli was selected. A fusion gene was generated by linking partial modE with a secretion signal and a domain of α-agglutinin to display the ModE on the surface of yeast cells. The expression of fusion protein on the cell surface was detected by immunofluorescence labeling. As for the recovery experiment, the engineered yeast cells were incubated in 10 mM of sodium molybdate solution for 2 h, and the recovery of molybdenum ion was measured by ICP-AES. The results of fluorescence micrographs showed that the designed fusion protein was successfully expressed on yeast cell surface. According to the results of ICP-AES, the cell surface engineered yeast adsorbed molybdenum and the cells after 72~84 h incubation gave the best adsorption. Besides, the results suggested that the optimization of each functional domain in the fusion protein was important. The selectivity and the lower limit of recoverable concentration are under investigation, while this study provides a preliminary result of bio-extraction technology using cell surface engineered yeast.

A critical bottleneck associated with bioremediation technology in multi-polluted environments is microbiostasis due to metal toxicity. Autochthonous Bacillus species that would harness a repertory of traits to catabolize hydrocarbons and simultaneously sequester heavy metals (HMs) is invaluable in the environment contaminated with divergent pollutants. Fourteen HM-resistant bacilli from polluted creek were characterized using phenotypic and molecular criteria, and studied for hydrocarbon degradation in chemically defined media amended with Co2+ and Ni2+ (5.0 mmol l−1 each). Phylogenetic analyses revealed distribution of the bacilli into three clades. Two dissimilar strains of Bacillus subtilis (M16K, and M19F) with 19.1% sequence divergence, exhibited excellent degradation of crude oil (>94.0%) with evidence of early degradation of isoprenoid hydrocarbons and concurrent metal removal 18 d post-inoculation. Similarly, phenanthrene degradation (>85.0%), and corresponding metal detoxification occurred in 28 d axenic culture of the strains. Strain M16K and M19F were metabolically active in matrices containing HMs, degraded hydrocarbons and simultaneously removed HMs from the medium. To the best of our knowledge, this is the first report of metal-resistant Bacillus subtilis strains showing simultaneous degradation of hydrocarbons and detoxification of metals, particularly in the Sub-Saharan Africa. The bacilli could be useful as potential biological agents in effective bioremediation campaign for multi-polluted environments.

Estuaries in the areas prone to anthropogenic activities are exposed to multifarious pollutants. Toxic concentrations of heavy metals do exist with persistent organic compounds in such estuaries prolonging the recalcitrance and ecotoxicological consequences of the chemicals, which impact on the health of the brackish water and by extension, the oceans. The quest for high aesthetic quality of the estuarine environment is gaining attention from global campaign, which requires effective remedial strategies to replace the physical and chemical methods in use that are costly and often leave behind toxic residues in the environment. Contrary to physico-chemical remedial processes, bioremediation strategies are projected as a promising green technology to remove pollutants from the estuarine environment. The concept of bioremediation involves the use of competent biological elements such as microorganisms and plants, along with or without the biomolecules they produced, to ameliorate pollution. Therefore, this paper reviews the various bioremediation technologies that would be applicable to decommissioning estuarine environments polluted with toxic metals and persistent organic compounds.

Biodegradation of 1,4-dioxane, a water contaminant of emerging concern, has drawn substantial attention over the last two decades. A number of dioxane-degraders have been identified, though many of them are unable to metabolically utilize 1,4-dioxane. Moreover, it is considered more preferable to use microbial consortia rather than the pure strains, especially in conventional bioreactors for industrial wastewater treatment. In the present study, a stable 1,4-dioxane-degrading microbial consortium was enriched, namely 112, from industrial wastewater by nitrate mineral salt medium (NMSM). The consortium 112 is capable of utilizing 1,4-dioxane as a sole carbon and energy source, and can completely degrade 1,4-dioxane up to 100 mg/l. From the consortium 112, two 1,4-dioxane-degrading bacterial strains were isolated and identified, in which the Variovorax sp. TS13 was found to be a novel 1,4-dioxane-degrader that can utilize 100 mg/l of 1,4-dioxane. The efficacy of the consortium 112 was increased significantly when we cultured the consortium with mineral salt medium (MSM). The new consortium, N112, could utilize 1,4-dioxane at a rate of 1.67 mg/l&middot, h. The results of the ribosomal RNA intergenic spacer analysis (RISA) depicted that changes in the microbial community structure of consortium 112 was the reason behind the improved degradation efficiency of consortium N112, which was exhibited as a stable and effective microbial consortium with a high potential for bioremediation of the dioxane-impacted sites and contaminated industrial wastewater.

Rhizodegradation of polycyclic aromatic hydrocarbons (PAHs) is a product of complex interactions between plant and bacteria. In this study, hydroponic culture of sudangrass was established in order to investigate the effects of the plant on PAHs degradation and vice versa through changes in rhizosphere bacterial community. Results showed a plant-induced variability in PAHs degradation dependent on a characteristic shift in bacterial community, with pH and plant age as driving factors. Moreover, bacterial communities with high diversity seemed to abate the phytotoxic effects of PAHs degradation as observed in the plant’s gross health. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and next-generation sequencing revealed that regardless of plant age and culture conditions, the increase or decrease of Sphingobium sp. could dictate the PAHs degradation potential of the bacterial consortium. Overall, this study utilized hydroponic culture of sudangrass to show that plant even of same species can suppress, support, or enhance PAHs degradation of bacteria depending on specific factors.

The main threats to the environment from heavy metals are associated with arsenic (As), lead (Pb) and cadmium (Cd). In this study, the potential of

Pteris vittata is the most well-known arsenic (As) hyperaccumulator, while the corresponding mechanism in molecular level is still not clear. In this study, As uptake and transport in P. vittata were demonstrated by time-course analyses under As addition. Then expression of 3 genes (PvPht1;3, a phosphate (P) transporter gene; PvACR2, a AsV reductase gene; PvACR3, a AsIII transport gene) was focused on to examine their contributions on As processing in root of P. vittata. Results of As addition analyses revealed that P. vittata had high-sensitivity to even 10 ppb AsV which was quickly depleted within 6 h, while this high affinity was inhibited when coexisting with P. Analyses to As in the plant showed that in the absence of P, 99 % of the As taken up by roots was reduced to AsIII at 7 d. And 85 % of As transported to rhizomes was present as AsIII, 74 % of the As accumulated in fronds was AsIII. Results of qRT-PCR demonstrated that the transcription of PvPht1;3 was temporally induced by 100 ppb AsV without P, while 500 ppb of AsV made this induction kept through the entire period which showed 3.7-fold higher than control at 7 d. Meanwhile, PvACR2 was only induced slightly (1.15–1.45-fold) by 500 ppb AsV with a time lag, and this induction wasn’t infected by P. PvACR3 was induced by 100 ppb AsV immediately, and the strength was positively related to AsV concentration. Intriguingly, the expression of PvACR3 fitted the AsIII concentration in the root. Our results suggested a collaboration of these three genes in sensitive AsV absorption, constitutive AsV reduction and subsequent AsIII transportation which contributes to As hyperaccumulation by P. vittata.

Molybdenum, a precious metal with important roles in industries, is projected to experience future shortage. Despite this, there is still no practical recycling process of this metal and around 25 thousand tons of molybdenum are discharged into wastewater annually. Biorecovery is a promising approach to resolve the above problem because of its high selectivity, high sensitivity, low running cost and low environmental burden. A bacterial molybdenum binding protein ModE has been constructed into yeast cells and named as ScBp5. In this study, the potential of genetic engineered yeast for recovering molybdenum from wastewater was further investigated. In order to stabilize the expression of ModE, strain ScBp5 was further modified by replacing promoter upstream of modE to generate ScBp6. The improvement of molybdenum adsorption efficiency by ScBp6 was confirmed especially in low concentration. The molybdenum isotherms parameters of ScBp6 was analyzed. To enable the usage as biorecovery agent in industrial settings, ScBp6 cells were immobilized using calcium alginate matrix, and the optimum immobilization conditions for ScBp6 were determined as 2% matrix density, 4 h of immobilization time, and 10 mg/ml cell density. The investigation of molybdenum adsorption kinetics by immobilized ScBp6 cells showed this adsorption was an efficient chemisorption. Overall, this research demonstrate the efficiency of immobilized yeast cell in molybdenum recovery.

Polyolefins are subject to chemical changes when they are brought in contact with the environment. In the presence of UV-radiation and oxygen, photo-oxidation causes chain scission and cross-linking in polyethylene and polypropylene. This review provides a detailed presentation of the reactions that take place and their effects on the properties of polymers. In this review, radical formation and Norrish reactions are discussed in depth, along with the formation of peroxides and carbonyl compounds. More than a dozen different types of carbonyl compounds can be observed by FTIR. While Norrish reactions are the main reason for chain scission and molecular weight reduction, the initial step of the photo-oxidation may be related to the formation of O2-polymer charge transfer complexes. Photo-oxidation takes place mainly in the amorphous region of the polymer, and polymers with a high tertiary-carbon content are more affected than those with straight chains. Chain scission occurs only in the presence of oxygen, whereas cross-linking in the absence of oxygen results in gel formation. Weathering conditions include seasonal changes, and the day-and-night cycle has a strong impact on photo-oxidation. The chemical changes occurring during weathering influence crystallinity and the mechanical properties of polyolefins. Most of the fundamental work in this field was published more than 30 years ago. It is necessary for the results of these early studies to be verified by methodologies developed in recent years.

Pteris vittata and Pteris multifida are widely studied As hyperaccumulators that absorb As mainly via roots. Hence, rhizobacteria exhibit promising potential in phytoextraction owing to their immense microbial diversity and interactions with plants. Pseudomonas vancouverensis strain m318 that contains aioA-like genes was screened from P. multifida’s rhizosphere through the high As resistance (minimum inhibitory concentrations (MICs) against As(III): 16 mM; MICs against As(V): 320 mM), rapid As oxidation (98% oxidation by bacterial cultures (OD600nm = 1) from 200 μL of 0.1 mM As(III) within 24 h), predominant secretion of IAA (12.45 mg L−1) and siderophores (siderophore unit: 88%). Strain m318 showed significant chemotactic response and high colonization efficiency to P. vittata roots, which suggested its wide host affinity. Interestingly, inoculation with strain m318 enhanced the proportion of aioA-like genes in the rhizosphere. And in field trials, inoculation with strain m318 increased As accumulation in P. vittata by 48–146% and in P. multifida by 42–233%. Post-transplantation inoculations also increased As accumulation in both ferns. The abilities of the isolated multifunctional strain m318 and the increase in the rhizosphere microbial aioA-like genes are thus speculated to be involved in As transformation in the rhizospheres and roots of P. vittata and P. multifida.

As a toxic and carcinogenic metalloid, arsenic has posed serious threat to human health. Phytoremediation has emerged as a promising approach to circumvent this problem. Arsenic uptake by Pteris vittata is largely determined by arsenic speciation and mainly occurs via roots; thus, rhizospheric microbial activities may play a key role in arsenic accumulation. The aim of this study was to investigate the potential of arsenic resistant rhizobacteria to enhance arsenic phytoextraction. A total of 49 cultivable rhizobacteria were isolated from the arsenic hyperaccumulating fern, Pteris vittata, and subjected to an initial analysis to identify potentially useful traits for arsenic phytoextraction, such as arsenic resistance and the presence of aioA(aroA)-like (arsenite oxidase-like) gene. Isolated strain r507, named as Cupriavidus basilensis strain r507, was a selected candidate for its outstanding arsenic tolerance, rapid arsenite oxidation ability, and strong colonization to P. vittata. Strain r507 was used in co-cultivation trials with P. vittata in the field for six months. Results showed that the inoculation with strain r507 potentiated As accumulation of P. vittata up to 171%. Molecular analysis confirmed that the inoculation increased the abundance of aioA-like genes in the rhizosphere, which might have facilitated arsenite oxidation and absorption. The findings of this study suggested the feasibility of co-cultivating hyperaccumulators with facilitator bacteria for practical arsenic phytoremediation.

Toxic metals/metalloid contaminations of estuarine sediments due to compromised tributaries arouse significant interest in studying bacterial community that triggers natural attenuation processes. Geo-accumulation index (Igeo), contamination factor (CF), pollution load index (PLI), and Hakanson potential ecological risk index (RI) as a sum of risk factors (Er) were used to quantify toxic metal/metalloid-pollution status of Lagos Lagoon (2W) and ‘Iya-Alaro’ tributary (4W) sediments in comparison with pristine ‘Lekki Conservation Centre’ sediment (L1-B). Bacteriology of the ecosystems was based on culture-independent analyses using pyrosequencing. 2W and 4W were extremely contaminated with mercury (Igeo > 7), whereas, cadmium contamination was only observed in 4W. The two ecosystems were polluted with toxic metal based on PLI, where mercury (Er = 2900 and 1900 for 4W and 2W, respectively) posed very high ecological risks. Molecular fingerprinting revealed that Proteobacteria, Firmicutes, and Acidobacteria predominately contributed the 20 most abundant genera in the two ecosystems. The 240 and 310 species present in 2W and 4W, respectively, but absent in L1-B, thrive under the metal concentrations in the polluted hydrosphere. Whereas, the 58,000 species missing in 2W and 4W but found in L1-B would serve as indicators for systems impacted with metal eco-toxicity. Despite toxic metal pollution of the ecosystems understudied, bacterial communities play vital roles in self-recovery processes occurring in the hydrosphere.

As a strategy of arsenic-containing mine tailing soil, the application of arsenic hyper-accumulator plants such as Pteris vittata shows high potential. Previous studies suggest that the arsenic uptake by P. vittata is largely determined by arsenic speciation, which is strongly influenced by microbial activities. In this study, two arsenic hyper-accumulators, P. vittata that is a subtropical plant and Pteris multifida that has been found in northeastern Japan, were selected and the their rhizobacteria were investigated. Pot experiments of P. vittata and P. multifida cultivation were performed. The concentration of total arsenic in the plant samples was monitored by inductively coupled plasma - mass spectrometry. Microbes in the rhizosphere samples were investigated by 16S rDNA library analysis and arsenic resistant bacteria isolation. The results showed that both ferns accumulated As, while P. multifida was more resistant to cold weather. Two ferns presented different rhizobacterial communities and cultivatable bacteria number, but bacteria that contain As(III) oxidase gene or As(III) oxidation activity were confirmed in both rhizosphere samples. The results of present study suggested that the cultivation of ferns changed the microbial communities in soil (rhizosphere), and microbial activity in the rhizosphere played a role in As(III) oxidation. Since ferns absorbs As(III) and As(V) in different efficiency, this study provided hints when linking microbial As transformation to As uptake by ferns which is important when designing pre-treatment procedures of phytoremediation.

Stable degrading 1,2-dichlorobenzene (1,2-DCB) enrichments were generated from original contaminated soil and groundwater via enrichment procedures using a mineral salt medium containing 1,2-DCB as the sole carbon and energy source. Four transferred enrichments showed stable 1,2-DCB-degrading ability and completely degraded 1,2-DCB within 32 h. PCR-denaturing gradient gel electrophoresis (DGGE) and 16S rRNA gene clone library analyses indicated that two bacterial strains, belonging to Acidovorax spp. and Ralstonia spp., respectively, were the predominant organisms in each enrichment. Moreover, these strains maintained a stable coexistence in the four transferred enrichments. These two bacteria were subsequently identified as Acidovorax sp. strain sk40 and Ralstonia sp. strain sk41. Strain sk40 was more tolerant to higher concentrations of 1,2-DCB than strain sk41, while strain sk41 maintained a shorter degradation time under lower concentrations of 1,2-DCB. Notably, however, both strains exhibited similar growth rates and degradation rates in media containing 40 mg/l 1,2-DCB, as well as complete degradation of the 1,2-DCB (40 mg/l) within 32 h. It is expected that these two strains will be used in future applications of bioremediation of 1,2-DCB contamination.

From several mercury removing microorganisms, we selected Bacillus megaterium MB1, which is nonpathogenic, broad-spectrum mercury resistant, mercuric ion reducing, heat tolerant, and spore-forming, as a useful bacterium for bioremediation of mercury pollution. In this study, mercury removal performance of the immobilized B. megaterium MB1 was investigated to develop safe, efficient and stable catalytic bio-agent for mercury bioremediation. The results showed that the alginate gel immobilized B. megaterium MB1 cells efficiently removed 80% of mercury from the solution containing 10 mg/L mercuric chloride within 24 h. These cells still had high activity of mercury removal even after mercuric ion loading was repeated for nine times. The analysis of mercury contents of the alginate beads with and without immobilized B. megaterium MB1 suggested that a large portion of reduced metallic mercury was trapped in the gel beads. It was concluded that the alginate gel immobilized B. megaterium MB1 cells have potential to remove and recover mercury from mercury-containing water.