Free Amino Acid Content Research Articles

Insight into the autochthonous lactic acid bacteria as starter culture for improving the quality of Sichuan radish paocai: Changes in microbial diversity and metabolic profiles

Paocai is a traditional Chinese fermented vegetable product popular in Asian countries. Recently, functional starters were used to control the fermentation process and improve the quality of paocai. In this study, three autochthonous lactic acid bacteria including Lactiplantibacillus plantarum LB6, Lactiplantibacillus pentosus LB3, and Weissella cibaria W51 were selected as starters and the effect of the starters on the fermentation of paocai was investigated. The results suggested that the inoculated fermentation led to a lower nitrite peak and more pronounced changes in pH and total titratable acid in the early stage of fermentation, compared with natural fermentation. Analysis of the flavor compounds indicated that the total content of volatile organic compounds of paocai through natural fermentation was significantly lower than that in inoculated fermentation. As for free amino acids, in the early stage of fermentation, the types and contents of free amino acids in the inoculated fermentation paocai were higher than those in the blank group. In the later stage of fermentation, the contents of amino acids representing umami and sweet tastes were also higher than those in the blank group. The bacterial community analysis showed that Lactobacillus and Lactococcus were the dominant bacteria in both inoculated fermentation and natural fermentation. Then, the correlations among physicochemical properties, microbial community and flavor compounds were revealed, and it was found that the dominant bacteria such as Lactococcus, Leuconostoc, Lactobacillus and Weissella displayed a considerable impact on the physical and chemical properties and flavor of paocai. In addition, the metabolic pathways involved in flavor formation and the abundance of related enzymes were elucidated. The abundance of enzymes involved in generating prephenic acid, 2-methylbutanoic acid, L-lactic acid, D-lactic acid, butanoic acid, etc., and in the pathway of producing flavor substances (His, Met, ethyl hexanoate, etc.) was up-regulated in the inoculated fermentation. Results presented in this study may provide a reference for the development of paocai starters and further guidance for the flavor improvement of Sichuan paocai.

Effect of balanced vs. standard protein on muscle mass development in exercising horses.

Twelve horses weighing 570 ± 35kg were split into two groups (standard protein, STD, and balanced protein, BAL) to evaluate the effect of balanced vs. unbalanced protein on muscle mass. Groups were fed grass hay and a 12% CP feed (one formulated for balanced protein). Horses were out of work for 14wk prior and participated in 1 to 2h of light-to-moderate exercise 5d/wk for 12wk. A 4-d total urine and feces collection period was conducted at the start and end of the study. Urine and feces samples were analyzed for nitrogen (N) to calculate N balance. Muscle mass status was evaluated using histochemistry, muscle scoring, and body measurements at the start and end of the study. Muscle biopsies were analyzed for free amino acid concentrations. An ANOVA was done using the Proc MIXED function of SAS (2006). Nitrogen retention was greater and urine nitrogen as a percent of intake less for the STD group at the end of the study (P = 0.01). Muscle free concentrations of methionine, leucine, phenylalanine, and arginine were greater in the BAL group at the end of the study compared to the STD group (P < 0.04) while muscle free histidine, threonine, and valine were less for the STD group at the end of the study compared to the start of the study (P < 0.05). Muscle fiber diameters were greater at the start of the study for the STD group (P = 0.004) but greater for the BAL group at the end of the study (P = 0.001). There is some evidence of improved muscle mass for the BAL group with greater muscle free amino acids (arginine, leucine, methionine, phenylalanine, and valine) as well as greater type II muscle fiber areas and diameters. While changes did not appear evident between groups at the "whole body" level, changes at the tissue level appear more evident.

Effect of pasteurization and storage on the bioavailability of milk proteins during in vitro intestinal digestion and Caco-2 cell transport

This study fills a specific knowledge gap by comprehensively investigating the intestinal digestive dynamics and transport kinetics of pasteurized milk proteins during cold storage, utilizing dynamic in vitro digestion models, human colorectal adenocarcinoma cell line (Caco-2) transport simulations, peptideomics and amino acid analysis. The content of free amino acids during intestinal digestion and their transport capacity (excluding lysine) were highest in pasteurized milk stored for 7 days (PAST-D7), intermediate in pasteurized milk stored for 0 days (PAST-D0) and lowest in raw milk (RM). Conversely, the quantity and intensity of bioactive peptides during digestion decreased with pasteurization and storage. Additionally, pasteurization and storage reduced the intensity of bioactive peptides transported through Caco-2 cells and the types and intensity of potential allergenic peptides. These findings indicate that while pasteurization and storage may diminish some physiological benefits of milk, they may also enhance protein bioavailability and reduce allergenicity.

Exposure to thimerosal induces behavioral abnormality in the early life stages of zebrafish via altering amino acid homeostasis

Thimerosal (THI) has become a significant source of organic mercury pollutants in aquatic ecosystems, but there is limited information regarding its adverse effects on fish. In this study, zebrafish embryos were exposed to THI at 0 (control), 5.0, and 50 ng/L from 0–5 days post fertilization (dpf), and variations in their survival, development, behavior, free amino acid contents, and the biochemical responses involved in monoaminergic systems were examined. Although THI exposure did not significantly affect the survival, heart rate, or hatching time of zebrafish embryos, it substantially increased swimming velocity (136–154 % of the control) and reduced exploratory behavior (141–142 % of the control) in zebrafish larvae at 5 dpf. Exposure also significantly altered the amino acid contents (51–209 % of the control) and monoamine levels (70–154 % of the control) in zebrafish larvae, some of which displayed significant correlations with behavioral traits. THI significantly elevated dopamine receptor gene expression and monoamine oxidase activity in zebrafish larvae. Adding extra phenylalanine or tryptophan to the E3 medium facilitates the recovery of zebrafish larvae from the abnormal behaviors induced by THI. These findings reveal for the first time that THI exposure at the level of ng/L is sufficient to induce neurobehavioral toxic effects in the early life stages of zebrafish, and disrupting amino acid homeostasis is a critical underlying mechanism. This study provides valuable insights into the toxicity of THI to fish and highlights the importance of assessing its potential risks to aquatic ecosystems.

Low temperature exposure influences nitrogen metabolism resulting in decreased Cry1Ac insecticidal endotoxin content in cotton seeds

BackgroundSudden temperature drops, resulting from extreme weather events, often occur during the boll-setting period of cotton in Xinjiang, China, causing decreased expression of Bacillus thuringiensis (Bt) insecticidal proteins in cotton bolls. The precise threshold temperatures and durations that lead to significant changes in Cry1Ac endotoxin levels under low temperatures remain unclear. To address this, we investigated the effects of different temperatures and stress durations on Cry1Ac endotoxin levels in cotton bolls. In 2020–2021, two Bt transgenic cotton varieties, conventional Sikang1 and hybrid Sikang3, were selected as experimental materials. Various low temperatures (ranging from 16 to 20 °C) with different durations (12 h, 24 h and 48 h) were applied during the peak boll-setting period.ResultsAs the temperature decreased, the Cry1Ac endotoxin content in the boll shell, fiber, and seed exhibited a declining trend. Moreover, the threshold temperature which caused a significant reduction in Cry1Ac endotoxin content increased with the prolonged duration of low-temperature stress. Among the components of cotton bolls, seeds were most affected by low-temperature stress, with the threshold temperature for a significant reduction in Cry1Ac endotoxin content ranging from 17 °C to 19 °C. Correlation analysis indicated that low temperatures led to a decrease in protein synthesis capacity and an increase in degradation ability, resulting in reduced Cry1Ac endotoxin content. Pathway analysis revealed that both free amino acid and peptidase had significant negative effects on Cry1Ac endotoxin content.ConclusionIn summary, when the daily average temperature was ≤ 19 °C, implementing cultural practices to reduce free amino acid content and peptidase activity could serve as effective cold defense strategies for Bt cotton production.

Yeast extracts weakened warmed-over flavor in surimi gels made from silver carp due to the masking effect by high concentrations of pyrazines and esters.

Warmed-over flavor (WOF) is an off-flavor in surimi gels. Yeast extract (YE) could improve the aroma properties of food. However, the effect of YE on the WOF in surimi gels and its mechanism was still unclear. In this study, aroma profiles, the composition of aroma compounds and aroma precursors, concentrations of WOF compounds, and thiobarbituric acid reactive substances (TBARS) of surimi gels with different amounts of YE were investigated by molecular sensory science and chromatographic techniques. Moreover, the effect of pyrazines and esters introduced by YE on WOF was also tested by sensory analysis. The addition of no less than 1% YE to surimi gels significantly weakened WOF. However, YE did not decrease the concentrations of WOF compounds and did not change the fatty acid composition and TBARS in surimi gels. Conversely, the addition of YE significantly increased the contents of free amino acids, N-containing compounds, and esters in surimi gels. The contents of total free amino acids, 2,6-dimethylpyrazine, and ethyl acetate in surimi gels with 2.5% YE were 1.5, 21, and 2.1 times higher than those in the control, respectively. Additionally, the sensory results of the spiked aroma models containing WOF compounds, 2,6-dimethylpyrazine, and esters showed that more than 9.4µg/kg of 2,6-dimethylpyrazine with a baked-potato note and more than 6.1µg/kg of ethyl acetate and 11.2µg/kg of butyl acetate with a fruity note could significantly mask WOF. In conclusion, WOF in surimi gels could be masked by YE due to the high concentrations of pyrazines and esters. Practical Application: Yeast extracts could decrease the warmed-over flavor (WOF) due to the high concentrations of pyrazines (baked-potato note) and esters (fruity note). This finding extends the application of yeast extracts in the food industry. On the other hand, this study presents a reasonable solution for the reduction of WOF in surimi products.

Vacuum freeze drying combined with catalytic infrared drying to improve the aroma quality of chives: Potential mechanisms of their formation

This study aimed to investigate the effect of vacuum freeze drying combined with catalytic infrared drying (FD-CIRD) process on aromas, free amino acids, reducing sugars and free fatty acids in chive leaves and stems. Gas chromatography-mass spectrometry combined with multivariate data analysis revealed that dipropyl disulfide was the key aroma that distinguished the differences between chive leaves and stems. The key aromas benzeneacetaldehyde, decanal and 1-octen-3-ol enhanced FD-CIRD chive leaves and stems aromas. The free amino acid content was highest at FD-CIRD stage in all samples except for the control (FD), while the reducing sugar content was lowest. The content of unsaturated fatty acids gradually decreased at FD stage and increased at FD-CIRD stage. Additionally, correlation analysis revealed that phenylalanine was a potential precursor of benzacetenealdehyde, oleic and linolenic acids were potential precursors of decanal and 1-octen-3-ol. Therefore, FD-CIRD technique helps to improve the sensory profile of dried chives.

Continuous flow high-pressure homogenization for preserving the nutritional quality and stability of watermelon juice under simulated market storage conditions

This study examined the efficacy of continuous flow high-pressure homogenization (CFHPH) under varying pressures, inlet temperatures, and flow rates, in preserving the nutritional quality and stability of watermelon juice during simulated market conditions and compared it with traditional high-temperature short-time (HTST) processing. The retention of ascorbic acid, carotenoids, and amino acids was analyzed using liquid chromatography, while PPO (polyphenol oxidase) and POD (peroxidase) enzyme activity was assessed using a UV–vis spectrophotometer.We observed a significant decrease (p ≤ 0.05) in ascorbic acid levels after 15 days of storage. For carotenoids, the impact was influenced by the interaction of pressure, flow rate, and inlet temperature within CFHPH, with no clear trend emerging regarding their preservation over 45 days of storage at 4 °C. However, overall retention of carotenoids surpassed that of HTST samples. Both methods enhanced free amino acid contents significantly and decreased PPO and POD activity, with HTST being slightly more effective. Ornithine and histidine concentrations significantly increased, with up to a fourfold rise in samples treated with 300 MPa pressure and up to a tenfold rise for HTST at 95 °C after 45 days of storage. This study suggests optimizing the CFHPH process to enhance the shelf-life and nutritional value of watermelon juice, offering consumers a healthier and longer-lasting choice. Industrial relevanceOur findings highlight CFHPH's higher retention of bioactive compounds, reduction in degradative enzyme activity, and enhancement of the amino acid profile, making it a compelling choice for the fruit juice processing industry. Despite the energy-intensive nature of CFHPH, its ability to preserve vital bioactive compounds like carotenoids and ascorbic acid addresses the growing consumer demand for nutritious and stable juice options. The benefits of CFHPH in maintaining juice quality and nutritional value may outweigh the associated energy costs, making it a promising technology for fruit juice processing.

System-wide analysis of groundnut's salinity resilience: Integrating plant-cell interactions with environmental stress dynamics through cutting-edge transcriptomics

Salinity stress is a major concern in regions where irrigation relies on saline water. This study aimed to investigate the relative water content (RWC), electrolytic leakage (EL), total chlorophyll content, free amino acid content, and total soluble sugar content were analyzed in different groundnut species subjected to various salinity treatments. The results showed that salinity stress significantly reduced the RWC in groundnut leaves, with A. duranensis (wild type) exhibiting higher RWC values compared to the Arachis hypogaea species. RNA sequencing was performed to identify differentially expressed genes (DEGs) during salt stress. A total of 9079 DEGs were identified, with 1372 genes upregulated and 2509 genes downregulated. Genes belonging to transcription factor families, such as WRKY, MYB, bHLH, E2F, and Auxin efflux carrier proteins, were induced under salt stress in the tolerant genotype. Conversely, genes encoding NADH dehydrogenase, glutathione S-transferase, protein kinases, UDP-glycosyltransferase, and peroxidase were downregulated. Gene ontology and pathway analyses revealed several enriched categories and metabolic pathways associated with salt stress response, including catalytic activity, response to salt stress, ATP-dependent activity, and oxidative phosphorylation. The findings of this study provide insights into the physiological and molecular responses of groundnut to salinity stress. A. duranensis exhibited better salinity tolerance than Arachis hypogaea, as indicated by higher RWC values, lower electrolytic leakage, and differential gene expression patterns. These results contribute to our understanding of the mechanisms underlying salt stress tolerance in groundnut and may guide future efforts to develop salinity-tolerant groundnut species, ultimately improving crop yield in saline-affected regions.

Dynamic changes in volatile profiles and bacterial communities during natural fermentation of Mei yu, traditional Chinese fermented fish pieces

Microbial metabolism is important for the unique flavor formation of Mei yu, a kind of traditional Chinese fermented fish pieces. However, the interactive relationship between microorganisms and flavor components during fermentation is still unclear. In this study, electronic nose and headspace-solid-phase microextraction-gas chromatography-mass spectrometry analysis were performed to identify flavor components in Mei yu during the fermentation, and the absolute microbial quantification was conducted to identify the diversity and succession of microbial communities. During fermentation, there was an increase in the types of volatile compounds. Alcohols, aldehydes, aromatics and esters were the main flavor compounds and significantly increased in Mei yu, while hydrocarbon and aldehydes significantly decreased. The absolute abundances of Lactobacillus, Lactococcus and Weissella increased significantly after 3 days’ fermentation, which were closely associated with the productions of 1-nonanol, 2-methoxy-4-vinylphenol, guaiacol, ethyl palmitate and ethyl caprylate that might though pathways related to fatty acid biosynthesis and amino acid metabolism. However, these genera were negatively correlated with the production of indole. Additionally, the total volatile basic nitrogen (TVB-N) levels of Mei yu fermented during 3 days were within the limits of 25 mg TVB-N/100 g fish, with the contents of free amino acids and lipoxygenase activities were significant lower than that of 4 days’ fermentation. In view of food safety and flavor, it suggested that the natural fermented Mei yu at room temperature should be controlled within 3 days. This study highlights the application of absolute quantification to microbiome analysis in traditional fermented Mei yu and provides new insights into the roles of microorganisms in flavor formation during fermentation.

Effect of Dry Processing of Coconut Oil on the Structure and Physicochemical Properties of Coconut Isolate Proteins.

The effects of the dry processing of coconut oil on the amino acid composition, molecular weight, secondary structure, solubility, surface hydrophobicity, microstructure, total sulfhydryl and free sulfhydryl content, free amino acid content, thermal properties, and water-holding, oil-holding, foaming, and emulsifying properties of coconut isolate protein were investigated. The results showed that the dry processing altered the amino acid composition of coconut isolate proteins as well as resulted in fewer irregular structural regions and more homogeneous particle sizes, leading to an improvement in the thermal stability of the proteins. SDS-PAGE analysis showed that globular proteins located at ~34 kDa in coconut isolate proteins underwent slight degradation during the dry processing of coconut oil. The dry processing reduced the surface hydrophobicity, total and free sulfhydryl groups, solubility, and free amino acid content of coconut isolate proteins. In addition, the water-holding capacity, oil-holding capacity, and foam stability of coconut isolate proteins were improved to different degrees after the dry processing. Therefore, the development and utilization of copra meal protein is of great significance to increase its added value.

Sea Bass Fish Head Broth Treated by Thermo-Ultrasonication: Improving the Nutritional Properties and Emulsion Stability.

This work investigated the underlying mechanism of thermo-ultrasonic treatment to improve the nutritional properties and emulsion stability of sea bass fish head broth. The effects of ultrasonication on the processing of fish broth were compared with boiling water treatment. The nutritional properties of fish broth mainly include protein, fat, total sugar, 5'-nucleotide and free amino acid content. To achieve a similar effect of nutrient extraction, the thermo-ultrasonic treatment required a shorter time (30 min) than boiling water (120 min). The water-soluble protein, fat and total sugar contents were at their maximum at 120 min of the thermo-ultrasonic treatment. In particular, the fat content increased with the time of thermo-ultrasonic treatment from 0.58% to 2.70%. The emulsion structure of the fish soup was characterized by measuring its color and particle size, using optical microscopy and confocal laser scanning microscopy, and determining its storage stability. Thermo-ultrasonic treatment reduced the particle size of the fish broth emulsion and the fat globules became smaller and more homogeneous. Ultrasonication not only accelerated the nutritional and flavor content of the fish head broth, but also reduced the particle size and enhanced the stability of the emulsified system of the fish broth. The fish head tissue was more severely disrupted by the cavitation effect of an ultrasound, and nutrients migrated more and faster. This was mainly due to the cavitation and mechanical breaking force of the ultrasound on the fish head tissue and the fat globules of the fish broth. Altogether, these findings suggest that the thermo-ultrasonic treatment technique is useful for processing nutrient-rich, storage-stable and ready-to-eat fish head broth.

Dissolved organic carbon (DOC) and labile organic compounds' spatial and temporal variations in coastal Indian groundwater: their bioavailability and transfer to neighboring coastal waters of India.

Submarine groundwater drainage (SGD) changes the elemental composition of the neighboring coastal ocean and impacts the biogeochemical cycles. To examine the seasonal and spatial variability in dissolved organic carbon (DOC) and labile organic compound biochemical compounds like dissolved carbohydrates (TDCHO), dissolved proteins (TDPRO), and dissolved free amino acid (TDFAA) concentrations during the dry and wet periods, groundwater samples were taken at 90 locations (180 samples) along the Indian coast. The mean DOC contents in Indian coastal groundwaters were more significant than the global mean values. DOC, TDCHO, TDPRO, and TDFAA concentrations are higher during wet than dry periods. The DOC and labile organic compound showed a substantial positive association with soil organic carbon, and respective labile compounds in soil, population, and land usage and poor relation with woodland territories, implying that soil organic compounds leaching is a source of DOC and other labile organic compounds into the groundwater. DOC and other labile compounds concentrations were linearly associated with population density, land usage, and sewage production, demonstrating that anthropogenic activities tightly regulate the formation of DOC in groundwater. During the wet and dry periods, total labile organic compounds (TDCHO, TDFAA, and TDPRO) constituted 21% and 10.5% of DOC, respectively. Compared to the wet time, more aromatic compounds accumulated during the dry season but were less bioavailable. SGD DOC flux contributed 2-7% of riverine DOC flux to the coastal ocean. The SGD flux from the Indian subcontinent to the nearby northern Indian Ocean accounts for approximately 2% of the worldwide SGD flux. The effect of DOC flux via SGD on coastal bacterial activity, the plankton food web, and the oxygen minimum zone must be studied.

Effect of lipoxygenase-catalyzed linoleic acid oxidation and 4-hydroxy-2-nonenal on digestibility and gel properties of myofibrillar protein

The oxidative modification of myofibrillar proteins (MPs) has been identified as a crucial factor affecting meat quality during processing. We compared the effects of 4-hydroxy-2-nonenal (HNE) and lipoxygenase (LOX)-catalyzed linoleic acid (LA) oxidation products on the digestibility and gel properties in MPs from bighead carp. Both treatments resulted in decreased free amino acid content, reduced digestibility, and loss of amino acids in MPs. The HNE treatment enhanced gel strength by increasing hydrophobic interactions within the gel matrix. Conversely, the LOX-catalyzed LA oxidation enhanced disulfide bonds, leading to an agglomerated microstructure. Reduced myofibrillar protein (MP) solubility, primarily due to protein aggregation, was observed in the LA group but not in the HNE group. This distinction suggests that the impact on MP functionality is predominantly influenced by the protein aggregation induced by LOX-catalyzed LA oxidation rather than by HNE alone.

Comprehensive analysis of flavor compounds and metabolites of vinasse hairtail fermentation based on GC-IMS and untargeted-based metabolomics

This study focused on investigating the degradation of proteins, metabolites, and flavors during the fermentation of vinasse hairtail, a local specialty fermented food in Zhoushan, China. The whole-protein SDS-PAGE results showed significant degradation of proteins, particularly actin and myosin. Total free amino acid content significantly increased, glutamate, leucine, alanine, and lysine were identified as the primary flavor amino acids conducive to the flavor, with umami, sweet, and bitter amino acids being predominant. The volatile constituents of the vinasse hairtail samples collected before fermentation (0 days) and after fermentation (8 days) were examined using gas chromatography-ion mobility spectrometry (GC-IMS). It revealed a total of 83 volatile flavor compounds, with the relative content of esters increasing and alcohols decreasing during fermentation. The untargeted metabolomics analysis identified 395 unique metabolites; the top 100 metabolites exhibited significant differences, including 52 oligopeptides, 18 organic acids and their derivatives, and 12 lipids and lipid molecules. The metabolic pathways involved in N-glycan biosynthesis, taurine and hypotaurine metabolism, pyrimidine metabolism, glycerophospholipid metabolism, alanine, aspartic acid, and glutamic acid metabolism, tricarboxylic acid cycle, and histidine metabolism. These pathways contribute to the generation of amino acids, sugars, organic acids, and other flavor compounds, ultimately influencing the evolution of the flavor of vinasse hairtail.

새싹인삼 함유 콤부차의 영양성분 및 생리활성

In this study, the physicochemical properties, nutritional components, and antioxidant activities of kombucha containing ginseng sprouts (control kombucha, CT; strawberry kombucha, ST ; strawberry kombucha with 2% ginseng sprout, ST+GS) were analyzed for comparison of quality characteristics. The total content of free amino acids in ST+GS (273.38 mg/100 mL) was 3.2-14.5 times higher than in CT (18.9 mg/100 mL) and ST (84.9 mg/100 mL). The total mineral content in ST+GS (63.99 mg/100 mL) was 3.3-4.1 times higher than those of CT and ST (15.45 and 19.28 mg/100 mL). The contents of soluble phenolic and soluble flavonoid were 1.2 mg GAE/mL and 0.14 mg RE/mL in ST+GS. Several ginsenosides were detected only in ST+GS; ginsenoside Rg2 (2.4 mg/100 mL), Rh1 (4.5 mg/100 mL), F2 (9.0 mg/100 mL), Rg3 (4.6 mg/100 mL), and compound K (7.8 mg/100 mL) were detected. The content of phenolic acids was 1.2-1.5 times higher in ST+GS than in CT and ST. The amount of flavonol of ST+GS was not significantly different from CT but was 1.4 times higher than in ST. In terms of antioxidant activities, the values of ST+GS were significantly higher in comparison to other kombucha samples. These results confirmed that incorporating ginseng sprouts amplifies the advantages of kombucha.

새싹인삼 함유 콤부차의 영양성분 및 생리활성

In this study, the physicochemical properties, nutritional components, and antioxidant activities of kombucha containing ginseng sprouts (control kombucha, CT; strawberry kombucha, ST ; strawberry kombucha with 2% ginseng sprout, ST+GS) were analyzed for comparison of quality characteristics. The total content of free amino acids in ST+GS (273.38 mg/100 mL) was 3.2-14.5 times higher than in CT (18.9 mg/100 mL) and ST (84.9 mg/100 mL). The total mineral content in ST+GS (63.99 mg/100 mL) was 3.3-4.1 times higher than those of CT and ST (15.45 and 19.28 mg/100 mL). The contents of soluble phenolic and soluble flavonoid were 1.2 mg GAE/mL and 0.14 mg RE/mL in ST+GS. Several ginsenosides were detected only in ST+GS; ginsenoside Rg2 (2.4 mg/100 mL), Rh1 (4.5 mg/100 mL), F2 (9.0 mg/100 mL), Rg3 (4.6 mg/100 mL), and compound K (7.8 mg/100 mL) were detected. The content of phenolic acids was 1.2-1.5 times higher in ST+GS than in CT and ST. The amount of flavonol of ST+GS was not significantly different from CT but was 1.4 times higher than in ST. In terms of antioxidant activities, the values of ST+GS were significantly higher in comparison to other kombucha samples. These results confirmed that incorporating ginseng sprouts amplifies the advantages of kombucha.

BjuB05.GS1.4 promotes nitrogen assimilation and participates in the domestication of shoot NUE in Brassica juncea

Elucidating crops' physiological and molecular mechanisms to adapt to low nitrogen environment and promoting nitrogen transfer from senescent leaves to new leaves is crucial in improving Brassica's nitrogen use efficiency (NUE). Glutamine synthetase (GS), a vital gene that helps plants to reassimilate ammonium released from protein degradation in leaves, was the focus of our research. In this study, we identified high (H141) and low NUE genotype (L65) genotypes of Brassica juncea with different responses to low-nitrogen stress. We observed that H141 has a lower nitrate content but higher ammonium and free amino acid contents as well as higher nitrate reductase and GS activities in the shoots. These physiological indicators are responsible for the high NUE of H141. Whole-genome resequencing data revealed that 5,880 genes associated with NUE are polymorphic between H141 and L65. These genes participate in amino acid, carbohydrate, and energy metabolic pathways. Haplotype analysis revealed two haplotypes for BjuB05.GS1.4. Hap1 and Hap2 have multiple single nucleotide polymorphisms or insertions/deletions in the regulatory regions of 5′ and 3′ untranslated regions and introns. Furthermore, the shoot NUE of Hap1 is significantly lower than that of Hap2. The two haplotypes of BjuB05.GS1.4 led to differences in the shoot NUEs of different genetic populations of mustard and are associated with the local soil nitrogen content, suggesting that they might help mustard to adapt to different geographies. In conclusion, the results of our study shed light on the physiological and molecular mechanisms underlying different mustard NUE genotypes and demonstrate the enormous potential of NUE breeding in B.juncea.

Exploring the stress response mechanisms to 2-phenylethanol conferred by Pdr1p mutation in Saccharomyces cerevisiae

BackgroundThe 2-phenylethanol (2-PE) tolerance phenotype is crucial to the production of 2-PE, and Pdr1p mutation can significantly increase the tolerance of 2-PE in Saccharomyces cerevisiae. However, its underlying molecular mechanisms are still unclear, hindering the rational design of superior 2-PE tolerance performance.ResultsHere, the physiology and biochemistry of the PDR1_862 and 5D strains were analyzed. At 3.5 g/L 2-PE, the ethanol concentration of PDR1_862 decreased by 21%, and the 2-PE production of PDR1_862 increased by 16% than those of 5D strain. Transcriptome analysis showed that at 2-PE stress, Pdr1p mutation increased the expression of genes involved in the Ehrlich pathway. In addition, Pdr1p mutation attenuated sulfur metabolism and enhanced the one-carbon pool by folate to resist 2-PE stress. These metabolic pathways were closely associated with amino acids metabolism. Furthermore, at 3.5 g/L 2-PE, the free amino acids content of PDR1_862 decreased by 31% than that of 5D strain, among the free amino acids, cysteine was key amino acid for the enhancement of 2-PE stress tolerance conferred by Pdr1p mutation.ConclusionsThe above results indicated that Pdr1p mutation enhanced the Ehrlich pathway to improve 2-PE production of S. cerevisiae, and Pdr1p mutation altered the intracellular amino acids contents, in which cysteine might be a biomarker in response to Pdr1p mutation under 2-PE stress. The findings help to elucidate the molecular mechanisms for 2-PE stress tolerance by Pdr1p mutation in S. cerevisiae, identify key metabolic pathway responsible for 2-PE stress tolerance.

Mechanism and threshold of environmental stressors on seagrass in high-turbidity estuary: case of Zostera japonica in Yellow River Estuary, China

Zostera japonica (Z. japonica), the most widely distributed seagrass species in temperate estuaries, has experienced a dramatic decline of nearly 75% over the past decade. While previous research has investigated the adaptation of seagrass individuals and populations to single stress factors, the molecular mechanisms underlying the interaction of multiple stressors remain poorly understood. This study conducted laboratory experiments to examine the response of Z. japonica at different life stages to environmental pressures, specifically salinity and turbidity, as indicated by changes in free amino acids (FAAs). The results demonstrate that Z. japonica exhibits stronger adaptability to high salinity environments but displays weaker adaptability to freshwater conditions. Through single stress experiments, the salinity and turbidity thresholds for FAA homeostatic disturbance in Z. japonica were determined at seedling, juvenile, and mature stages. As Z. japonica matures, its metabolic pathways expand and diversify, allowing the regulation of key FAAs to enhance stress resistance. Turbidity stress exerts a more pronounced negative impact on the cellular homeostasis of Z. japonica compared to salinity stress, and when turbidity levels exceed 150 NTU, they significantly intensify the negative effects of salinity stress on the seagrass. Furthermore, under strong salinity-turbidity interactions, the concentration of key FAAs generally decreases by 20-30%, indicating inhibition of growth and development in Z. japonica. These findings have important implications for the conservation of intertidal seagrass beds and estuarine ecosystems in the face of multiple human activities and environmental stressors. The study provides valuable insights into the molecular mechanisms underlying Z. japonica’s adaptations to salinity and turbidity stress, contributing to the development of targeted strategies to mitigate the impacts of environmental pressures on seagrass populations and promote the resilience of these critical marine ecosystems.