Choline Dehydrogenase Contributes to Salt Tolerance in Dunaliella through Betaine Synthesis.

In Dunaliella tertiolecta, a microalga renowned for its extraordinary tolerance to high salinity levels up to 4.5 M NaCl, the mechanisms underlying its stress response have largely remained a mystery. In a groundbreaking discovery, this study identifies a choline dehydrogenase enzyme, termed DtCHDH, capable of converting choline to betaine aldehyde. Remarkably, this is the first identification of such an enzyme not just in D. tertiolecta but across the entire Chlorophyta. A 3D model of DtCHDH was constructed, and molecular docking with choline was performed, revealing a potential binding site for the substrate. The enzyme was heterologously expressed in E. coli Rosetta (DE3) and subsequently purified, achieving enzyme activity of 672.2 U/mg. To elucidate the role of DtCHDH in the salt tolerance of D. tertiolecta, RNAi was employed to knock down DtCHDH gene expression. The results indicated that the Ri-12 strain exhibited compromised growth under both high and low salt conditions, along with consistent levels of DtCHDH gene expression and betaine content. Additionally, fatty acid analysis indicated that DtCHDH might also be a FAPs enzyme, catalyzing reactions with decarboxylase activity. This study not only illuminates the role of choline metabolism in D. tertiolecta's adaptation to high salinity but also identifies a novel target for enhancing the NaCl tolerance of microalgae in biotechnological applications.

Product Selection Toward High-Value Hydrogen and Bamboo-Shaped Carbon Nanotubes from Plastic Waste by Catalytic Microwave Processing.

The escalating levels of plastic waste and energy crises underscore the urgent need for effective waste-to-energy strategies. This study focused on converting polypropylene wastes into high-value products employing various iron-based catalysts and microwave radiative thermal processing. The Al-Fe catalysts exhibited exceptional performance, achieving a hydrogen utilization efficiency of 97.65% and a yield of 44.07 mmol/g PP. The gas yields increased from 19.99 to 94.21 wt % compared to noncatalytic experiments. Furthermore, this catalytic system produced high-value bamboo-shaped carbon nanotubes that were absent in other catalysts. The mechanism analysis on catalytic properties and product yields highlighted the significance of oxygen vacancies in selecting high-value products through two adsorption pathways. Moreover, the investigation examined the variations in product distribution mechanisms between conventional and microwave pyrolysis, in which microwave conditions resulted in 4 times higher hydrogen yields. The technoeconomic assessment and Monte Carlo risk analysis further compared the disparity. The microwave technique had a remarkable internal rate of return (IRR) of 39%, leading to an income of $577/t of plastic with a short payback period of 2.5 years. This research offered sustainable solutions for the plastic crisis, validating the potential applicability of commercializing the research outcomes in real-world scenarios.

DbMADS regulates carotenoid metabolism by repressing two carotenogenic genes in the green alga Dunaliella sp. FACHB-847.

MADS transcription factors are involved in the regulation of fruit development and carotenoid metabolism in plants. However, whether and how carotenoid accumulation is regulated by algal MADS are largely unknown. In this study, we first used functional complementation to confirm the functional activity of phytoene synthase from the lutein-rich Dunaliella sp. FACHB-847 (DbPSY), the key rate-limiting enzyme in the carotenoid biosynthesis. Promoters of DbPSY and DbLcyB (lycopene ß-cyclase) possessed multiple cis-acting elements such as light-, UV-B-, dehydration-, anaerobic-, and salt-responsive elements, W-box, and C-A-rich-G-box (MADS-box). Meanwhile, we isolated one nucleus-localized MADS transcription factor (DbMADS), belonging to type I MADS gene. Three carotenogenic genes, DbPSY, DbLcyB, and DbBCH (ß-carotene hydroxylase) genes were upregulated at later stages, which was well correlated with the carotenoid accumulation. In contrast, DbMADS gene was highly expressed at lag phase with low carotenoid accumulation. Yeast one-hybrid assay and dual-luciferase reporter assay demonstrated that DbMADS could directly bind to the promoters of two carotenogenic genes, DbPSY and DbLcyB, and repress their transcriptions. This study suggested that DbMADS may act as a negative regulator of carotenoid biosynthesis by repressing DbPSY and DbLcyB at the lag phase, which provide new insights into the regulatory mechanisms of carotenoid metabolism in Dunaliella.

Characteristics, application and modeling of solid amine adsorbents for CO2 capture: A review.

In recent years, global warming has become an important topic of public concern. As one of the most promising carbon capture technologies, solid amine adsorbents have received a lot of attention because of their high adsorption capacity, excellent selectivity, and low energy cost, which is committed to sustainable development. The preparation methods and support materials can influence the thermal stability and adsorption capacity of solid amine adsorbents. As a supporting material, it needs to meet the requirements of high pore volume and abundant hydroxyl groups. Industrial and biomass waste are expected to be a novel and cheap raw material source, contributing both carbon dioxide capture and waste recycling. The applied range of solid amine adsorbents has been widened from flue gas to biogas and ambient air, which require different research focuses, including strengthening the selectivity of CO2 to CH4 or separating CO2 under the condition of the dilute concentration. Several kinetic or isotherm models have been adopted to describe the adsorption process of solid amine adsorbents, which select the pseudo-first order model, pseudo-second order model, and Langmuir isotherm model most commonly. Besides searching for novel materials from solid waste and widening the applicable gases, developing the dynamic adsorption and three-dimensional models can also be a promising direction to accelerate the development of this technology. The review has combed through the recent development and covered the shortages of previous review papers, expected to promote the industrial application of solid amine adsorbents.

The expression pattern of ß-carotene ketolase gene restricts the accumulation of astaxanthin in Dunaliella under salt stress.

Dunaliella salina can accumulate a large amount of ß-carotene which is generally considered to be its terminal product of carotenoid metabolism. In this study, it was proved that D. salina has the ketolase (DsBKT) of catalyzing the synthesis of astaxanthin, the downstream products of ß-carotene. Therefore, the reason why D. salina does not synthesize astaxanthin is the purpose of this study. The enzymatic activity of DsBKT was detected by functional complementation assays in Escherichia coli, results showed that DsBKT had efficient ketolase activity toward ß-carotene and zeaxanthin to produce astaxanthin, indicating that there were complete astaxanthin-producing genes in Dunaliella. Unlike the induced expression of Lycopene cyclase (catalyzing ß-carotene synthesis) under salt stress, the expression of DsBKT was very low under both normal and stress conditions, which may be the main reason why D. salina cannot accumulate astaxanthin. On the contrary, with the astaxanthin-rich Haematococcus pluvialis as a control, its BKT gene was significantly upregulated under salt stress. Further study showed that DsBKT promoter had strong promoter ability and could stably drive the expression of ble-egfp in D. salina. Obviously, DsBKT promoter is not the reason of DsBKT not being expressed which may be caused by Noncoding RNA.

Biodrying with the hot-air aeration system for kitchen food waste.

Biodrying is a promising method that produces bio-stabilized output with minimum pretreatment requirements. In this study, a hot-air supply system was added to the traditional biodrying process for kitchen waste, which showed significant reduction in moisture content in 5 days (maximum reduction of 37.45%). A series of experiments was conducted to optimize the hot-air biodrying system utilizing different aeration rates, temperatures, and mixing ratios of feedstock to bulking agents. The results showed that a 65 °C aeration temperature led to the highest water removal rate and low volatile solids consumption rate, with the biodrying index reaching 4.9 g water per gram of volatile solids. On the other hand, evaluation of the overall biodrying efficiency based on the weight loss and bio-stabilization showed that intermittent aeration temperature at 55 °C performed best, offering suitable conditions for water evaporation and bio-degradation. In combination with a flow rate of 0.8 L/kg*min and 1:1 mixing ratio, these conditions resulted in the maximum volatile solids consumption of 26.26% in 5 days. The volatile solids consumption and 34.47% water removal rate of the trial had contributed to a total of 64.13% weight loss. The weight loss was even higher than that of a conventional biodrying system which was conducted for more than 14 days.

Regulation of carotenoid degradation and production of apocarotenoids in natural and engineered organisms.

Carotenoids are important precursors of a wide range of apocarotenoids with their functions including: hormones, pigments, retinoids, volatiles, and signals, which can be used in the food, flavors, fragrances, cosmetics, and pharmaceutical industries. This article focuses on the formation of these multifaceted apocarotenoids and their diverse biological roles in all living systems. Carotenoid degradation pathways include: enzymatic oxidation by specific carotenoid cleavage oxygenases (CCOs) or nonspecific enzymes such as lipoxygenases and peroxidases and non-enzymatic oxidation by reactive oxygen species. Recent advances in the regulation of carotenoid cleavage genes and the biotechnological production of multiple apocarotenoids are also covered. It is suggested that different developmental stages and environmental stresses can influence both the expression of carotenoid cleavage genes and the formation of apocarotenoids at multiple levels of regulation including: transcriptional, transcription factors, posttranscriptional, posttranslational, and epigenetic modification. Regarding the biotechnological production of apocarotenoids especially: crocins, retinoids, and ionones, enzymatic biocatalysis and metabolically engineered microorganisms have been a promising alternative route. New substrates, carotenoid cleavage enzymes, biosynthetic pathways for apocarotenoids, and new biological functions of apocarotenoids will be discussed with the improvement of our understanding of apocarotenoid biology, biochemistry, function, and formation from different organisms.

Transgenic microalgae as bioreactors.

Microalgae are unicellular organisms that act as the crucial primary producers all over the world, typically found in marine and freshwater environments. Most of them can live photo-autotrophically, reproduce rapidly, and accumulate biomass in a short period efficiently. To adapt to the uninterrupted change of the environment, they evolve and differentiate continuously. As a result, some of them evolve special abilities such as toleration of extreme environment, generation of sophisticated structure to adapt to the environment, and avoid predators. Microalgae are believed to be promising bioreactors because of their high lipid and pigment contents. Genetic engineering technologies have given revolutions in the microalgal industry, which decoded the secrets of microalgal genes, express recombinant genes in microalgal genomes, and largely soar the accumulation of interested components in transgenic microalgae. However, owing to several obstructions, the industry of transgenic microalgae is still immature. Here, we provide an overview to emphasize the advantage and imperfection of the existing transgenic microalgal bioreactors.

Epidemiological characteristics of pulmonary tuberculosis among health-care workers in Henan, China from 2010 to 2017.

BACKGROUND: Health-care workers (HCWs) are an epidemiological group with increased exposure to tuberculosis (TB), especially at health-care facilities (HCFs) with poor TB infection control in high-TB-burden settings. China is a high-TB-burden country, and the comprehensive measures for stopping TB transmission at some HCFs were not implemented well owing to limited resources and other factors. The purpose of this study was to review risk of occupational exposure to TB among HCWs and its change trend, and identify epidemiological characteristics of pulmonary tuberculosis (PTB) among HCWs in Henan, central part of China. METHODS: A retrospective cohort study was conducted from 2010 to 2017. All HCWs and teachers in Henan were enrolled to the study as exposed group and non-exposed control group, respectively. Relative risk (RR), attributable risk (AR) and AR percent (AR%) were used to measure the association between the occupational exposure and PTB, and estimated with Poisson regression. RESULTS: The study results showed a total of 1663 cases of PTB were reported among the HCWs in Henan, accounting for 3.2‰ of all PTB cases reported in the whole population, and annual incidence rate of PTB among HCWs declined by 34% from 2010 to 2017. Over the eight years, the incidence rate of PTB among HCWs was 43.7 cases per 100,000 person-years (PYs), significantly higher than that among teachers (18.8 cases/100,000 PYs), and RR, AR and AR% were estimated to 2.3, 24.9 cases per 100,000 PYs and 57%, respectively. Among HCWs, males were more likely to suffer from PTB than females (adjusted RR: 1.3; 95%CI: 1.2-1.4), and HCWs aged under 25 years had the highest relative risk over all age groups with adjusted RR equaling to 8.3 (95%CI: 6.9-9.9) calculated with those aged 45-54 years as the reference. CONCLUSIONS: Although overall incidence rate of PTB among HCWs showed decreasing temporal trends over the period of 2010-2017, attributable risk of occupational exposure to TB among HCWs did not decrease in Henan, and TB infection at HCFs for males, young or senior HCWs, especially for young HCWs is of much concern.

Phosphate microbial mineralization consolidation of waste incineration fly ash and removal of lead ions.

This paper proposes a green environment-friendly Bacillus subtilis to mineralize and consolidate waste incineration fly ash and heavy metal cations, and there is no harmful by-product in the mineralization process. Different phosphate products can be prepared, and are more stable than the microbially-induced carbonate precipitation (MICP) in nature. Typical heavy metal oxides were mainly PbO, ZnO, CdO, NiO, CuO and Cr2O3 in the chemical composition of waste incineration fly ash. Microstructure and chemical composition of waste incineration fly ash before and after treatment were characterized by powder X-ray diffraction (XRD) analysis and scanning electron microscopy. Scanning electron microscopy (SEM) images showed that the morphology of the Bacillus subtilis was mainly a rod-like structure. The optimal hydrolysis dosage of the organic phosphate monoester sodium salt was 0.2mol in the bacterial solution (1L, 20 g/L). The optimum required mass of the bacterial powder was 15 g/kg in treatment process of the waste incineration fly ash. The initial concentration of lead ions was 40.28 mg/L in waste incineration fly ash solution. After the optimum dosage treatment, the removal efficiency of lead ions was 78.15%, 79.64%, 77.70% and 80.14% when curing time was 1, 2, 4 and 6d, respectively. The waste incineration fly ash had a Shore hardness of 22 after the optimum amount of bacterial liquid treatment. Results of wind erosion test showed that the wind erosion rate of waste incineration fly ash was 2.6, 0, 0, 0, 0 and 0 g/h when blank group, deionized water, 100, 200, 300 and 400 mL of bacterial solutions treated, respectively. The bio-mineralization method provides an approach for the safe disposal of heavy metals in the contaminated areas of tailings, electroplating sewage, waste incineration plants, and so on.

Two-Stage Cultivation of Dunaliella tertiolecta with Glycerol and Triethylamine for Lipid Accumulation: a Viable Way To Alleviate the Inhibitory Effect of Triethylamine on Biomass.

Microalgae are promising alternatives for sustainable biodiesel production. Previously, it was found that 100 ppm triethylamine greatly enhanced lipid production and lipid content per cell of Dunaliella tertiolecta by 20% and 80%, respectively. However, triethylamine notably reduced biomass production and pigment contents. In this study, a two-stage cultivation with glycerol and triethylamine was attempted to improve cell biomass and lipid accumulation. At the first stage with 1.0 g/liter glycerol addition, D. tertiolecta cells reached the late log phase in a shorter time due to rapid cell growth, leading to the highest cell biomass (1.296 g/liter) for 16 days. However, the increased glycerol concentrations with glycerol addition decreased the lipid content. At the second-stage cultivation with 100 ppm triethylamine, the highest lipid concentration and lipid weight content were 383.60 mg/liter and 37.7% of dry cell weight (DCW), respectively, in the presence of 1.0 g/liter glycerol, which were 27.36% and 72.51% higher than those of the control group, respectively. Besides, the addition of glycerol alleviated the inhibitory effect of triethylamine on cell morphology, algal growth, and pigment accumulation in D. tertiolecta The results indicated that two-stage cultivation is a viable way to improve lipid yield in microalgae.IMPORTANCE Microalgae are promising alternatives for sustainable biodiesel production. Two-stage cultivation with glycerol and triethylamine enhanced the lipid productivity of Dunaliella tertiolecta, indicating that two-stage cultivation is an efficient strategy for biodiesel production from microalgae. It was found that glycerol significantly enhanced cell biomass of D. tertiolecta, and the presence of glycerol alleviated the inhibitory effect of triethylamine on algal growth. Glycerol, the major byproduct from biodiesel production, was used for the biomass accumulation of D. tertiolecta at the first stage of cultivation. Triethylamine, as a lipid inducer, was used for lipid accumulation at the second stage of cultivation. Two-stage cultivation with glycerol and triethylamine enhanced lipid productivity and alleviated the inhibitory effect of triethylamine on the algal growth of D. tertiolecta, which is an efficient strategy for lipid production from D. tertiolecta.

Citrus aurantium L. var. amara Engl. inhibited lipid accumulation in 3T3-L1 cells and Caenorhabditis elegans and prevented obesity in high-fat diet-fed mice.

Natural products with anti-obesity effects and few side effects have attracted great attention recently. Citrus aurantium L. var. amara Engl. (CAVA) is popularly consumed as an edible and medicinal resource in China. However, its anti-obesity effects were poorly understood. The anti-obesity effects of CAVA extracts were systematically evaluated using 3T3-L1 cells, Caenorhabditis elegans (C. elegans) and high fat diet (HFD)-fed mice. Flavonoid-rich (EA) extracts with neohesperidin, hesperidin and naringin comprising 32.15%, were isolated from CAVA. EA extracts treatment significantly inhibited differentiation of 3T3-L1 preadipocytes by modulating lipid metabolism-related mediators. EA extracts supplementation also inhibited antioxidant responses in C. elegans by decreasing reactive oxygen species generation and malonaldehyde value, and increasing superoxide dismutase content. EA extracts feeding markedly decreased triglyceride (TG) content, and affected expression of genes involved in lipid and glucose metabolism in wild type C. elegans. TG content in mdt-15 (XA7702) mutants was not decreased by EA extracts administration, suggesting that EA extracts treatment might inhibit lipid accumulation in C. elegans dependent on mdt-15. EA extracts intervention further reduced body weight gain and modulated plasma biochemical parameters in HFD-fed mice. EA extracts treatment prevented HFD-induced epididymal adipose hypertrophy, liver oxidative injuries and steatosis. EA extracts administration also strongly prevented HFD-induced reduction of gut microbial diversity, decreased the Firmicutes-to-Bacteroidetes ratio and the Erysipelotrichaceae abundance, and enhanced the Bifidobacteriace abundance in HFD-fed mice. EA extracts from blossoms of CAVA were excellent antiobesogenic candidates that acted through multiple mechanisms that acted simultaneously.

Antidepressant active ingredients from herbs and nutraceuticals used in TCM: pharmacological mechanisms and prospects for drug discovery.

Depression is a widespread psychological disorder that affects up to 20% of the world's population. Traditional Chinese medicine (TCM), with its unique curative effect in depression treatment, is gaining increasing attention as the discovery of novel antidepressant drug has become the pursuit of pharmaceutical. This article summarizes the work done on the natural products from TCM that have been reported to conceive antidepressant effects in the past two decades, which can be classified according to various mechanisms including increasing synaptic concentrations of monoamines, alleviating the hypothalamic-pituitary-adrenal (HPA) axis dysfunctions, lightening the impairment of neuroplasticity, fighting towards immune and inflammatory dysregulation. The antidepressant active ingredients identified can be generally divided into saponins, flavonoids, alkaloids, polysaccharides and others. Albiflorin, Baicalein, Berberine chloride, beta-Asarone, cannabidiol, Curcumin, Daidzein, Echinocystic acid (EA), Emodin, Ferulic acid, Gastrodin, Genistein, Ginsenoside Rb1, Ginsenoside Rg1, Ginsenoside Rg3, Hederagenin, Hesperidin, Honokiol, Hyperoside, Icariin, Isoliquiritin, Kaempferol, Liquiritin, L-theanine, Magnolol, Paeoniflorin, Piperine, Proanthocyanidin, Puerarin, Quercetin, Resveratrol (trans), Rosmarinic acid, Saikosaponin A, Senegenin, Tetrahydroxystilbene glucoside and Vanillic acid are Specified in this review. Simultaneously, chemical structures of the active ingredients with antidepressant activities are listed and their sources, models, efficacy and mechanisms are described. Chinese compound prescription and extracts that exert antidepressant effects are also introduced, which may serve as a source of inspiration for further development. In the view of present study, the antidepressant effect of certain TCMs are affirmative and encouraging. However, there are a lot of work needs to be done to evaluate the exact therapeutic effects and mechanisms of those active ingredients, specifically, to establish a unified standard for diagnosis and evaluation of curative effect.

High-value bioproducts from microalgae: Strategies and progress.

Microalgae have been considered as alternative sustainable resources for high-value bioproducts such as lipids (especially triacylglycerides [TAGs]), polyunsaturated fatty acids (PUFAs), and carotenoids, due to their relatively high photosynthetic efficiency, no arable land requirement, and ease of scale-up. It is of great significance to exploit microalgae for the production of high-value bioproducts. How to improve the content or productivity of specific bioproducts has become one of the most urgent challenges. In this review, we will describe high-value bioproducts from microalgae and their biosynthetic pathways (mainly for lipids, PUFAs, and carotenoids). Recent progress and strategies for the enhanced production of bioproducts from microalgae are also described in detail, and these strategies take advantages of optimized cultivation conditions with abiotic stress, chemical stress (addition of metabolic precursors, phytohormones, chemical inhibitors, and chemicals inducing oxidative stress response), and molecular approaches such as metabolic engineering, transcriptional engineering, and gene disruption strategies (mainly RNAi, antisense RNA, miRNA-based knockdown, and CRISPR/Cas9).

N-Terminal Acetylation and C-Terminal Amidation of Spirulina platensis-Derived Hexapeptide: Anti-Photoaging Activity and Proteomic Analysis.

Ultraviolet (UV) irradiation is a potent inducer for skin photoaging. This paper investigated the anti-photoaging effects of the acetylated and amidated hexapeptide (AAH), originally identified from Spirulina platensis, in (Ultraviolet B) UVB-irradiated Human immortalized keratinocytes (Hacats) and mice. The results demonstrated that AAH had much lower toxicity on Hacats than the positive matrixyl (81.52% vs. 5.32%). Moreover, AAH reduced MDA content by 49%; increased SOD, CAT, and GSH-Px activities by 103%, 49%, and 116%, respectively; decreased MMP-1 and MMP-3 expressions by 27% and 29%, respectively, compared to UVB-irradiated mice. Employing isobaric tags for relative and absolute quantitation (iTRAQ)-based proteomics, 60 differential proteins were identified, and major metabolic pathways were determined. Network analysis indicated that these differential proteins were mapped into an interaction network composed of two core sub-networks. Collectively, AAH is protective against UVB-induced skin photoaging and has potential application in skin care cosmetics.

Geochemical simulation of the stabilization process of vanadium-contaminated soil remediated with calcium oxide and ferrous sulfate.

Vanadium (V)-contaminated soil poses health risks to plants, animals, and humans via both direct exposure and through the food chain. Stabilization treatment of metal-contaminated soil can chemically convert metal contaminants into less soluble, mobile, and toxic forms. However, the stabilization mechanisms of V-contaminated soil have not been thoroughly investigated. Therefore, we performed geochemical modeling of V-contaminated soil stabilized with the common binders calcium oxide (CaO) and ferrous sulfate (FeSO4), as well as their mixture, using Visual MINTEQ software. The results were validated and exhibited good agreement with experimental results. For CaO, the formation of Ca2V2O7(s) and Ca3(VO4)2·4H2O(s) under mild and strong alkaline conditions (pH = 8.0-11.5 and 11.5-12.5), respectively, were predicted as the main immobilization routes. For FeSO4, there appeared to be three reaction routes, corresponding to approaches A, B, and C, during the stabilization process. In the simulation, approach C (adsorption of V(V) onto ferrihydrite) was undervalued, whereas approaches A (formation of Fe(VO3)2(s)) and B (reduction of V(V) into V(IV) to form V2O4(s) or adsorb onto soil organic matter) were overvalued. Among the three approaches, approach C had a dominant role and exhibited good agreement with the experimental results. Additionally, soil pH and the saturation index of precipitation had major roles in the stabilization process. The optimal pH ranges for the stabilization of V-contaminated soil using CaO and FeSO4 were pH = 9.5-12.5 and pH = 4.0-5.0, respectively.

Phosphate microbial mineralization removes nickel ions from electroplating wastewater.

Nickel ions in electroplating wastewater can be removed by the bio-mineralization method. Bacillus subtilis can produce alkaline phosphatase, which hydrolyzes organophosphate monoesters and produces phosphate ions. Fourier-transform infrared spectroscopy (FTIR) showed that the precipitated material contains phosphate ions. X-ray diffraction (XRD) showed that nickel ions in electroplating wastewater react with Bacillus subtilis and organophosphate monoesters to obtain nickel phosphate octahydrate (Ni3(PO4)2·8H2O). The removal efficiency of nickel ions could reach 76.41% with the optimum content of the organophosphate monoester (0.02 mol), Bacillus subtilis powder (2 g), pH (6), standing time (36 h), and reaction temperature (25 °C) in the medium solution (100 mL). The average particle size of Ni3(PO4)2·8H2O was 80.51 nm, which was calculated by the Scherrer formula. The Lorentz-Transmission Electron Microscope (L-TEM) further showed that Ni3(PO4)2·8H2O was composed of clusters of irregular nanoparticles, and the individual particle size was in the range of 40-90 nm. The TGA curve shows that the mass loss of crystal water was 25.45%, which was close to the theoretical total mass loss of 28.24% in bio-Ni3(PO4)2·8H2O.

Vanadium and chromium-contaminated soil remediation using VFAs derived from food waste as soil washing agents: A case study.

Food waste (FW) is environmentally unfriendly and decays easily under ambient conditions. Vanadium (V) and chromium (Cr) contamination in soils has become an increasing concern due to risks to human health and environmental conservation. Volatile fatty acids (VFAs) derived from FW was applied as soil washing agent to treat V and Cr-contaminated soil collected from a former V smelter site in this work. The Community Bureau of Reference (BCR) three-step sequential extraction procedure was used to identify geochemical fractions of V and Cr influencing their mobility and biological toxicity. Optimal parameters of a single washing procedure were determined to be a 4 h contact time, liquid-solid ratio of 10:1, VFAs concentration of 30 g/L, and reaction temperature of 25 °C, considering for typical soil remediation projects and complete anaerobic fermentation of FW. Under the optimal conditions, butyric acid fermentation VFAs attained removal rates of 57.09 and 23.55% for extractable fractions of V and Cr, respectively. Simultaneously, a multi-washing process under a constant liquid-solid ratio using fresh and recycled VFAs was conducted, which led to an improvement on the total removal efficiency of toxic metals. The washing procedure could reach the pollution thresholds for several plants, such as of S. viridis, K. scoparia, M. sativa, and E. indica. This strategy enhances the utilization of VFAs derived from food waste, has a positive effect on V and Cr-contaminated soil remediation, wastewater control of soil washing and FW disposal.

The effect of vanadium on essential element uptake of Setaria viridis' seedlings.

High concentrations of vanadium, a ubiquitous element in the environment, in growing media leads to deformation of root structure and leaf chlorosis and necrosis, consequently affecting the translocations of nutrients and essential elements. However, the effects of vanadium on essential element uptake, and the interactions of essential elements in the presence of vanadium, remain incompletely understood. To elucidate the effects of different concentrations of vanadium on major and trace essential elements and plant growth, a native plant species growing in a vanadium mining area, Setaria viridis (dog tail's grass), was incubated in solutions containing 0-55.8 mg/L vanadium. The shoot accumulation of four major essential elements and five trace essential elements was detected, and the root length and stem height were measured. The results showed that vanadium in soil solution enhanced the accumulation of all major essential elements in shoot. Vanadium concentrations lower than 47.4 mg/L showed an obvious positive (p < 0.05) effect on P accumulation and translocation. In the case of trace essential elements, there were threshold values for solution vanadium stimulation of element uptake. The threshold values for Cu and Zn, Fe, and Mo uptake were 4.3, 16.3, and 40.6 mg/L, respectively. When vanadium levels surpassed these values, accumulation was suppressed and the solution vanadium concentrations attenuated the solution-to-shoot translocation of most of the essential elements. Among the trace essential elements, translocation of Fe was obviously enhanced (p < 0.05) by vanadium. Solution vanadium also enhanced plant growth at lower concentrations and inhibited it at higher levels. The threshold values for stem height and root length were 36.8 and 16.3 mg/L, respectively. Concentrations of 40 and 55.8 mg/L vanadium in soil solution caused a 50% decrease in root length and stem height, respectively, showing that root length of Setaria viridis is more susceptible to vanadium toxicity than stem growth.

Removal of phosphate from aqueous solution using MgO-modified magnetic biochar derived from anaerobic digestion residue.

A novel MgO-modified magnetic biochar (MgO@MBC) was made by chemical co-precipitation of Mg2+/Fe3+ on anaerobic digestion residue (ADR) and subsequently pyrolyzing at different temperatures. MgO@MBC was used for phosphate recovery from aqueous solution. The physicochemical properties of MgO@MBC were comprehensively investigated using TEM-EDS, FT-IR, XRD, VSM, N2 adsorption-desorption and TGA. Results showed that MgO/γ-Fe2O3 nanoparticles were successfully deposited onto the surface of BC. The effects of reaction temperature, initial solution pH, MgO@MBC dosage, coexisting anions and phosphate concentration on the removal of phosphate by MgO@MBC were researched. Additionally, the adsorption process of phosphate onto MgO@MBC was well described by the pseudo second-order and pseudo first-order models, which indicated a chemisorption and physisorption process. Besides, the maximum adsorption capacity of MgO@MBC for phosphate by the Langmuir model were 149.25 mg/g at 25 °C. Moreover, the thermodynamic study suggested that the adsorption of phosphate onto MgO@MBC was a spontaneous and endothermic process. The adsorption mechanisms including physical absorption, surface electrostatic attraction, surface complexation and precipitation were revealed. It could be concluded that MgO@MBC exhibited high removal efficiency of phosphate and excellent magnetic property for the recovery. MgO@MBC could be utilized as a magnetically recoverable adsorbent to realize phosphate recovery and MgO@MBC after the adsorpion of phosphate could be applied in agricultural production as a fertilizer.