Adsorptive removal of cadmium ions by Spirulina platensis dry biomass

The biomolecules of Euglena gracilis: Harnessing biology for natural solutions to future problems

Over the past decade, the autotrophic and heterotrophic protist Euglena gracilis (E. gracilis) has gained popularity across the studies of environmental science, biosynthesis experiments, and nutritional substitutes. The unique physiology and versatile metabolism of E. gracilis have been a recent topic of interest to many researchers who continue to understand the complexity and possibilities of using E. gracilis biomolecule production. In this review, we present a comprehensive representation of recent literature outlining the various uses of biomolecules derived from E. gracilis across the fields of natural product biosynthesis, as a nutritional substitute, and as bioremediation tools. In addition, we highlight effective strategies for altering metabolite production using abiotic stressors and growth conditions. To better understand metabolite biosynthesis and its role in E. gracilis, integrated studies involving genomics, metabolomics, and proteomics should be considered. Together, we show how the ongoing advancements in E. gracilis related research continue to broaden applications in the biosynthetic sector and highlight future works that would strengthen our understanding of overall Euglena metabolism.

Biomedical engineering utilizing living photosynthetic cyanobacteria and microalgae: Current status and future prospects

Cyanobacteria are the only prokaryotes capable of performing oxygenic photosynthesis on Earth. Besides their traditional roles serving as primary producers, cyanobacteria also synthesize abundant secondary metabolites including carotenoids, alkaloids, peptides, which have been reported to possess medicinal potentials. More importantly, the advancement of synthetic biology technology has further expanded their potential biomedical applications especially using living/engineered cyanobacteria, providing promising and attractive strategies for future disease treatments. To improve the understanding and to facilitate future applications, this review aims to discuss the current status and future prospects of cyanobacterial-based biomedical engineering. Firstly, specific properties of cyanobacteria related with biomedical applications like their natural products of bioactive compounds and heavy metal adsorption were concluded. Subsequently, based on these properties of cyanobacteria, we discussed the progress of their applications in various disease models like hypoxia microenvironment alleviation, wound healing, drug delivery, and so on. Finally, the future prospects including further exploration of cyanobacteria secondary metabolites, the integration of bioactive compounds synthesized by cyanobacteria in situ with medical diagnosis and treatment, and the optimization of in vivo application were critically presented. The review will promote the studies related with cyanobacteria-based biomedical engineering and its practical application in clinical trials in the future.

The extracellular polymeric substances (EPS) accumulation of Spirulina platensis responding to Cadmium (Cd2+) exposure

Spirulina platensis can secrete extracellular polymeric substances (EPS) helping to protect damage from stress environment, such as cadmium (Cd2+) exposure. However, the responding mechanism of S. platensis and the secreted EPS to exposure of Cd2+ is still unclear. This research focuses on the effects of Cd2+ on the composition and structure of the EPS and the response mechanism of EPS secretion from S. platensis for Cd2+ exposure. S. platensis can produce 261.37 mg·g-1 EPS when exposing to 20 mg·L-1 CdCl2, which was 2.5 times higher than the control group. The S. platensis EPS with and without Cd2+ treatment presented similar and stable irregularly fibrous structure. The monosaccharides composition of EPS in Cd2+ treated group are similar with control group but with different monosaccharides molar ratios, especially for Rha, Gal, Glc and Glc-UA. And the Cd2+ treatment resulted in a remarkable decline of humic acid and fulvic acid content. The antioxidant ability of S. platensis EPS increased significantly when exposed to 20 mg·L-1 CdCl2, which could be helpful for S. platensis protecting damage from high concentration of Cd2+. The transcriptome analysis showed that sulfur related metabolic pathways were up-regulated significantly, which promoted the synthesis of sulfur-containing amino acids and the secretion of large amounts of EPS.

New insights into the potential cardioprotective effects of telmisartan and nanoformulated extract of Spirulina platensis via regulation of oxidative stress, apoptosis, and autophagy in an experimental model

Background

Cardiotoxicity is one of the limiting side effects of the commonly used anticancer agent cyclophosphamide (Cyclo).

Materials and methods

The possible protective effects of telmisartan and nanoformulated Spirulina platensis (Sp) methanolic extract against Cyclo-induced cardiotoxicity were examined in this study. Experimental groups of rats were randomly divided into nine groups as control vehicle, control polymer, telmisartan (TEL, 10 mg/kg), free Sp extract (300 mg/kg), nano Sp extract (100 mg/kg), Cyclo (200 mg/kg), TEL + Cyclo, free Sp + Cyclo, and nano Sp + Cyclo. The groups with Cyclo combinations were treated in the same manner as their corresponding ones without Cyclo, with a single dose of Cyclo on day 18.

Results

The results indicate that Cyclo causes significant cardiotoxicity, manifesting in the form of notable increases of 155.49%, 105.74%, 451.76%, and 826.07% in the serum levels of glutamic oxaloacetic transaminase (SGOT), lactate dehydrogenase (LDH), creatine kinase MB (CK-MB), and cardiac troponin I (cTnI) enzyme activities, respectively, as compared to the control. In addition, the cardiac glutathione (GSH) content and activity of glutathione peroxidase-1 (GPX-1) enzyme decreased by 65.94% and 73.85%, respectively. Treatment with nano Sp extract showed the most prominent restorations of the altered biochemical, histopathological, and immunohistochemical features as compared with those by TEL and free Sp; moreover, reductions of 30.64% and 43.02% in the p-AKT content as well as 60.43% and 75.30% of the endothelial nitric oxide synthase (eNOS) immunoreactivity were detected in the TEL and free Sp treatment groups, respectively. Interestingly, nano Sp boosted the autophagy signal via activation of beclin-1 (36.42% and 153.4%), activation of LC3II (69.13% and 195%), downregulation of p62 expressions (39.68% and 62.45%), and increased gene expressions of paraoxonase-1 (PON-1) (90.3% and 225.9%) compared to the TEL and free Sp treatment groups, respectively.

Conclusion

The findings suggest the protective efficiency of telmisartan and nano Sp extract against cardiotoxicity via activations of the antioxidant, antiapoptotic, and autophagy signaling pathways.

Dielectrophoresis-assisted removal of Cd and Cu heavy metal ions by using Chlorella microalgae

A novel dielectrophoresis (DEP)-assisted device for the bioremediation of heavy metal ions by using Chlorella microalgae is presented in this paper. To generate the DEP forces, pairs of electrode mesh were inserted in the DEP-assisted device. By applying DC electric field via the electrodes, the inhomogeneous electric field gradient is induced and the strongest non-uniform electric field exists near the mesh cross-corner. After the adsorption of Cd and Cu heavy metal ions by Chlorella, the Chlorella chain were trapped along the vicinity of the electrode mesh. Then, the effects of Chlorella concentration on the adsorption of heavy metal ions, and the applied voltage and electrode mesh size on the removal of Chlorella are conducted. In the co-existing Cd and Cu solutions, the individual adsorption ratio of Cd and Cu reaches as high as approximately 96% and 98%, respectively, showing excellent bioremediation capability of multiple heavy metal ions in wastewater. By adjusting the applied electric voltage and the mesh size, the Chlorella adsorbed with Cd and Cu are captured by negative DC-DEP effects and the removal ratio of Chlorella reach an average of 97%, providing a method for the removal of multiple heavy metal ions in wastewater by using Chlorella microalgae.

Removal of As(III) using a microorganism sustained secrete laccase-straw oxidation system

While laccase oxidation is a novel and promising method for treating arsenite-containing wastewater, the high cost and unsustainability of commercially available enzymes indicate a need to investigate more cost-effective viable alternatives. Here, a microorganism sustained secrete laccase-straw oxidation system (MLOS) was established and subsequently evaluated for the removal of As(III). MLOS showed efficient biological As(III) oxidation, with an As(III) removal efficiency reaching 99.9% at an initial As(III) concentration of 1.0 mg·L^-1. IC-AFS and XPS analysis showed that As(III) was partially oxidized to As(V), and partially As(III) adsorbed on the surface of rice straw. FTIR analysis revealed that hydroxyl, amine and amide groups were all involved in the As(III) removal process. SEM-EDS demonstrated that the surface structure of rice straw was destroyed following Comamonas testosteroni FJ17 (C. testosteroni FJ17) treatment, and the metal ions binding sites of rice straw were increased resulting in elemental arsenic being detected on the material surface. Molecular docking revealed the interaction between key residues of laccase and As(III). Laccase activity was negatively correlated with Cu(II) concentration in the As(III) oxidation. EEM showed that humic-like acids were also involved in the interaction with As(III). Overall, a MLOS derived from biomass waste has a significant potential to be developed as a green and sustainable technology for the treatment of wastewater containing As(III).

Biosorption of Cadmium and Lead by Dry Biomass of Nostoc sp. MK-11: Kinetic and Isotherm Study

Cadmium (Cd) and lead (Pb) are global environmental pollutants. In this study, Nostoc sp. MK-11 was used as an environmentally safe, economical, and efficient biosorbent for the removal of Cd and Pb ions from synthetic aqueous solutions. Nostoc sp. MK-11 was identified on a morphological and molecular basis using light microscopic, 16S rRNA sequences and phylogenetic analysis. Batch experiments were performed to determine the most significant factors for the removal of Cd and Pb ions from the synthetic aqueous solutions using dry Nostoc sp. MK1 biomass. The results indicated that the maximum biosorption of Pb and Cd ions was found under the conditions of 1 g of dry Nostoc sp. MK-11 biomass, 100 mg/L of initial metal concentrations, and 60 min contact time at pH 4 and 5 for Pb and Cd, respectively. Dry Nostoc sp. MK-11 biomass samples before and after biosorption were characterized using FTIR and SEM. A kinetic study showed that a pseudo second order kinetic model was well fitted rather than the pseudo first order. Three isotherm models Freundlich, Langmuir, and Temkin were used to explain the biosorption isotherms of metal ions by Nostoc sp. MK-11 dry biomass. Langmuir isotherm, which explains the existence of monolayer adsorption, fitted well to the biosorption process. Considering the Langmuir isotherm model, the maximum biosorption capacity (q_max) of Nostoc sp. MK-11 dry biomass was calculated as 75.757 and 83.963 mg g^-1 for Cd and Pb, respectively, which showed agreement with the obtained experimental values. Desorption investigations were carried out to evaluate the reusability of the biomass and the recovery of the metal ions. It was found that the desorption of Cd and Pb was above 90%. The dry biomass of Nostoc sp. MK-11 was proven to be efficient and cost-effective for removing Cd and especially Pb metal ions from the aqueous solutions, and the process is eco-friendly, feasible, and reliable.

Recent advances in bioremediation of heavy metals and persistent organic pollutants: A review

Heavy metals and persistent organic pollutants are causing detrimental effects on the environment. The seepage of heavy metals through untreated industrial waste destroys the crops and lands. Moreover, incineration and combustion of several products are responsible for primary and secondary emissions of pollutants. This review has gathered the remediation strategies, current bioremediation technologies, and their primary use in both in situ and ex situ methods, followed by a detailed explanation for bioremediation over other techniques. However, an amalgam of bioremediation techniques and nanotechnology could be a breakthrough in cleaning the environment by degrading heavy metals and persistant organic pollutants.

Recent progress in microalgae-derived biochar for the treatment of textile industry wastewater

Textile industry utilize a massive amount of dyes for coloring. The dye-containing effluent is released into wastewater along with heavy metals that are part of dye structure. The treatment of textile industry wastewater using conventional techniques (coagulation, membrane technique, electrolysis ion exchange, etc.) is uneconomical and less efficient (for a low concentration of pollutants). Moreover, most of these techniques produce toxic sludge, making them less environmentally friendly. Algae base industry is growing for food, cosmetics and energy needs. Algae biomass in unique compared to lignocellulosic biomass due to presence of various functional group on its surface and presence of various cations. These two characteristics are unique for biochar as a tool for environmental decontamination. Algae biomass contain functional groups and cations that can be effective for removal of organic contaminants (dyes) and heavy metals. Algae can be micro and macro and both have entirely different biomass composition which will lead to a synthesis of different biochar even under same synthesis process. This study reviews the recent progress in the development of an economically viable and eco-friendly approach for textile industry wastewater using algae biomass-derived absorbents. The strategy employed microalgal biochar to remove organic pollutants (dyes) and heavy metals from textile effluents by biosorption. This article discusses different methods for preparing algal biochar (pyrolysis, hydrothermal carbonization and torrefaction), and the adsorption capacity of biochar for dyes and heavy metals. Work on hydrothermal carbonization and torrefaction of microalgal biomass for biochar is limited. Variation in structural and functional groups changes on biochar compared to original microalgal biomass are profound in contract with lignocellulosic biomass. Existing Challenges, future goals, and the development of these technologies at the pilot level are also discussed.

Synergistic Impacts of Arsenic and Antimony Co-contamination on Diazotrophic Communities

Nitrogen (N) shortage poses a great challenge to the implementation of in situ bioremediation practices in mining-contaminated sites. Diazotrophs can fix atmospheric N₂ into a bioavailable form to plants and microorganisms inhabiting adverse habitats. Increasing numbers of studies mainly focused on the diazotrophic communities in the agroecosystems, while those communities in mining areas are still not well understood. This study compared the variations of diazotrophic communities in composition and interactions in the mining areas with different extents of arsenic (As) and antimony (Sb) contamination. As and Sb co-contamination increased alpha diversities and the abundance of nifH encoding the dinitrogenase reductase, while inhibited the diazotrophic interactions and substantially changed the composition of communities. Based on the multiple lines of evidence (e.g., the enrichment analysis of diazotrophs, microbe-microbe network, and random forest regression), six diazotrophs (e.g., Sinorhizobium, Dechloromonas, Trichormus, Herbaspirillum, Desmonostoc, and Klebsiella) were identified as keystone taxa. Environment-microbe network and random forest prediction demonstrated that these keystone taxa were highly correlated with the As and Sb contamination fractions. All these results imply that the above-mentioned diazotrophs may be resistant to metal(loid)s.

A comprehensive study on aquatic chemistry, health risk and remediation techniques of cadmium in groundwater

Cadmium (Cd), a non-essential trace element, it's intrusion in groundwater has ubiquitous implications on the environment and human health. This review is an approach to comprehensively emphasize on i) chemistry and occurrence of Cd in groundwater and its concomitant response on human health ii) sustainable Cd remediation techniques, iii) and associated costs. Current study is depending on meta-analysis of Cd contaminations in groundwater and discusses its distributions around the globe. Literature review primarily comprises from the last three decades online electronic published database, which mainly includes i) research literatures, ii) government reports. On the basis of meta-data, it was concluded that Cd mobility depends on multiple factors: such as pH, redox state, and ionic strength, dissolved organic (DOC) and inorganic carbon (DIC). A substantially high Cd concentration has been reported in Lagos, Nigeria (0.130 mg/L). In India, groundwater is continuing to be contaminated by Cd in the proximity of industrial, agricultural areas, high concentrations (>8.20 mg/L) were reported in Tamil Nadu and Maharashtra. Depending on chemical behavior and ionic radius cadmium disseminate into the food chain and ultimately cause health hazard that can be measured by various index-based assessment tools. Instead of chemical adsorbents, nanoparticles, phytoextraction, and bioremediation techniques can be very useful in the remediation and management of Cd polluted groundwater at a low-cost. For Cd pollution, the development of a comprehensive framework that links the hydro-geological, bio-geochemical processes to public health is important and need to be further studied.

Waste Stabilization Pond (WSP) for wastewater treatment: A review on factors, modelling and cost analysis

Waste stabilization pond (WSP) is natural technology which can be installed in centralized or semi-centralized sewerage systems for treatment of domestic and industrial wastewater, septage and sludge, etc. WSPs are highly efficient, simple to construct, low cost and easy to operate. It can be used as secondary or tertiary treatment unit in a treatment plant either individually or in a coupling manner. The algal-bacterial symbiosis in WSP makes it completely natural treatment process for which it becomes economic as compared to other treatment technologies in terms of its maintenance cost and energy requirement. Effluent from WSP can also be used for agricultural purpose, gardening, watering road, vehicle wash, etc. Advance technologies are being integrated for better design and efficiency of WSP, but the main challenges are the separation and removal of algal species which lead to deterioration of the water if stays long. Research is necessary to maximize algal growth yield, selection of beneficial strain and optimizing harvesting methods. This review focuses on the treatment mechanism in the pond, affecting factors, types of ponds, design equation, cost analysis.

Genomic and proteomic insights into the heavy metal bioremediation by cyanobacteria

Heavy metals (HMs) pose a global ecological threat due to their toxic effects on aquatic and terrestrial life. Effective remediation of HMs from the environment can help to restore soil's fertility and ecological vigor, one of the key Sustainable Development Goals (SDG) set by the United Nations. The cyanobacteria have emerged as a potential option for bioremediation of HMs due to their unique adaptations and robust metabolic machineries. Generally, cyanobacteria deploy multifarious mechanisms such as biosorption, bioaccumulation, activation of metal transporters, biotransformation and induction of detoxifying enzymes to sequester and minimize the toxic effects of heavy metals. Therefore, understanding the physiological responses and regulation of adaptation mechanisms at molecular level is necessary to unravel the candidate genes and proteins which can be manipulated to improve the bioremediation efficiency of cyanobacteria. Chaperons, cellular metabolites (extracellular polymers, biosurfactants), transcriptional regulators, metal transporters, phytochelatins and metallothioneins are some of the potential targets for strain engineering. In the present review, we have discussed the potential of cyanobacteria for HM bioremediation and provided a deeper insight into their genomic and proteomic regulation of various tolerance mechanisms. These approaches might pave new possibilities of implementing genetic engineering strategies for improving bioremediation efficiency with a future perspective.

Primary biosorption mechanism of lead (II) and cadmium (II) cations from aqueous solution by pomelo (Citrus maxima) fruit peels

The present work investigates the primary adsorption mechanisms of lead (II) and cadmium (II) cations onto pomelo fruit peel (PFP) from aqueous solution. pH, adsorption time, ion strength, and initial metal cation concentrations, which are factors affecting the uptake of these cations, are investigated. Results show that pH and ion strengths strongly affect the removal of these cations from aqueous solution. Different isotherm adsorption models, such as Langmuir, Freundlich, and Sips, are utilized to fit the experimental data in order to determine the adsorption in nature. The Langmuir monolayer adsorption capacities are found to be 47.18 mg/g for lead (II) and 13.35 mg/g for cadmium (II). Kinetic and thermodynamic studies based on a combination of FT-IR and TG-DSC spectroscopies demonstrate that electrostatic attraction plays a primary adsorption mechanism of lead (II) and cadmium (II) cations onto pomelo fruit peel.

Effect of zinc-containing systems on Spirulina platensis bioaccumulation capacity and biochemical composition

Cyanobacteria Spirulina platensis due to its high biosorption and bioaccumulation capacity toward metal ions can be considered as an excellent candidate for environmental bioremediation. The effect of Zn and in different combinations on the accumulation capacity of Spirulina platensis biomass and its biochemical composition was investigated. Four Zn-containing systems with a different combination of metal ions (Zn; Zn/Cu/Sr; Zn/Cu/Ni; Zn/Cu/Sr/Ba) and different metal concentrations were modeled. Studied systems were introduced in the cultivation medium on the fifth day of biomass grow and experiments were performed in three variants, which differed by metal ions concentrations. Metal uptake by biomass was traced using neutron activation analysis. Spirulina platensis showed a high accumulation capacity for all metal ions present in the analyzed system. Because the metals were added at the beginning of the stationary growth phase, the contact with the biomass was only 24 h, even at the highest metal concentration in the systems, the accumulation of Spirulina platensis biomass was reduced by no more than 11.2%. Spirulina platensis biomass grown in a mono-metallic system expressed two biochemical indicators of stress: decrease of phycobiliprotein content and increase of malondialdehyde content. In biomass grown in the presence of Zn-containing multi-metallic systems, three indicators of stress were expressed: decrease of protein content, reduction of phycobiliprotein content, and increase of malondialdehyde content. Spirulina platensis biomass can be considered as an effective accumulator for the treatment of zinc-containing industrial effluents.

Efficiency of extremophilic microbial mats for removing Pb(II), Cu(II), and Ni(II) ions from aqueous solutions

Two different extremophilic films were used as natural biosorbents to remove Cu(II), Ni(II), and Pb(II) from aqueous solutions. Surface area, scanning electron microscopy imaging, and Fourier transformation infrared spectroscopy were used to characterize the surfaces of the biosorbents. The results indicated high affinity of the biosorbents to remove Pb(II), Cu(II), and Ni(II), with adsorption rates ranging from 73.6 to 100% for both biosorbents. The biosorbents succeed in removing the metal ions from aqueous mixtures in the following order: Pb(II) > Cu(II) > Ni(II). The maximum removal rates of metal ions were achieved at pH 6, contact time of 150 min, biosorbent dose of 2.5 g/L, and metal ion concentration of 50 mg/L. The isothermal studies showed that both Langmuir and Freundlich models well expressed the adsorption process. Kinetically, the pseudo-second-order reaction better expressed the type of reaction than the pseudo-first-order reaction.

Integrated approach for enhanced bio-oil recovery from disposed face masks through co-hydrothermal liquefaction with Spirulina platensis grown in wastewater

Currently, the enormous generation of contaminated disposed face masks raises many environmental concerns. The present study provides a novel route for efficient crude bio-oil production from disposed masks through co-hydrothermal liquefaction (Co-HTL) with Spirulina platensis grown in wastewater. Ultimate and proximate analysis confirmed that S. platensis contains relatively high nitrogen content (9.13%dw), which decreased by increasing the mask blend ratio. However, carbon and hydrogen contents were higher in masks (83.84 and 13.77%dw, respectively). In addition, masks showed 29.6% higher volatiles than S. platensis, which resulted in 94.2% lower ash content. Thermal decomposition of masks started at a higher temperature (≈330 °C) comparing to S. platensis (≈208 °C). The highest bio-oil yield was recorded by HTL of S. platensis and Co-HTL with 25% (w/w) masks at 300 °C, which showed insignificant differences with each other. GC/MS analysis of the bio-oil produced from HTL of algal biomass showed a high proportion of nitrogen- and oxygen-containing compounds (3.6% and 11.9%, respectively), with relatively low hydrocarbons (17.4%). Mask blend ratio at 25% reduced the nitrogen-containing compounds by 55.6% and enhanced the hydrocarbons by 43.7%. Moreover, blending of masks with S. platensis enhanced the compounds within the diesel range in favor of gasoline and heavy oil. Overall, the present study provides an innovative route for enhanced bio-oil production through mask recycling coupled with wastewater treatment.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13399-021-01891-2.

Integrated approach for enhanced bio-oil recovery from disposed face masks through co-hydrothermal liquefaction with Spirulina platensis grown in wastewater

Currently, the enormous generation of contaminated disposed face masks raises many environmental concerns. The present study provides a novel route for efficient crude bio-oil production from disposed masks through co-hydrothermal liquefaction (Co-HTL) with Spirulina platensis grown in wastewater. Ultimate and proximate analysis confirmed that S. platensis contains relatively high nitrogen content (9.13%dw), which decreased by increasing the mask blend ratio. However, carbon and hydrogen contents were higher in masks (83.84 and 13.77%dw, respectively). In addition, masks showed 29.6% higher volatiles than S. platensis, which resulted in 94.2% lower ash content. Thermal decomposition of masks started at a higher temperature (≈330 °C) comparing to S. platensis (≈208 °C). The highest bio-oil yield was recorded by HTL of S. platensis and Co-HTL with 25% (w/w) masks at 300 °C, which showed insignificant differences with each other. GC/MS analysis of the bio-oil produced from HTL of algal biomass showed a high proportion of nitrogen- and oxygen-containing compounds (3.6% and 11.9%, respectively), with relatively low hydrocarbons (17.4%). Mask blend ratio at 25% reduced the nitrogen-containing compounds by 55.6% and enhanced the hydrocarbons by 43.7%. Moreover, blending of masks with S. platensis enhanced the compounds within the diesel range in favor of gasoline and heavy oil. Overall, the present study provides an innovative route for enhanced bio-oil production through mask recycling coupled with wastewater treatment.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13399-021-01891-2.

Bioaccumulation of fluoride from aqueous system and genotoxicity study on Allium cepa using Bacillus licheniformis

Removal of fluoride (F^-) was performed using a novel bacterium isolated from F^- contaminated soil collected from Pappireddipatti block of Dharmapuri District in Tamil Nadu, India. Impact of changing variables for the removal of F^- from synthetic medium at different concentrations of carbon and nitrogen sources (0.5, 1.0 and 1.5 g) was studied with bio inoculants of the bacterial strain (PPR8). The effects of different environmental parameters viz., pH (5.0-9.0) and temperature (25-45 °C) on the biosorption of F^- biosorption were also evaluated. The strain PPR8 was identified as Bacillus licheniformis through 16S rRNA sequencing and phylogenetic analysis. Bioaccumulation of F^- in the bacterial cells was confirmed by FTIR, SEM and TEM-EDAX and almost 97% of F^- removal was established. To test the potential applicability of the bacterium, the bioreactor study was carried out with F^- contaminated groundwater collected from the contaminated area. Furthermore, the treated and untreated F^- contaminated waters were used to evaluate the genotoxicity on the root cells of onion (Allium cepa) by root tip assay. The experimental results proved that the significant removal of F^- by Bacillus licheniformis PPR8 (KX646393) and it could be used as a potential adsorbent in removing F^- from contaminated ground waters.

Deciphering and engineering photosynthetic cyanobacteria for heavy metal bioremediation

Environmental pollution caused by heavy metals has received worldwide attentions due to their ubiquity, poor degradability and easy bioaccumulation in host cells. As one potential solution, photosynthetic cyanobacteria have been considered as promising remediation chassis and widely applied in various bioremediation processes of heavy-metals. Meanwhile, deciphering resistant mechanisms and constructing tolerant chassis towards heavy metals could greatly contribute to the successful application of the cyanobacteria-based bioremediation in the future. In this review, first we summarized recent application of cyanobacteria in heavy metals bioremediation using either live or dead cells. Second, resistant mechanisms and strategies for enhancing cyanobacterial bioremediation of heavy metals were discussed. Finally, potential challenges and perspectives for improving bioremediation of heavy metals by cyanobacteria were presented.

Mycoremediation of heavy metals: processes, mechanisms, and affecting factors

Industrial processes and mining of coal and metal ores are generating a number of threats by polluting natural water bodies. Contamination of heavy metals (HMs) in water and soil is the most serious problem caused by industrial and mining processes and other anthropogenic activities. The available literature suggests that existing conventional technologies are costly and generated hazardous waste that necessitates disposal. So, there is a need for cheap and green approaches for the treatment of such contaminated wastewater. Bioremediation is considered a sustainable way where fungi seem to be good bioremediation agents to treat HM-polluted wastewater. Fungi have high adsorption and accumulation capacity of HMs and can be potentially utilized. The most important biomechanisms which are involved in HM tolerance and removal by fungi are bioaccumulation, bioadsorption, biosynthesis, biomineralisation, bioreduction, bio-oxidation, extracellular precipitation, intracellular precipitation, surface sorption, etc. which vary from species to species. However, the time, pH, temperature, concentration of HMs, the dose of fungal biomass, and shaking rate are the most influencing factors that affect the bioremediation of HMs and vary with characteristics of the fungi and nature of the HMs. In this review, we have discussed the application of fungi, involved tolerance and removal strategies in fungi, and factors affecting the removal of HMs.

Nitrate-N-mediated toxicological responses of Scenedesmus acutus and Daphnia pulex to cadmium, arsenic and their binary mixture (Cd/Asmix) at environmentally relevant concentrations

Several biomarkers used for ecological risk assessment have been established for single contaminant toxicity, many of which are less predictive of the influence of media and/or dietary nutrients on toxicity outcomes of contaminant mixtures. In this study, we investigate toxicological responses and life traits of Scenedesmus acutus and Daphnia pulex to heavy metals (cadmium-Cd, arsenic-As, binary mixture-Cd/As_mix) in media and diets with varied nutrient (nitrate-N) conditions (low-LN, median-MN, optimum-COMBO). Results showed that nitrate-N-mediated metal inhibitory effects on growth and productivity of primary producer (S. acutus) were significantly interactive (p < 0.05; effect size, ƞ²≤56 %). Cadmium toxicities (Cd-IC₅₀s) in S. acutus were 1.2×, 5.3×, and 4.3× As-IC₅₀s in LN, MN and COMBO media, respectively, while mixture (Cd/As_mix) toxicities were synergistic in MN medium and partial additivity in COMBO and LN media. Nitrate-N and metal exposure effects on S. acutus nutrient stoichiometry, metal uptake and bioaccumulation were significantly interactive (p < 0.05, ƞ²≤100 %). Moreover, survival of primary consumer (D. pulex) was significantly impaired by single and mixed dietary-metal exposures with greater effect under LN condition coupled with significant interactive effects on reproductive capacity (p < 0.05, ƞ²≤21.2 %) but not on swimming activity. We recommend that nitrate-N-mediated metal exposure effects/toxicity in bioindicator species should be considered during ecological risk assessments.

A review: a comparison of different adsorbents for removal of Cr (VI), Cd (II) and Ni (II)

A review of the studies dealing with the removal of chromium, cadmium, and nickel ions with different adsorbents published in the literature between 2014 and 2018 is given in tabular form, along with the adsorption conditions, adsorption isotherm, and kinetic models applied by the authors to model the experimental data and adsorption capacities. The review focuses on the efficiency of ion removal.

Photoreduction and Removal of Cadmium Ions over Bentonite Clay-Supported Zinc Oxide Microcubes in an Aqueous Solution

Cadmium ion is toxic to organisms and shows persistence because of its nondegradability. Photoreduction of the cadmium ion (Cd(II)) was studied using a bentonite-supported Zn oxide (ZnO/BT) photocatalyst in an aqueous medium under ultraviolet light. The prepared ZnO/BT photocatalyst was characterized by diffuse reflectance spectroscopy, field-emission scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, photoluminescence spectroscopy, transmission electron microscopy, energy-dispersive spectroscopy, and Brunauer-Emmett-Teller/Barrett-Joyner-Halenda analysis. The effects of main parameters including pH, contact time, initial concentration of cadmium(II) ion, light intensity, temperature, and the photocatalyst dosage were investigated for obtaining appreciate reduction/removal efficiency. The maximum reduction/removal efficiency of 74.8% was obtained at optimized values which were found to be at pH 5, 6 h contact time, 6 ppm Cd(II) ion, 200 W UV light, 45 °C temperature, and 4 g/L of ZnO/BT. Reduction/removal of Cd(II) was significantly affected by light intensity so that the increment in UV intensity from 0 to 200 increased the reduction/removal efficiency from 61.2 to 76.8%. This study reports an inexpensive and environmentally friendly photocatalyst for Cd²⁺ reduction in real samples and prospective photoelectric materials.

Trophic-Level Interactive Effects of Phosphorus Availability on the Toxicities of Cadmium, Arsenic, and Their Binary Mixture in Media-Exposed Scenedesmus acutus and Media and Dietary-Exposed Daphnia pulex

Various anthropogenic activities simultaneously alter essential mineral nutrients and contaminant content in the environment. Depending on essential nutrient conditions, the uptake and effects of contaminants in exposed organisms may be altered. The addressing of ecological risk assessment (ERA) of contaminant mixtures has proven difficult. Furthermore, most assessments involving single contaminant exposures do not consider the interaction of essential nutrients on toxicological end points. Hypotheses for toxicological effects of cadmium (Cd), arsenic (As), and their binary mixture (Cd/As_mix) include alteration under varying dietary and media phosphorus (P) conditions. However, interactive effects and effect size (η²) are largely unknown. Here, we investigated the toxicities of Cd-, As-, and Cd/As_mix-treated media and diets on Scenedesmus acutus (a primary producer) and Daphnia pulex (a primary consumer), under varied media and dietary P conditions [low (LP), median (MP), and optimum (COMBO)]. Our results showed significant (p < 0.05) interactive effects and concentration dependent growth inhibition of S. acutus. The toxicity (at day 7) of Cd against S. acutus was 2×, 11×, and 4× that of As in LP, MP, and COMBO conditions, respectively, while the joint toxicity effects of Cd/As_mix were partially additive in LP and COMBO, and synergistic in MP media. Furthermore, acute lethal toxicity (96 h) of Cd in D. pulex was ∼60× that of As, while Cd/As_mix joint toxicity was synergistic. Chronic toxicity (14 d) in D. pulex showed significant (p < 0.05) interaction of As and P-availability on survival, reproduction, and behavior (distance moved, velocity, acceleration and mobility), while Cd and P availability showed significant interactive effect on rotational behavior. Dose response effects of Cd, As, and Cd/As_mix in S. acutus and D. pulex were either monophasic or biphasic under varying nutrient conditions. This study provides empirical evidence of the interactive effects of media/dietary P and toxic metals (Cd, As, and Cd/As_mix) at environmentally relevant concentrations, emphasizing the need for consideration of such interactions during ERA.

Immune status of Oreochromis niloticus subjected to long-term lead nitrate exposure and a Arthrospira platensis treatment trial

In this study, the impacts of lead toxicity on Oreochromisniloticus were investigated. Additionally, the potential ameliorative effects of the Spirulina algae Arthrospira platensis were evaluated. The median lethal concentration (LC₅₀) of PbNO₃ was determined to be 143.3 mg/l for O. niloticus weighing 42 ± 2.5 g. O. niloticus were exposed to 10 % of the estimated PbNO₃ LC₅₀ for 12 weeks. The cumulative mortality rate (CMR) increased with exposure time. The results of assays for red blood cells (RBCs), haemoglobin (Hb), packed cell volume (PCV), mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), and mean corpuscular haemoglobin concentration (MCHC) indicated that the exposed O. niloticus suffered from anaemia. The levels of liver enzymes, namely, aspartate transaminase (AST) and alanine transaminase (ALT), as well as metallothionein)MT(revealed deterioration of hepatic tissue. The activity of the antioxidant enzymes glutathione peroxidase (GPx) as well as catalase (CAT) was stimulated in the hepatic tissue of O. niloticus exposed to PbNO₃ and in those treated with A. platensis. Based on the results of serum bactericidal activity (SBA) and oxidative burst activity (OBA) assays as well as challenge tests with Aeromonas hydrophila, it was clear that supplementation with 5 or 10 g/kg A. platensis significantly enhanced the fish immune status and decreased the mortality rate (MR). However, these effects were reduced by PbNO₃ exposure with no differences in MR percentage. Therefore, it was clear that O. niloticus reared in lead nitrate-polluted water were immunosuppressed, while diet supplementation with A. platensis could ameliorate such impacts.

Algal characterization and bioaccumulation of trace elements from polluted water

Algae are a group of autotropic and eukaryotic organisms that play a significant role in the food, pharmaceutical, cosmetic, fuel, and textile industries. They are an important part of our ecosystem, and they can help control the growing problem of pollution. In this work, the carotenoid, sterol, polyphenol and mineral content, spectral and thermal characteristics of six common river algae, viz. Chara spp., Hydrodictyon spp., Lyngbya spp., Nitella spp., Pithophora spp., and Spirogyra spp., collected from Kharun river (India), were evaluated. The concentration of oil, total polyphenols, flavonoids, and mineral ranged from 0.4 to 4.3%, from 2705 to 4450 mg/kg, from 1590 to 2970 mg/kg, and from 85,466 to 122,871 mg/kg of algae (dw), respectively. The concentration of carotenoids and sterols varied from 1.6 to 109 mg/kg and from 522 to 35,664 mg/kg. The potentiality towards the bioaccumulation of 22 trace elements from the surface reservoir was assessed and discussed in relation to carbonate inlay of the algae wall and to the ions ability to bind to pectin, polypeptides, carotenoids, polyphenols, and flavonoids, on the basis of infrared spectroscopy data. In view of the extremely high enrichment factors found for certain elements, such as P, Co, Cu, Pb, and Fe, some of these algae hold promise as bioindicators for the detection of these elements in aquatic environments. Ordination analysis was used to measure the variance gradient of the algal data.

Statistical optimization for cadmium removal using Ulva fasciata biomass: Characterization, immobilization and application for almost-complete cadmium removal from aqueous solutions

Cadmium is a global heavy metal pollutant. Marine green algae were used as efficient, low cost and eco-friendly biosorbent for cadmium ions removal from aqueous solutions. Plackett-Burman design was applied to determine the most significant factors for maximum cadmium removal from aqueous solutions using dry Ulva fasciata biomass. The most significant factors affecting cadmium removal process were further optimized by the face centered central composite design. The results indicated that 4 g of dry Ulva fasciata biomass was found to successfully remove 99.96% of cadmium from aqueous solution under the conditions of 200 mg/L of initial cadmium concentration at pH 5, 25 °C for 60 min of contact time with static condition. Dry Ulva fasciata biomass samples before and after cadmium biosorption were analyzed using SEM, EDS and FTIR. Furthermore, the immobilized biomass in sodium alginate-beads removed 99.98% of cadmium from aqueous solution at an initial concentration of 200 mg/L after 4 h which is significantly higher than that for control using sodium alginate beads without incorporation of the algal biomass (98.19%). Dry biomass of Ulva fasciata was proven to be cost-effective and efficient to eliminate heavy metals especially cadmium from aquatic effluents and the process is feasible, reliable and eco-friendly.

Potential use of green algae as a biosorbent for hexavalent chromium removal from aqueous solutions

The hexavalent chromium Cr(VI) poses a threat as a hazardous metal and its removal from aquatic environments through biosorption has gained attention as a viable technology of bioremediation. We evaluated the potential use of three green algae (Cladophora glomerata, Enteromorpha intestinalis and Microspora amoena) dry biomass as a biosorbent to remove Cr(VI) from aqueous solutions. The adsorption capacity of the biomass was determined using batch experiments. The adsorption capacity appeared to depend on the pH. The optimum pH with the acid-treated biomass for Cr(VI) biosorption was found to be 2.0 at a constant temperature, 45 °C. Among the three genera studied, C. glomerata recorded a maximum of 66.6% removal from the batch process using 1.0 g dried algal cells/100 ml aqueous solution containing an initial concentration of 20 mg/L chromium at 45 °C and pH 2.0 for 60 min of contact time. Langmuir and Freundlich isotherm equations fitted to the equilibrium data, Freundlich was the better model. Our study showed that C. glomerata dry biomass is a suitable candidate to remove Cr(VI) from aqueous solutions.

Anti-inflammatory, antioxidant and antihepatotoxic effects of Spirulina platensis against d-galactosamine induced hepatotoxicity in rats

Spirulina platensis has been advocated as safe food for human use by several investigators. In this study its beneficial dietary effect against liver injuries caused by d-galactosamine (d-GalN) was studied ensuring safety to human health using animal model. Acute hepatotoxicity was induced in Wister rats with d-GalN followed by treatment with butylated hydroxytoluene (BHT) and with Spirulina aqueous extract at various concentrations. The effect of Spirulina at different concentrations were tried and compared with BHT treatment. The animals treated with d-GalN on subsequent treatment by supplementation with Spirulina (6, 9%) in the diets, led to significant reversal in the levels of the antioxidant enzymes through hepatocytes by suppression of negative effect. Spirulina aqueous extract at 9% resulted in a significant decrease in the levels of alkaline phosphatase and infalmatory markers TNFα, IL6 and IL1β and also decreased TBARS, while it showed an increase in oxidative stress marker such as GR, GSH, GST, SOD, GPX and CAT and total protein when compared to the levels recorded with that group treated with d-GalN. Results also indicated that Spirulina aqueous extract at 9% concentration was equally effective in protecting liver damage as it was observed with BHT. Histological studies on liver treated with d-GalN, BHT and Spirulina aqueous extract showed that S. platensis is effective as diet in providing beneficial protective effect. The results obtained in the present study very clearly indicated the positive beneficial protective effect of Spirulina, when used as diet, on the safety and protection of liver from injuries caused by toxicants.

Artificial intelligence and regression analysis for Cd(II) ion biosorption from aqueous solution by Gossypium barbadense waste

In this study, batch biosorption experiments were conducted to determine the removal efficiency of Cd(II) ion from aqueous solutions by Gossypium barbadense waste. The biosorbent was characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) connected with energy dispersive X-ray (EDX). The sorption mechanism was described by complexation/chelation of Cd²⁺ with the functional groups of O-H, C=O, -COO-, and C-O, as well as, cation-exchange with Mg²⁺ and K⁺. At initial Cd(II) ion concentration (C _o), 50 mg/L, the adsorption equilibrium of 89.2% was achieved after 15 min under the optimum experimental factors of pH 6.0, biosorbent dosage 10 g/L, and particle diameter 0.125-0.25 mm. Both Langmuir and Freundlich models fitted well to the sorption data, suggesting the co-existence of monolayer coverage along with heterogenous surface biosorption. Artificial neural network (ANN) with a structure of 5-10-1 was performed to predict the Cd(II) ion removal efficiency. The ANN model provided high fit (R ² 0.923) to the experimental data and indicated that C _o was the most influential input. A pure-quadratic model was developed to determine the effects of experimental factors on Cd(II) ion removal efficiency, which indicated the limiting nature of pH and biosorbent dosage on Cd(II) adsorption. Based on the regression model (R ² 0.873), the optimum experimental factors were pH 7.61, biosorbent dosage 24.74 g/L, particle size 0.125-0.25 mm, and adsorption time 109.77 min, achieving Cd²⁺ removal of almost 100% at C _o 50 mg/L.

Hepatoprotective efficacy of Spirulina platensis against lead-induced oxidative stress and genotoxicity in catfish; Clarias gariepinus

Lead (Pb) is a toxic environmental pollutant that induces a broad range of biochemical and physiological hazards in living organisms. We investigated the possible hepatoprotective effects of Spirulina platensis (SP) in counteracting the Pb-induced oxidative damage. Ninety-six adult African catfish were allocated into four equal groups. The 1st group (control) fed basal diet while the 2nd group (Pb-treated) fed on basal diet and exposed to 1mg Pb(NO₃)₂/L. The 3rd and 4th groups fed SP-supplemented basal diets at levels of 0.25% and 0.5%, respectively and exposed to Pb. Serum samples were used to analyze hepatic function biomarkers, electrolytes, and oxidant and antioxidant status. Lipid peroxidation and DNA fragmentation were determined in the liver tissues. Pb exposure induced hepatic dysfunction, electrolytes (Na⁺, K⁺, Ca⁺², and Cl^-) imbalance, as well a significant decrease in GSH content, and LDH, AChE, SOD, CAT and GST enzymes activity. SP supplementation reverted these biochemical and genetic alterations close to control levels. This amelioration was higher with 0.5% SP and at the 4th week of exposure, showing concentration- and time-dependency. Thus, the current study suggests that SP could protect the catfish liver against lead-induced injury by scavenging ROS, sustaining the antioxidant status and diminishing DNA oxidative damage. The dietary inclusion of SP can be used as a promising protective agent to counteract oxidative stress-mediated diseases and toxicities.

Antioxidant, Immunomodulating, and Microbial-Modulating Activities of the Sustainable and Ecofriendly Spirulina

The highly nutritional and ecofriendly Spirulina (Arthrospira platensis) has hypolipidemic, hypoglycemic, and antihypertensive properties. Spirulina contains functional compounds, such as phenolics, phycocyanins, and polysaccharides, with antioxidant, anti-inflammatory, and immunostimulating effects. Studies conducted on Spirulina suggest that it is safe in healthy subjects, but attitude to eating probably affects the acceptability of Spirulina containing foods. Although the antioxidant effect of Spirulina is confirmed by the intervention studies, the concerted modulation of antioxidant and inflammatory responses, suggested by in vitro and animal studies, requires more confirmation in humans. Spirulina supplements seem to affect more effectively the innate immunity, promoting the activity of natural killer cells. The effects on cytokines and on lymphocytes' proliferation depend on age, gender, and body weight differences. In this context, ageing and obesity are both associated with chronic low grade inflammation, immune impairment, and intestinal dysbiosis. Microbial-modulating activities have been reported in vitro, suggesting that the association of Spirulina and probiotics could represent a new strategy to improve the growth of beneficial intestinal microbiota. Although Spirulina might represent a functional food with potential beneficial effects on human health, the human interventions used only supplements. Therefore, the effect of food containing Spirulina should be evaluated in the future.

Natural remedies for non-steroidal anti-inflammatory drug-induced toxicity

The liver is an important organ of the body, which has a vital role in metabolic functions. The non-steroidal anti-inflammatory drug (NSAID), diclofenac causes hepato-renal toxicity and gastric ulcers. NSAIDs are noted to be an agent for the toxicity of body organs. This review has elaborated various scientific perspectives of the toxicity caused by diclofenac and its mechanistic action in affecting the vital organ. This review suggests natural products are better remedies than current clinical drugs against the toxicity caused by NSAIDs. Natural products are known for their minimal side effects, low cost and availability. On the other hand, synthetic drugs pose the danger of adverse effects if used frequently or over a long period. Copyright © 2016 John Wiley & Sons, Ltd.