Effect of zero-valent iron nanoparticles on taxonomic composition and hydrogen production from kitchen waste.

This study investigated the effects of varying zero-valent iron (ZVI) (0 to 5,000 mg/L) on fermentative hydrogen (H2) production, metabolic pattern, and taxonomic profile by using kitchen waste as substrate. The study demonstrated that the supplementation of 500 mg ZVI/L resulted in the highest H2 yield (219.68 ± 11.19 mL H2/g-volatile solids (VS)added), which was 19% higher than the control. The metabolic pattern analysis showed that acetic and butyric acid production primarily drove the H2 production. The taxonomic analysis further revealed that Firmicutes (relative abundance (RA): 80-96%) and Clostridium sensu stricto 1 (RA: 68-88%) were the dominant phyla and genera, respectively, during the exponential gas production phase, supporting the observation of accumulation of acetic and butyric acids. These findings suggest that supplementation of ZVI can enhance H2 production from organic waste and significantly influence the metabolic pattern and taxonomic profile, including the metalloenzymes.

Emerging trends in the pretreatment of microalgal biomass and recovery of value-added products: A review.

Microalgae are a promising source of raw material (i.e., proteins, carbohydrates, lipids, pigments, and micronutrients) for various value-added products and act as a carbon sink for atmospheric CO2. The rigidity of the microalgal cell wall makes it difficult to extract different cellular components for its applications, including biofuel production, food and feed supplements, and pharmaceuticals. To improve the recovery of products from microalgae, pretreatment strategies such as biological, physical, chemical, and combined methods have been explored to improve whole-cell disruption and product recovery efficiency. However, the diversity and uniqueness of the microalgal cell wall make the pretreatment process more species-specific and limit its large-scale application. Therefore, advancing the currently available technologies is required from an economic, technological, and environmental perspective. Thus, this paper provides a state-of-art review of the current trends, challenges, and prospects of sustainable microalgal pretreatment technologies from a microalgae-based biorefinery concept.

COVID-19 drugs in aquatic systems: a review.

The outbreak of the human coronavirus disease 2019 (COVID-19) has induced an unprecedented increase in the use of several old and repurposed therapeutic drugs such as veterinary medicines, e.g. ivermectin, nonsteroidal anti-inflammatory drugs, protein and peptide therapeutics, disease-modifying anti-rheumatic drugs and antimalarial drugs, antiretrovirals, analgesics, and supporting agents, e.g. azithromycin and corticosteroids. Excretion of drugs and their metabolites in stools and urine release these drugs into wastewater, and ultimately into surface waters and groundwater systems. Here, we review the sources, behaviour, environmental fate, risks, and remediation of those drugs. We discuss drug transformation in aquatic environments and in wastewater treatment systems. Degradation mechanisms and metabolite toxicity are poorly known. Potential risks include endocrine disruption, acute and chronic toxicity, disruption of ecosystem functions and trophic interactions in aquatic organisms, and the emergence of antimicrobial resistance.

Recent progress in microbial fuel cells for industrial effluent treatment and energy generation: Fundamentals to scale-up application and challenges.

Microbial fuel cells (MFCs) technology have the potential to decarbonize electricity generation and offer an eco-friendly route for treating a wide range of industrial effluents from power generation, petrochemical, tannery, brewery, dairy, textile, pulp/paper industries, and agro-industries. Despite successful laboratory-scale studies, several obstacles limit the MFC technology for real-world applications. This review article aimed to discuss the most recent state-of-the-art information on MFC architecture, design, components, electrode materials, and anodic exoelectrogens to enhance MFC performance and reduce cost. In addition, the article comprehensively reviewed the industrial effluent characteristics, integrating conventional technologies with MFCs for advanced resource recycling with a particular focus on the simultaneous bioelectricity generation and treatment of various industrial effluents. Finally, the article discussed the challenges, opportunities, and future perspectives for the large-scale applications of MFCs for sustainable industrial effluent management and energy recovery.

Simultaneous removal of lead and selenium through biomineralization as lead selenide by anaerobic granular sludge.

This study demonstrated the simultaneous removal of lead (Pb) and selenium (Se) as lead selenide biomineralization using anaerobic granular sludge. The microbial community of the granular sludge was first enriched for 140 days in the presence of Pb(II) only, selenate and selenite only, Pb(II)+selenate, and Pb(II)+selenite. In the absence of Se, removal of Pb(II) mainly occurred via biosorption and deposited on the biomass as lead oxide and lead carbonate. The Pb removal efficiency (94% of initial 50 mg L-1) was reduced to 90% and 86% in the presence of selenate and selenite, respectively, due to biosorption. Addition of Pb(II) didn't exert any toxic effect on the Se-reducing microbial community, on the contrary: Pb(II) addition improved the Se removal efficiency for selenate from 85% to 90%, but did not affect selenite removal after 14 d of incubation. The bioreduction of the Se-oxyanions produced elemental Se (Se(0)) and selenide, which later interacted with Pb(II) to produce lead selenide (PbSe). Adsorption of Pb(II) onto the Se(0) nanoparticles and precipitation as the Se(0)-Pb complex might also have contributed to the simultaneous removal of Pb and Se. XPS and XRD analysis further confirmed the immobilization of Pb as PbSe, PbO and PbCO3 in the biomass.

Novel coronavirus disease 2019 (COVID-19) pandemic: From transmission to control with an interdisciplinary vision.

There a lot of review papers addressing specific COVID-19 research sectors, then devoted to specialists. This review provides an in-depth summary of the available information about SARS-CoV-2 and the corresponding disease (also known as COVID-19), with a multi-disciplinary approach. After the paper introduction, the first section treats the virological characteristics of SARS-CoV-2, the medical implications of the infection, and the human susceptivity. Great attention is devoted to the factor affecting the infection routes, distinguishing among the possible human-to-human, environmental-to-human, and pollution-to-human transmission mechanisms. The second section is devoted to reporting the impact of SARS-CoV-2 not only on the healthcare systems but also on the economy and society. The third section is devoted to non-pharmaceutical behaviours against COVID-19. In this context, this review section presents an analysis of the European second wave allowing not only to focalize the importance of some restrictions, but also the relevance of social acceptance of some measures. The data reassumed in this work are very useful for interdisciplinary researchers that work in a team to find the basic available information about all the aspects connected with this pandemic (from virus diffusion mechanism to health information, from economic and social impacts to measures to reduce the pandemic spread), with great attention to social acceptance of restriction measures and of vaccines (that currently results to be insufficient to achieve community immunity). Then, this review paper highlights the fundamental role of the trans-multi-disciplinary research that is devoted not only to understand the basics of the pandemic to propose solutions but has also the commitment to find strategies to increase population resilience. For this aim, the authors strongly suggest the establishment of an international health-care trans-multi-disciplinary workforce devoted to investigate, mitigate, and control also future viral events.

Cadmium Selenide Formation Influences the Production and Characteristics of Extracellular Polymeric Substances of Anaerobic Granular Sludge.

Feeding cadmium (II) and selenium (IV) simultaneously to anaerobic granular sludge with the aim of synthesizing cadmium selenide (CdSe) nanoparticles induces compositional changes in the extracellular polymeric substances (EPS) matrix of this sludge. A methanogenic anaerobic granular sludge was repeatedly exposed to Cd(II) (10-50 mg L-1) and selenite (79 mg L-1) for 300 days at pH 7.3 and 30 °C in a fed-batch feeding regime for enrichment of Se-reducing bacteria and synthesis of CdSe nanoparticles. EPS fingerprints of the granular sludge, obtained by size exclusion chromatography coupled to a fluorescence detector, showed a significant increase in the intensity of protein-like substances with > 100 kDa apparent molecular weight (aMW) upon repeated exposure to Cd(II) and Se(VI). This was accompanied by a prominent decrease in protein-like substances of aMW < 10 kDa. The fingerprint of the humic-like substances showed emergence of a new peak with aMW of 13 to 300 kDa in the EPS extracted from the Cd/Se fed granular sludge. Experiments on metal(loid)-EPS interactions showed that the CdSe nanoparticles interact mainly with loosely bound EPS (LB-EPS). This study showed that the formation of Se(0) and CdSe nanoparticles occurs in the LB-EPS fraction of the granular sludge and repeated exposure to Cd and Se induces compositional changes in the EPS matrix.

Role of extracellular reactive sulfur metabolites on microbial Se(0) dissolution.

The dissolution of elemental selenium [Se(0)] during chemical weathering is an important step in the global selenium cycle. While microorganisms have been shown to play a key role in selenium dissolution in soils, the mechanisms of microbial selenium solubilization are poorly understood. In this study, we isolated a Bacillus species, designated as strain JG17, that exhibited the ability to dissolve Se(0) under oxic conditions and neutral pH. Growth of JG17 in a defined medium resulted in the production and accumulation of extracellular compounds that mediated Se(0) dissolution. Analysis of the spent medium revealed the presence of extracellular sulfite, sulfide, and thiosulfate. Abiotic Se(0) dissolution experiments with concentrations of sulfite, sulfide, and thiosulfate relevant to our system showed similar extents of selenium solubilization as the spent medium. Together, these results indicate that the solubilization of Se(0) by JG17 occurs via the release of extracellular inorganic sulfur compounds followed by chemical dissolution of Se(0) by the reactive sulfur metabolites. Our findings suggest that the production of reactive sulfur metabolites by soil microorganisms and the formation of soluble selenosulfur complexes can promote selenium mobilization during chemical weathering.

Formation of Se(0), Te(0), and Se(0)-Te(0) nanostructures during simultaneous bioreduction of selenite and tellurite in a UASB reactor.

Simultaneous removal of selenite and tellurite from synthetic wastewater was achieved through microbial reduction in a lab-scale upflow anaerobic sludge blanket reactor operated with 12 h hydraulic retention time at 30 °C and pH 7 for 120 days. Lactate was supplied as electron donor at an organic loading rate of 528 or 880 mg COD L-1 day-1. The reactor was initially fed with a synthetic influent containing 0.05 mM selenite and tellurite each (phase I, day 1-60) and subsequently with 0.1 mM selenite and tellurite each (phase II, day 61-120). At the end of phase I, selenite and tellurite removal efficiencies were 93 and 96%, respectively. The removal percentage dropped to 87 and 81% for selenite and tellurite, respectively, at the beginning of phase II because of the increased influent concentrations. The removal efficiencies of both selenite and tellurite were gradually restored within 20 days and stabilized at ≥ 97% towards the end of the experiment. Powder X-ray diffraction and Raman spectroscopy confirmed the formation of biogenic Se(0), Te(0), and Se(0)-Te(0) nanostructures. Scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy showed aggregates comprising of Se(0), Te(0), and Se-Te nanostructures embedded in a layer of extracellular polymeric substances (EPS). Infrared spectroscopy confirmed the presence of chemical signatures of the EPS which capped the nanoparticle aggregates that had been formed and immobilized in the granular sludge. This study suggests a model for technologies for remediation of effluents containing Se and Te oxyanions coupled with biorecovery of bimetal(loid) nanostructures.

Continuous removal and recovery of tellurium in an upflow anaerobic granular sludge bed reactor.

Continuous removal of tellurite (TeO32-) from synthetic wastewater and subsequent recovery in the form of elemental tellurium was studied in an upflow anaerobic granular sludge bed (UASB) reactor operated at 30°C. The UASB reactor was inoculated with anaerobic granular sludge and fed with lactate as carbon source and electron donor at an organic loading rate of 0.6g CODL-1d-1. After establishing efficient and stable COD removal, the reactor was fed with 10mg TeO32-L-1 for 42 d before increasing the influent concentration to 20mg TeO32-L-1. Tellurite removal (98 and 92%, respectively, from 10 and 20mg TeL-1) was primarily mediated through bioreduction and most of the removed Te was retained in the bioreactor. Characterization using XRD, Raman spectroscopy, SEM-EDX and TEM confirmed association of tellurium with the granular sludge, typically in the form of elemental Te(0) deposits. Furthermore, application of an extracellular polymeric substances (EPS) extraction method to the tellurite reducing sludge recovered up to 78% of the tellurium retained in the granular sludge. This study demonstrates for the first time the application of a UASB reactor for continuous tellurite removal from tellurite-containing wastewater coupled to elemental Te(0) recovery.

A comparison of fate and toxicity of selenite, biogenically, and chemically synthesized selenium nanoparticles to zebrafish (Danio rerio) embryogenesis.

Microbial reduction of selenium (Se) oxyanions to elemental Se is a promising technology for bioremediation and treatment of Se wastewaters. But a fraction of biogenic nano-Selenium (nano-Seb) formed in bioreactors remains suspended in the treated waters, thus entering the aquatic environment. The present study investigated the toxicity of nano-Seb formed by anaerobic granular sludge biofilms on zebrafish embryos in comparison with selenite and chemogenic nano-Se (nano-Sec). The nano-Seb formed by granular sludge biofilms showed a LC50 value of 1.77 mg/L, which was 3.2-fold less toxic to zebrafish embryos than selenite (LC50 = 0.55 mg/L) and 10-fold less toxic than bovine serum albumin stabilized nano-Sec (LC50 = 0.16 mg/L). Smaller (nano-Secs; particle diameter range: 25-80 nm) and larger (nano-Secl; particle diameter range: 50-250 nm) sized chemically synthesized nano-Sec particles showed comparable toxicity on zebrafish embryos. The lower toxicity of nano-Seb in comparison with nano-Sec was analyzed in terms of the stabilizing organic layer. The results confirmed that the organic layer extracted from the nano-Seb consisted of components of the extracellular polymeric substances (EPS) matrix, which govern the physiochemical stability and surface properties like ζ-potential of nano-Seb. Based on the data, it is contented that the presence of humic acid like substances of EPS on the surface of nano-Seb plays a major role in lowering the bioavailability (uptake) and toxicity of nano-Seb by decreasing the interactions between nanoparticles and embryos.