Physiological responses and cadmium bioremediation efficiency of Chlamydomonas sp. GUEco1016

The problem of heavy metal pollution in water bodies poses a significant threat to both the environment and human health, as these toxic substances can persist in aquatic ecosystems and accumulate in the food chain. This study investigates the promising potential of using Microcystis aeruginosa extracellular polymeric substances (EPS) as an environmentally friendly, highly efficient solution for capturing copper (Cu2+) and nickel (Ni2+) ions in water treatment, emphasizing their exceptional ability to promote green technology in heavy metal sequestration. We quantified saccharides, proteins, and amino acids in M. aeruginosa biomass and isolated EPS, highlighting their metal-chelating capabilities. Saccharide content was 36.5mgg-1 in biomass and 21.4mgg-1 in EPS, emphasizing their metal-binding ability. Proteins and amino acids were also prevalent, particularly in EPS. Scanning electron microscopy (SEM) revealed intricate 3D EPS structures, with pronounced porosity and branching configurations enhancing metal sorption. Elemental composition via energy dispersive X-ray analysis (EDAX) identified essential elements in both biomass and EPS. Fourier transform infrared (FTIR) spectroscopy unveiled molecular changes after metal treatment, indicating various binding mechanisms, including oxygen atom coordination, π-electron interactions, and electrostatic forces. Kinetic studies showed EPS expedited and enhanced Cu2+ and Ni2+ sorption compared to biomass. Thermodynamic analysis confirmed exothermic, spontaneous sorption. Equilibrium biosorption studies displayed strong binding and competitive interactions in binary metal systems. Importantly, EPS exhibited impressive maximum sorption capacities of 44.81mgg-1 for Ni2+ and 37.06mgg-1 for Cu2+. These findings underscore the potential of Microcystis EPS as a highly efficient sorbent for heavy metal removal in water treatment, with significant implications for environmental remediation and sustainable water purification.

Sequestration and oxidation of heavy metals mediated by Mn(II) oxidizing microorganisms in the aquatic environment

Heavy metal toxicity is one of the major concerns for agriculture and health. Accumulation of toxic heavy metals at high concentrations in edible parts of crop plants is the primary cause of disease in humans and cattle. A dramatic increase in industrialization, urbanization, and other high anthropogenic activities has led to the accumulation of heavy metals in agricultural soil, which has consequently disrupted soil conditions and affected crop yield. By now, plants have developed several mechanisms to cope with heavy metal stress. However, not all plants are equally effective in dealing with the toxicity of high heavy metal concentrations. Plants have modified their anatomy, morphophysiology, and molecular networks to survive under changing environmental conditions. Heavy metal sequestration is one of the essential processes evolved by some plants to deal with heavy metals' toxic concentration. Some plants even have the ability to accumulate metals in high quantities in the shoots/organelles without toxic effects. For intercellular and interorganeller metal transport, plants harbor spatially distributed various transporters which mainly help in uptake, translocation, and redistribution of metals. This review discusses different heavy metal transporters in different organelles and their roles in metal sequestration and redistribution to help plants cope with heavy metal stress. A good understanding of the processes at stake helps in developing more tolerant crops without affecting their productivity.

Microalgae hold promise as producers of sustainable biomass for the production of biofuels and other biomaterials. However, the selection of strains with efficient and robust production of desirable resources remains challenging. In this study, we isolated a green microalga from Korea and analyzed its morphological, molecular, and biochemical characteristics. Microscopic and phylogenetic analyses demonstrated that the isolate could be classified into the genus Chlamydomonas, and we designated the isolate Chlamydomonas s p. K IOST -1. Compositions of protein, lipid, and carbohydrate in the microalgal cells were estimated to be 58.8 ± 0.2%, 22.7 ± 1.2%, and 18.5 ± 1.0%, respectively. Similar to other microalgae belonging to Chlorophyceae, the dominant amino acid and monosaccharide in Chlamydomonas sp. KIOST-1 were glutamic acid and glucose. On the other hand, the proportions of saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids clearly differed from other species in the genus Chlamydomonas, and monounsaturated fatty acids accounted for a large portion (41.3%) of the total fatty acids in the isolate. Based on these results, Chlamydomonas sp. KIOST-1 has advantageous characteristics for biomass production.

Mechanism of heavy metal ion biosorption by microalgal cells: A mathematic approach

As industrialization increases to meet the demands of 21st century life, incidences of heavy metal contamination increases as well. Non‐essential heavy metals serve no biological function and can have devastating effects across all spectra of life. Lead (Pb) is of significant research importance due to its toxicity at both acute and chronic levels of exposure. Industrial sources of lead contamination include production of crude oils, and paints. Bioavailable Pb contamination can damage key metabolic processes in eukaryotic and prokaryotic organisms. Plants and algal cells are particularly affected by Pb, as unchecked exposure can cause metabolic dysfunction and eventually damage the chloroplast's photosystems. Alga and plants employ an array of physical and chemical defenses to maintain heavy metal homeostasis. Among these are the production of non‐specific heavy metal binding proteins known as phytochelatins (PC) and metallothioneins (MT). Both protein families share similar amino acid motifs, particularly moieties of cysteine, whose sulfhydryl (‐SH) active site has a high affinity for heavy metal ions. MT and PC aid in the chelation and eventual removal of heavy metal ions. Investigation of heavy metal tolerance genes in green algae is of importance due to their position as primary producers in most aquatic ecosystems. Chlamydomonas reinhardtii, a unicellular green alga, has been a model organism for the study of photosynthesis, bioremediation, and heavy metal toxicity. Though its genome has been sequenced, several genes and their protein products remain unannotated. One such gene, Cia7, is hypothesized to play a role in maintaining C. reinhardtii's heavy metal homeostasis. Preliminary evidence shows that CIA7 contains a highly conserved motif similar to other metal sequestering proteins. To aid in confirming CIA7's ability to sequester heavy metals, this study presents the results of a bioaccumulation experiment involving a wild type (CC4425) and a Cia7 mutant (CC5013). CC4425 and the CC5013 were grown simultaneously in separate treatment flasks containing either 0uM/150 uM PbCl2 in replete TAP media for 4 days under constant lighting. Pb ion bioaccumulation was measured utilizing an Induced Coupled Plasma Optical Emission Spectrophotometer (ICP‐OES) following a microwave acid digestion step. A 2×2 factorial analysis of variance was conducted to determine the significance of the data obtained. Results of bioaccumulation experiments indicated that there is a significant difference in Pb bioaccumulation between the mutant cia7 and wild‐type at 150 μM Pb treatment. The mutant cia7 bioaccumulated higher concentration of Pb compared to wild‐type. This difference is significant at 95% confidence interval. Flow cytometry and fluorescent microscopy experiments were conducted to further explore the differences in morphology and cell count between strains across both treatments.Support or Funding InformationNorman Hackerman Advanced Research Program

Heavy metal pollutant such as Cu and Cd may affects the life of aquatic organisms such as Chlamydomonas sp. A study aims to understand the effects of Cu and Cd present in the water toward the growth of Chlamydomonas sp, a study has been conducted on March – May 2019. The toxicity of the heavy metals toward the growth of Chlamydomonas sp was tested following the standard methods of Asean-Canada Cooperative Program on Marine Science Phase-II (ACCPMS-II). Results shown that IC50-96 hours of Cu and Cd on the growth of Chlamydomonas sp. was 0.6 mgL-1, and 24.92 mgL-1 respectively. Data obtained proved that the presence of Cu and Cd in the water inhibit the growth of Chlamydomonas sp, and Cu is more toxic than Cd. The Cu toxicity was 42 times greater than that of Cd. The NOEC values for Cu was < 1 mgL-1, while that of Cd was 18 mgL-1. LOEC value was 1 mgL-1 for Cu, and 32 mgL-1 for Cd.

Investigation of heavy metal tolerance genes in green algae is of great importance because heavy metals have become one of the major contaminants in the aquatic ecosystem. In plants, accumulation of heavy metals modifies many aspects of cellular functions. However, the mechanism by which heavy metals exert detrimental effects is poorly understood. In this study, we identified a role for HO-1 (encoding heme oxygenase-1) in regulating the response of Chlamydomonas reinhardtii, a unicellular green alga, to mercury (Hg). Transgenic algae overexpressing HO-1 showed high tolerance to Hg exposure, with a 48.2% increase in cell number over the wild type, but accumulated less Hg. Physiological analysis revealed that expression of HO-1 suppressed the Hg-induced generation of reactive oxygen species. We further identified the effect of carbon monoxide (CO), a product of HO-1-mediated heme degradation, on growth and physiological parameters. Interestingly, administration of exogenous CO at non-toxic levels also conferred the tolerance of algae to Hg exposure. The CO-mediated alleviation of Hg toxicity was closely related to the lower accumulation of Hg and free radical species. These results indicate that functional identification of HO-1 is useful for molecular breeding designed to improve plant tolerance to heavy metals and reduce heavy metal accumulation in plant cells.

Heavy metal pollution from industrial effluents poses significant environmental and public health challenges, particularly in aquatic ecosystems. Traditional wastewater treatment methods, are effective but often expensive, labor-intensive, and generate hazardous waste. Biosorption, using biological materials, presents a cost-effective and environment friendly alternative for heavy metal removal. The present study investigates the potential of Madhuca indica oil cake, a by-product of oil extraction can be used as a biosorbent for heavy metal sequestration. The oil cake was characterized by its physicochemical properties, including specific gravity (1.298 g/cm3), bulk density (0.66184 kg/m3), moisture content (11.34%), and dry matter content (88.66%). These properties suggest the oil cake is dense, nutrient-rich, and easy to handle and store. Fourier Transform Infrared (FTIR) spectroscopy was used to analyze the functional groups in the oil cake before and after drying at 105 °C. The results showed minimal changes in the chemical composition, with a slight shift in peak intensities indicating concentration effects due to drying. This stability is crucial for applications requiring intact bioactive compounds. The study highlights the versatility of Madhuca indica oil cake for multiple uses, including animal feed, fertilizer, and biomass for bioenergy. Furthermore, its potential as a biosorbent for heavy metal removal underscores its promise for environmental remediation. The study concludes that further research could optimize the utilization of Madhuca indica oil cake in agriculture and pollution control, contributing to sustainable environmental management.

Melatonin has a protective effect against heavy metal stress in plants by immobilizing HM in cell walls and sequestering them in root cell vacuoles, reducing HM's translocation from roots to shoots. It enhances osmolyte production, increases antioxidant enzyme activity, and improves photosynthesis, thereby improving cellular functions. Understanding the melatonin-mediated response and signalling can sustain crop production in heavy metal-stressed soils. Melatonin is a pleiotropic signal molecule that plays a critical role in plant growth and stress tolerance, particularly against heavy metals in soil. Heavy metals (HMs) are ubiquitously found in the soil-water environment and readily taken up by plants, thereby disrupting mineral nutrient homeostasis, osmotic balance, oxidative stress, and altered primary and secondary metabolism. Plants combat HM stress through inbuilt defensive mechanisms, such as metal exclusion, restricted foliar translocation, metal sequestration and compartmentalization, chelation, and scavenging of free radicals by antioxidant enzymes. Melatonin has a protective effect against the damaging effects of HM stress in plants. It achieves this by immobilizing HM in cell walls and sequestering them in root cell vacuoles, reducing HM's translocation from roots to shoots. This mechanism improves the uptake of macronutrients and micronutrients in plants. Additionally, melatonin enhances osmolyte production, improving the plant's water relations, and increasing the activity of antioxidant enzymes to limit lipid peroxidation and reactive oxygen species (ROS) levels. Melatonin also decreases chlorophyll degradation while increasing its synthesis, and enhances RuBisCO activity for better photosynthesis. All these functions contribute to improving the cellular functions of plants exposed to HM stress. This review aims to gain better insight into the melatonin-mediated response and signalling under HM stress in plants, which may be useful in sustaining crop production in heavy metal-stressed soils.

Heavy metal (HM) pollution in aquatic ecosystems has an adverse effect on both aquatic life forms as well as terrestrial living beings, including humans. Since HMs are recalcitrant, they accumulate in the environment and are subsequently biomagnified through the food chain. Conventional physical and chemical methods used to remove the HMs from aquatic habitats are usually expensive, slow, non-environment friendly, and mostly inefficient. On the contrary, phytoremediation and microbe-assisted remediation technologies have attracted immense attention in recent years and offer a better solution to the problem. These newly emerged remediation technologies are eco-friendly, efficient and cost-effective. Both phytoremediation and microbe-assisted remediation technologies adopt different mechanisms for HM bioremediation in aquatic ecosystems. Recent advancement of molecular tools has contributed significantly to better understand the mechanisms of metal adsorption, translocation, sequestration, and tolerance in plants and microbes. Albeit immense possibilities to use such bioremediation as a successful environmental clean-up technology, it is yet to be successfully implemented in the field conditions. This review article comprehensively discusses HM accumulation in Indian aquatic environments. Furthermore, it describes the effect of HMs accumulation in the aquatic environment and the role of phytoremediation as well as microbe-assisted remediation in mitigation of the HM toxicity. Finally, the review concludes with a note on the challenges, opportunities and future directions for bioremediation in the aquatic ecosystems.

In this study, the bacterium was identified as Sphingomonas sp. XJ2 by means of microscopic examination, physiological, biochemical detection, and modern molecular biology technology. After acclimatization for several times, this bacterium has good performance in removing heavy metals and organic matter from seawater. Alginate immobilized cells has obvious holes on the surface and has big specific surface area, which are conducive to the adsorption of metal ions. Hydration heat of Pb2+ is small, and is most likely to drop out of ligand water then become exposed Pb2+; in addition, the ionic radius of Pb2+ and is very similar to the ball K+ and is adsorbed by the ball easily. FTIR and XPS study indicated that Pb (II) was complexed by C-H and C-O bonds. The concentration of Pb(Ⅱ)of mine wastewater reach the first class of irrigation water quality standards after the first time of adsorption treatment, and reach the first class of fishery water quality standard after the second treatment. 1． Introduction Mine waste water mainly comes from mine production, the main pollutants including heavy metals, acid, organic pollutants, oil pollutants, cyanide, fluoride and soluble salts and so on. Heavy metal pollution and acid pollution are the most common water pollutions, the mainly heavy metals from wastewater are lead, zinc, nickel, copper, mercury, chromium, cadmium, cobalt, manganese, titanium, vanadium and bismuth. Hazards of mine waste water including environmental degradation and toxic to organisms; mine waste water contains heavy metal ions and other metal ions, through infiltration, percolation and runoff channels walk into the environment, then pollute water. After precipitation, absorption, complexation, chelation and redox, migrate and change in the water, and ultimately affect human health and aquatic growth. Heavy metals and metalloids and other pollutants in wastewater once enter the water environment, they can not be biodegradable, but by precipitation - dissolution, oxidation - reduction, coordinate effect, colloid formation effect, adsorption - desorption process and a series of physical and chemical migration transformation, which will eventually as one or more form stay in the environment for a long term, causing permanent potentially damage [1]. How to prevent non-ferrous metal mine waste water polluting water and farmland is one of the current problems which arising large public attention. Traditional treat methods of heavy metal waste water are chemical precipitation, ion exchange, evaporation and electrolysis, etc., these methods have disadvantages of high investment and operating costs, precipitation removal is not satisfactory, and could easily lead to secondary pollution and other defects. Since 1980s, people began to turn to research microbial treatment of heavy metal waste water, and found that microbial treatment of wastewater had advantages of low cost, effective and no secondary pollution. The economical and ecological feasibility of biosorption processes depend on the biosorbent metal uptake capacity to reach metal concentration legal limits for wastewater discharge and the ability of eluants to release sequestered metal in subsequent recovery [2-4]. Recovery allows metal recycling, leading to energy savings and materials conservation[5]. Finally, biosorbent regeneration used in multiple adsorption–desorption cycles [6], contributes to process cost effectiveness. Living cells have so broad assortment of mechanisms for surviving in environment that have elevated metal concentrations, including transport and intracellular and extracellular sequestration .The active process of metal accumulation by cells is usually referred to as bioaccumulation, while the passive metal sequestration by cell components is generally called biosorption. The physicochemical basis for metal sequestration at the cell surface may include complexation, coordination, chelation, ion exchange, adsorption, and inorganic microprecipitation processes. Bacteria make excellent biosorbents because of their high surface-to-volume ratios. Metal-binding behaviour has been evaluated on the basis of bacterial cell Gram reaction for viable cells and cell walls and envelopes. In this study, we conducted separation domesticated culture to Sphingomonas sp. XJ2 and used them to treat waste water preliminarily. Establishing an efficient, cheap, adaptable and easy to operate way of treating non-ferrous metal mine wastewater is a new development.

Abstract: In recent years, the substantial influx of heavy metal pollutants into aquatic environments due to human activities has emerged as a critical issue. Heavy metals are characterized by their high toxicity, persistence, and resistance to degradation, which not only result in significant economic losses but also exert severe impacts on ecosystems and human health. Microalgae, due to their adsorption capacity for heavy metals, have become a new avenue for the biological remediation of heavy metal pollution in aquatic environments. With the advantages of low cost, renewability, environmental friendliness, and strong adaptability, microalgae showed broad application prospects in the management of heavy metal pollution. This manuscript provides a comprehensive review of microalgae- based remediation of heavy metal pollution in aquatic environments. It examines the factors influencing heavy metal adsorption by microalgal cells, compares the adsorption capacities of different algal species, and evaluates the adsorption effectiveness of live versus dead algal cells. The review also summarizes the mechanisms of heavy metal accumulation and transfer in microalgae and identifies future research priorities and directions for enhancing the heavy metal enrichment capabilities of microalgae.

Carbamazepine removal by the synergistic effect of manganese-oxidizing microalgae and biogenic manganese oxides

Fighting climate change and ensuring sustainable development is one of the greatest concerns nowadays. In this regard, energy production from biomass is already a r eality and presents tremendous possibilities of use as an alternative source. Among the various technologies, hydrogen production from microalgae is a p romising clean energy alternative. Indeed, some unicellular green algae have the ability to produce hydrogen simply in the presence of water and light. However, an important factor governing the efficiency of hydrogen production by microalgae depends on the method of production. Designing a suitable bioreactor is therefore very important in order to control the main production parameters. Hence, a s uitable bubble agitation system, with proper bubble size, that keeps algal cells in suspension is proposed. The present work foresees a tentative method of hydrogen production from Chlamydomonas sp, a l ocal alga from the arid area of Adrar (southern Algeria). This is performed in a photobioreactor of the type of a bubble column. It should be noted that a hydrodynamic study of the bubble column has been previously conducted. This has led to a p roper choice of the diffuser and an approximate assessment of microalgae culture parameters. Moreover, various process parameters were monitored under a given light intensity, namely: pH, temperature, dissolved oxygen, etc. The observations show massive growth of the algae biomass which indicates a good adaptation of this type of photobioreactors for microalgae production, and subsequently hydrogen production as long as low rates are required.