Insights into the growth and biochemical defense responses associated with fenitrothion toxicity and uptake by freshwater cyanobacteria

The extensive use of fenitrothion (FNT) in agricultural practices induces its persistence in soil and waterways. Therefore, it is essential to implement effective management practices such as using cyanobacteria for FNT removal and accumulation, particularly under accidental contamination. To this end, we evaluated the responses of two freshwater cyanobacteria taxa, Nostoc muscorum and Anabaena laxa to mild (7.5 mg L-1) and high (15 mg L-1) levels of FNT over a period of 7 d. Compared to N. muscorum, A. laxa was more tolerant to FNT, exhibiting higher FNT uptake and removal efficiencies at mild (16.3%) and high (17.5%) levels. FNT induced a dose-dependent decrease in cell growth, Chl a, phosphoenolpyruvate carboxylase and ribulose-1,5-bisphosphate carboxylase/oxygenase activities, which were more pronounced in N. muscorum. Moreover, FNT significantly increased oxidative damage markers i.e., increased lipid peroxidation (MDA), protein oxidation, H2O2 levels and NADPH oxidase enzyme activity, to more extent in N. muscorum. Compared to N. muscorum, A. laxa had high antioxidant capacity (FRAP), glutathione and increased activities of glutathione-S-transferase, glutathione reductase, glutathione peroxidase and superoxide dismutase, suggesting a robust antioxidant defense mechanism to mitigate FNT toxicity. However, N. muscorum devoted the induction of ascorbate content and the activity of catalase, peroxidase, monodehydroascorbate reductase, ascorbate peroxidase, and dehydroascorbate reductase enzymes. Although A. laxa had greater intracellular FNT, it experienced less FNT-induced oxidative stress, likely due to over production of antioxidants. Consequently, A. laxa is considered as a promising candidate for FNT phycoremediation. Our findings provide fundamental information on species-specific toxicity of FNT among cyanobacteria and the environmental risk of FNT toxicity in aquatic environments.

Sustainable permeable biobarriers for atrazine removal in packed bed biofilm reactors

The synergy between two supported bacterial biofilms of S. equisimilis and P. putida and a sustainable biocarrier (raw pine) was studied, working both as biobarriers for the treatment of water contaminated with atrazine. Firstly, the effects of ATZ exposure on bacterial growth were evaluated, with Gram-positive S. equisimilis being a more tolerant bacterium to higher amounts of the herbicide. The bioremoval of ATZ by S. equisimilis concentrated biomass was then assessed, reaching around 83.5% after 15 days due to the potential degradation by the biomass and biosorption by the solids, with overlapping of both mechanisms. The optimization of bacterial biofilm attachment onto raw pine prior to bioremoval assays in lab-scale packed bed biofilm reactors was performed by varying initial biomass concentration, inocula growth time and hydrodynamic conditions. Lastly, the optimized biosystems were tested as sustainable remediation designs to treat water contaminated with the selected herbicide. Results reveal an added beneficial effect towards the bioremoval of atrazine using supported biofilms onto raw pine, reaching 90.42% and 79.71% by S. equisimilis and P. putida biofilms, respectively, over 58.31% increase when compared to sorption on fixed bed of pine. The coupling of biosorption/biodegradation favors the bioremoval process significantly.

Dibenzothiophene removal by environmental bacteria with differential accumulation of intracellular inorganic polyphosphate

Dibenzothiophene (DBT), which belongs to the group of polycyclic aromatic heterocycles of sulfur, is a model substance to study the removal of sulfur compounds from oil due to its recalcitrance to traditional and specific removal processes. The aim of this work was to evaluate DBT bioremoval by environmental bacteria and its relationship with polyphosphate (polyP) accumulation, cell surface characteristics and bioemulsifying activity. Pseudomonas sp. P26 achieved the highest DBT removal percentage (48%) after 7 days of incubation. Moreover, positive correlations were estimated between DBT removal and bioemulsifying activity and biofilm formation. A strain-dependent relationship between the content of intracellular polyP and the presence of DBT in the culture medium was also demonstrated. The study of these bacterial characteristics, which could promote DBT transformation, is a first approach to select DBT-removing bacteria, in order to develop bioformulations that are able to contribute to desulfurization processes of petroleum-derived pollutants in the future.

Comparison of the microalgae Phormidium tenue and Chlorella vulgaris as biosorbents of Cd and Zn from aqueous environments

Heavy metals are accumulating into sediments and enriching in aquatic food chains. The efficiency of two microalgae, Phormidium tenue and Chlorella vulgaris, to remove zinc and cadmium from aqueous solutions was studied. The microalgae were incubated in different heavy metal concentrations for 18 days. Morphological and anatomical changes in microalgae were investigated using a scanning electron microscope (SEM) and a transmission electron microscope (TEM). Both algae removed both Zn2+ and Cd2+in vitro. C. vulgaris removed Zn2+ almost totally (99%) and Cd2+ slightly less (87%). The concentration factors were 2210 and 1117, respectively. SEM and TEM figures showed some alterations in the form and cellular components of both algae. C. vulgaris appeared to be more tolerant to both Cd and Zn than P. tenue. C. vulgaris is a promising microalgal species used to remove heavy metals from aqueous environments.

Hierarchically-structured laccase@Ni3(PO4)2 hybrid nanoflowers for antibiotic degradation: Application in real wastewater effluent and toxicity evaluation

Laccase@Ni₃(PO₄)₂ hybrid nanoflowers (HNFs) were prepared by the anisotropic growth of biomineralized nickel phosphate. The immobilization yield was 77.5 ± 3.6 %, and the immobilized enzyme retained 50 % of its initial activity after 18 reusability cycles. The immobilized and free enzymes lost 80 % of their activity after 18 and 6 h incubation in municipal wastewater effluent (MWWE), respectively. The increase in α-helix content (8 %) following immobilization led to a more rigid enzyme structure, potentially contributing to its improved stability. The removal of ciprofloxacin from MWWE by laccase@Ni₃(PO₄)₂·HNFs/p-coumaric acid oxidation system was optimized using a Box-Behnken design. Under the optimized conditions [initial laccase activity (0.05 U mL^-1), the concentration of p-coumaric acid (2.9 mM), and treatment time (4.9 h)], the biocatalyst removed 90 % of ciprofloxacin (10 mg L^-1) from MWWE. The toxicity of ciprofloxacin against some G⁺ and G^- bacteria was reduced by 35-70 %, depending on their strain. The EC₅₀ of ciprofloxacin for the alga Raphidocelis subcapitata reduced from 3.08 to 1.07 mg L^-1 (p-value <0.05) after the bioremoval. Also, the acute and chronic toxicity of identified biodegradation products was lower than ciprofloxacin at three trophic levels, as predicted by ECOSAR software.

Hybridization of laccase with dendrimer-grafted silica-coated hercynite-copper phosphate magnetic hybrid nanoflowers and its application in bioremoval of gemifloxacin

Laccase was successfully hybridized with polyamidoamine (PAMAM) dendrimer-grafted silica-coated hercynite-copper phosphate magnetic hybrid nanoflowers (MHNFs) to increase the catalytic performance of the enzyme and apply in an effective bioremoval of gemifloxacin. For this purpose, the magnetic nanoparticles (MNPs) of hercynite were covered with a silica layer, and the core-shell SiO₂@hercynite was then modified with PAMAM dendrimer to increase the surface area of the carrier for the enzyme attachment. Subsequently, the whole complex was hybridized with laccase and copper phosphate to attain a large surface area (104.3 m² g^-1). The fabricated MHNFs acquired the entrapment yield and efficiency of 90 ± 3% and 66 ± 5%, respectively. The catalytic activity of the fabricated biocatalyst was remained up to 50% after 13 reusability cycles. Approximately 90% of gemifloxacin was removed by the constructed MHNFs after 3 h incubation by adsorption and degradation mechanisms. The biotransformation products were then identified, and degradation pathways were proposed as defluorination, decarboxylation, elimination of a cyclopropyl group, and cleavage of the pyrrolidine moiety. Furthermore, the toxicity of gemifloxacin was effectively diminished against some bacterial strains.

Effective removal of Pb(II) and Ni(II) ions by Bacillus cereus and Bacillus pumilus: An experimental and mechanistic approach

Herein, we report a bacteria-based strategy as an efficient, reasonable, benign, and promising methodology for remediating heavy metals fed waterbodies. The contemporary study deals with isolating, screening, and characterizing heavy metal resistive bacteria from metal-rich sites. The transcriptome analysis reveals the identity of the isolated species as Bacillus pumilus and Bacillus cereus. Batch studies put forth the bioremoval results in designed conditions of different pH, concentration, dose, and time. The mechanistic actions are drawn using complementary techniques such as Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). The theory of surface adsorption of lead (Pb(II)) and nickel (Ni(II)) is further fostered by the application of adsorption isotherms. The conducted studies establish the bacterial morphological stratagems and multifarious biochemical approaches for countering metallic ions of Pb(II) and Ni(II). The exhibition of significant removal results by the isolated bacterial strains in simulated water samples with remarkable proliferation rates has opened up its favorability for industrial platforms.

Laccase-loaded magnetic dialdehyde inulin nanoparticles as an efficient heterogeneous natural polymer-based biocatalyst for removal and detoxification of ofloxacin

An efficient heterogeneous natural polymer-based biocatalyst was fabricated through the immobilization of laccase onto dialdehyde inulin (DAI)-coated silica-caped magnetic nanoparticles (laccase@DAI@SiO₂@Fe₃O₄⋅MNPs). The carrier was developed using SiO₂@Fe₃O₄⋅MNPs and functionalized with DAI. The construction of immobilized laccase was confirmed by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. Immobilization yield and efficiency were calculated as 61.0 ± 0.3% and 93.0 ± 0.6%, respectively. The immobilized laccase maintained 50% and 85% of its relative activity after 25 repeated cycles and 20 days of storage at 4 °C, respectively. The prepared biocatalyst effectively eliminated ofloxacin, a fluoroquinolone-type antibiotic, with a 63% removal capacity. Besides, antimicrobial activity study on some soil microorganisms involved in the biodegradation of xenobiotics revealed that the laccase-treated ofloxacin resulted in less toxic metabolites. The obtained data indicated that the fabricated biocatalyst is promising for the removal of ofloxacin or other analogs of fluoroquinolones in the environment.

Bioremoval of PVP-coated silver nanoparticles using Aspergillus niger: the role of exopolysaccharides

Extensive use of engineered nanoparticles has led to their eventual release in the environment. The present work aims to study the removal of Polyvinylpyrrolidone-coated silver nanoparticles (PVP-Ag-NPs) using Aspergillus niger and depict the role of exopolysaccharides in the removal process. Our results show that the majority of PVP-Ag-NPs were attached to fungal pellets. About 74% and 88% of the PVP-Ag-NPs were removed when incubated with A. niger pellets and exopolysaccharide-induced A. niger pellets, respectively. Ionized Ag decreased by 553 and 1290-fold under the same conditions as compared to stock PVP-Ag-NP. PVP-Ag-PVP resulted in an increase in reactive oxygen species (ROS) in 24 h. Results show an increase in PVP-Ag-NPs size from 28.4 to 115.9 nm for A. niger pellets and 160.3 nm after removal by stress-induced A. niger pellets and further increased to 650.1 nm for in vitro EPS removal. The obtained findings show that EPS can be used for nanoparticle removal, by increasing the net size of nanoparticles in aqueous media. This will, in turn, facilitate its removal through conventional filtration techniques commonly used at wastewater treatment plants.

Magnetic casein aggregates as an innovative support platform for laccase immobilization and bioremoval of crystal violet

In this study, casein@CoFe₂O₄ was fabricated through a green synthesis methodology and applied to immobilize laccase. The constructed casein@CoFe₂O₄ exhibited porous structures with distinct cavities and suitable magnetic properties. The abundance of aromatic functional groups on the surface renneted casein and possible π-type interaction between laccase and para-κ-casein resulted in a successful immobilization. The biocatalyst retained 50% of its initial activity after 24 reusability cycles, indicating stable immobilization of laccase onto the casein microstructures. The stability of laccase after immobilization was improved by 300% in comparison with the free enzyme, especially in basic pH values. The constructed laccase@casein@CoFe₂O₄ was then incorporated to remove crystal violet (CV) as an environmentally harmful synthetic tri-phenylmethane dye. The prepared heterogeneous biocatalyst effectively diminished the antimicrobial activity of CV up to 81.3% in 40 min against some bacterial strains, resulting from the formation of more minor toxic metabolites identified by liquid chromatography coupled with mass spectroscopy after degradation procedure. The proposed green and feasible method for the preparation of magnetic casein aggregates has not been previously reported. The incorporation of casein, which acted as a molecular chaperon, resulted in a significant improvement in the enzymatic stability and exhibited appropriate reusability for the constructed biocatalytic system.

The efficient biomineralization and adsorption of cadmium (Cd2+) using secretory organo-biominerals (SOBs) produced by screened Alcaligenes faecalis K2

Cadmium-contaminated wastewater has attracted increasing concerns due to its non-biodegradable properties and high toxicity. To explore eco-friendly and economically feasible strategies, the screened Alcaligenes faecalis K2 were employed for the biomineralization and recovery of Cd²⁺ from wastewater while producing considerable secretory organo-biominerals (SOBs) as bioadsorbents. At 75 mg/L Cd²⁺ exposure, 85.5% of Cd²⁺ was removed by K2, 43.0% of which was fixed in the granular SOBs. SOBs were convenient for separating from the solution. The adsorption capacity of granular sorbent made from SOBs was verified to be greater than 77.1 mg/g. Practically, 89.5% of 75 mg/L of Cd²⁺ could be stably removed while ereK2 continuously generated SOBs in a moving-bed biofilm reactor (MBBR). To sum up, the production of bioadsorbents can be achieved by K2, while removing Cd with live microorganisms, which was conducive to making full use of materials and improving Cd removal efficiency.

Bioremoval of graffiti using novel commercial strains of bacteria

Previous studies have provided evidence that bioremediation deals a novel approach to graffiti removal, thereby overcoming well-known limitations of current cleaning methods. In the present study eight bacteria aerobic, mesophilic and culturable from the American ATCC and the German DSMZ collections of microorganisms, some isolated from car paint waste, colored deposits in a pulp dryer and wastewater from dye works, were tested in the removal of silver and black graffiti spray paints using immersion strategies with glass slides. Absorbance at 600 nm and live/dead assays were performed to estimate bacterial density and activity in all samples. Also, pH and dissolved organic carbon (DOC) and inorganic carbon (DIC) measurements in the liquid media were made, as well as, thickness, colorimetric and infrared (FTIR) spectroscopy measurements in graffiti paint layers were used to evaluate the presence of the selected bacteria in the samples and the graffiti bioremoval capacity of bacteria. Data demonstrated that of the eight bacteria studied, Enterobacter aerogenes, Comamonas sp. and a mixture of Bacillus sp., Delftia lacustris, Sphingobacterium caeni, and Ochrobactrum anthropi were the most promising for bioremoval of graffiti. According to significant changes in FTIR spectra, indicating an alteration of the paint polymeric structure, coupled with the presence of a consistent quantity of live bacteria in the medium as well as a significant increase of DIC (a measure of metabolic activity) and a change in paint color.

Detoxification of Heterocyclic Aromatic Amines by Probiotic to Inhibit Medical Hazards

Cancer is the second leading factor of human death in the world. Long-term consumption of cooked red meat brings about various types of cancers like colorectal cancer due to the formation of Heterocyclic Aromatic Amines (HAAs) during the heating process of meat. There are various solutions for the reduction of these toxicants. The aim of this article is to describe probiotic as one of the possible strategies for bioremoval of these carcinogenic and mutagenic substances and change food to functional one as well. The mechanism of biodetoxification is binding by probiotics, which depends on some variables including the probiotic characteristics, kind and content of the mutagens, as well as some properties of media. In this article, after introducing detoxification ability of probiotics and listing of all reported probiotics in this field, the influencing variables are surveyed and finally, opportunities and problems of HAA bioremoval by probiotics are described.

Physiological and thylakoid ultrastructural changes in cyanobacteria in response to toxic manganese concentrations

In this study, two cyanobacterial strains (morphologically identified as Microcystis novacekii BA005 and Nostoc paludosum BA033) were exposed to different Mn concentrations: 7.0, 10.5, 15.7, 23.6 and 35.4 mg L^-1 for BA005; and 15.0, 22.5, 33.7, 50.6, and 76.0 mg L^-1 for BA033. Manganese toxicity was assessed by growth rate inhibition (EC₅₀), chlorophyll a content, quantification of Mn accumulation in biomass and monitoring morphological and ultrastructural effects. The Mn EC₅₀ values were 16 mg L^-1 for BA005 and 39 mg L^-1 for BA033, respectively. Reduction of chlorophyll a contents and ultrastructural changes were observed in cells exposed to Mn concentrations greater than 23.6 and 33.7 mg L^-1 for BA005 and BA033. Damage to intrathylakoid spaces, increased amounts of polyphosphate granules and an increased number of carboxysomes were observed in both strains. In the context of the potential application of these strains in bioremediation approaches, BA005 was able to remove Mn almost completely from aqueous medium after 96 h exposure to an initial concentration of 10.5 mg L^-1, and BA033 was capable of removing 38% when exposed to initial Mn concentration of 22.5 mg L^-1. Our data shed light on how these cyanobacterial strains respond to Mn stress, as well as supporting their utility as organisms for monitoring Mn toxicity in industrial wastes and potential bioremediation application.

DIN-3 isolated from biological activated carbon process

The presence of non-steroidal anti-inflammatory drugs (NSAIDs) in the environment is an emerging concern owing to their potential threat on aquatic ecosystems and living organisms. To investigate the bioremoval potential of a biological activated carbon (BAC) filter for the removal of NSAIDs, removal of diclofenac (DCF), ibuprofen (IBU), and naproxen (NAP) by biofilms on a bench-scaled BAC column operated for 400 days was studied. The results showed that the BAC column effectively removed the three NSAIDs (>90%). One bacterial strain isolated from the BAC, Pseudoxanthomonas sp. DIN-3, was able to simultaneously remove DCF, IBU, and NAP, which were supplied as the sole carbon source. In 14 days, 23%, 41%, and 39% of DCF, IBU, and NAP (50 μg L^-1) were bioremoved, respectively, and strain DIN-3 eliminated IBU more rapidly than the other two NSAIDs. If only a single drug was added as the sole carbon source, ignoring the other drugs, the removal ability was overestimated by 5.0-27.0%. More efficient bioremoval was achieved, concomitantly with bacterial growth, via a co-metabolism with acetate, glucose, or methanol. Their intermediates were identified by UPLC-QQQ-MS, and their respective degradation pathways were also proposed. Moreover, based on the complete genome sequence of strain DIN-3, 49 related genes encoding the main enzymes involved in DCF, IBU, and NAP biodegradation were identified, including hemE, lpd, yihx, ligC, pobA, and ligA. These results suggested that Pseudoxanthomonas sp. DIN-3 is a potential degrader of DCF, IBU, and NAP, and to the best of our knowledge, this is the first report that demonstrates the bioremoval of DCF, IBU, and NAP simultaneously by an individual bacterial strain isolated from the environment. However, the bioremoval potential should be evaluated when assessing the applicability of the strain in the environment because of the combined effects of various pharmaceutical contaminants. The obtained results provide a foundation for the use of Pseudoxanthomonas sp. DIN-3 in the bioremoval of polycyclic NSAID-contaminated environments.

The critical utilization of active heterotrophic microalgae for bioremoval of Cr(VI) in organics co-contaminated wastewater

Considering the importance of removing toxic Cr(VI) from practical wastewater containing complex pollutants, this study presented for the first time the utilization of the live heterotrophic microalgae (Botryocossuss sp. NJD-1) to achieve a concurrent abatement of Cr(VI), TOC, NO₃-N and PO₄-P, through a comprehensive biochemical process. The experimental results showed that the Cr(VI) removal efficiencies in the culture with different types of organic descended in the order of sodium acetate, ethanol and methanol. The highest removal efficiencies were achieved as 94.2%, 98.2%, 66.9% and 99.2% for Cr(VI), TOC, NO₃-N and PO₄-P, respectively, in the culture with 5 mg L^-1 Cr(VI) and sodium acetate of equivalent to 2.92 g C L^-1. Through mass balance calculation and characterization, the fate of Cr(VI) and Cr(III) was tracked and quantified in the culture system, which indicates that 87.17% of initial Cr(VI) were reduced to Cr(III) and then adsorbed in algal biomass for the optimal removal case. Consequently, the mechanism demonstrating the correlation among the removal process of Cr(VI), the biological activity of microalgae and the effect of organic compounds was proposed.

Cobalt and nickel content in Hydrocharis morsus-ranae and their bioremoval from single- and binary solutions

Aquatic macrophytes are known to remove trace metals from surrounding water. In the present study, an attempt was made to evaluate the phytofiltration capacity of Hydrocharis morsus-ranae and to show competition between cobalt (Co) and nickel (Ni) for the better understanding of metal bioaccumulation in the species. In a laboratory experiment, H. morsus-ranae was exposed to separate (single) and binary solutions of these metals: Ni 10.7, 18.7, 32.7, 57.1, and 100 (μg L^-1); Co 5.33, 9.32, 16.3, 28.6, and 50.0 (μg L^-1); and 10.7 Ni + 5.33 Co, 18.7 Ni + 9.32 Co, 32.7 Ni + 16.3 Co, 57.1 Ni + 28.6 Co, 100 Ni + 50.0 Co (μg L^-1). The content of Co and Ni in the plant increased with the increasing concentration in the growth medium. Competition between the metals was seen during uptake in binary solutions. Ni interfered with the accumulation of Co, resulting in a lower Co content than in plants cultivated in Co solutions. A particularly high Co content (up to 155 mg kg^-1 dry weight [d.w.]) and high efficiency of Ni uptake (Bioaccumulation Factor (BF) 2572-7239) makes the species a very good accumulator of these metals. The high content of both trace metals in plant tissues (up to 511 mg kg^-1 d.w. Ni and 155 mg kg^-1 d.w. Co) did not affect its growth, indicating tolerance of these toxicants. The plant showed excellent ability in removing Co (up to 98.6% in solution with 5.33 μg L^-1 Co) and Ni (up to 91.4% in solution with 57.1 μg L^-1 Ni and 28.6 μg L^-1 Co) from nutrient solution. The results suggest that H. morsus-ranae may be useful for the phytoremediation of water bodies contaminated with Co and Ni.

Removal and recovery of Critical Rare Elements from contaminated waters by living Gracilaria gracilis

The experiments performed in this work proved the ability of Gracilaria gracilis to concentrate and recover Critical Rare Elements (CRE) from contaminated waters. The importance of recycling these elements is related to their very limited sources in Nature and progressive use in technologies. Moreover, their mining exploitation has negative environmental impact, and recent studies point them as new emerging pollutants. To the best of our knowledge, this is the first report on the application of living macroalgae for the removal and recovery of CRE. G. gracilis (2.5gL^-1, fresh weight) was exposed to mono- and multi-element saline solutions of 500μgL^-1 of Y, Ce, Nd, Eu and La. Removal was up to 70% in 48h, with bioaccumulation following Elovich kinetic model. In multi-element solutions, selectivity was not observed although removal of lanthanides improved comparatively to single-element solutions. No mortality or adverse effect on growth was registered. The subsequent macroalgae digestion allowed collecting virtually 100% of all elements in a 300-fold more concentrated solution. The overall results suggest the application of living macroalgae as a simple and effective alternative technology for removing and recovering CRE from wastewaters, contributing to an improvement of water quality and CRE recycling.

Optimal reduction of chemical oxygen demand and NH3-N from landfill leachate using a strongly resistant novel Bacillus salmalaya strain

Background

When the unavoidable waste generation is considered as damaging to our environment, it becomes crucial to develop a sustainable technology to remediate the pollutant source towards an environmental protection and safety. The development of a bioengineering technology for highly efficient pollutant removal is this regard. Given the high ammonia nitrogen content and chemical oxygen demand of landfill leachate, Bacillus salmalaya strain 139SI, a novel resident strain microbe that can survive in high ammonia nitrogen concentrations, was investigated for the bioremoval of ammonia nitrogen from landfill leachate. The treatability of landfill leachate was evaluated under different treatment parameters, such as temperature, inoculum dosage, and pH.

Results

Results demonstrated that bioaugmentation with the novel strain can potentially improve the biodegradability of landfill leachate. B. salmalaya strain 139SI showed high potential to enhance biological treatment given its maximum NH₃–N and COD removal efficiencies. The response surface plot pattern indicated that within 11 days and under optimum conditions (10% v/v inoculant, pH 6, and 35 °C), B. salmalaya strain139SI removed 78% of ammonia nitrogen. At the end of the study, biological and chemical oxygen demands remarkably decreased by 88% and 91.4%, respectively. Scanning electron microscopy images revealed that ammonia ions covered the cell surface of B. salmalaya strain139SI.

Conclusions

Therefore, novel resistant Bacillus salmalaya strain139SI significantly reduces the chemical oxygen demand and NH₃–N content of landfill leachate.

Graphical abstract

Leachate treatment by B. salmalaya strain 139SI within 11 days.

SCSE709-6: Comparative study on growing and grown cells

Comparison of the bioremoval and recovery of Cd(II) by growing and grown marine bacterium Pseudoalteromonas sp. SCSE709-6 was performed in batch systems. Bioremoval with growing cells (Sorption I) showed better performance at low Cd(II) concentrations, whereas bioremoval with grown cells (Sorption II) had significant advantages in both removal efficiency and time consumption at high Cd(II) concentrations. The optimal pH was higher for Sorption I than for Sorption II for achieving the maximum Cd(II) removal efficiency. Complete desorption was achieved using either Na2EDTA or HNO3 as eluent. Cd(II) adsorbed on grown cells had higher tendency to be desorbed. Na2EDTA was a preferable eluent for the recycling biomaterials, whereas HNO3 performed better for the final security disposal of sludge. For Sorption II, both Langmuir and Freundlich isotherms well explained the biosorption behavior, and the pseudo-second-order model better expressed biosorption and desorption kinetics.

Presence of Fe3+ and Zn2+ promoted biotransformation of Cd-citrate complex and removal of metals from solutions

The promotion to Cd-citrate complex biotransformation via addition of Fe(3+) and Zn(2+) was investigated. Single Fe(III)- or Zn-citrate complex was completely degraded by Pseudomonas sp. MBR, Cd-citrate complex was not. In the Cd-citrate media with molar ratio of 1:2 and 1:3, pH increase obtained from the metabolism of excess citrate slightly promoted the biotransformation of Cd-citrate complex, Cd remained in solutions. The presence of Fe(3+) and Zn(2+) resulted in complete biotransformation of Cd-citrate complex in the 1:1:2 Fe:Cd:citrate and Zn:Cd:citrate and 1:1:1:3 Fe:Zn:Cd:citrate media. Alkaline pH obtained from biotransformation of metal-citrate complexes caused almost complete removal of metals (>98%) through precipitation and co-precipitation. Pseudomonas sp. MBR potentially could be used to treat wastewater containing mixed citrate complexes of Fe(III), Zn and Cd.