Comparative studies on growth and Pb(II) removal from aqueous solution by Nostoc muscorum and Anabaena variabilis

Comprehensive approaches to heavy metal bioremediation: Integrating microbial insights and genetic innovations

The increasing contamination of ecosystems with heavy metals (HMs) due to industrial activities raises significant jeopardies to environmental health and human well-being. Addressing this issue, recent advances in the field of bioremediation have highlighted the potential of plant-associated microbiomes and genetically engineered organisms (GEOs) to mitigate HMs pollution. This review explores recent advancements in bioremediation strategies for HMs detoxification, with particular attention to omics technologies such as metagenomics, metabolomics, and metaproteomics in deepening the understanding of microbial interactions and their potential for neutralizing HMs. Additionally, Emerging strategies and technologies in GEOs and microorganism-aided nanotechnology have proven to be effective bioremediation tools, particularly for alleviating HM contamination. Despite the promising strategies developed in laboratory settings, several challenges impede their practical application, including ecological risks, regulatory limitations, and public concerns regarding the practice of genetically modified organisms. A comprehensive approach that involves interdisciplinary research is essential to enhance the efficacy and safety of bioremediation technologies. This approach should be coupled with robust regulatory frameworks and active public engagement to ensure environmental integrity and societal acceptance. This review underscores the importance of developing sustainable bioremediation strategies that align with ecological conservation goals and public health priorities.

A critical review on the symbiotic effect of bacteria and microalgae on treatment of sewage with biofertilizer production

Wastes like sewage, kitchen and industrial are the major sources of environmental pollution and health hazards. Sewage contains 99.9% water and 0.1% solid waste including urinal waste and faecal matter alongwith large amounts of nitrate, nitrite, ammonium and phosphate ions. Sewage may also contain a variety of harmful contaminants like analgesics, antihypertensive drugs, antibiotics, dioxin, furans, polychlorinated biphenyls, chlorinated hydrocarbon pesticides, chlorine derivatives and plasticizers etc. making it more harmfull to environment and public health. Hence, sewage must be adequately treated by an effective process before its final discharge into the environment. Biological treatment of sewage is an emerging idea in recent years, which has diverse economic and environmental advantages. Sewage treatment by bacteria and microalgae has numerous advantages as it removes various excessive nutrients from waste with large biomass production and also prevents the utilization of toxic chemicals in conventional treatment process. Microalgae-bacterial biomass have potential to be used as biofertilizers, bio-stimulants and bio-seed primers in agricultural field as these contain various biologically active substances like polysaccharides, carotenoids, free fatty acids, phenols, and terpenoids. This review paper mainly discussing the sewage characteristics and different kinds of organic and inorganic pollutants it contained alongwith its harmfull impacts on environment and public health. It also deals the different conventional as well as emerging treatment technologies and different factors affecting the treatment efficiency. In addition, the utilization of developed microalgal and bacterial biomass as biofertilizer and its effects on crop plant alongwith future prospects has been also discussed in detail.

Toxicity and bioremediation of the lead: a critical review

Lead is a naturally occurring, bluish-gray metal that is found in small quantities in the earth's crust. The existing literature demonstrates that non-biodegradable character and continuous use results in accumulation of lead concentration in the environment and causes various ill effects such as neurotoxicity, change in psychological and behavioral development of different organisms. Nowadays the most effective technique in the revival of the environment is bioremediation and it is environmentally friendly and cost-effective. Bacterial strains such as Oceanobacillus profundus and Lactobacillus acidophilus ATCC4356 have the ability to reduce lead 97% and 73.9%, respectively. Similarly some species of algae and fungal strains also showed lead removal efficiency as 74% (spirulina), 97.1% (Chlorella kessleri), 95.5% (Penicillium janthinillum) and 86% (Aspergillus flavus). Biodegradation of lead by various microbes would be the most efficient and sustainable approach. This review focuses on toxicity, fate of lead in the environment and its microbial degradation.

An integrated approach for the phycoremediation of Pb(II) and the production of biofertilizer using nitrogen-fixing cyanobacteria

In recent years, growing attention has been directed toward the phycoremediation of heavy metals from bodies of water; however, many challenges remain. The nitrogen requirements for algal growth in nutrient-poor waters can lead to substantial costs. Moreover, proper management of the metal-loaded biomass is a concern. This study assessed the performance of two nitrogen-fixing cyanobacteria, Anabaena sp. and Nostoc muscorum, in treating Pb(II)-contaminated water without nitrogen under batch and fed-batch modes, as well as the subsequent utilization of the produced biomass as a biofertilizer. After 12 days of the batch mode with initial Pb(II) concentrations of 10, 20, 35, and 60 mg/L, Pb(II) removal efficiencies were 98.90%, 98.95%, 97.20%, and 84.98% by Anabaena sp. and 88.00%, 73.10%, 54.54%, and 26.83% by N. muscorum, respectively. Anabaena sp. sustained growth and Pb(II) removal under the fed-batch mode by adjusting hydraulic retention time based on the influent Pb(II) concentration. Decontamination of the metal-loaded Anabaena sp. biomass was performed and resulted in a Pb(II) desorption of 93%. The desorbed Anabaena sp. extract provided the nutrient requirements for Chlorella vulgaris. The proposed strategy provides simultaneous Pb(II) bioremediation and biofertilizer production in a system driven by light energy, atmospheric N₂, and CO₂.

Bacillus and microalgae biofertilizers improved quality and biomass of Salvia miltiorrhiza by altering microbial communities

Objective

Biofertilizers are reliable alternatives to chemical fertilizers due to various advantages. However, the effect of biofertilizers on Salvia miltiorrhiza yield and quality and the possible mechanisms remain little known. Here, an experiment was conducted in S. miltiorrhiza field treated with two kinds of biofertilizers including Bacillus and microalgae.

Methods

A field experiment was conducted on S. miltiorrhiza of one year old. The biofertilizers were applied at six treatments: (i) control check, CK; (ii) microalgae, VZ; (iii) Bacillus, TTB; (iv) microalgae + Bacillus (1:1), VTA; (v) microalgae + Bacillus (0.5:1), VTB; (vi) microalgae + Bacillus (1:0.5), VTC. Here, high-throughput sequencing, ICP-MS and UPLC were employed to systematically characterize changes of microbial diversity and structure composition, heavy metals content and bioactive compounds, respectively.

Results

Compared to CK, root biomass increased by 29.31%-60.39% (P < 0.001). Meanwhile, bioactive compounds were higher than CK after the application of the biofertilizers, peculiarly in TTB and VTB. However, the content of Pb contents in roots significantly reduced by 46.03% and 37.58% respectively in VTC and TTB (P < 0.05). VTA application notably increased the available nitrogen content by 53.03% (P < 0.05), indicating the improvement of soil fertility. Significantly, bacterial and fungal Chao I diversity indices showed an increasing trend with biofertilizer application (P < 0.05), and biofertilizer amendment enriched the rhizosphere soil with beneficial microorganisms that have abilities on promoting plant growth (Achromobacter and Penicillium), adsorbing heavy metal (Achromobacter and Beauveria), controlling plant pathogen (Plectosphaerella, Lechevalieria, Sorangium, Phlebiopsis and Beauveria) and promoting the accumulation of metabolites (Beauveria and Phoma).

Conclusion

Bacillus and microalgae biofertilizers improved the quality and biomass of S. miltiorrhiza by altering microbial communities in soil.

Plants-Microorganisms-Based Bioremediation for Heavy Metal Cleanup: Recent Developments, Phytoremediation Techniques, Regulation Mechanisms, and Molecular Responses

Rapid industrialization, mine tailings runoff, and agricultural activities are often detrimental to soil health and can distribute hazardous metal(loid)s into the soil environment, with harmful effects on human and ecosystem health. Plants and their associated microbes can be deployed to clean up and prevent environmental pollution. This green technology has emerged as one of the most attractive and acceptable practices for using natural processes to break down organic contaminants or accumulate and stabilize metal pollutants by acting as filters or traps. This review explores the interactions between plants, their associated microbiomes, and the environment, and discusses how they shape the assembly of plant-associated microbial communities and modulate metal(loid)s remediation. Here, we also overview microbe-heavy-metal(loid)s interactions and discuss microbial bioremediation and plants with advanced phytoremediation properties approaches that have been successfully used, as well as their associated biological processes. We conclude by providing insights into the underlying remediation strategies' mechanisms, key challenges, and future directions for the remediation of metal(loid)s-polluted agricultural soils with environmentally friendly techniques.

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.

Evolution and resistance of a microbial community exposed to Pb(II) wastewater

This study investigated the treatment performance of activated sludge on Pb(II)-containing wastewater, including contaminant removal efficiency, extracellular polymeric substances, pbrT gene content and the microbial community. The average removal efficiencies of ammonia nitrogen, chemical oxygen demand, total phosphorus, total nitrogen and Pb(II) were 40% ± 4%, 91% ± 3%, 95% ± 3%, 51% ± 5% and 92% ± 9% during the stable operation stage, respectively. Moreover, the extracellular polymeric substance -protein contents increased significantly from day 0 to day 60 (p < 0.05). The most abundant fluorescent component in extracellular polymeric substances was a humic acid-like substance, and its fluorescence intensity increased significantly from day 0 to day 60 (p < 0.05). Adsorption of negatively charged organic functional groups in extracellular polymeric substances was identified as a major component of the removal of Pb(II). Most of the denitrifying bacteria associated with nitrogen removal showed an increasing trend during the acclimation stage, which may have resulted in high total nitrogen removal efficiency. In addition, pbrT uptake protein was found to be responsible for the uptake of Pb(II) into cells. The abundance of the pbrT gene showed a downward trend (p < 0.05) after adding Pb(II), probably because expression of the pbrT gene was inhibited under Pb(II) stress. Sphingopyxis containing the pbrT gene was the dominant resistance genus, and its relative abundance increased significantly (p < 0.05) from day 0 to day 60. This study provided a theoretical basis for the treatment of Pb(II)-containing wastewater.

High heavy metal load does not inhibit nitrogen fixation in moss-cyanobacteria associations

Nitrogen (N₂) fixation by moss-associated cyanobacteria is one of the main sources of new N input in pristine ecosystems such as boreal forests and arctic tundra. Given the non-vascular physiology of mosses, they are especially sensitive to e.g. increased N input and heavy metal deposition. While the effects of increased N input on moss-associated N₂ fixation has been comprehensively assessed, hardly any reports exist on the effects of increased heavy metal load on this key ecosystem function. To address this knowledge gap, we made use of an extreme metal pollution gradient in boreal forests of Northern Sweden originating from a metal mine and its associated smelters. We collected the common moss Pleurozium schreberi, known to host cyanobacteria, along a distance gradient away from the metal source of pollution and measured moss-metal content (Fe, Cu, Zn, Pb) as well as N₂ fixation. We found a strong distance gradient in moss-metal content for all investigated metals: a sharp decline in metal content with distance away from the metal pollution source. However, we found a similarly steep gradient in moss-associated N₂ fixation, with highest activity closest to the metal source of pollution. Hence, while mosses may be sensitive to increased heavy metal inputs, the activity of colonising cyanobacteria seem to be unaffected by heavy metals, and consequently, ecosystem function may not be compromised by elevated metal input.