Phosphorus recovery and sustainable nutrient management are increasingly important for agricultural and industrial systems as global phosphate reserves decline. The disruption of the global phosphorus cycle, driven by fertilizer overuse and wastewater discharge, has intensified eutrophication and ecosystem degradation. In biological systems, inorganic phosphate fuels the very essence of life, forming the energetic basis of cellular function. However, fluctuating environmental phosphate conditions compel cells to store this element in the form of polyphosphate inside specialized organelles like acidocalcisomes. Polyphosphate homeostasis varies across microorganisms. Herein, by focusing on yeast and microalgae, this review follows the path of phosphate from its extracellular uptake by high and low affinity transporters (e.g., Pho89 and Pho90 yeast phosphate transporters; and PTA and PTC families of microalgal phosphate transporters) until its polymerization by Vacuolar Transporter Chaperone complex complex, which represents a functionally comparable polyphosphate synthesis mechanism in these two microbial taxa. Despite extensive research, a comparative overview linking molecular mechanisms to environmental bioprocess performance remains limited. Here, we bridge this gap by synthesizing mechanistic, physiological, and ecological insights to assess the potential of both groups as sustainable phosphorus recovery systems. This review synthesizes multi-omics analyses, structural studies, metabolic modeling approaches, and genome engineering strategies to advance understanding of microbial polyphosphate metabolism and its relevance for phosphorus recovery. Collectively, this review identifies key opportunities for leveraging microbial polyphosphate metabolism to advance environmentally resilient and resource-efficient phosphorus recovery technologies.

Silicon is increasingly applied in agriculture to improve plant productivity under both abiotic and biotic stress constraints. Nevertheless, its mechanisms of action are often studied separately at the soil, plant, or microbiome levels, limiting a comprehensive understanding of its overall impact on agroecosystem functioning. This review proposes an integrated perspective of the soil–plant–microbiome continuum, linking silicon chemistry in soil solutions with the effects of silicon amendments on soil properties and the processes of uptake, transport, and deposition in the plants. We show that silicon bioavailability depends on maintaining a pool of dissolved silicon dominated by orthosilicic acid, regulated by mineral weathering, adsorption–desorption dynamics, polymerization, pH, iron and aluminum oxides, and organic matter. In soils, silicon inputs can improve structure, modulate acidity and cation exchange balances, influence nutrient availability, and reduce the mobility of certain metals. They may also affect enzymatic activities and microbial community composition. In plants, silicon uptake and transport, mediated by specific transporters, contribute to tissue silicification, the maintenance of leaf architecture, and the regulation of water, ionic, and redox homeostasis. These processes provide a basis for enhanced tolerance to drought, salinity, and metal toxicity, as well as biotic stress caused by pathogens and pests. Finally, we discuss key limitations to the agronomic application of silicon, including the diagnosis of the silicic status of soils, the choice of source and mode of application, and the genotypic variability of acquisition, as well as the need for multi-site tests and more robust mechanistic validations. This synthesis provides a coherent mechanistic framework to better define the conditions under which silicon can serve as a reliable tool for sustainable crop management under climate change.

Cadmium (Cd), a toxic heavy metal, poses a significant threat to aquatic ecosystems by impairing primary producers such as microalgae. This study investigated the adaptive responses of Chlamydomonas reinhardtii to Cd stress through physiological, biochemical, and GC-MS-based lipidomic analysis. Cultures were exposed to the EC50 concentration of Cd (20 ppm) for 8 days. Cd exposure significantly increased oxidative stress markers, including hydrogen peroxide (+69%), malondialdehyde (+336%), and proline (+144%). Total carbohydrate and lipid contents increased by 21.7% and 14%, respectively, whereas protein and total photosynthetic pigment contents decreased by 39.5% and 44%, respectively, indicating metabolic reprogramming under Cd stress. Antioxidant capacity was enhanced as reflected by a 50% reduction in the DPPH IC50 value. Lipidomic analysis revealed a decrease in unsaturated fatty acids accompanied by the accumulation of lipid-derived aldehydes and saturated hydrocarbons. KEGG pathway enrichment analysis identified significant alterations in fatty acid biosynthesis, fatty acid elongation, glutathione metabolism, and butanoate metabolism, highlighting coordinated oxidative and lipid metabolic reprogramming as key adaptive responses to Cd stress.

In response to the growing demand for rare earth elements (REEs) and the limited availability of primary resources, the recovery of REEs from secondary resources through bioleaching has attracted increasing research interest. This review highlights biohydrometallurgical processing as an environmentally friendly, technically feasible, and economically sustainable approach for REEs recovery, providing valuable insights into the development and optimization of practical bioleaching strategies. The roles of both autotrophic and heterotrophic microorganisms are examined in relation to the characteristics of REEs-containing feedstock and their bioleaching performance. Particular attention is given to the underlying bioleaching mechanisms, including acidolysis, complexolysis, and redoxolysis, which are mediated by microbial metabolites and biochemical activities. Recent advances in bioreactor engineering are also discussed, with an emphasis on continuous stirred-tank reactors, airlift bioreactors, fluidized-bed reactors, and other emerging reactor configurations for controlled and efficient REEs bioleaching. In addition, the influence of key physicochemical and process parameters on bioleaching efficiency is critically evaluated. Finally, techno-economic assessment and life cycle assessment studies are reviewed to compare the economic and environmental performance of bioleaching with that of conventional hydrometallurgical processes. The current state of knowledge indicates that bioleaching offers a sustainable pathway for REEs recovery from secondary resources, although further advances are required to address the scientific, technological, and economic barriers to industrial-scale implementation.

Among emerging green hydrogen (H2) production strategies, microbial biohydrogen (BioH2) technologies represent promising low-carbon and waste-valorization pathways. This review presents a comprehensive analysis of waste to H2 production systems within a circular H2 economy framework. A bibliometric assessment first maps research trends, thematic evolution, and global scientific dynamics in microbial BioH2 production. The review then examines solid biomass pretreatment technologies (physical, chemical, and biological) as critical steps for efficient substrate conversion, followed by fermentative, enzymatic, and photosynthetic production routes, highlighting key microbial catalysts and metabolic pathways. The valorization of wastewater streams is further explored, emphasizing their dual function in renewable H2 generation and environmental remediation. Advances in genetic engineering and multi-omics approaches are critically discussed for their role in enhancing H2 yields, optimizing microbial consortia, and unraveling regulatory networks governing H2 metabolism. Finally, environmental sustainability, techno-economic feasibility, and downstream H2 storage and distribution challenges are evaluated to identify barriers and development pathways for large-scale implementation of waste-derived BioH2 systems.

Natural dyeing of protein fibers remains limited by the weak affinity of wool for most plant-based chromophores, which often requires metallic mordants to achieve acceptable color strength and fastness. Although chitosan is widely applied directly onto wool as a biomordant to introduce cationic sites, its performance is constrained by the physical nature of the coating and does not provide the consistency needed for reliable metal-free dyeing. To address these limitations, this study investigates a chitosan-citric acid treatment that enables the formation of a crosslinked cationic network on wool fibers. Esterification reactions involving citric acid, chitosan, and accessible keratin functional groups lead to a chemically stabilized surface modification that maintains a positive charge over a broad pH range. FTIR, SEM-EDS, AFM, and zeta-potential measurements confirm the formation of new ester linkages and the presence of a uniform modified surface, with the isoelectric point shifting to around pH 10.1. This cationic character significantly improves the interaction of wool with the polyphenolic compounds of pomegranate peel extract, enabling metal-free dyeing with higher color strength and improved fastness. Kinetic and equilibrium data indicate a surface-controlled process on a heterogeneous surface, while the observed decrease in optical band-gap energy suggests strengthened charge-transfer interactions after grafting. In parallel, the treated fibers exhibit notable antibacterial activity, achieving complete inhibition of Staphylococcus aureus and a strong reduction of Escherichia coli.

The release of hexavalent chromium (Cr(VI)) into ecosystems pose a serious threat to both environment and public health due to its high toxicity, mobility, and persistence in aqueous systems. Conventional remediation methods, including chemical reduction–precipitation, adsorption, and membrane processes, are often limited by high chemical consumption, operational costs, and the generation of secondary wastes. These limitations highlight the need for sustainable and cost-effective technologies, particularly for dilute Cr(VI)-contaminated effluents. In this context, the present study investigates ionic bio-flotation as an alternative approach to overcome these constrains. Cr(VI) removal was evaluated using a microbial biosurfactant (BioS) produced by a Bacillus paramycoides isolated from olive oil waste-contaminated soil. This strain exhibited non-pathogenic traits and was sensitive to common antibiotics (inhibition zones: amikacin 24 mm; gentamicin 20 mm), with no detectable protease or lipase activities, supporting safe handling during BioS production. The extracted BioS was characterized by surface tension measurements, FTIR spectroscopy, biochemical composition analysis, and CHNS elemental analysis, indicating its lipopeptidic nature. Microflotation experiments were conducted, and key process parameters were optimized using the Box-Behnken design. Under optimal conditions (air flow rate: 0.69 L min−1, BioS concentration: 172.69 mg l−1, pH 2), a maximum Cr(VI) removal efficiency of 93.67% was achieved. Mechanistic investigations based on zeta potential and UV–visible analyses revealed that the removal process is governed by electrostatic interactions between dichromate ions and protonated amine groups of the BioS. These results demonstrate the potential of BioS as an eco-friendly collector for the efficient Cr(VI) removal from wastewater.

This study examines recent advances in anaerobic digestion across Africa, introducing a bibliometric and patent analysis, as well as a technical, techno-economic and life cycle assessment. The African case studies reported indicate methane (CH4) yields generally ranging from 200 to 350 L of CH4 kg(-1) of volatile solids, and system performance is greatly impacted by the nature of the feedstock chosen for fermentation, the reactor configuration and the assurance of process stability. Techno-economic assessments reveal payback periods ranging from 2 to 10 years, with internal rates of return of 5 to 20% for large-scale systems benefiting from favorable policies and good conditions in terms of biomass availability. New low-cost digital control and monitoring techniques increase the reliability of decentralized systems. Based on this information, a modular 20 m(3) "smart" biodigester is proposed, capable of producing approximately 15 m(3) per day of biogas (55 to 65% CH4) at mesophilic temperatures.

Biosurfactants are surface-active molecules derived from biological sources mainly microorganisms. Their use in mineral flotation as eco-friendly alternatives to synthetic surfactants has recently drawn significant attention due to their biodegradability, low toxicity, and diverse physicochemical properties. This review provides a comprehensive analysis of microbial biosurfactants in improving flotation efficiency, with a particular focus on phosphate ore beneficiation. A bibliometric analysis highlights research trends and major contributors in this evolving field. The microbial biosurfactant-producing strains, along with standard extraction and purification methods are covered, emphasizing key functional traits that can impact flotation performance. Mechanistic insights are detailed, including adsorption behavior, and selective interaction with mineral surfaces, as demonstrated by recent experimental studies. Biosurfactants offer significant advantages that position them as promising sustainable candidates in mineral processing. Nevertheless, several challenges persist, including high production costs, limited scalability, and the need for effective integration into existing flotation circuits. The review concludes with future perspectives, including the need for process optimization, pilot-scale validation, cost-effective production strategies, and the engineering of application-specific biosurfactants. These advancements are essential to bridge the gap between laboratory research and industrial implementation, and to realize the full potential of biosurfactants in mineral beneficiation.

The growing concerns about the environmental impact of the mining industry, particularly the intensive use of petroleum-derived chemical reagents, surge a radical transformation towards adopting more sustainable and eco-friendly approaches. The widespread use of chemical surfactants in mineral flotation is crucial for efficiently separating valuable minerals from ores in the mining industry. However, recently attention has been drawn to the development and usage of bio-catalyzed and enzymatically synthesized biosurfactants in the field of mineral enrichment towards building a sustainable and ecological flotation process. This review primarily discusses the current state of ecological flotation from three perspectives: enzymatic synthesis of biosurfactants with desirable properties, the expanded application of these agents in bio-flotation, and the prospect of large-scale implementation. Recent investigations have been summarized by categorizing sugar- and fatty alcohol-based biosurfactants according to their direct or indirect implications for improving flotation across a wide range of minerals. Importantly, this review integrates available quantitative comparisons between enzymatically synthesized biosurfactants and conventional surfactants, highlighting key performance indicators such as recovery rates, selectivity indices, and environmental impact metrics. The current review also aims to shed light on the use of enzymes in the synthesis of these biosurfactants through illustrative examples such as enzyme-mediated production of rhamnolipids and sugar fatty acid esters, which have shown promising results in enhancing flotation efficiency and selectivity. Tackling the scientific and technological challenges in ecological flotation will drive efforts to minimize environmental pollution, enhance the sustainability of mining practices, and advance the goals of a green economy.

Phosphogypsum (PG) is the largest by-product of the phosphate industry. Nearly 300 M tons of PG are annually discarded, of which 58% is dry stacked. The exposure of PG stacks to rainwater and processed waters moisture creates hydraulic pressure, generating acidic PG leachates into nearby aquifer systems. Because of its elevated levels of sulfates, phosphorus (P) and metals, the PG water leachate can negatively affect the surrounding environments. This work investigates the effect of water activity on the PG leaching, by studying the effect of different PG:Water ratios on the leaching process, followed by the anaerobic bioremediation of PG leachate through biological sulfate removal activity (BSRA). This later involves using sulfate-reducing bacteria consortium within an anaerobic bioreactor, allowing a simultaneous monitoring of the leachate's biochemical changes, impurities removal, and microbial community dynamics. The results determined the highest sulfates and impurities leaching from PG with a PG:Water ratio of 1:200 (w:v). Subsequently, the biological treatment of the leachate exhibited an efficient removal of sulfates (79%), P (99%) and chemical oxygen demand (93%), with a substantial decline in metal concentrations (Cd, As and Al by 99%, and Zn by 70%) from the leachate. Moreover, the acidity of the leachate was also neutralized through the BSRA process by increasing the pH from 4 to 7.52. Furthermore, the microbial community dynamics unveiled a significant correlation between the leachate's biochemical changes and co-existence of specific sulfate-reducing bacteria within various bacterial phyla, including Desulfobacterota, Firmicutes, and Proteobacteria, allowing efficient and eco-friendly bioremediation process of PG leachate.

This work investigated elemental sulfur (S0) biorecovery from Phosphogypsum (PG) using sulfur-oxidizing bacteria in an O2-based membrane biofilm reactor (MBfR). The system was first optimized using synthetic sulfide medium (SSM) as influent, then switched to biogenic sulfide medium (BSM) generated by biological reduction of PG alkaline leachate. The results using SSM had high sulfide-oxidation efficiency (98 %), sulfide to S0 conversion (-90 %), and S0 production rate up to 2.7 g S0/(m2.d), when the O2/S ratio was -0.5 g O2/g S. With the BSM influent, the system maintained high sulfide-to-S0 conversion rate (97 %), and S0-production rate of 1.6 g S0/(m2.d). Metagenomic analysis revealed that Thauera was the dominant genus in SSM and BSM biofilms. Furthermore, influent composition affected the bacterial community structure and abundances of functional microbial sulfur genes, modifying the sulfur-transformation pathways in the biofilms. Overall, this work shows promise for O2-MBfR usage in S0 biorecovery from PG-leachate and other sulfidogenic effluents.

Phytotherapy, which involves the use of plant extracts and natural compounds for medicinal purposes, is indeed a promising alternative for managing urinary lithiasis. Many plants have been studied for their potential to prevent and treat kidney stones, and they may offer a more natural and potentially less harmful approach compared to conventional treatments. Additionally, phytotherapy may be more cost-effective. The aim of the present study was to investigate the antilithic potential of extracts and essential oils of Saussurea costus (Falc) Lipsch in two in vivo models, one on ethylene glycol-induced calcium oxalate crystal formation and the other to assess the effects of these extracts on magnesium oxide-induced struvite crystal formation. The experiment involved the administration of different doses of aqueous and ethanolic extracts of S. costus (200 and 400 mg/kg) and essential oils (25 and 50 mg/kg) to male Wistar rats, followed by the evaluation of various physiological, biochemical and histopathological parameters. The results demonstrated that the administration of S. costus essential oils and extracts had significant effects on the rats, influencing body weight, urine volume, crystal deposition, cytobacteriological examination of urine, and serum biochemical parameters. Histopathological examinations revealed varying impacts on the kidneys and livers of the treated rats. The findings suggest that S. costus extracts and essential oils may hold promise in inhibiting calcium oxalate crystal formation in vivo and influencing various physiological and biochemical parameters in rats. Overall, the 200 mg/kg ethanolic extract of S. costus demonstrated antilithiatic efficacy, did not exhibit signs of toxicity and reduced the number of crystals in the kidneys. Furthermore, the study did not find a significant effect on reducing struvite crystals.

Organic contaminants are among the main pollutants of ecosystems because of their presence in domestic, agricultural, or industrial effluents. Indeed, many organic xenobiotics such as aromatic hydrocarbons, pesticides, synthetic dyes, etc., are not easily biodegradable in the environment and can therefore accumulate in ecosystems causing various toxic symptoms in exposed organisms, including humans. Yeast-assisted biological treatment has emerged as a promising new strategy for the biodegradation of such hazardous contaminants. Firstly, this chapter provides an overview of the applications of yeast in the biodegradation of organic contaminants. Subsequently, synthetic dyes were chosen as a model of organic pollutants to highlight the enzymes involved in their biodegradation process using various yeast strains. Indeed, the main oxidases involved are laccase, tyrosinase, lignin peroxidase, and manganese peroxidase. While the main reductases are Azoreductase, NADH-DCIP reductase, and malachite green reductase. The last section highlights the effects of physicochemical conditions on the effectiveness of mycoremediation.

Microalgae and cyanobacteria are photosynthetic microorganisms that can be used to bioremediate anthropogenic pollutants from air, water and soil. These organisms can remediate several anthropogenic pollutants, such as carbon dioxide, nitrates and phosphates, heavy metals, pharmaceuticals, pesticides and persistent organic pollutants. The biomass generated in this process can be used as a feedstock source for the production of a multitude of valuable biobased products and applications. Polymers, resins, binders, lubricants, and coatings are some of the promising examples. This chapter provides an overview of the entire process: bioremediation using microalgae and production of value-added products, based on a biorefinery concept, focusing on circular economy and sustainability. Essential aspects of legislation and regulations are also approached.

Phosphogypsum (PG), a by-product of the phosphate industry, is high in sulfate, (SO42-), which makes it an excellent substrate for sulfate-reducing bacteria (SRB) to produce hydrogen sulfide. This work aimed to optimize SO42- leaching from PG to achieve a high biological reduction of SO42- and generate high sulfide concentrations for subsequent use in the biological recovery of elemental sulfur. Five SRB consortia were isolated and enriched from: IS (Industrial sludges), MS (Marine sediments), WC (Winogradsky column), SNV (petroleum industry sediments) and PG (stored Phosphogypsum). The five consortia showed reduction activity when using PG leachate (with water) as source of SO42- and lactate, acetate, or glucose as the electron donor. The highest reduction rate (81.5 %) was registered using lactate and the IS consortium (81.5 %) followed by MS (79 %) and PG (71 %). To enhance the concentration of leached SO42- from PG for future utilization with the isolated consortia, PG was treated with NaOH solutions (2 % and 5 %). SO42- release of 97 % was achieved with a 5 % concentration and the resulting leachate was further diluted to target a SO42- concentration of 12.4 g·L-1 for utilization with the isolated consortia. Compared to water leachate, a significantly higher reduction rate was registered (2 g·L-1 of SO42) using the IS consortium, demonstrating limited inhibition effect of sulfide- concentration on SRB functionalities. Moreover, metagenomic analysis of the consortia revealed that using PG as a source of SO42- increased the abundance of Deltaproteobacteria, including known SRB like Desulfovibrio, Desulfomicrobium, and Desulfosporosinus, as well as novel SRB genera (Cupidesulfovibrio, Desulfocurvus, Desulfococcus) that showed, for the first time, significant potential as novel sulfate-reducers using PG as a SO42- source.

Biological sulfide oxidation is an efficient means to recover elemental sulfur (S0) as a valuable resource from sulfide-bearing wastewater. This work evaluated the autotrophic sulfide oxidation to S0 in the O2-based membrane biofilm reactor (O2-MBfR). High recovery of S0 (80-90% of influent S) and high sulfide oxidation (∼100%) were simultaneously achieved when the ratio of O2-delivery capacity to sulfide-to S0 surface loading (SL) (O2/S2- → S0 ratio) was around 1.5 (g O2/m2-day/g O2/m2-day). On average, most of the produced S0 was recovered in the MBfR effluent, although the biofilm could be a source or sink for S0. Shallow metagenomic analysis of the biofilm showed that the top sulfide-oxidizing genera present in all stages were Thauera, Thiomonas, Thauera_A, and Pseudomonas. Thiomonas or Pseudomonas was the most important genus in stages that produced almost only S0 (i.e., the O2/S2- → S0 ratio around 1.5 g of the O2/m2-day/g O2/m2-day). With a lower sulfide SL, the S0-producing genes were sqr and fccAB in Thiomonas. With a higher sulfide SL, the S0-producing genes were in the soxABDXYZ system in Pseudomonas. Thus, the biofilm community of the O2-MBfR adapted to different sulfide-to-S0 SLs and corresponding O2-delivery capacities. The results illustrate the potential for S0 recovery using the O2-MBfR.

Synthetic toxic dyes from liquid wastes can be harmful for living organisms and the environment, even at low concentrations. This research investigated the utilization of the Chenopodium quinoa pericarp bio-waste (QBW) after saponin glycosides extraction as biosorbent in the removal of methylene blue (MB) dye as a model contaminant from aqueous solution. QBW was successfully modified by chemical (sulfuric acid) and thermal (pyrolysis) treatments. The biosorbent was characterized by FTIR, TGA, BET, Zeta Potential, SEM/EDX, and contact angle analysis to get further insight into the adsorbent's behavior and to propose a suitable biosorption mechanism. Batch experiments were explored to study the effect of various parameters on MB removal effi-ciency, including contact time, adsorbent quantity, initial concentration, and process temperature. The optimum conditions for QBW biosorption of MB were at neutral pH and contact time of 60 min. The maximum adsorption capacity of the biosorbent (QBW-II), which demonstrated the highest MB removal efficiency in the biosorption test was 193.802 & PLUSMN; 4.365 mg.g  1. The kinetic and isotherm study of MB dye biosorption revealed that the pseudo-second-order model and Langmuir isotherm were the best fit. Thermodynamic parameters for the bio-sorption showed that the process was spontaneous and exothermic. Our findings demonstrate that QBW has a high potential to be used as an environmentally friendly and promising bio-sorbent to effectively remove organic contaminants from aqueous systems.