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High-frequency drought hazards have presented persistent challenges for environmental management and sustainable development in the South Hebei Plain, China. In this paper, the assessment of meteorological droughts in the South Hebei Plain was conducted using a multifaceted approach to ensure a comprehensive analysis. Our results demonstrated that distinct timescale cycles, ranging from centennial–semicentennial to interdecadal variations, can be identified over the past few centuries. These cycles aligned with patterns observed in the middle Yangtze basin and corresponded to regional climatic conditions. The drought cycles in the South Hebei Plain showed significant correlations with variations in the monsoon climate, sunspot activity, global changes, and human disturbances. Changes in the frequency, duration, and intensity of droughts have notably impacted hydrological variations. Extreme droughts, in particular, have heightened concerns about their effects on river systems, potentially increasing the risk of channel migration. This study enhanced our understanding of meteorological hazard patterns in the South Hebei Plain and provided valuable insights into different stages of drought management. It thus can offer lessons for improving drought preparedness and resilience and for formulating adaptive measures to mitigate future droughts and promote regional sustainability. [ABSTRACT FROM AUTHOR]

The performance of microalgae-based wastewater treatment processes for ammonium-N (NH4+-N) removal depends on the maintenance of a favorable pH that is critical for minimizing nitrogen escape in the form of free ammonia (NH3) and preventing high-NH3 or extreme-pH stress. This study developed a CO2-inorganic carbon (CO2-IC) buffering system that automatically stabilized pH with the supply of a carbon source for efficient photosynthetic reclamation of NH4+-N by a euryhaline microalga Tetraselmis subcordiformis. The soluble (NaHCO3) and insoluble (CaCO3 and MgCO3) ICs were compared for this purpose. The pH was well controlled in the range of 6.5~8.5 in the CO2-IC system, which was suitable for the photosynthetic growth of T. subcordiformis. The NH4+-N (100 mg/L) was almost completely removed in three days, with the maximum removal rate of 60.13 mg N/L/day and minimal N escape of 19.65% obtained in the CO2-NaHCO3 system. The CO2-IC system also restricted the release of extracellular organic matter by preventing stress conditions. The CO2-NaHCO3 system enabled the highest "normal" starch production suitable for fermentation, while the CO2-CaCO3/MgCO3 system facilitated high-amylose starch accumulation that was conducive to producing bio-based materials and health-promoting ingredients. The proteins accumulated in T. subcordiformis were of good quality for animal feeds. [ABSTRACT FROM AUTHOR]

Chrysolaminarin, a kind of water-soluble bioactive β-glucan produced by certain microalgae, is a potential candidate for food/pharmaceutical applications. This study identified a marine microalga Isochrysis zhangjiangensis, in which chrysolaminarin production was investigated via nutrient (nitrogen, phosphorus, or sulfur) deprivations (-N, -P, or -S conditions) along with an increase in light intensity. A characterization of the antioxidant activities of the chrysolaminarin produced under each condition was also conducted. The results showed that nutrient deprivation caused a significant increase in chrysolaminarin accumulation, though this was accompanied by diminished biomass production and photosynthetic activity. -S was the best strategy to induce chrysolaminarin accumulation. An increase in light intensity from 80 (LL) to 150 (HL) µE·m−2·s−1 further enhanced chrysolaminarin production. Compared with -N, -S caused more suitable stress and reduced carbon allocation toward neutral lipid production, which enabled a higher chrysolaminarin accumulation capacity. The highest chrysolaminarin content and concentration reached 41.7% of dry weight (%DW) and 632.2 mg/L, respectively, under HL-S, with a corresponding productivity of 155.1 mg/L/day achieved, which exceeds most of the photoautotrophic microalgae previously reported. The chrysolaminarin produced under HL-N (Iz-N) had a relatively competitive hydroxyl radical scavenging activity at low concentrations, while the chrysolaminarin produced under HL-S (Iz-S) exhibited an overall better activity, comparable to the commercial yeast β-glucan, demonstrating I. zhangjiangensis as a promising bioactive chrysolaminarin producer from CO2. [ABSTRACT FROM AUTHOR]

Objective: To investigate the impact of the use of different imaging units and projections on radiation dose and image quality during chest digital radiography (DR) in 3- and 4-year-old children. Methods: Two hundred forty 3- and 4-year-old participants requiring chest DR were included; they were divided into three groups: supine anterior-posterior projection (APP), standing APP and standing posterior-anterior projection (PAP). Each group included 40 participants who were evaluated using the same imaging unit. The dose area product (DAP) and the entrance surface dose (ESD) were recorded after each exposure. The visual grading analysis score (VGAS) was used to evaluate image quality, and the longitudinal distance (LD) from the apex of the right lung to the apex of the right diaphragm was used to evaluate the inspiration extent. Results: DAP and ESD were significantly lower in the standing PAP and APP groups than in the supine APP group (P<0.05), but LD was significantly higher in the standing PAP and APP groups than in the supine APP group (P<0.05). Additionally, the pulmonary field area was significantly higher for the standing PAP group than for the standing and supine APP groups (P<0.05). The correlations between ESD, DAP, and VGAS were positive (P<0.001), showing that larger ESD and DAP correspond to higher VGAS. The correlations between ESD, DAP, and body mass index (BMI) were also positive (P<0.05), indicating that higher BMI corresponds to larger ESD and DAP. Finally, no differences in DAP, ESD, VGAS, LD, pulmonary field area, or BMI were noted between males and females (P>0.05). Conclusion: The radiation dose to superficial organs may be lower with standing PAP than with standing APP during chest DR. Standing PAP should be selected for chest DR in 3- and 4-year-old children, as it may decrease the required radiation dose. [ABSTRACT FROM AUTHOR]

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In a marine green starch-producing microalga Tetraselmis subcordiformis , the role of starch phosphorylase (SP) in the starch biosynthesis was disclosed by characterizing the enzyme properties and activity variations during the starch accumulation process. TsSP4, a SP isoform accounting for the major SP activity in T. subcordiformis , was unique to be active in a monomer form with a molecular weight of approximately 110 kDa. It resembled one of the chloroplast-located SPs (PhoA) in Chlamydomonas reinhardtii with a similarity of 63.3% in sequence, though it possessed the typical L78/80 domain found in the plastidial SPs (Pho1) of higher plants that was absent in PhoA. TsSP4 exhibited moderate sensitivity to ADP-Glc inhibition and had a high activity for longer-chain linear maltooligosacchride (MOS) and amylopectin against highly branched glycogen as the substrates. TsSP4 had 2-fold higher affinity for Glc-1-P in the synthetic direction than for Pi in the phosphorolytic direction, and the catalytic constant k cat for Glc-1-P was 2-fold of that for Pi. Collectively, TsSP4 preferred synthetic rather than phosphorolytic direction. TsSP4 could elongate MOSs even initially with Pi alone in the absence of Glc-1-P, which further supported its synthetic role in the starch biosynthesis. TsSP4 displayed increased activities in the developing and mature stage of starch biosynthesis under nitrogen-starvation conditions, indicating its possible contribution to the amylopectin amplification. [ABSTRACT FROM AUTHOR]

Nannochloropsis , an ocean microalgal genus, is a promising resource of biodiesel feedstock because of its capacity for triacylglycerol (TAG) accumulation. Polar glycerolipids have big contribution for TAG accumulation by providing acyl group or diacylglycerol (DAG). Due to the diversities and amount of polar glycerolipids in species, a suitable approach has not been developed well to quantify and qualify, which veils the clarification of how important roles the polar glycerolipids play in microalgal lipid metabolism and TAG accumulation. In this study, a total of 112 polar glycerolipid species, covering eight classes, were identified using UPLC/Q-TRAP plus Orbitrap coupled with quantified using UPLC/Q-TOF. A comprehensive profiling of polar glycerolipid was established to study the polar glycerolipids variations in response to nitrogen deprivation in Nannochloropsis oceanica . Through targeted lipidomics analysis it was proposed that in N . oceanica , phosphatidylcholine (PC) serve as linoleic and γ-linolenic acyl donors via oleic acyl desaturation, and under nitrogen stress condition PC transfers acyl 16:0 and 18:1 to TAG. The result disclosed PC played import roles for TAG accumulation not only in high plants but also in PC-containing microalgae even PC is not the most extraplastidial lipid. In addition, it was showed that phosphatidylethanolamine (PE) and diacylglyceryl- N -trimethylhomoserine (DGTS) are suppliers of eicosapentaenoic acid (EPA) to other lipids. These new discoveries reveal the diversity of microalgae in acyl metabolism and shed light on the understanding of lipid biosynthesis by stoichiometry. [ABSTRACT FROM AUTHOR]

Thermogravimetric (TG) techniques are widely used in thermal characteristic studies of microalgae combustion and pyrolysis. Ash content is an important parameter for evaluating the cultivation efficiency of photosynthetic microalgae. In this study, microalgal ash content was determined using an optimized protocol that included a heating rate of 20 °C/min from room temperature to 600 °C; a temperature of 600 °C was then maintained for 30 min under an air atmosphere for TG analysis. At temperatures over 600 °C, the ash content was reduced due to the loss of relatively volatile minerals. Four species of microalgae with selectively enriched carbohydrate, protein or lipid contents under different culture conditions were identified via derivative thermogravimetric (DTG) graph analysis, for which characteristic DTG fitting peaks for carbohydrates, protein and lipids were used as reference peaks. Therefore, a qualitative or semi-quantitative analysis of the carbohydrates, proteins and lipids in microalgae based on TG analysis, which concomitantly determines ash content, can be easily performed using only 5–10 mg of sample. The proposed method is rapid and easy, providing composition information for strain screening and physiological studies during microalgae cultivation. [ABSTRACT FROM AUTHOR]

Background: Microalgal starch is regarded as a promising alternative to crop-based starch for biorefinery such as the production of biofuels and bio-based chemicals. The single or separate use of inorganic carbon source, e.g., CO2 and NaHCO3, caused aberrant pH, which restricts the biomass and starch production. The present study applied an in situ CO2–NaHCO3 system to regulate photosynthetic biomass and starch production along with starch quality in a marine green microalga Tetraselmis subcordiformis under nitrogen-depletion (−N) and nitrogen-limitation (±N) conditions. Results: The CO2 (2%)–NaHCO3 (1 g L−1) system stabilized the pH at 7.7 in the −N cultivation, under which the optimal biomass and starch accumulation were achieved. The biomass and starch productivity under −N were improved by 2.1-fold and 1.7-fold, respectively, with 1 g L−1 NaHCO3 addition compared with the one without NaHCO3 addition. NaHCO3 addition alleviated the high-dCO2 inhibition caused by the single CO2 aeration, and provided sufficient effective carbon source HCO3− for the maintenance of adequate photosynthetic efficiency and increase in photoprotection to facilitate the biomass and starch production. The amylose content was also increased by 44% under this CO2–bicarbonate system compared to the single use of CO2. The highest starch productivity of 0.73 g L−1 day−1 under −N cultivation and highest starch concentration of 4.14 g L−1 under ±N cultivation were both achieved with the addition of 1 g L−1 NaHCO3. These levels were comparable to or exceeded the current achievements reported in studies. The addition of 5 g L−1 NaHCO3 under ±N cultivation led to a production of high-amylose starch (59.3% of total starch), which could be used as a source of functional food. Conclusions: The in situ CO2–NaHCO3 system significantly improved the biomass and starch production in T. subcordiformis. It could also regulate the starch quality with varied relative amylose content under different cultivation modes for diverse downstream applications that could promote the economic feasibility of microalgal starch-based biofuel production. Adoption of this system in T. subcordiformis would facilitate the CO2 mitigation couple with its starch-based biorefinery. [ABSTRACT FROM AUTHOR]

Abstract To understand the function of DGTS (diacylglyceryl- N , N , N -trimethyl-homoserine) as substitution of PC (phosphatidylcholine), Nannochloropsis oceanica has been chosen as the model system because it has DGTS and PC simultaneously. Phosphorus is a regulator for DGTS and PC. Generally, DGTS increases and correspondingly PC decreases under phosphorous starvation. However, the function of DGTS and its fatty acid origin under phosphorous starvation, and the resurgence of PC triggered by phosphorus recovery remain not clarified completely. In the present study, we investigated the effect of phosphorus starvation and recovery on polar glycerolipid remodeling in N. oceanica based on quantitative lipidomic data. Through targeted lipidomics analysis, we proposed that, under phosphorus deprivation, DGTS serves as the central intermediate in glycerolipid remodeling via acting as the carrier of the C18 fatty acids desaturation by replacement of PC, maintaining the biosynthesis of EPA (eicosapentaenoic acid) and providing the EPA acyl as a precursor for formation of chloroplast glycolipids. The prokaryotic molecular species of DGTS are mainly from de novo biosynthesis pathway and make the major contribution for the DGTS increase. In the process of resupplying phosphorus, PC increased attributing to hydrolysis of TAG, generating diacylglycerol for PC biosynthesis. These new information demonstrated that DGTS and PC varied conversely in different metabolic pathways as revealed by targeted lipidomic data. Highlights • The acyl origin of DGTS in P-limited process was dissected via lipidomic. • DGTS replaces PC as the carrier of C18 fatty acid desaturation after P starvation. • The acyl origin of regenerated PC in P-resupply process was first reported. [ABSTRACT FROM AUTHOR]

Background: Triacylglycerol (TAG) from photosynthetic microalgae is a sustainable feedstock for biodiesel production. Physiological stress triggers microalgal TAG accumulation. However excessive physiological stress will impair the photosynthesis system seriously thus decreasing TAG productivity because of the low biomass production. Hence, it is critical to quantitatively and timely monitor the degree of the stress while the microalgal cells growing so that the optimal TAG productivity can be obtained. Results: The lack of an on-line monitored indicator has limited our ability to gain knowledge of cellular "health status" information regarding high TAG productivity. Therefore, to monitor the degree of nitrogen stress of the cells, we investigated the correlation between the photosynthetic system II (PS II) quantum yield and the degree of stress based on the high relevancy between photosynthetic reduction and nitrogen stress-induced TAG accumulation in microalgal cells. ΔF/Fm′, which is the chlorophyll fluorescence parameter that reflects the effective capability of PS II, was identified to be a critical factor to indicate the degree of stress of the cells. In addition, the concept of a nitrogen stress index has been defined to quantify the degree of stress. Based on this index and by monitoring ΔF/Fm′ and guiding the supply of nitrogen in culture medium to maintain a stable degree of stress, a stable and efficient semi-continuous process for TAG production has been established. Conclusion: The results indicate that the semi-continuous cultivation process with a controlled degree of stress by monitoring the ΔF/Fm′ indicator will have a significant impact on microalgal TAG production, especially for the outdoor controllable cultivation of microalgae on a large scale. [ABSTRACT FROM AUTHOR]

Anaerobic digester effluent containing high levels of ammonia poses a threat to the environment. To hinder this issue, a modern and promising treatment method incorporates both microalgae and their bioconversion potential. When culturing Chlorella vulgaris at a 1:7 digestate supernatant dilution ratio, biomass concentration was 1.33 g L−1 and 66% of ammonia nitrogen was removed. Furthermore, a prior nitrogen-starved seed method, namely over-compensation strategy, was applied to improve both biomass production and nutrient removal. By using nitrogen-starved seeds after a 48 h nitrogen-free stimulation, biomass yield increased by 1.7-times to 2.56 g L−1. Simultaneously, ammonia nitrogen and total phosphorus removal efficiencies reached 99% and 97% respectively. The enhanced production corresponds to higher chlorophyll fluorescence in the middle and late stages of the culture. In addition, the bioproduct contained 39% carbohydrates, and the proportion of polyunsaturated fatty acids in lipids was 66%. These findings demonstrated that the over-compensation strategy contributed to greater nitrogen removal and high-value bioproduct production in the microalgae-digestate treatment system. Unlabelled Image • Microalgae are effective in recycling digestate up to 350 mg L−1 ammonia nitrogen. • Microalgal growth was improved by 70% using nitrogen-starved seed. • Over-compensation boosted ammonia nitrogen removal from the digestate to 99%. • Microalgae with over-compensation had nearly triple photosynthetic activity. • Biomass has 39% carbohydrates and lipids contain 66% polyunsaturated fatty acids. [ABSTRACT FROM AUTHOR]

The wide application of biodegradation technology makes it particularly significant to use immobilized microorganisms to achieve continuous degradation of pollutants. In this study, the performance of Ca-alginate (CA) immobilized Phanerochaete chrysosporium beads in a consecutive biocycle treatment of bisphenol A (BPA) effluent was researched. The effects of initial BPA concentration, biomass dosage, pH and curing time were investigated. Results showed that CA-immobilized P. chrysosporium can be successive cycle at least 9 times (12 h each), and each time the removal efficiency of BPA reached 100%. The degradation process of BPA in the treatment process was investigated. According to the analyses of glucose, ammonia nitrogen, total nitrogen, extracellular proteins and biomass, it was found that consumed carbon and nitrogen sources were used for the rapid growth of fungal hyphae and the synthesis of a series of proteins. These extracellular proteins can be utilized as a nitrogen source by P. chrysosporium , and played a key role in the removal of BPA. Biodegradation process followed the pseudo-first-order kinetics. Moreover, intermediates in the BPA degradation process were identified by gas chromatography-mass spectrometry (GC–MS) and liquid chromatography-mass spectrometry (LC-MS), and three possible degradation pathways were proposed. This strategy presented in the study provides a convenient and efficient biological method for the continuous treatment of BPA effluent. [Display omitted] • P. chrysosporium immobilized with sodium alginate can efficiently degrade BPA. • Immobilized fungal beads were successfully applied to continuous cycle degradation of BPA. • The BPA removal efficiency was still up to 100% after eight consecutive cycles of degradation. • Three possible degradation pathways were identified. [ABSTRACT FROM AUTHOR]