Search Results (105)

The mechanism of the quality formation of dark tea is not fully clear, particularly under variable fermentation temperatures. In this study, the tea fermented with Aspergillus niger (AN) at 25 (AN25) and 37 °C (AN37) exhibited the highest quality. Different fermentation temperatures primarily influenced the degradation of fatty acids and the hydrolysis of glycosides in the tea, with 37 °C being the most favorable for the release and accumulation of volatile compounds. Eighteen key volatiles were identified. Among these, benzaldehyde (a 120.9% increase compared to CK), α-ionone (957.8%), linalool (172.2%), and nonanal (22.8%) were present at high levels in AN37, and these compounds served as the main aroma contributors. Inoculation with AN and fermentation temperature primarily influences the levels of total polyphenols, organic acids and their derivatives, as well as amino acids and their metabolites in dark tea. Total polyphenols, flavonoids, and nucleotide and its metabolites were more rapidly consumed at 25–37 °C, contributing to the improved taste of the tea infusion. Additionally, EGC, GC, melezitose, and sucrose showed significant negative correlations with the taste quality of the tea infusion (p < 0.05). These results are conducive to further understanding of the quality formation of dark tea. Full article

Salt–alkali stress is a major abiotic factor limiting plant growth. Dracocephalum moldavica L., an aromatic plant with medicinal and edible value, shows some potential for salt–alkali tolerance, but its response mechanisms remain unclear. In this study, physiological, transcriptomic, and metabolomic approaches were employed to compare the responses of D. moldavica seedlings to salt (NaCl/Na₂SO₄ = 1:1), alkali (NaHCO₃/Na₂CO₃ = 1:1), and mixed saline–alkali stress (NaCl/Na₂SO₄/NaHCO₃/Na₂CO₃ = 1:1:1:1). The results showed that all stress types increased the MDA content, with osmotic regulators and antioxidant enzymes helping mitigate damage. Alkali stress caused the most severe chlorophyll and photosynthetic damage. Transcriptomic analysis identified 12,838, 11,124, and 11,460 differentially expressed genes (DEGs) under salt, alkali, and mixed saline–alkali stress, respectively. Metabolomic analysis identified 1802, 1937, and 1794 differentially accumulated metabolites (DAMs) under each stress condition. Combined analysis revealed that all stresses activated pathways involved in galactose metabolism, the TCA cycle, pentose–glucuronic acid interconversion, and phenylpropanoid biosynthesis. Salt stress enhanced sucrose hydrolysis and lignification via INV and HCT. Alkali stress promoted the synthesis of 1-O-sinapoyl-β-D-glucose through COMT, improving antioxidant capacity and pH stability. Mixed saline–alkali stress activated genes related to sugar and energy metabolism, leading to the accumulation of xylitol and citric acid. These findings provide insights into D. moldavica’s mechanisms for tolerance, supporting its potential for saline–alkali land use. Full article

In this study, sucrase A (SacA) from Bacillus subtilis was successfully displayed on the outer membrane of Escherichia coli via fusion with the AIDA-I autotransporter from E. coli. The pAIDA-sacA plasmid was constructed by fusing sacA with the ctxB signal sequence and the β-barrel domain of aida gene, enabling surface expression under both aerobic and anaerobic conditions. Functional expression of AIDA–SacA was confirmed by the appearance of reducing sugars in enzymatic assays of sucrose hydrolysis and by acid production on phenol red agar. Structural prediction suggested correct localisation of the catalytic domain on the extracellular surface. Enzymatic characterisation revealed that AIDA-SacA exhibits optimal activity at 40 °C and pH 7. The calculated Km for sucrose was 1.18 mM, while the corresponding Vmax was 2.32 U mL⁻¹. Thermal stability assays showed that the enzyme retained over 80% of its activity after 60 min at 45 °C, indicating notable resistance to moderate temperatures. Metal ion assays indicated that K⁺ enhanced enzymatic activity, while Zn²⁺, Cu²⁺, and Mg²⁺ were inhibitory. SDS-PAGE analysis confirmed the expression of the recombinant fusion protein, with a distinct band at approximately 114 kDa corresponding to the expected size. These results demonstrate the feasibility of employing the AIDA-I system for the surface display of SacA in E. coli, providing a functional platform for future applications in whole-cell biocatalysis. Full article

Disorders in soybean seed-filling can lead to wrinkled seeds, affecting yield and quality. Previous studies have demonstrated that some soybean cultivars from Jiamusi, Heilongjiang Province (cold-temperate continental monsoon, ~3.5 °C mean annual temperature, ~530 mm precipitation) exhibit seed-filling disorders when cultivated in Shenyang, Liaoning Province (mid-temperate semi-humid continental monsoon, ~8.3 °C, ~610 mm). However, the causes and regulatory mechanisms remain unclear. In this study, Henong 76 (a soybean cultivar with seeds less prone to wrinkling) and Heihe 43 (a soybean cultivar with seeds prone to wrinkling) were used as experimental materials. They were sown simultaneously in Jiamusi and Shenyang, respectively, to explore the causes of seed-filling disorders in Heihe 43. The results indicated that there were significant differences in the contents of soluble sugars and starch, as well as in the activities of sucrose synthase and invertase, between the seeds of Henong 76 and Heihe 43 grown in Shenyang. However, no significant differences were found between them in Jiamusi. Transcriptomic and metabolomic analyses suggested that genes related to controlling starch hydrolysis (isoamylase, α-amylase, and glycogen phosphorylase) and sucrose synthesis and decomposition (sucrose synthase, invertase, glucose-6-phosphate isomerase, and phosphoglucomutase) in Heihe 43 were upregulated in Shenyang. In contrast, genes regulating plant hormone signal transduction (auxin, gibberellin, abscisic acid, and cytokinin) were generally downregulated. These changes led to differences in metabolites, resulting in the occurrence of seed-filling disorders. Furthermore, we analyzed the climatic conditions of the two cultivars during the soybean seed-filling period. The results indicated that high temperature might be the primary meteorological factor contributing to the occurrence of seed-filling disorders. All results indicated that the insufficient accumulation of sugars in seeds due to exposure to high temperatures during the seed-filling period is the primary cause of the prone-to-wrinkling phenomenon of the Heihe 43 cultivar under the ecological conditions of Shenyang. Full article

Although the role of OsHY5L2 in promoting photomorphogenic development is well characterized, its function in regulating rice quality is poorly understood. In this study, we found that OsHY5L2 plays an important role in regulating starch metabolism and modulating its fine structure and physicochemical properties. Overexpression of OsHY5L2 significantly reduced the chalky grain rate and degree of chalkiness but dramatically increased the head rice rate. OsHY5L2 was found to negatively regulate the accumulation of starch in rice endosperm by inhibiting starch biosynthesis and promoting starch hydrolysis. Transcriptomic analysis revealed that OsHY5L2 mainly regulated the expression of genes encoding enzymes involved in starch and sucrose metabolism. Moreover, OsHY5L2 overexpression induced the formation of numerous pinhole structures on the surfaces of starch granules. Analysis of the amylopectin chain length distribution showed that overexpression of OsHY5L2 decreased the proportion of ultra-short chains (DP 6–7) and intermediate chains (DP 13–24) of amylopectin while increasing the proportion of short chains (DP 8–12) and long chains (DP 25–36). Further studies demonstrate that OsHY5L2 overexpression altered the pasting properties of rice starch by affecting its multi-level structure and function. The results of this study improve our understanding of the functions of OsHY5L2 in regulating rice quality. Full article

Many factors related to obesity can impact how mitochondria produce ATP, such as the uncoupling of oxidative phosphorylation (OXPHOS) caused by proton leaks from built-up free fatty acids (FFA), the increased levels of uncoupling proteins (UCPs), and changes in the levels of ATPase inhibitory protein factors 1 (IF1). Therefore, the present study aimed to assess the rate of ATP synthesis in mitochondria isolated from skeletal and cardiac muscle from animal models of sucrose diet-induced obesity at different time periods. Short periods of sucrose intake (6 and 12 weeks) are sufficient to induce fat accumulation, hypertriglyceridemia, and high plasma FFA. However, a significant decline in the ATP synthesis rate starts to be obvious in mitochondria from skeletal muscle after 24 weeks of sucrose consumption. This impairment of ATP synthesis is associated with increased FFA in skeletal muscle homogenate. ATP synthesis rates in both skeletal and cardiac muscle were found to be sensitive to oleic acid and GDP, a physiological inhibitor of UCPs that has been shown to increase with aging. In addition, a sucrose diet increases the IF1 content in both skeletal and heart muscle, probably to avoid the hydrolytic activity of ATP synthase. In mitochondria from heart muscle, a decrease in the ATP synthesis rate was only observed according to the age in both groups of rats, and it was not affected by sucrose feeding. Our results suggest that the decline of the ATP synthesis rate in mitochondria from skeletal muscle can be due to the accumulation of FFA in skeletal muscle tissue as uncouplers, and the IF1 overexpression induced by the sucrose diet is a response mechanism to avoid the ATP hydrolysis and to save the energy charge reduced by FFA-uncoupling OXPHOS. Full article

Safflower (Carthamus tinctorius L.) seeds, rich in triacylglycerols, have poor fatty acid-to-sugar conversion during storage, affecting longevity and vigor. Previous experiments have shown that the aging of safflower seeds is mainly related to the impairment of energy metabolism pathways such as glycolysis, fatty acid degradation, and the tricarboxylic acid cycle. The treatment with exogenous sucrose can partially promote the germination of aged seeds. However, the specific pathways through which exogenous sucrose promotes the germination of aged safflower seeds have not yet been elucidated. This study aimed to explore the molecular mechanism by which exogenous sucrose enhances the vitality of aged seeds. Phenotypically, it promoted germination and seedling establishment in CDT-aged seeds but not in unaged ones. Biochemical analyses revealed increased soluble sugars and fatty acids in aged seeds with sucrose treatment. Enzyme activity and transcriptome sequencing showed up-regulation of key enzymes and genes in related metabolic pathways in aged seeds, not in unaged ones. qPCR confirmed up-regulation of genes for triacylglycerol and fatty acid-to-sugar conversion. Transmission electron microscopy showed a stronger connection between the glyoxylate recycler and oil bodies, accelerating oil body degradation. In conclusion, our research shows that exogenous sucrose promotes aged safflower seed germination by facilitating triacylglycerol hydrolysis, fatty acid conversion, and glycometabolism, rather than simply serving as a source of energy to supplement the energy deficiency of aged seeds. These findings offer practical insights for aged seeds, especially offering an effective solution to the aging problem of seeds with high oil content. Full article

Lactic acid fermentation has emerged as a promising strategy to enhance the functional and health-promoting qualities of plant-based foods. This study evaluates the impact of lactic acid fermentation on the antioxidant capacity, microbial viability, and chemical stability of freeze-dried peaches, aiming to develop a functional food with probiotic potential. Two bacterial strains—Fructilactobacillus fructivorans (P_FF) and Lactiplantibacillus plantarum (P_LP)—were used to assess strain-dependent effects on microbial and bioactive compound profiles. Microbiological analyses included total viable count (TVC), fungal count (TFC), and total lactic acid bacteria (TCLAB). Chemical analyses comprised polyphenol, flavonoid, anthocyanin, carotenoid, sugar, and vitamin C content, as well as antioxidant activity (DPPH, ABTS, reducing power). Thermal and structural stability were examined via thermogravimetric analysis (TGA) and Fourier-transform infrared spectroscopy (FTIR). Fermentation significantly increased the counts of lactic acid bacteria, achieving 8.38 and 7.86 log CFU/g after freeze-drying, respectively. While total polyphenols slightly decreased (by 9.5% and 1.1% for L. plantarum and F. fructivorans, respectively), flavonoid content increased notably by 16.1% in F. fructivorans-fermented samples. Antioxidant activities, assessed by ABTS and DPPH assays, were largely maintained, although a reduction in reducing power was observed. Additionally, fermentation led to sucrose hydrolysis, resulting in higher glucose and fructose contents, and increased water content in the final products. Minor increases in total fungal counts were noted after freeze-drying but remained within acceptable limits. Overall, the combination of fermentation and freeze-drying processes preserved key antioxidant properties, enhanced microbial safety, and produced functional peach-based products with improved bioactivity and extended shelf life. These findings highlight the potential of fermented freeze-dried peaches as innovative, health-oriented alternatives to traditional fruit snacks. Full article

Climate change significantly influences plants’ physiology, flowering phenology, and nectar production, affecting pollinator interactions and apicultural sustainability. This study examines the physiological responses of Pseudolysimachion rotundum (Nakai) Holub var. subintegrum (Nakai) T.Yamaz. (Plantaginaceae) under projected climate change scenarios, focusing on flowering traits, nectar secretion, and honey production potential. Elevated CO₂ levels enhanced its net photosynthesis and water-use efficiency, supporting sustained carbohydrate assimilation and promoting aboveground biomass accumulation. However, the increased nitrogen demand for vegetative growth and inflorescence production may have led to reduced allocation of nitrogen to the nectar, contributing to a decline in its amino acid concentrations. The flowering period advanced with rising temperatures, with peak bloom occurring up to four days earlier under the SSP5 conditions. While the nectar secretion per flower remained stable, an increase in floral abundance led to a 3.8-fold rise in the estimated honey production per hectare. The analysis of the nectar’s composition revealed that sucrose hydrolysis intensified under higher temperatures, shifting the nectar toward a hexose-rich profile. Although nectar quality slightly declined due to reductions in sucrose and nitrogen-rich amino acids, phenylalanine—the most preferred amino acid by honeybees—remained dominant across all scenarios. These findings confirm the strong climate resilience of P. rotundum var. subintegrum, highlighting its potential as a sustainable nectar source in future apicultural landscapes. Given the crucial role of nitrogen in both plant growth and nectar composition, future research should explore soil nitrogen dynamics and plant nitrogen metabolism to ensure long-term sustainability in plant–pollinator interactions and apicultural practices. Full article

Fusarium head blight (FHB) is one of the most devastating diseases in wheat. Besides its negative impact on grain yield, FHB also negatively influences quality. Changes in sugar and free amino acid content were analyzed in flour from Fusarium-infected and non-infected grains of six wheat varieties differing in Fusarium resistance. The concentrations of sugars and free amino acids were determined using a high-performance liquid chromatography device. In flour from FHB-infected grains, the average total amount of fructose, glucose, maltose, total sugars, and total reducing sugars was significantly increased, compared to non-treated flour from the Tika Taka variety, which was the most FHB-susceptible. The total content of free amino acids in flour from FHB-infected varieties increased in proportion to their susceptibility. In Tika Taka, there was a significant increase in free amino acid content of about 46%, while a significant decrease of 16% was observed in the highly resistant Vulkan variety. A highly significant correlation was established between the degree of FHB susceptibility and the content of aspartic acid, glutamic acid, glutamine and histidine, glycine, alanine, methionine, valine, tryptophan, phenylalanine, leucine, and threonine. Most amino acids had strong positive correlations with each other, but among the sugars, only fructose and glucose content showed a strong positive correlation with specific amino acids that were induced by Fusarium infection. Overall, it can be concluded that FHB-susceptible varieties have a high risk of FHB infection, which results in the hydrolysis of sucrose into fructose and glucose, together with an increase in free amino acids, which deteriorates the quality of wheat. Full article

In perennial trees, wood development is a carbon-demanding process, pivotal for secondary cell wall (SCW) formation and xylem development. Sugars, functioning both as carbon substrates and signaling molecules, orchestrate cambial proliferation and xylem differentiation. However, few molecular candidates involved in the sugar-mediated regulation of wood development have been characterized. Cell wall invertases (CWINs), a subclass of the invertase enzyme family localized in the apoplastic space, catalyze the irreversible hydrolysis of sucrose into glucose and fructose, thereby governing carbon allocation in sink tissues. Here, PtoCWIN4 shows preferential expression in the stem of Populus tomentosa and has a high efficiency in sucrose cleavage activity. We demonstrated that the knockout of PtoCWIN4 results in stunted growth, aberrant branching patterns, and compromised secondary xylem formation. In contrast, mutant lines displayed enhanced SCW thickness accompanied by elevated cellulose and hemicellulose accumulation. Following this, the knockout of PtoCWIN4 led to impaired carbon partitioning from sucrose to hexose metabolites during wood development, corroborating the enzyme’s role in sustaining sucrose hydrolysis. Collectively, these findings establish PtoCWIN4 as a master regulator of sucrose-to-hexose conversion, a metabolic gateway critical for balancing structural biomass production and developmental growth during wood formation. Full article

Cordyceps cicadae (C. cicadae) is an important edible medicinal fungus; however, owing to its wild growth and lack of genome annotation, construction of a stable genetic transformation system in C. cicadae is greatly limited, impeding the extensive exploitation of C. cicadae in industry. Here, we successfully established an efficient plasmid transformation method within protoplasts of C. cicadae by PEG mediation using pCas9-EGFP as a marker plasmid. In order to overcome low transformation efficiency and acquire sufficient protoplasts for transformation, the influence of enzyme species, enzymatic hydrolysis time, enzymatic hydrolysis temperature, and fungal age on protoplast preparation were analyzed sequentially, and the optimal conditions for protoplast preparation were determined as follows: 2-day-old C. cicadae mycelia with 1.5% lywallzyme hydrolysis at 34 °C for 5 h. Our results indicate that no less than 5.1 × 10⁷ CFU/mL protoplasts could be acquired. Additionally, five osmotic pressure stabilizers including potassium chloride (KCl), sodium chloride (NaCl), glucose, mannitol, and sucrose were employed to enhance the regeneration of protoplasts, among which sucrose exhibited the highest regeneration rate of 10.43%. The transformation efficiency of plasmid was 37.3 CFU/µg DNA. On this basis, a genetic transformation method was successfully constructed, laying the foundation for further gene editing and metabolic engineering of C. cicadae. Full article

Porous carbon particles (PCPs) prepared from sucrose via the hydrothermal method and its modified forms with polyethyleneimine (PEI) as PCP-PEI were used as templates as in situ metal nanoparticles as M@PCP and M@PCP-PEI (M:Co, Ni, or Cu), respectively. The prepared M@PCP and M@PCP-PEI composites were used as catalysts in the hydrolysis of NaBH₄ and NH₃BH₃ to produce hydrogen (H₂). The amount of Co nanoparticles within the Co@PCP-PEI structure was steadily increased via multiple loading/reducing cycles, e.g., from 29.8 ± 1.1 mg/g at the first loading/reducing cycles to 44.3 ± 4.9 mg/g after the third loading/reducing cycles. The Co@PCP-PEI catalyzed the hydrolysis of NaBH₄ within 120 min with 251 ± 1 mL H₂ production and a 100% conversion ratio with a 3.8 ± 0.3 mol H₂/(mmol cat·min) turn-over frequency (TOF) and a lower activation energy (Ea), 29.3 kJ/mol. In addition, the Co@PCP-PEI-catalyzed hydrolysis of NH₃BH₃ was completed in 28 min with 181 ± 1 mL H₂ production at 100% conversion with a 4.8 ± 0.3 mol H₂/(mmol cat·min) TOF value and an Ea value of 32.5 kJ/mol. Moreover, Co@PCP-PEI composite catalysts were afforded 100% activity up to 7 and 5 consecutive uses in NaBH₄ and NH₃B₃ hydrolysis reactions, respectively, with all displaying 100% conversions for both hydrolysis reactions in the 10 successive uses of the catalyst. Full article

α-Arbutin is the fourth generation whitening factor in the field of cosmetics, which can block the synthesis of melanin in epidermal cells and has the advantages of good stability and less toxic side effects. Moreover, α-arbutin has potential application value in food, medicine, and other fields. However, the extraction yield from plant tissues is relatively low, which restricts its application value. Currently, enzymatic catalysis is universally deemed the safest and most efficient method for α-arbutin synthesis. Amylosucrase (ASase), one of the most frequently employed glycosyltransferases, has been extensively reported for α-arbutin synthesis. To discover new resources of amylosucrase (ASase), this study synthesized α-arbutin using low-cost sucrose as a glycosyl donor. Probe sequences were used to identify homologous sequences from different microbial strains in protein databases as candidate ASases. Recombinant plasmids were constructed, and the enzymes were successfully expressed in Escherichia coli, followed by the enzymatic synthesis of α-arbutin. One ASase from Calidithermus terrae, named CtAs, was selected for its effective α-arbutin synthesis. The expression conditions for CtAs were optimized, its enzymatic properties were analyzed, and the conditions for the enzymatic synthesis of α-arbutin were further refined to improve its molar yield. The optimal induction conditions for CtA expression were achieved by adding IPTG at a final concentration of 0.5 mmol/L to LB medium when OD₆₀₀ reached 1.0, followed by an incubation at 20 °C and 200 r/min for 18 h. The optimal temperature and pH for CtAs were found to be 42 °C and 9.5, respectively, with good stability across the pH range of 5.0–12.0. CtAs was activated by Na⁺, K⁺, Mg²⁺, EDTA, methanol, and ethanol, but inhibited by Ca²⁺, Zn²⁺, Ba²⁺, and Ni²⁺. The kinetic parameters were V_max = 6.94 μmol/min/mL, K_m = 89.39 mmol/L, K_cat = 5183.97 min⁻¹, and K_cat/K_m = 57.99 L/(mmol·min). At 42 °C and pH 9.5, the hydrolysis/polymerization/isomerization reaction ratios were 23.27:32.96:43.77 with low sucrose concentrations and 38.50:37.12:24.38 with high sucrose concentrations. The optimal conditions for the enzymatic synthesis were determined to be at 25 °C and pH 5.0 using sucrose at a final concentration of 42 mmol/L and hydroquinone at 6 mmol/L (donor-to-acceptor ratio of 7:1), with the addition of 200 μL (0.2 mg/mL) of purified enzyme and 0.10 mmol/L ascorbic acid, under dark conditions for 6 h. The final molar yield of α-arbutin was 62.78%, with a molar conversion rate of hydroquinone of 74.60%, nearly doubling the yield compared to pre-optimization. Full article

Low temperature, as a major abiotic stress, impacts the formation of high-quality tobacco seedlings. It is urgent to take appropriate measures to improve the low-temperature tolerance of tobacco seedlings. A hydroponics experiment was conducted with a tobacco cv. Y2001 under 25 °C (control temperature) and 10 °C (low-temperature stress). Three phosphorus (P) levels including the traditional P concentration (2 mM PO₄³⁻) and higher P levels (3 mM PO₄³⁻ and 4 mM PO₄³⁻) were applied to investigate their effects on antioxidant metabolism and carbohydrate metabolism in low-temperature-stressed tobacco seedlings. The results showed that the low temperature decreased plant height, stem diameter, and biomass of shoots and roots, while the higher P levels promoted plant height and shoot biomass of low-temperature-stressed tobacco seedlings compared to the traditional P level. The leaf net photosynthetic rate (A_N) was decreased by the low temperature, while the A_N of low-temperature-stressed tobacco leaves was increased by 38.6–61.3% for the higher P levels than the traditional P level. Higher O₂⁻ and H₂O₂ were observed in tobacco leaves exposed to low-temperature stress, damaging the A_N, although the low temperature upregulated the expression of encoding superoxide dismutase (NtSOD), peroxidase (NtPOD), and catalase (NtCAT). However, compared with the traditional P level, the higher P levels further upregulated the expression of NtSOD and NtCAT in low-temperature-stressed tobacco leaves to accelerate O₂⁻ and H₂O₂ removal. Higher leaf sucrose content was detected since the low temperature significantly downregulated the expression of NtSuSy, NtCWINV, and NtNINV encoding sucrose synthase, the cell wall, and alkaline invertases, respectively, inhibiting sucrose hydrolysis. Compared with the traditional P level, higher P levels downregulated the expression of NtCWINV in low-temperature-stressed tobacco leaves, further promoting leaf sucrose content. The low temperature downregulated the expression of NtAGP encoding ADP-glucose pyrophosphorylase, NtSSS encoding soluble starch synthase, and NtGBSS encoding granule-bound starch synthase, thereby restricting starch biosynthesis. Additionally, the low temperature upregulated the expression of α-amylase and β-amylase, accelerating starch hydrolysis. These led to a lower starch content in low-temperature-stressed tobacco leaves. The higher P levels further upregulated the expression of α-amylase in low-temperature-stressed tobacco leaves than the traditional P level, further lowering the starch content. Moreover, the leaf soluble sugar content was higher under the low temperature than the control temperature, which helped the tobacco plants resist low-temperature stress. And higher P levels further promoted the soluble sugar content in low-temperature-stressed tobacco leaves compared with the traditional P level, further improving tobacco seedlings’ low-temperature tolerance. Therefore, these results indicated that increasing the P application level can alleviate the adverse impacts of cold stress on antioxidant metabolism and carbohydrate metabolism in tobacco seedlings. Full article