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.

Cuproptosis related ceRNA axis AC008083.2/miR-142-3p promotes the malignant progression of nasopharyngeal carcinoma through STRN3.

Background: CeRNA axis is an important way to regulate the occurrence and development of Nasopharyngeal carcinoma (NPC). Although the research on inducing cuproptosis of tumor cells is in the early stage of clinical practice, its mechanism of action is still of great significance for tumor treatment, including NPC. However, the regulation mechanism of cuproptosis in NPC by ceRNA network remains unclear. Methods: The ceRNA network related to the survival of nasopharyngeal carcinoma related genes was constructed by bioinformatics. Dual-luciferase reporter assay and other experiments were used to prove the conclusion. Results: Our findings indicate that the AC008083.2/miR-142-3p axis drives STRN3 to promote the malignant progression of NPC. By performing enrichment analysis and phenotypic assays, we demonstrated that the changes in the expressions of AC008083.2/miR-142-3p/NPC can affect the proliferation of NPC. Mechanistically, luciferase reporter gene assays suggested that AC008083.2 acts as a ceRNA of miR-142-3p to regulate the content of STRN3. Furthermore, the regulations of STRN3 and the malignant progression of NPC by AC008083.2 depends on miR-142-3p to some extent. Conclusions: Our study reveals an innovative ceRNA regulatory network in NPC, which can be considered a new potential target for diagnosing and treating NPC.

Comparative Anti-Cancer and Anti-Inflammatory Activities of Essential Oils from the Bark and Flower of Magnolia officinalis Rehd. et Wils.

This study was designed to compare the antioxidant, antitumor and anti-inflammatory effects of essential oils from the bark and flower of Magnolia officinalis Rehd. et Wils. Distillation extraction and steam distillation were used to extract EOs from the bark and flower. The results showed that the contents of EOs of SDE-F and SDE-B were much higher than that of SD-F and SD-B. EOs from the bark were rich in eudesmol (especially α-eudesmol) and exhibited a stronger antioxidant effect than the flower. The anti-tumor effects of SD-B and SD-F on HepG2 and MDA-MB-231 cells were better than that of SDE-B and SDE-F. The inhibitory rates of SD-B and SD-F on MDA-MB-231 cells were 59.21% and 48.27%, exceeding that of positive control 5-fluorouracil (47.04%) at 50 µg/mL. All four EOs exhibited excellent anti-inflammatory activities through the regulation of nitric oxide production and pro-inflammation cytokines in LPS-induced RAW 264.7 cells and they also remarkably suppressed the mRNA expressions of nitric oxide synthase, IL-6 and TNF-α at the concentration higher than that of positive control dexamethasone. These results indicated significant differences in the composition, and anti-inflammatory and anti-tumor activities of EOs extracted by different methods and provided a theoretical basis for their development and utilization.

Structural characteristics and anti-photoaging effect of Pyracantha fortuneana fruit polysaccharides in vitro and in vivo.

Pyracantha fortuneana is a cultivated pant extensively cultivated worldwide for its ornamental value and ecological benefits. In this study, a polysaccharide with anti-photoaging activity was extracted and purified from P. fortuneana fruit (PPFP). The structural constitution of PPFP was elucidated by molecular weight determination, FT-IR, monosaccharide composition analysis, smith degradation, methylation, and NMR spectroscopy. The results revealed that PPFP is a macromolecular polysaccharide with a weight-average molecular weight of 70,895 Da. The PPFP is predominantly characterized by →3,6)-ß-Galp-(1→, →5,3)-α-Araf-(1 → and →4,2)-α-Xylp-(1→, →4)-ß-Galp-(1 → and →4)-ß-GalpA-(1 → glycosidic linkages, with t-α-Araf-(1 → and t-α-Glcp-(1 → terminal units. The anti-photoaging activity and potential mechanism of action of PPFP was investigated in vitro and in vivo. Results showed that PPFP exerted anti-photoaging effect on UVB-damaged HaCaT cells by ameliorating cell apoptosis, regulating the mitochondrial membrane potential and oxidative stress level, alleviating the phosphorylation level of the proteins in MAPK pathways, and repairing the expression of tight junction proteins. Moreover, PPFP enhanced the lifespan and diminished the oxidative stress in UVB-injured Caenorhabditis elegans. Collectively, this study comprehensively elucidates the anti-photodamaging potential of P. fortuneana fruit polysaccharide and offers a novel plant-derived adjuvant therapy for the treating photodamage.

Development of a chloroplast expression system for Dunaliella salina.

Dunaliella salina is an innovative expression system due to its distinct advantages such as high salt tolerance, low susceptibility to contamination, and the absence of the cell wall. While nuclear transformation has been extensively studied, research on D. salina chloroplast transformation remains in the preliminary stages. In this study, we established an efficient chloroplast expression system for D. salina using Golden Gate assembly. We developed a D. salina toolkit comprising essential components such as chloroplast-specific promoters, terminators, homologous fragments, and various vectors. We confirmed its functionality by expressing the EGFP protein. Moreover, we detailed the methodology of the entire construction process. This expression system enables the specific targeting of foreign genes through simple homologous recombination, resulting in stable expression in chloroplasts. The toolkit achieved a relatively high transformation efficiency within a shorter experimental cycle. Consequently, the construction and utilization of this toolkit have the potential to enhance the efficiency of transgenic engineering in D. salina and advance the development of microalgal biofactories.

A polysaccharide PRCP from Rosa cymosa Tratt fruit: Structural characteristics and immunomodulatory effects via MAPK pathway modulation in vitro.

The Rosa cymosa Tratt, an herbal plant from the Rosaceae family, has historically been valued in China for its medicinal and edible properties. In this study, a novel polysaccharide from R. cymosa fruit, termed PRCP (purified R. cymosa polysaccharide), was isolated using water extraction, decolorization, deproteinization, and ion-exchange chromatography. The structural characteristics of PRCP were investigated using monosaccharide composition analysis, methylation, GPC, FTIR, CD, and NMR spectroscopy. The immunomodulatory effect and potential mechanism of PRCP were evaluated in vitro using a macrophage cell model. Results indicated that PRCP (37.28 kDa) is a highly branched polysaccharide (72.61 %) primarily composed of arabinogalactan, rhamnogalacturonan, and galactoglucan domains with 13 types of glycosidic linkage fragments. Furthermore, PRCP appears to modulate immunomodulatory effects by influencing the phosphorylation of P38 and JNK proteins in the MAPK pathway. Collectively, these findings highlight the potential of PRCP as a promising natural functional food ingredient for immunostimulation.

Enhancing astaxanthin accumulation through the expression of the plant-derived astaxanthin biosynthetic pathway in Dunaliella salina.

Dunaliella salina, a microalga that thrives under high-saline conditions, is notable for its high ß-carotene content and the absence of a polysaccharide cell wall. These unique characteristics render it a prime candidate as a cellular platform for astaxanthin production. In this study, our initial tests in an E. coli revealed that ß-ring-4-dehydrogenase (CBFD) and 4-hydroxy-ß-ring-4-dehydrogenase (HBFD) genes from Adonis aestivalis outperformed ß-carotene hydroxylase (BCH) and ß-carotene ketolase (BKT) from Haematococcus pluvialis counterparts by two-fold in terms of astaxanthin biosynthesis efficiency. Subsequently, we utilized electroporation to integrate either the BKT gene or the CBFD and HBFD genes into the genome of D. salina. In comparison to wild-type D. salina, strains transformed with BKT or CBFD and HBFD exhibited inhibited growth, underwent color changes to shades of red and yellow, and saw a nearly 50% decline in cell density. HPLC analysis confirmed astaxanthin synthesis in engineered D. salina strains, with CBFD + HBFD-D. salina yielding 134.88 ± 9.12 µg/g of dry cell weight (DCW), significantly higher than BKT-D. salina (83.58 ± 2.40 µg/g). This represents the largest amount of astaxanthin extracted from transgenic D. salina, as reported to date. These findings have significant implications, opening up new avenues for the development of specialized D. salina-based microcell factories for efficient astaxanthin production.

A review on the evaluation models and impact factors of greenhouse gas emissions from municipal solid waste management processes.

The total amount of global municipal solid waste (MSW) will reach 3.5 billion tons by 2050, thereby bringing tremendous environmental pressure, especially global warming. Large amounts of greenhouse gases (GHGs) have been released during MSW management (MSWM). Accounting for GHG emissions is a prerequisite for providing recommendations on appropriate treatment options to mitigate emissions from MSWM systems. There are many methods involved in estimating emissions. This paper summarizes the computing models commonly used in each process of the integrated MSWM system and emphasizes the influence of parameters and other factors. Compared with other disposal methods, landfilling has the highest emissions, commonly estimated using first-order decay (FOD) methods. Emission reduction can be realized through waste to energy (WtE) and resource recovery measures. IPCC is commonly used for calculating direct emissions, while LCA-based models can calculate emissions including upstream and downstream processes, whose results depend on assumptions and system boundaries. The estimation results of models vary greatly and are difficult to compare with each other. Besides, large gaps exist between the default emission factors (EFs) provided by models and those F measured in specific facilities. These findings provide a systematic view for a bettering understanding of MSW emissions as well as the estimating methods and also reveal the key points that need be developed in the future.

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.

Functional Characterization of a CruP-Like Isomerase in Dunaliella.

Dunaliella bardawil is a marine unicellular green algal that produces large amounts of ß-carotene and is a model organism for studying the carotenoid synthesis pathway. However, there are still many mysteries about the enzymes of the D. bardawil lycopene synthesis pathway that have not been revealed. Here, we have identified a CruP-like lycopene isomerase, named DbLyISO, and successfully cloned its gene from D. bardawil. DbLyISO showed a high homology with CruPs. We constructed a 3D model of DbLyISO and performed molecular docking with lycopene, as well as molecular dynamics testing, to identify the functional characteristics of DbLyISO. Functional activity of DbLyISO was also performed by overexpressing gene in both E. coli and D. bardawil. Results revealed that DbLyISO acted at the C-5 and C-13 positions of lycopene, catalyzing its cis-trans isomerization to produce a more stable trans structure. These results provide new ideas for the development of a carotenoid series from engineered bacteria, algae, and plants.

Sedative and hypnotic effects of the saponins from a traditional edible plant Liriope spicata Lour. in PCPA-induced insomnia mice.

ETHNOPHARMACOLOGICAL RELEVANCE: Liriope spicata Lour., a species listed in the catalogue of 'Medicinal and Edible Homologous Species', is traditionally used for the treatment of fatigue, restlessness, insomnia and constipation. AIM OF THE STUDY: This study is aimed to evaluate the sedative and hypnotic effect of the saponins from a natural plant L. spicata Lour. in vivo. MATERIALS AND METHODS: The total saponin (LSTS) and purified saponin (LSPS) were extracted from L. spicata, followed by a thorough analysis of their major components using the HPLC-MS. Subsequently, the therapeutic efficacy of LSTS and LSPS was evaluated by the improvement of anxiety and depression behaviors of the PCPA-induced mice. RESULTS: LSTS and LSPS exhibited similar saponin compositions but differ in their composition ratios, with liriopesides-type saponins accounting for a larger proportion in LSTS. Studies demonstrated that both LSTS and LSPS can extend sleep duration and immobility time, while reducing sleep latency in PCPA-induced mice. However, there was no significant difference in weight change among the various mice groups. Elisa results indicated that the LSTS and LSPS could decrease levels of NE, DA, IL-6, and elevate the levels of 5-HT, NO, PGD2 and TNF-α in mice plasma. LSTS enhanced the expression of neurotransmitter receptors, while LSPS exhibited a more pronounced effect in regulating the expression of inflammatory factors. In conclusion, the saponins derived from L. spicata might hold promise as ingredients for developing health foods with sedative and hypnotic effects, potentially related to the modulation of serotonergic and GABAAergic neuron expression, as well as immunomodulatory process.

Translocation of a fish spike from the pharynx to the thyroid gland: A case report.

BACKGROUND: A fish spike stuck in the throat is a common ear, nose, and throat (ENT) emergency. However, it is very rare for a fish spike to reach the thyroid tissue through the throat, which is very dangerous and can lead to pharyngeal fistula, cervical abscess, mediastinal abscess, and thyroid abscess. Proper and timely management can help reduce complications, especially in elderly patients. CASE SUMMARY: In the case presented here, the causative factor was dentures, but improper management aggravated the condition. In the case presented here, an elderly woman with a history of accidentally swallowing fish bones for 20 d had a sensation of foreign bodies in her throat. Eventually, computed tomography (CT) of the neck showed that the left side of the thyroid gland had a dense shadow in the form of a stripe. CONCLUSION: If a fishbone foreign body is not visible during endoscopic examination but the patient has significant symptoms, the surgeon should be aware that the fishbone may be lodged in the thyroid. To avoid a misdiagnosis, ultrasound, CT, and other tests can be used to clarify the diagnosis. T The first step in treating a fish bone in the thyroid gland is to determine the position of the foreign body and the extent of the infection, and to develop a personalized surgical plan for its removal. At the same time, scientific information should be made available to the general public so that people know that if a fish bone is accidentally lodged, they should not force it to be swallowed or be spit out by inducing vomiting, which are incorrect methods and may aggravate the condition or even cause it to migrate outside the cavity, leading to serious complications, as in this reported case.

Comparative Activities of Three Compounds from Citrus aurantium L. var. amara Engl. to Improve Oxidized Low-Density Lipoprotein-Induced Lipid Deposition.

The active ingredients of Citrus aurantium have been shown to possess a variety of biological activities, especially anti-inflammatory effects. However, its antiatherosclerotic effects need to be further investigated. The aim of this study is to identify compounds with antiatherosclerotic effects from C. aurantium and to further investigate their mechanisms. Three compounds were separated, and then their antiatherosclerotic effect on foam cells induced by oxidized low-density lipoprotein (ox-LDL) was screened by oil red O staining, BODIPY staining, and Dil-ox-LDL uptake measurement. Cholesterol uptake, cholesterol efflux, RT-PCR, and Western blot analysis were used to comprehensively and comparatively explore the potential mechanisms. Nobiletin (NOB), caffeine (CAF), and naringin (NARG), which were separated from C. aurantium, mainly inhibit the formation of foam cells in different ways. NOB reduced cholesterol uptake and enhanced cholesterol efflux and mainly regulated the expressions of ABCA1, ABCG1, and SRA1. CAF promoted cholesterol efflux, mainly by stimulating the expressions of ABCA1 and ABCG1. NARG was more effective in reducing the expression of SRA1 and CD36, which indicated that NARG mainly prevented atherosclerosis by blocking cholesterol uptake. The above results show in detail the antiatherosclerotic activity and mechanism of these compounds, making contributions to their potential applications.

Impacts of seasonal variation on volatile fatty acids production of food waste anaerobic fermentation.

This study aims to investigate the influence of seasonal variations on Volatile fatty acids (VFAs) production from food waste (FW) and to quantify their impact. Results of batch experiments with external pH control indicated that the properties of FW exhibited significant seasonal variations and were markedly different from kitchen waste (KW). The spring group demonstrated the highest VFA concentration and VFA/SCOD, at 31.24 g COD/L and 92.20 % respectively, which were 1.22 and 1.27 times higher than those observed in the summer season. The combined proportion of acetic acid and butyric acid accounted for 81.10 % of the total VFAs in spring, suggesting the highest applicability to the carbon source. The VFA content of all seasonal groups in descending order was butyric acid, propionic acid and acetic acid. Carbohydrates, along with spicy and citrusy substances, promoted the conversion of total VFA and butyric acid, while proteins and lipids favored the production of acetic acid and propionic acid.

Mitigating heavy metal volatilization during thermal treatment of MSWI fly ash by using iron(III) sulfate as a chlorine depleting agent.

In the thermal treatment of municipal solid waste incineration fly ash (FA), the presence of chlorides leads to the pronounced volatilization of heavy metals at high temperature, making heavy metals stabilization challenging. Conventional washing processes struggle to remove chlorides completely, and even minor residual chlorides can lead to significant heavy metal volatilization. This study innovatively applied iron(III) sulfate as a chlorine depleting agent, which can form FeCl3 (boiling point 316 °C) and volatilize to remove the residual chlorides at below 500 °C, thus preventing the chlorination and volatilization of heavy metals at 600-1000 °C. Using water-washed FA to produce lightweight aggregate (LWA) preparation, after adding iron(III) sulfate, the volatilization rates of Pb and Cd at 1140 °C decreased to 5.4% and 9.3%, respectively, a reduction of 82.8% and 84.1% compared to before its addition. The LWA met standard requirements in both performance and heavy metal leaching toxicity. The mechanism was further studied through thermodynamic equilibrium calculations and heating experiments of pure chemicals. This study presents novel approaches and insights for suppressing the volatilization of heavy metals in FA at high temperature, thereby promoting the advancement of thermal treatment techniques and the safe, resourceful disposal of FA.

Sedative and hypnotic effects of Polygala tenuifolia willd. saponins on insomnia mice and their targets.

ETHNOPHARMACOLOGICAL RELEVANCE: Polygala tenuifolia Willd. has been widely used in the treatment of cancer, forgetfulness, depression and other diseases. AIM OF REVIEW: The purpose of this study was to investigate the sleep-enhancing effect and mechanism of P. tenuifolia saponins (PTS). MATERIALS AND METHODS: The total saponin (YZ-I) and purified saponin (YZ-II) fractions were extracted and ICR mice model of insomnia was established by p-chlorophenylalanine (PCPA) induction to observe anxiety and depression behaviors. Effects of YZ-I and YZ-II on the levels of neurotransmitters, hormones, and inflammation cytokines were detected by ELISA, RT-qPCR and western blotting. RESULTS: The results showed that YZ-I and YZ-II reduced the immobility time of mice and prolonged the sleep time of mice and significantly increased the concentrations of 5-HT, NE, PGD2, IL-1ß and TNF-α. YZ-I and YZ-II regulated GABAARα2, GABAARα3, GAD65/67, 5-HT1A and 5-HT2A, while regulated the levels of inflammatory cytokines such as DPR, PGD2, iNOS and TNF-α to exert sedative and hypnotic effects. CONCLUSION: PTS are mainly achieved sedative and hypnotic effects by altering serotonergic, GABAergic and immune systems, but the effects and mechanisms of action of YZ-I were different from YZ-II.

Dual Roles of Two Malic Enzymes in Lipid Biosynthesis and Salt Stress Response in Dunaliella salina.

Triacylglycerols (TAG) from microalgae can be used as feedstocks for biofuel production to address fuel shortages. Most of the current research has focused on the enzymes involved in TAG biosynthesis. In this study, the effects of malic enzyme (ME), which provides precursor and reducing power for TAG biosynthesis, on biomass and lipid accumulation and its response to salt stress in Dunaliella salina were investigated. The overexpression of DsME1 and DsME2 improved the lipid production, which reached 0.243 and 0.253 g/L and were 30.5 and 36.3% higher than wild type, respectively. The transcript levels of DsME1 and DsME2 increased with increasing salt concentration (0, 1, 2, 3, and 4.5 mol/L NaCl), indicating that DsMEs participated in the salt stress response in D. salina. It was found that cis-acting elements associated with the salt stress response were present on the promoters of two DsMEs. The deletion of the MYB binding site (MBS) on the DsME2 promoter confirmed that MBS drives the expression of DsME2 to participate in osmotic regulation in D. salina. In conclusion, MEs are the critical enzymes that play pivotal roles in lipid accumulation and osmotic regulation.

Semen Ziziphus jujube Saponins Protects HaCaT Cells against UV Damage and Alleviates the Aging of Caenorhabditis elegans.

The role of Semen Ziziphus jujube saponins in sedative and hypnosis has attracted much attention. The study aimed to investigate its possible UV damage protection and anti-aging effects. Total saponins (SZR I) and purified saponins (SZR II) were analyzed and compared by infrared spectroscopy and high-performance liquid chromatography (HPLC). The protective effects of SZR I, SZR II, and their three monomers on HaCaT cells damaged by UV were studied, and their anti-aging activities were observed by Caenorhabditis elegans with paraquat-induced oxidative stress. The results showed that SZR I and SZR II differ in chemical composition but both have the same three monomers. The cell survival rate treated with SZR I and SZR II at a concentration of 400 µg/mL increased by 34.45 and 88.98%, respectively, indicating that they could promote the proliferation of UVB-damaged HaCaT cells. Jujuboside A, Jujuboside B, and spinosin from the saponins exhibited similar effects on UVB-damaged HaCaT cells. SZR I and SZR II had little effect on reproductive performance but could delay the senescence caused by heat and oxidative stress of the C. elegans model. These results provide useful data that Semen Z. jujube saponin is a potential natural product with UV damage protection and anti-aging characteristics.

Analysis of enrichment, correlation, and leaching patterns of rare earth elements in coal fly ash assisted by statistical measures.

Coal fly ash (CFA) is a typical industrial solid waste, which has recently been reported to contain rare earth elements (REEs). REEs are important materials in many industrial fields. Therefore, extracting REEs from CFA becomes a win-win strategy to both make full use of CFA and reclaim REEs. However, the stable crystalline structure of CFA is hard to break, which limits the extraction of REEs. The inter-correlation and the leaching patterns of the REEs in CFA also remain unclear. In this work, REEs were enriched by desilication, and the correlation and the influences of multiple acids of the leached REEs were investigated. It was found that desilication could increase the leachable amount of REEs from 137.37 ppm to 346.12 ppm. The light rare earth elements (LREEs) were less inter-correlated than heavy rare earth elements (HREEs) and desilication enhanced the leaching of LREEs more than that of HREEs. The ratio and type of the leaching acids both influenced the extraction of REEs from CFA: HCl and HF played important roles in the extraction from the untreated CFA while HNO3 and HF were more decisive for the desilicated CFA. In addition, we used statistical analysis to quantificationally confirm that desilication and acids both significantly influenced the extraction of REEs. This work provides evidence for the enrichment of REEs in CFA and acid choosing when leaching REEs from CFA.

Roles of Two Phytoene Synthases and Orange Protein in Carotenoid Metabolism of the ß-Carotene-Accumulating Dunaliella salina.

Phytoene synthase (PSY) is a key enzyme in carotenoid metabolism and often regulated by orange protein. However, few studies have focused on the functional differentiation of the two PSYs and their regulation by protein interaction in the ß-carotene-accumulating Dunaliella salina CCAP 19/18. In this study, we confirmed that DsPSY1 from D. salina possessed high PSY catalytic activity, whereas DsPSY2 almost had no activity. Two amino acid residues at positions 144 and 285 responsible for substrate binding were associated with the functional variance between DsPSY1 and DsPSY2. Moreover, orange protein from D. salina (DsOR) could interact with DsPSY1/2. DbPSY from Dunaliella sp. FACHB-847 also had high PSY activity, but DbOR could not interact with DbPSY, which might be one reason why it could not highly accumulate ß-carotene. Overexpression of DsOR, especially the mutant DsORHis, could significantly improve the single-cell carotenoid content and change cell morphology (with larger cell size, bigger plastoglobuli, and fragmented starch granules) of D. salina. Overall, DsPSY1 played a dominant role in carotenoid biosynthesis in D. salina, and DsOR promoted carotenoid accumulation, especially ß-carotene via interacting with DsPSY1/2 and regulating the plastid development. Our study provides a new clue for the regulatory mechanism of carotenoid metabolism in Dunaliella. IMPORTANCE Phytoene synthase (PSY) as the key rate-limiting enzyme in carotenoid metabolism can be regulated by various regulators and factors. We found that DsPSY1 played a dominant role in carotenogenesis in the ß-carotene-accumulating Dunaliella salina, and two amino acid residues critical in the substrate binding were associated with the functional variance between DsPSY1 and DsPSY2. Orange protein from D. salina (DsOR) can promote carotenoid accumulation via interacting with DsPSY1/2 and regulating the plastid development, which provides new insights into the molecular mechanism of massive accumulation of ß-carotene in D. salina.