Microbial and plant derived biomass for removal of heavy metals from wastewater

Nano-manganese oxides-modified biochar for efficient chelated copper citrate removal from water by oxidation-assisted adsorption process

Removal of chelated copper from wastewater is more difficult than that of copper ions owing to its stable structure, wide range of pH tolerance, and stronger mobility. Copper citrate (CuCA) widely exists in the water system and inevitably poses serious hazards to human health and environment. Biochar as economic functional material has been widely used for environmental applications, especially in wastewater treatment. This study focused on the performance of manganese oxide-modified biochar (BC-MnO_x) toward uptake and removal of CuCA and to understand the related mechanism. The result indicated that the CuCA removal efficiency reached up to 99%. High removal efficiency and low concentration of dissolved Mn over a wide pH range proved that the BC-MnO_x is efficient and chemically stable. Furthermore, the removal mechanism may involve the following processes: First, CuCA was removed via the chemical bonds formed between CuCA and MnO_x on the surface of BC. Second, chemisorption due to the oxygen-containing functional groups or physisorption of porous structure in BC worked synergistically on CuCA. Third, CuCA was partially oxidized into low molecular weight acids by means of MnO_x, while the released Cu ions were retained on the adsorbent surface. This study demonstrates that BC-MnO_x is a promising material for the removal of CuCA from wastewater.

Novel application of maghemite nanoparticles coated bacteria for the removal of cadmium from aqueous solution

Heavy metals are classified as persistent pollutants owing to their nature of bioaccumulation and affect human life and environment, even in minor concentrations. Divalent Cadmium (Cd²⁺) is one of the heavy metal pollutants that are highly toxic. The present study investigates the novel application of maghemite nanoparticles coated Bacillus subtilis for the removal of Cd²⁺ ions from its aqueous solution by batch adsorption studies. Surface characterization of the biosorbent done by Scanning Electron Microscope (SEM) and the presence of maghemite nanoparticle coat was confirmed. Parameters like pH, initial metal ion concentration, contact time, and temperature that affect the biosorption of cadmium ions are analyzed, and the equilibrium adsorption capacity expressed as a function of each of the parameters. The mechanism of biosorption was studied by plotting adsorption isotherms, and it follows pseudo-second-order kinetics. Thermodynamic studies showed the process to be spontaneous and endothermic. At optimum conditions of pH 4, 30 °C, 120 rpm, maximum removal percentage of 83.5%, which accounts for an equilibrium adsorption capacity of 32.6 mg/g of biosorbent. There was a recovery of 76.4% of the biosorbent after adsorption studies. Based on the adsorptive capacity and good recovery of the biosorbent, maghemite coated Bacillus subtilis proves to be an efficient adsorbent for the removal of Cd²⁺ ions from its aqueous solution.

Characterization of Cd2+ biosorption by Pseudomonas sp. strain 375, a novel biosorbent isolated from soil polluted with heavy metals in Southern China

Water pollution with heavy metals is a global problem. Using microbial adsorbents to remediate water bodies contaminated with heavy metals has been garnering considerable attention. In this study, a cadmium (Cd²⁺)-resistant bacterium, isolated from soil polluted with heavy metals, was characterized as Pseudomonas sp. 375 based on its biochemical characteristics and 16S rRNA gene. The minimum inhibitory concentration (MIC) of Cd²⁺ for strain 375 was 6 mM. We evaluated the effects of different parameters, such as initial pH, contact time, and initial Cd²⁺ concentration, on Cd²⁺ uptake. The data acquired using nonliving biomass were fitted to a Langmuir isotherm model; however, the Freundlich isotherm model showed better fit for data acquired using living biomass. The maximum biosorption capacities were 92.59 mg g^-1 and 63.29 mg g^-1 for living and nonliving cells, respectively. The kinetics of biosorption was described using a pseudo-second order kinetic model. The tightly bound Cd on the cell wall played a major role in Cd²⁺ adsorption for both biosorbents. SEM-EDX analysis also showed that Cd²⁺ was bound to the cell wall. FTIR spectral analysis showed that -CH₂, -OH, -SO₃, CO, N-H, C-N, phosphate, or sulfate functional groups were the main functional sites for the binding of Cd²⁺ ions. Effectively Cd²⁺ removal from Cd²⁺ contaminated water suggested Pseudomonas sp. 375 was an (a) inexpensive, effective, and promising biosorbent that can be used for bioremediation Cd²⁺-contaminated wastewater.

Removal of lead from acidic wastewater by bio-mineralized bacteria with pH self-regulation

Microorganisms with the function of bio-mineralization were isolated from a soil. They were identified as urease-producing bacteria and phosphate-solubilizing bacteria. These two kinds of bacteria belong to the eosinophilic bacteria, which regulated the pH of solution and removed Pb²⁺ the best at the initial solution pH of 4. The Pb²⁺ removal mechanism was further explored using various techniques including zeta potential measurement, three-dimensional fluorescence, FTIR, XRD, and TEM-EDS. The results showed that extracellular adsorption, intracellular accumulation and bio-mineralization occurred at the same time and converted to each other. The extracellular adsorption of urease-producing bacteria was through electrostatic adsorption and gradually decomposed urea to produce PbCO₃ minerals. The extracellular adsorption of phosphate-solubilizing bacteria was controlled by extracellular polymeric substances (EPS) and rapidly formation of Pb₃(PO₄)₂ stable minerals. In addition, the stabilities of Lead minerals of the two strains were compared. The results showed that the precipitates of phosphate-solubilizing bacteria were more stable. While phosphate-solubilizing bacteria have some advantages, both strains can play important roles in bio-mineralization of HMs in acidic wastewater.

Evolution of Environmentally Friendly Strategies for Metal Extraction

The demand for the recovery of valuable metals and the need to understand the impact of heavy metals in the environment on human and aquatic life has led to the development of new methods for the extraction, recovery, and analysis of metal ions. With special emphasis on environmentally friendly approaches, efforts have been made to consider strategies that minimize the use of organic solvents, apply micromethodology, limit waste, reduce costs, are safe, and utilize benign or reusable materials. This review discusses recent developments in liquid- and solid-phase extraction techniques. Liquid-based methods include advances in the application of aqueous two- and three-phase systems, liquid membranes, and cloud point extraction. Recent progress in exploiting new sorbent materials for solid-phase extraction (SPE), solid-phase microextraction (SPME), and bulk extractions will also be discussed.

Advanced converter sludge utilization technologies for the recovery of valuable elements: A review

Due to the high proportion of the steel output produced by oxygen converter, significant quantities of converter sludge (CS) is generated annually as waste material. This study aims to review the latest CS utilization technologies and illuminate the migration behaviors of harmful substances as well as valuable elements. The intrinsic characteristics, including chemical constitution, size distribution, mineralogical composition, microstructure, and viscosity of the CS are studied. Migration behaviors of harmful substances are analyzed based on thermodynamic calculation. The results indicated that less eutectic mineral was found in CS, the iron oxides and other impurities like CaO, MgO and ZnFe₂O₄ mixed in the way of physical accumulation. The treatments through oxidation methods, such as iron ore sintering and oxidized pellets, are the most common and effective methods to recovery Fe in actual production. Due to the diverse physicochemical properties of CS from different enterprises, it is really difficult to choose one universal recovery method. In view of resources recovery and clean production, the authors believe that the best utilization technology at present is to prepare metallized pellets. It is regarded that technologies of preparing high value-added products, such as Li(FeM)PO₄ and iron powder are the most prospective methods in the future.

Data set on performance evaluation of discharged wastewater quality from Guna water treatment plant for potable water purpose

This article provides to evaluate the quality of discharged water from Guna spring water treatment plant and to compare with WHO drinking water standards and Ethiopian bottled drinking water specification to reuse for potable water purpose. The discharged waste water quality analysis was conducted by Physical, Chemical, Biological and Bacteriological parameters of water in association with set of standards. Atomic adsorption spectroscopy (AAS), Flame photometer, UV–Visible spectrometer and Photo meter were used for characterization discharged water. All water quality parameter was determined in all unit process (softener, sand filter, activated carbon and ultra-filter). Bacteriological analysis (total coli form, fecal coli form and Escherichia coli type1) were conducted. During discharge water quality analysis, the effect of flow rate (2 m³/h, 4 m³/h and 6 m³/h) and discharge time (5,10 and 15 min) have been performed. We provided data set about Atomic adsorption spectroscopy (AAS), Flame photometer, Turbidity meter, Photometer and Bacteriological analysis parameter were verified.

Microbial mercury methylation in the cryosphere: Progress and prospects

Mercury (Hg) is one of the most toxic heavy metals, and its cycle is mainly controlled by oxidation-reduction reactions carried out by photochemical or microbial process under suitable conditions. The deposition and accumulation of methylmercury (MeHg) in various ecosystems, including the cryospheric components such as snow, meltwater, glaciers, and ice sheet, and subsequently in the food chain pose serious health concerns for living beings. Unlike the abundance of knowledge about the processes of MeHg production over land and oceans, little is known about the sources and production/degradation rate of MeHg in cryosphere systems. In addition, processes controlling the concentration of Hg and MeHg in the cryosphere remains poorly understood, and filling this scientific gap has been challenging. Therefore, it is essential to study and review the deposition and accumulation by biological, physical, and chemical mechanisms involved in Hg methylation in the cryosphere. This review attempts to address knowledge gaps in understanding processes, especially biotic and abiotic, applicable for Hg methylation in the cryosphere. First, we focus on the variability in Hg concentration and mechanisms of Hg methylation, including physical, chemical, microbial, and biological processes, and transportation in the cryosphere. Then, we elaborate on the mechanism of redox reactions and biotic and abiotic factors controlling Hg methylation and biogeochemistry of Hg in the cryosphere. We also present possible mechanisms of Hg methylation with an emphasis on microbial transformation and molecular function to understand variability in Hg concentration in the cryosphere. Recent advancements in the genetic and physicochemical mechanisms of Hg methylation are also presented. Finally, we summarize and propose a method to study the unsolved issues of Hg methylation in the cryosphere.

Process optimization for simultaneous antibiotic removal and precious metal recovery in an energy neutral process

Conventional chemical and physical methods to remove antibiotics from wastewater consume large amount of energy and chemicals, and the efficiency of biological process in converting antibiotics is relatively low. Microbial electrolysis cell (MEC) has been employed to degrade recalcitrant organic compounds recently. Given it is an energy consuming device, it would be more sustainable if driven by renewable energy, e.g. power from microbial fuel cell (MFC). Here, chloramphenicol (CAP) was chosen as a representative antibiotic that is abundant in the environment, and Ag ion contained wastewater as electron acceptor in MFC, to demonstrate the feasibility of a self-driven system for recalcitrant removal and resource recovery. It was found that CAP removal in MEC can be successfully driven by Ag(I) reduced MFC without external energy consumption. Method of one-factor-at-a-time (OFAT) and response surface methodology (RSM) with central composite design were used to evaluate the system performance. Under the optimum condition, 99.8% of Ag(I) in MFC and 98.8% of CAP in MEC can be converted. EDX and XPS revealed that pure silver was obtained on the surface of electrode in MFC, reflecting Ag(I) was reduced to valuable product. The concept and methods developed in this study can be also applied to design other types of self-driven BES systems for simultaneous pollutants removal and resources recovery.

Hexavalent chromium removal from water by microalgal-based materials: Adsorption, desorption and recovery studies

The current study presents a comprehensive comparison towards the potential of different microalgal-based materials for the removal of hexavalent chromium (Cr(VI)) from water. Among the tested materials, microalgal biochar showed the highest removal efficiency (100%) of Cr(VI). The highest monolayer estimated adsorption capacities were 23.98, 25.19 and 24.27 mg/g at 5, 22 and 35 °C, respectively. Experimental data showed good compliance with pseudo-second-order kinetic model. The results of continuous column studies showed that the column removal efficiency increased from 52.33 to 57.58% by increasing the adsorbent dose from 0.125 to 0.200 g. Desorption efficiency of Cr(VI) by 0.1 M NaOH was increased from 51.16 to 59.41% by sonication bath as compared to roller shaker. More than 97% of desorbed Cr(VI) was recovered in less than 10 min by BaCl₂. This study shows that non-living microalga materials are more effective than living cells in the removal and recovery of Cr(VI) from water.

Bioremediation Options for Heavy Metal Pollution

BACKGROUND

Rapid industrialization and anthropogenic activities such as the unmanaged use of agro-chemicals, fossil fuel burning and dumping of sewage sludge have caused soils and waterways to be severely contaminated with heavy metals. Heavy metals are non-biodegradable and persist in the environment. Hence, remediation is required to avoid heavy metal leaching or mobilization into environmental segments and to facilitate their extraction.

OBJECTIVES

The present work briefly outlines the environmental occurrence of heavy metals and strategies for using microorganisms for bioremediation processes as reported in the scientific literature.

METHODS

Databases were searched from different libraries, including Google Scholar, Medline and Scopus. Observations across studies were then compared with the standards for discharge of environmental pollutants.

DISCUSSION

Bioremediation employs microorganisms for removing heavy metals. Microorganisms have adopted different mechanisms for bioremediation. These mechanisms are unique in their specific requirements, advantages, and disadvantages, the success of which depends chiefly upon the kind of organisms and the contaminants involved in the process.

CONCLUSIONS

Heavy metal pollution creates environmental stress for human beings, plants, animals and other organisms. A complete understanding of the process and various alternatives for remediation at different steps is needed to ensure effective and economic processes.

COMPETING INTERESTS

The authors declare no competing financial interests.

Optimization of Ni (II) biosorption from aqueous solution on modified lemon peel

The valorization of agricultural waste peels as a low-cost biosorbent is a promising approach to water treatment. In this work, the improvement of the adsorption capacity of lemon peel to remove Ni (II) from aqueous effluents was explored using several chemical modifiers: HNO₃, HCl, H₃PO₄, CaCl₂, NH₃ and NaOH. The surface pretreatment using NaOH was selected as the best option because of the improvement of the maximum adsorption capacity. The maximum adsorption capacity was of 36.74 mg g^-1 according to the Langmuir model at optimum conditions (pH = 5, S/L = 5 g L^-1, 25 °C). The pseudo-first order model of biosorption kinetics provides the best fit for experimental data. From thermodynamic studies, it was concluded that Ni (II) biosorption by modified lemon peel was endothermic and spontaneous. After five consecutives adsorption-desorption cycles using 0.1 M of HNO₃ and H₂SO₄, a recovery of 90% of Ni (II) was obtained. Regarding characterization of the biosorbent, the surface morphology was studied by Scanning Electron Microscopy while the functional groups responsible for Ni (II) adsorption were evaluated by Fourier transform infrared spectroscopy.

One-Step Removal of Calcium, Magnesium, and Nickel in Desalination by Alcaligenes aquatilis via Biomineralization

In desalination, a high level of calcium (Ca) and magnesium (Mg) ions in seawater can cause scale deposition on the reverse osmosis membranes and water treatment systems. This process can significantly affect the efficiency of desalination. In addition, heavy metals in seawater affect human health. Therefore, Alcaligenes aquatilis from seawater was used to remove Ca, Mg, and nickel (Ni) by microbial-induced carbonate precipitation (MICP). The purification system was then analyzed by ionic analysis and surface characterization. This study shows that the bacteria can utilize amino acids to produce carbonate and form precipitates with a high removal rate. MICP via A. aquatilis removed 91.8%, 68.5%, and 92.2% of the initial soluble Ca, Mg, and Ni, respectively. Furthermore, A. aquatilis can remove ammonium after the MICP process under oxygen-rich conditions. Therefore, we provide interesting insight into the use of Alcaligenes (in the absence of urea) to improve the seawater quality in the process of desalination.

Super Effective Removal of Toxic Metals Water Pollutants Using Multi Functionalized Polyacrylonitrile and Arabic Gum Grafts

Super adsorbent polymers can be considered to be a very efficient solution for wastewater treatment. In general, their adsorption capacities depend on the type and amount of the functional groups present on the surface of the polymers, while their economic value is affected by their cost. Therefore, this study aims to understand the effect of multi-functionalization of cheap Arabic gum on the adsorption capability toward heavy metals. Graft copolymers of polyacrylonitrile (PAN) onto Arabic gum (AG) were prepared in aqueous solution using (KMnO₄/HNO₃) as a redox initiator. Chemical modification of the graft copolymer was carried out by reaction with hydrazine hydrochloride followed by hydrolysis in the basic medium. The modified graft product was characterized by various techniques, such as Fourier transform infrared spectroscopy (FTIR), elemental analysis, scanning electron microscope (SEM), and X-ray powder diffraction (XRD). The modified graft copolymer was used to adsorb Pb²⁺, Cd²⁺ and Cu²⁺ from their aqueous solutions using batch extraction. Different parameters influence the uptake behavior, including contact time, pH, and the initial concentration of the metal ions; all of these were investigated. The kinetics were investigated using the pseudo first order and pseudo second order, and the equilibrium data were analyzed using the Langmuir and Freundlich model. The modified graft product showed the superadsorbent capacity to obtain maximum values (Qmax) 1017, 413 and 396 mg/g for Pb²⁺, Cd²⁺ and Cu²⁺, respectively. Acid treatment with 0.2 M HNO₃ resulted in 96%, 99% and 99% metal recovery for the Pb²⁺, Cd²⁺ and Cu²⁺, respectively. This indicates the recyclability of product for further usage upon drying between treatments.

Adsorption of indium by waste biomass of brown alga Ascophyllum nodosum

The biosorption capacities of dried meal and a waste product from the processing for biostimulant extract of Ascophyllum nodosum were evaluated as candidates for low-cost, effective biomaterials for the recovery of indium(III). The use of indium has significantly grown in the last decade, because of its utilization in hi-tech. Two formats were evaluated as biosorbents: waste-biomass, a residue derived from the alkaline extraction of a commercial, biostimulant product, and natural-biomass which was harvested, dried and milled as a commercial, "kelp meal" product. Two systems have been evaluated: ideal system with indium only, and double metal-system with indium and iron, where two different levels of iron were investigated. For both systems, the indium biosorption by the brown algal biomass was found to be pH-dependent, with an optimum at pH3. In the ideal system, indium adsorption was higher (maximum adsorptions of 48 mg/g for the processed, waste biomass and 63 mg/g for the natural biomass), than in the double metal-system where the maximum adsorption was with iron at 0.07 g/L. Good values of indium adsorption were demonstrated in both the ideal and double systems: there was competition between the iron and indium ions for the binding sites available in the A. nodosum-derived materials. Data suggested that the processed, waste biomass of the algae, could be a good biosorbent for its indium absorption properties. This had the double advantages of both recovery of indium (high economic importance), and also definition of a virtuous circular economic innovative strategy, whereby a waste becomes a valuable resource.

Amino modification of rice straw-derived biochar for enhancing its cadmium (II) ions adsorption from water

To enhance the adsorption capacity of Cd²⁺, -NH₂ groups were introduced into the rice straw-derived biochar surface by combining nitrification and amination. The batch and continuous Cd²⁺ adsorption experiments were performed to determine the role of -NH₂ groups on the surface of biochar. The physical and chemical characteristics were analyzed for comparison. The results indicated that the adsorption capacity of the modified biochar (BC-NH₂) was boosted by 72.1%. The results of continuous adsorption experiments in fixed bed columns showed that the penetration time of BC-NH₂ was three times that of original biochar. The adsorption of Cd²⁺ by BC-NH₂ is a spontaneous endothermic chemical reaction, which was obtained by combing sorption kinetics, isotherms and thermodynamic analysis. The Cd²⁺ adsorption was mainly the complexation between -NH₂ group on biochar surface and Cd²⁺ in solution. Finally, a possible interaction mechanism between Cd²⁺ and BC-NH₂ was proposed.

Microwave pyrolysis of walnut shell for reduction process of low-grade pyrolusite

Replacing fossil energy by utilizing biomass as carbon source to convert metal oxides has meaning for reduction of minerals. Microwave pyrolysis of walnut shell for reduction process of low-grade pyrolusite was proposed. Thermogravimetric analysis indicated biomass pyrolysis process for reduction of pyrolusite was divided into four phases identified by temperatures: dehydration stage (<150 °C), pre-pyrolysis stage (150 °C-290 °C), curing decomposition stage (290 °C-480 °C) and carbonization stage (>480 °C), and manganese recovery reached 92.01% at 650 °C for 30 min with 18% walnut shell. The strongest preferential orientation of MnO was appeared, with good crystalline structure and no MnO₂ and FeO peaks detected. The product surface became loose and porous with numerous cracks, pits and holes, and molten granules were interconnected and stacked with regular shape. The methods propose new idea of selective reduction of pyrolusite based on biomass pyrolysis by microwave heating.

Isolation and molecular characterization of the indigenous Staphylococcus aureus strain K1 with the ability to reduce hexavalent chromium for its application in bioremediation of metal-contaminated sites

BACKGROUND

Urbanization and industrialization are the main anthropogenic activities that are adding toxic heavy metals to the environment. Among these, chromium (in hexavalent: Cr+6 and/or trivalent Cr+3) is being released abundantly in wastewater due to its uses in different industrial processes. It becomes highly mutagenic and carcinogenic once it enters the cell through sulfate uptake pathways after interacting with cellular proteins and nucleic acids. However, Cr+6 can be bio-converted into more stable, less toxic and insoluble trivalent chromium using microbes. Hence in this study, we have made efforts to utilize chromium tolerant bacteria for bio-reduction of Cr+6 to Cr+3.

METHODS

Bacterial isolate, K1, from metal contaminated industrial effluent from Kala Shah Kaku-Lahore Pakistan, which tolerated up to 22 mM of Cr6+ was evaluated for chromate reduction. It was further characterized biochemically and molecularly by VITEK®2 system and 16S rRNA gene sequencing respectively. Other factors affecting the reduction of chromium such as initial chromate ion concentration, pH, temperature, contact-time were also investigated. The role of cellular surface in sorption of Cr6+ ion was analyzed by FTIR spectroscopy.

RESULTS

Both biochemical and phylogenetic analyses confirmed that strain K1 was Staphylococcusaureus that could reduce 99% of Cr6+ in 24 hours at 35 °C (pH = 8.0; initial Cr6+ concentration = 100 mg/L). FTIR results assumed that carboxyl, amino and phosphate groups of cell wall were involved in complexation with chromium. Our results suggested that Staphylococcusaureus K1 could be a promising gram-positive bacterium that might be utilized to remove chromium from metal polluted environments.

Lignocellulosic fraction of the pericarps of the acorns of Quercus suber and Quercus ilex: isolation, characterization, and biosorption studies in the removal of copper from aqueous solutions

Pericarps of Algerian Quercus ilex (Q. ilex) and Quercus suber (Q. suber) were used as copper adsorbents in artificially contaminated solutions. Exposing accessible lignocellulosic binding sites enhanced adsorption. The lignocellulosic fractions of Q. suber and Q. ilex (36.47±9.1 and 47.66±9.3, respectively) were characterized by FTIR before and after adsorption. The aim was to identify the functional groups adsorbing Cu(II). SEM/EDX determined lignocellulose surface morphology and composition. The amount of adsorbent-bound Cu(II) increased with initial [Cu(II)]. Cu(II) adsorption range was 23.59–48.06 mg.g−1 for Q. Suber and 22.56–38.19 mg.g−1 for Q. ilex when [Cu(II)] was 100–500 mg.L−1. Adsorption isotherms and Langmuir and Freundlich models of the Q. suber and Q. ilex lignocellulosic fractions indicated natural Cu(II)adsorption capacities (Qmax) of 53.76 mg.g−1 and 36.06 mg.g−1 and KF of 5.9 mg.g−1 and 7.43 mg.g−1, respectively.

Bioflocculant production and heavy metal sorption by metal resistant bacterial isolates from gold mining soil

Two bioflocculant producing bacterial isolates from mining soil samples were investigated for their application in heavy metal removal. The bacterial isolates were identified as Pseudomonas koreensis and Pantoea sp. using 16S rRNA gene. Cadmium resistant genes cadA and CzcD were detected in Pantoea sp. while P. koreensis harbor CzcD and chrA responsible for Cd and Cr resistance respectively. The isolates showed maximum flocculating activity of 71.3% and 51.7% with glucose and yield of 2.98 g L^-1 and 3.26 g L^-1 for Pantoea sp. and P. koreensis respectively. The optimum flocculating activity was achieved at pH 7.5 and temperature of 30 °C. Fourier transform infrared analysis of the bioflocculants produced by the two isolates showed the presence of carboxyl, hydroxyl and amino groups characteristic of polysaccharide and protein. Heavy metal sorption by bioflocculant of Pantoea sp. removed 51.2% Cd, 52.5% Cr and 80.5% Pb while that of P. koreensis removed 48.5% Cd, 42.5% Cr and 73.7% Pb. The bioflocculants produced have potential in metal removal from industrial wastes.

Chlorella vulgaris Modulates Genes and Muscle-Specific microRNAs Expression to Promote Myoblast Differentiation in Culture

Background

Loss of skeletal muscle mass, strength, and function due to gradual decline in the regeneration of skeletal muscle fibers was observed with advancing age. This condition is known as sarcopenia. Myogenic regulatory factors (MRFs) are essential in muscle regeneration as its activation leads to the differentiation of myoblasts to myofibers. Chlorella vulgaris is a coccoid green eukaryotic microalga that contains highly nutritious substances and has been reported for its pharmaceutical effects. The aim of this study was to determine the effect of C. vulgaris on the regulation of MRFs and myomiRs expression in young and senescent myoblasts during differentiation in vitro.

Methods

Human skeletal muscle myoblast (HSMM) cells were cultured and serial passaging was carried out to obtain young and senescent cells. The cells were then treated with C. vulgaris followed by differentiation induction. The expression of Pax7, MyoD1, Myf5, MEF2C, IGF1R, MYOG, TNNT1, PTEN, and MYH2 genes and miR-133b, miR-206, and miR-486 was determined in untreated and C. vulgaris-treated myoblasts on Days 0, 1, 3, 5, and 7 of differentiation.

Results

The expression of Pax7, MyoD1, Myf5, MEF2C, IGF1R, MYOG, TNNT1, and PTEN in control senescent myoblasts was significantly decreased on Day 0 of differentiation (p<0.05). Treatment with C. vulgaris upregulated Pax7, Myf5, MEF2C, IGF1R, MYOG, and PTEN in senescent myoblasts (p<0.05) and upregulated Pax7 and MYOG in young myoblasts (p<0.05). The expression of MyoD1 and Myf5 in young myoblasts however was significantly decreased on Day 0 of differentiation (p<0.05). During differentiation, the expression of these genes was increased with C. vulgaris treatment. Further analysis on myomiRs expression showed that miR-133b, miR-206, and miR-486 were significantly downregulated in senescent myoblasts on Day 0 of differentiation which was upregulated by C. vulgaris treatment (p<0.05). During differentiation, the expression of miR-133b and miR-206 was significantly increased with C. vulgaris treatment in both young and senescent myoblasts (p<0.05). However, no significant change was observed on the expression of miR-486 with C. vulgaris treatment.

Conclusions

C. vulgaris demonstrated the modulatory effects on the expression of MRFs and myomiRs during proliferation and differentiation of myoblasts in culture. These findings may indicate the beneficial effect of C. vulgaris in muscle regeneration during ageing thus may prevent sarcopenia in the elderly.

Utilization of acid hydrolysate of recovered bacterial cell as a novel organic nitrogen source for L-tryptophan fermentation

In this study, waste bacterial cell (WBC) was recovered and used as an alternative to yeast extract in L-tryptophan fermentation. The effects of sulfuric acid concentration and temperature on the hydrolysis of WBC were optimized and the amino acid content in the waste bacterial cell hydrolysate (WBCH) was increased. Plackett-Burman and Box-Behnken design analysis revealed the optimum composition of the WBCH-based fermentation medium to be 22.47 g/L WBCH, 2.26 g/L KH₂PO₄, and 1.25 mg/L vitamin H. L-tryptophan yield and productivity with WBCH as the nitrogen source were 52.3 g/L and 2.16 g/L/h, respectively, which were 13% and 18% higher than those obtained with the yeast extract as the nitrogen source. In addition, WBCH did not affect the growth of Escherichia coli during L-tryptophan fermentation. Cost accounting showed that WBCH could be used as a novel and cheap organic nitrogen source for industrial L-tryptophan production.

Metal Resistance in Bacteria from Contaminated Arctic Sediment is Driven by Metal Local Inputs

Anthropogenic impact over the Pasvik River (Arctic Norway) is mainly caused by emissions from runoff from smelter and mine wastes, as well as by domestic sewage from the Russian, Norwegian, and Finnish settlements situated on its catchment area. In this study, sediment samples from sites within the Pasvik River area with different histories of metal input were analyzed for metal contamination and occurrence of metal-resistant bacteria in late spring and summer of 2014. The major differences in microbial and chemical parameters were mostly dependent on local inputs than seasonality. Higher concentrations of metals were generally detected in July rather than May, with inner stations that became particularly enriched in Cr, Ni, Cu, and Zn, but without significant differences. Bacterial resistance to metals, which resulted from viable counts on amended agar plates, was in the order Ni²⁺>Pb²⁺>Co²⁺>Zn²⁺>Cu²⁺>Cd²⁺>Hg²⁺, with higher values that were generally determined at inner stations. Among a total of 286 bacterial isolates (mainly achieved from Ni- and Pb-amended plates), the 7.2% showed multiresistance at increasing metal concentration (up to 10,000 ppm). Selected multiresistant isolates belonged to the genera Stenotrophomonas, Arthrobacter, and Serratia. Results highlighted that bacteria, rapidly responding to changing conditions, could be considered as true indicators of the harmful effect caused by contaminants on human health and environment and suggested their potential application in bioremediation processes of metal-polluted cold sites.

Removal of Platinum and Palladium from Wastewater by Means of Biosorption on Fungi Aspergillus sp. and Yeast Saccharomyces sp

The emission of platinum group metals from different sources has caused elevated concentrations of platinum and palladium in samples of airborne particulate matter, soil, surface waters and sewage sludge. The ability of biomass of Aspergillus sp. and yeast Saccharomyces sp. for removal of Pt(IV) and Pd(II) from environmental samples was studied in this work. The pH of the solution, the mass of biosorbent, and contact time were optimized. The Langmuir and Freundlich adsorption isotherms and kinetic results were used for interpretation of the process equilibrium of Pt(IV) and Pd(II) on both microorganisms. The maximal efficiency of retention of Pt(IV) on yeast and fungi was obtained at acidic solutions (pH 2.0 for Pt(IV) and pH 2.5–3.5 for Pd(II)). The equilibrium of the biosorption process was attained within 45 min. The best interpretation for the experimental data was given by the Langmuir isotherm. Kinetics of the Pt and Pd adsorption process suit well the pseudo-second-order kinetics model. Fungi Aspergillus sp. shows higher adsorption capacity for both metals than yeast Saccharomyces sp. The maximum adsorption capacity of fungi was 5.49 mg g−1 for Pt(IV) and 4.28 mg g−1 for Pd(II). The fungi possess the ability for efficient removal of studied ions from different wastewater samples (sewage and road run-off water). It was also demonstrated, that quantitative recovery of Pd from industrial wastes could be obtained by biosorption using Aspergillus sp.

Graphene Composites for Lead Ions Removal from Aqueous Solutions

The indiscriminate disposal of non-biodegradable, heavy metal ionic pollutants from various sources, such as refineries, pulp industries, lead batteries, dyes, and other industrial effluents, into the aquatic environment is highly dangerous to the human health as well as to the environment. Among other heavy metals, lead (Pb(II)) ions are some of the most toxic pollutants generated from both anthropogenic and natural sources in very large amounts. Adsorption is the simplest, efficient and economic water decontamination technology. Hence, nanoadsorbents are a major focus of current research for the effective and selective removal of Pb(II) metal ions from aqueous solution. Nanoadsorbents based on graphene and its derivatives play a major role in the effective removal of toxic Pb(II) metal ions. This paper summarizes the applicability of graphene and functionalized graphene-based composite materials as Pb(II) ions adsorbent from aqueous solutions. In addition, the synthetic routes, adsorption process, conditions, as well as kinetic studies have been reviewed.

Multimetal tolerance mechanisms in bacteria: The resistance strategies acquired by bacteria that can be exploited to 'clean-up' heavy metal contaminants from water

Heavy metal pollution is one of the major environmental concerns worldwide. Toxic heavy metals when untreated get accumulated in environment and can pose severe threats to living organisms. It is well known that metals play a major role either directly or indirectly in different metabolic processes of bacteria. This allows bacterial cells to grow even in the presence of some toxic heavy metals. Microbial biotechnology has thus emerged as an effective and eco friendly solution in recent years for bioremediation of heavy metals. Therefore, this review is focused on summarising bacterial adaptation mechanisms for various heavy metals. It also shares some applications of have metal tolerant bacteria in bioremediation. Bacteria have evolved a number of processes for heavy metal tolerance viz., transportation across cell membrane, accumulation on cell wall, intra as well as extracellular entrapment, formation of complexes and redox reactions which form the basis of different bioremediation strategies. The genetic determinants for most of these resistances are located on plasmids however some may be chromosomal as well. Bacterial cells can uptake heavy by both ATP dependent and ATP independent processes. Bacterial cell wall also plays a very important role in accumulating heavy metals by bacterial cells. Gram-positive bacteria accumulate much higher concentrations of heavy metals on their cell walls than that of metals gram -ve bacteria. The role of bacterial metallothioneins (MTs) in heavy metal has also been reported. Thus, heavy metal tolerant bacteria are important for bioremediation of heavy metal pollutants from areas containing high concentrations of particular heavy metals.

Efficient Adsorption of Lead (II) from Aqueous Phase Solutions Using Polypyrrole-Based Activated Carbon

In this study, polypyrrole-based activated carbon was prepared by the carbonization of polypyrrole at 650 °C for 2 h in the presence of four-times the mass of KOH as a chemical activator. The structural and morphological properties of the product (polypyrrole-based activated carbon (PPyAC4)), analyzed by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and thermogravimetric analysis, support its applicability as an adsorbent. The adsorption characteristics of PPyAC4 were examined through the adsorption of lead ions from aqueous solutions. The influence of various factors, including initial ion concentration, pH, contact time, and adsorbent dose, on the adsorption of Pb²⁺ was investigated to identify the optimum adsorption conditions. The experimental data fit well to the pseudo-second-order kinetic model (R² = 0.9997) and the Freundlich isotherm equation (R² = 0.9950), suggesting a chemisorption pathway. The adsorption capacity was found to increase with increases in time and initial concentration, while it decreased with an increase in adsorbent dose. Additionally, the highest adsorption was attained at pH 5.5. The calculated maximum capacity, q_m, determined from the Langmuir model was 50 mg/g.

The effect of biochar mild air oxidation on the optimization of lead(II) adsorption from wastewater

In the present study, the effects of mild air oxidation of a biochar produced by the Pyrovac Inc. pyrolysis process, on the adsorption of lead(II) from synthetic wastewater under batch experimental conditions have been investigated. The adsorption experiments were performed under several conditions suggested by the response surface methodology, which allowed finding the optimal conditions, in order to maximize the adsorption capacity (Q(mgg^-1)), as well as the extraction efficiency (E (%)). The optimal conditions of lead ions adsorption were as follows: pH = 5, agitation time = 300 min, adsorbent mass = 0.5 g (per 50 cm³ of solution), and lead initial concentration = 100gm^-3, resulted in an adsorption capacity of 7.9 mg g^-1. Equilibrium adsorption was then obtained by keeping pH and adsorbent mass at the optimal values and changing the lead initial concentration for a sufficient agitation time. Results showed that mild air oxidation increased the equilibrium adsorption capacity of biochar from 2.5 to 44 mg g^-1. Oxidized biochar after equilibrium adsorption was submitted to SEM/EDX and XPS analysis. From SEM it was found that lead particles were distributed heterogeneously after adsorption. From XPS analysis, it was revealed that the external surface of oxidized biochar particles becomes saturated for the initial point of equilibrium diagram, obtained at lead initial concentration of 100gm^-3, suggesting that for a higher concentration, the internal surfaces of particles participate in the cations adsorption. The participation of surface functional groups in the adsorption process showed that carbonyl, carboxylic, and aromatic rings of oxidized biochar were involved in the adsorption. This work suggests that the very simple process of mild air oxidation can be used instead of the usual costly chemical activation, in order to improve biochar cation exchange capacity.

Technologies applicable to the removal of heavy metals from landfill leachate

This article presents a review of the main physical, chemical, electrochemical, and biological technologies used for treating heavy metals in the wastewater of industrial processes and in synthetic aqueous solutions which could be applied to leachate from landfills. This paper outlines the generalities, operating principles, and modifications made to the technologies described. It discusses and assesses which of these have better removal rates and higher levels of efficiency in minimizing the heavy metal concentrations contained in leachates, such as mercury, chromium, lead, nickel, and copper among others. The first part of the document presents the so-called conventional technologies, such as chemical, physical, and electrochemical treatment. These have been used to treat different wastewater, especially industrial waste, operating adequately from the technical topic, but with high costs and the secondary products' production. The second part exposes biological treatments tend to be most widely used due to their versatility, effectiveness, and low cost, when compared with traditional technologies. It is important to note that there is no single treatment and that each of the technologies reviewed has different heavy metal decontamination rates. All technologies search to reduce concentrations of heavy metals to values that are safe for the natural resources where they are discharged or disposed, thereby complying with the regulatory limits regulated in each of the regions.

Enhanced biosorption of transition metals by living Chlorella vulgaris immobilized in Ca-alginate beads

In this study freely suspended and Ca-alginate immobilized C. vulgaris cells were used for the biosorption of Fe(II), Mn(II), and Zn(II) ions, from the aqueous solution. Experimental data showed that biosorption capacity of algal cells was strongly dependent on the operational condition such as pH, initial metal ions concentration, dosages, contact time and temperature. The maximum biosorption of Fe(II) 43.43, Mn(II) 40.98 and Zn(II) 37.43 mg/g was achieved with Ca-alginate immobilized algal cells at optimum pH of 6.0, algal cells dosage 0.6 g/L, and contact time of 450 min at room temperature. The biosorption efficiency of freely suspended and immobilized C. vulgaris cells for heavy metals removal from the industrial wastewater was validated. Modeling of biosorption kinetics showed good agreements with pseudo-second-order. Langmuir and D-R isotherm models exhibited the best fit of experimental data. The thermodynamic parameters (ΔG°, ΔH°, and ΔS°) revealed that the biosorption of considered metal ions was feasible, spontaneous and exothermic at 25-45°C. The SEM showed porous morphology which greatly helps in the biosorption of heavy metals. The Fourier transform infrared spectrophotometer (FTIR) and X-rays Photon Spectroscopy (XPS) data spectra indicated that the functional groups predominately involved in the biosorption were C-N, -OH, COO-, -CH, C=C, C=S and -C-. These results shows that immobilized algal cells in alginate beads could potentially enhance the biosorption of considered metal ions than freely suspended cells. Furthermore, the biosorbent has significantly removed heavy metals from industrial wastewater at the optimized condition.

Amidoxime-Functionalized Macroporous Carbon Self-Refreshed Electrode Materials for Rapid and High-Capacity Removal of Heavy Metal from Water

Heavy metal pollution continues to be one of the most serious environmental problems which has attracted major global concern. Here, a rapid, high-capacity, yet economical strategy for deep cleaning of heavy metals ions in water is reported based on amidoxime-functionalized macroporous carbon electrode materials. The active sites of our material can be self-refreshed during the electrochemical removal process, which is different from traditional methods. The novel filter device in this work can purify contaminated water very rapidly (3000 L h^-1 m^-2), and can decrease heavy metal ion concentrations to below 5 ppb with a very short contact time (only 3 s). The original treatment efficiency of the device can be retained even after 1 week of continuous device operation. An extremely high removal capacity of over 2300 mg g^-1 can be achieved with 2-3 orders of magnitude higher efficiency than that of surface adsorption-based commercial filters without any decay. Additionally, the cost of energy consumed in our method is lower than $6.67 × 10^-3 per ton of wastewater. We envision that this approach can be routinely applied for the rapid, efficient, and thorough removal of heavy metals from both point-of-use water and industrial wastewater.

Integrated bio-oxidation and adsorptive filtration reactor for removal of arsenic from wastewater

Recently, removal of arsenic from different industrial effluent discharged using simple, efficient and low-cost technique has been widely considered. In this study, removal of arsenic (As) from real wastewater has been studied employing modified bio-oxidation followed by adsorptive filtration method in a novel continuous flow through the reactor. This method includes biological oxidation of ferrous to ferric ions by immobilized Acidothiobacillus ferrooxidans bacteria on granulated activated carbon (GAC) in fixed bed bio-column reactor with the adsorptive filtration unit. Removal efficiency was optimized regarding the initial flow rate of media and ferrous ions concentration. Synthetic wastewater sample having different heavy metal ions such as Arsenic (As), Cobalt (Co), Chromium (Cr), Copper (Cu), Iron (Fe), Lead (Pb) and Manganese (Mn) were also used in the study. The structural and surface changes occurring after the treatment process were scrutinized using FT-IR and Scanning Electron Microscopy (SEM) analysis. The finding showed that not only arsenic can be removed considerably in the bioreactor system, but also removing efficiency was much more (<90%) for other heavy metals in real wastewater sample. The results from TCPL test confirms that solid spent media was non-hazardous and can be safely disposed of. This study verified that combination of bio-oxidation with adsorptive filtration method improves the removal efficiency of arsenic and other heavy metal ions in wastewater sample.

Green alga-mediated treatment process for removal of zinc from synthetic solution and industrial effluent

The present work explored biosorption of Zn(II) ions from aqueous and zinc-bearing factory effluent using marine seaweed Ulva lactuca. The batch pH edge experiments using aqueous zinc solution indicated that Zn(II) uptake by U. lactuca was found to be maximum at pH 4.5 and the batch isotherm trials performed at pH 4.5 resulted in maximum uptake capacity of 128.0 mg Zn(II)/g. With 0.1 M CaCl₂ (pH 3.5, HCl) as elutant, the elution of Zn(II) ions from Zn(II)-laden U. lactuca biosorbent was effective with possible regeneration and reuse for three cycles. The zinc industrial effluent was found to comprise of 87.8 mg/L of zinc ions along with excess co-ions and high total dissolved solids (838.1 mg/L). Owing to this, Zn(II) uptake from electroplating effluent by U. lactuca was suppressed due to competition from other ions. Continuous-flow sorption trials were conducted at flow rate of 5 mL/min in an up-flow fixed column. The existence of surplus competing ions in zinc wastewater influenced the Zn(II) biosorption by U. lactuca. U. lactuca-loaded packed column exhibited uptakes of 78.3 and 70.8 mg Zn(II)/g for aqueous solution and effluent, respectively. The results of three continuous sorption-desorption cycles demonstrated that reuse of U. lactuca biosorbent in remediation of zinc-containing wastewaters was practical and economical.

The Use of Microalgae for Coupling Wastewater Treatment With CO2 Biofixation

Production and emission of CO2 from different sources have caused significant changes in the climate, which is the major concern related to global warming. Among other CO2 removal approaches, microalgae can efficiently remove CO2 through the rapid production of algal biomass. In addition, microalgae have the potential to be used in wastewater treatment. Although, wastewater treatment and CO2 removal by microalgae have been studied separately for a long time, there is no detailed information available on combining both processes. In this review article, microalgae-based CO2 biofixation, various microalgae cultivation systems,¯ and microalgae-derived wastewater treatment are separately discussed, followed by the concept of integration of CO2 biofixation process and wastewater treatment. In each section, details of energy efficiency and differences across microalgae species are also given.

Application of phytoremediation technology in decontamination of a fish culture pond fed with coal mine effluent using three aquatic macrophytes

In the present study, three aquatic macrophytes, Eichhornia crassipes, Salvinia molesta, and Pistia stratiotes were used to assess their relative efficacies in decontamination of a fish culture pond, regularly fed with coal mine effluent (CME). The level of metals like Fe, Mn, Ni, Zn, Cu, Pb, Cr, and Cd were much higher in CME-fed pond water than their recommended limits in drinking water set by the Bureau of Indian standards and in effluents by the Environmental Protection Agency. The levels of metal were lowered substantially in CME-fed pond water after exposure of the above plants to such water, however, metal levels in the plants increased tremendously. The increased metal levels in plants severely damaged their physiological and biochemical processes. The contents of chlorophyll a, b and carotenoid were reduced by 63.2, 64.2, and 46.3%, respectively, in E. crassipes, 41, 57.4, and 57.8% in S. molesta, and 42, 62, and 61% in P. stratiotes. The accumulating metals also generated oxidative stress in plants, as evident from the increased superoxide dismutase and catalase activities and enhanced malondialdehyde content. The E. crassipes was the most potent in absorbing the metals from the CME-fed pond water, followed by S. molesta and P. stratiotes.

Novel Magnetic Nanostructured Beads for Cadmium(II) Removal

This study presents an effective magnetic separation method for cadmium removal, based on the use of a novel nanostructured material as an adsorbent. This adsorbent involves the incorporation of magnetite nanoparticles (Fe₃O₄-NPs), synthesized by the reverse coprecipitation method, into sodium alginate and activated carbon to form spherical structures by crosslinking Ca2+ ions with the charged alginate chains, referred to as magnetic alginate activated carbon (MAAC) beads. The effect of the experimental parameters, such as pH, contacting time, adsorbent dosage, agitation type, and rotating speed were investigated and optimized for an efficient removal of Cd(II) ions at an initial concentration of 250 mg/L. The amount of adsorbed Cd(II) by MAAC beads increased at a pH of 6 with a removal efficiency over 90%. The maximum adsorption capacity reached was 70 mg/g of adsorbent at an initial Cd(II) concentration of 150 mg/L, whereas at 250 mg/L the adsorption capacity lowered until 60 mg/g. Sorption isotherms were calculated using Langmuir, Freundlich, Temkin, and Dubinin⁻Radushkevich equations, and were better described by the Freundlich and Temkin models. These results proved the removal efficiency and the potential use under real environmental conditions of the MAAC beads, due to their easy recovery from contaminated aqueous solutions.