Aroma dynamic characteristics during the process of variable-temperature final firing of Congou black tea by electronic nose and comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry

The drying technology is crucial to the quality of Congou black tea. In this study, the aroma dynamic characteristics during the variable-temperature final firing of Congou black tea was investigated by electronic nose (e-nose) and comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC × GC-TOFMS). Varying drying temperatures and time obtained distinctly different types of aroma characteristics such as faint scent, floral aroma, and sweet fragrance. GC × GC-TOFMS identified a total of 243 volatile compounds. Clear discrimination among different variable-temperature final firing samples was achieved by using partial least squares discriminant analysis (R2Y = 0.95, Q2 = 0.727). Based on a dual criterion of variable importance in the projection value (VIP > 1.0) and one-way ANOVA (p < 0.05), ninety-one specific volatile biomarkers were identified, including 2,6-dimethyl-2,6-octadiene and 2,5-diethylpyrazine with VIP > 1.5. In addition, for the overall odor perception, e-nose was able to distinguish the subtle difference during the variable-temperature final firing process.

Prevalence and correlates of overweight and obesity among adolescents in northeastern China: a cross-sectional study

OBJECTIVES

To estimate the prevalence of overweight/obesity among adolescents and evaluate the associated factors in this group in Changchun City in northeastern China.

METHODS

A cross-sectional study of 1955 adolescents aged 11-18 years was conducted in Changchun City using stratified cluster sampling. Parents and caregivers of children completed the questionnaires as requested without objection. The questionnaire included demographic characteristics and anthropometric parameters. Univariate and multivariate logistic regression analyses were performed to analyse the relationship between overweight/obesity and related factors.

RESULTS

In total, the prevalence of overweight was 12.7% (male 17.4%; female 10.1%) and of obesity was 4.9% (male 8.8%; female 3.1%) in Changchun, Jilin Province. The prevalence of overweight and obesity was higher in boys than in girls (p<0.001). Multivariate logistic regression showed that overweight and obesity were significantly associated with male sex (OR=1.91, 95% CI 1.48 to 2.47), eating fresh fruits more than 2 days per week (OR=1.41, 95% CI 1.09 to 1.84) and eating quickly (OR=1.37, 95% CI 1.06 to 1.78). Students who were not picky (OR=0.69, 95% CI 0.53 to 0.90) were less likely to be overweight, and adolescents whose father was overweight or obese (OR=0.67, 95% CI 0.52 to 0.86) or whose mother was overweight or obese (OR=0.72, 95% CI 0.52 to 0.99) were less likely to be overweight.

CONCLUSION

The prevalence of overweight and obesity among adolescents in Changchun has been high in recent years, and the prevalence was higher among boys than among girls. Sex, dietary habits (weekly frequency of fruit consumption, picky eating and slowness in eating) and parental weight were important factors for overweight and obesity in adolescents. Further research should be conducted on the health of adolescents in China, and further intervention measures should be implemented to reduce the prevalence of overweight/obesity.

[Effect of fragmented sleep on postoperative cognitive function and central neuroinflammation]

Objective: To investigate the effect of sleep fragmentation on perioperative neurocognitive disorders (PND) and central neuroinflammation by simulating sleep patterns of postoperative patients with sleep fragmentation in aged mice. Methods: Thirty-two elderly ICR mice were randomly divided into four groups (n=8): normal group (C), surgery group (S), fragmented sleep group (F), and surgery+fragmented sleep group (D). Fragmented sleep was conducted after internal fixation of tibia fractures, cognitive function was evaluated by novel object recognition (NOR) and fear conditioning (FC) test, and changes in expression of inflammatory cytokines in hippocampus were detected by ELISA. Results: NOR test: the recognition index (RI) of mice in group C, group S, group F and group D was 0.69±0.07, 0.48±0.07, 0.54±0.10 and 0.50±0.12, respectively. The RI of mice in group S, group F and group D was significantly lower than that in group C (t=4.885, 3.521 and 4.433, all P<0.01). There was no significant difference in RI between group S and group D (t=0.967 1, P>0.05). Contextual FC test: the freezing time of mice in group C, group S, group F and group D was(21.34±6.48), (13.83±4.26), (11.50±6.25) and (6.17±4.77) s, respectively. The freezing time of mice in group S, group F and group D was significantly lower than that in group C (t=2.722, 3.566, 5.496, P<0.05 or P<0.01). The freezing time of mice in group D was significantly lower than that in group S (t=2.774, P<0.05). Cue FC test: the freezing time of mice in group C, group S, group F and group D was (74.36±17.09), (43.91±9.71), (46.34±13.43) and (24.90±14.21) s, respectively. The freezing time of mice in group S, group F and group D was significantly lower than that in group C (t=4.393, 4.043 and 7.136, all P<0.01). The freezing time of mice in group D was significantly lower than that in group S (t=2.743, P<0.05). The levels of TNF-α, IL-6 and IL-1β in hippocampus of mice in group S, F and D were significantly higher than those in group C, while the levels of TNF-α and IL-6 in hippocampus of mice in group D were significantly higher than those in group S, with statistically significant differences (P<0.05 or P<0.01). Conclusion: Postoperative fragmented sleep aggravates postoperative cognitive impairment and increases the hippocampal neuroinflammation in aged mice.

Influence of fixation methods on the chestnut-like aroma of green tea and dynamics of key aroma substances

Fixation is the key process to ensure green tea quality; however, the effect of various fixation methods on the formation of green tea with a chestnut-like aroma and the evolution of key volatile compounds has not been assessed to date. In this study, we compared four types of fixation methods for green tea: roller-hot air-steam, roller-hot air, roller-steam, and single roller. Infrared-assisted headspace solid-phase microextraction and gas chromatography-tandem dual mass spectrometry technology were used to detect the volatile compounds of green tea samples during processing. Partial least-squares discriminant analysis (PLS-DA), multiple experiment viewer (MEV), odor activity value (OAV), and least-significant difference analyzes were then applied to clarify the best fixation method for forming a chestnut-like aroma and associated compounds, and to explore the change law of key volatile compounds using different green tea fixation processes. One hundred and eighty-four volatile compounds were detected in the processed samples, with roller-hot air fixation found as the optimal method for generating an intense and long-lasting chestnut-like aroma and floral taste, based on sensory evaluation. The PLS-DA model clearly distinguished the four kinds of fixation samples and obtained 32 differential volatile compounds. Combining OAVs with screening by MEV analysis, 2,6,10,10-tetramethyl-1-oxaspiro [4.5] dec-6-ene, linalool, cedrol, 3-methyl-butanal, trans-β-ionone, and τ-cadinol emerged as key differential volatile compounds between green teas with and without a chestnut-like aroma. The evolution of these six differential volatile compounds throughout the tea-making process confirmed that rolling-hot air coupling treatment is most conducive to produce a chestnut-like aroma, which is beneficial to form and transform 2,6,10,10-tetramethyl-1-oxaspiro[4.5] dec-6-ene, 3-methyl-butanal, and τ-cadinol with baking aromas and fruity substances. These results provide a theoretical basis and technical guidance for the precise and directional processing of high-quality green tea with a chestnut-like aroma.

A robust model for estimating thermal conductivity of liquid alkyl halides

Thermal conductivity is an essential thermodynamic property in chemical engineering application. As a result, estimating the thermal conductivity of organic compounds is of significance in industry production. Alkyl halides are important organic intermediates and raw materials, but little investigations have been performed to estimate their thermal conductivity. In this study, the structures of compounds were optimized in Gaussian 09W and molecular descriptors were extracted by Dragon software. Finally, we developed a 6-descriptor linear quantitative structure-property relationship (QSPR) model to estimate the thermal conductivity of alkyl halides using the genetic function approximation (GFA) method. Validation proved that the developed model had goodness-of-fit, robustness and predictive ability. The r²_pred and root-mean-square error (RMSE_P) of prediction set for the model were equal to 0.9745 and 0.0035, respectively. Meanwhile, the applicability domain was visualized by means of the Williams plot. This study provides a new model for estimating the thermal conductivity of this important class of chemicals.

[Spectrum analysis of pathological classification in 463 cases with nasal and paranasal sinuses malignant tumors]

Objective:The characteristics of pathological histological classification of nasal and paranasal sinuses malignant tumors in the past 10 years were analyzed, so as to provide possible basis, direction and ideas for the development of relevant effective treatment measures for nasal and paranasal sinuses malignant tumors in clinical practice. Method:The clinical data of patients with nasal and paranasal sinuses malignant tumors admitted to PLA general hospital from January 2009 to December 2018 were collected. Pathological types were retrospectively analyzed, and disease spectrum distribution, composition ratio and variation tendency of these patients were calculated. Result:Among the 463 patients, the overall pathological types in the top 5 were as follows: squamous cell carcinoma, adenoid cystadenocarcinoma, olfactory neuroblastoma, melanoma, adenocarcinoma. As for male patients, the pathological types in the top 5 were squamous cell carcinoma, adenoid cystic carcinoma, olfactory neuroblastoma, adenocarcinoma, neuroendocrine carcinoma and rhabdomyosarcoma were tied for fifth; the top 5 most common pathological types in female patients were squamous cell carcinoma, adenoid cystic carcinoma, melanoma, rhabdomyosarcoma, and adenocarcinoma. From 2009 to 2013, there were 183 patients with nasal and paranasal sinuses malignant tumors, the top 5 pathological types were squamous cell carcinoma, adenoid cystadenocarcinoma, olfactory neuroblastoma, melanoma, neuroendocrine carcinoma and rhabdomyosarcoma were tied for fifth; From 2014 to 2018, 280 patients with nasal and paranasal sinuses malignant tumors were diagnosed, the top 5 pathological types were squamous cell carcinoma, adenoid cystadenocarcinoma, melanoma, adenocarcinoma, and rhabdomyosarcoma. The ratio of the number of patients from 2009 to 2013 and 2014 to 2018 was about 0.65∶1. Malignant tumors of the nasal and paranasal sinuses tend to occur between the ages of 41 and 60, and the pathological types in the top 5 were squamous cell carcinoma,adenoid cystic carcinoma, adenocarcinoma, melanoma, neuroendocrine carcinoma. Conclusion:Malignant tumors of nasal cavity and sinus were more common in male, and the pathological types such as squamous cell carcinoma, adenoid cystic carcinoma, olfactory neuroblastoma were more common. All age groups have the disease, but the age group of 41-60 years old is the high-risk group of nasal and nasal sinus malignant tumors. However, the incidence rate of melanoma has gradually increased in the past five years, which needs to be paid more attention to.

Immobilization of the engineered Raoultella ornithinolytica BF60 for biocatalytic synthesis of 2, 5-furandicarboxylic acid

As a bio-based platform chemical, 2, 5-furandicarboxylic acid (FDCA) is a promising substitute of terephthalic acid to synthesize poly (ethylene furanoate) used for bio-substitute of polyethylene terephthalate (PET). In previous work, we engineered a Raoultella ornithinolytica BF60 strain and achieved the effective biocatalytic synthesis of FDCA from 5-hydroxymethylfurfural (HMF). Herein, to improve the reusability of the engineered R. ornithinolytica BF60 cells, we used two materials PVA1799-boric acid and sodium alginate-Ca2+ to immobilize the cells. The sodium alginate-Ca2+ was more suitable for FDCA production, and 22 mmol/L FDCA was obtained with Ca(H2PO4)2 as the cross-linker. In addition, the immobilization conditions were optimized and FDCA production was further increased to 74.8 mmol/L. Here the developed immobilization strategy for R. ornithinolytica BF60 cells may be helpful for the economical production of FDCA in the future.

Biocatalytic production of 2,5-furandicarboxylic acid: recent advances and future perspectives

2,5-Furandicarboxylic acid (FDCA) is attracting increasing attention because of its potential applications as a sustainable substitute to petroleum-derived terephthalic acid for the production of bio-based polymers, such as poly(ethylene 2,5-furandicarboxylate) (PEF). Many catalytic methods have been developed for the synthesis of FDCA, including chemocatalysis, biocatalysis, photocatalysis, and electrocatalysis. Biocatalysis is a promising approach with advantages that include mild reaction condition, lower cost, higher selectivity, and environment amity. However, the biocatalytic production of FDCA has hardly been reviewed. To fully understand the current research developments, this review comprehensively considers the research progress on toxic effects and biodegradation of furan aldehydes, and then summarizes the latest achievements concerning the synthesis of FDCA from 5-hydroxymethylfurfural and other chemicals, such as 2-furoic acid and 5-methoxymethylfurfural. Our primary focus is on biocatalytic methods, including enzymatic catalysis (in vitro) and whole-cell catalysis (in vivo). Furthermore, future research directions and general developmental trends for more efficient biocatalytic production of FDCA are also proposed.

Quality Evaluation of Green and Dark Tea Grade Using Electronic Nose and Multivariate Statistical Analysis

Aroma assessment remains difficult and uncertain in the present sensory assessment system. It is highly desirable to develop a new assessment method to discriminate the quality of various teas in the tea market. In the present work, based on linear discriminant analysis and principal component analysis, the aroma of dry and wet samples of different Xi-hu Longjing and Pu-erh teas were tested and differentiated by electronic noses (e-nose). The results confirm that e-nose can discriminate different priced Xi-hu Longjing tea samples in the range of 80-800 RMB/500 g and varying storage years of Pu-erh tea samples. Furthermore, for the detection of both dry and wet samples of Longjing and Pu-erh teas, the results reveal that all samples have specific aroma characteristics that e-nose can recognize. More importantly, contribution analysis in sensors indicates that nitrogen oxides, methane and alcohols are the characteristic components that contribute to the fragrances of different priced Xi-hu Longjing teas, while nitrogen oxides, aromatic benzene and amines make the fragrances of Pu-erh teas with different storage years disparate. PRACTICAL APPLICATION: This work demonstrates that e-nose can rapidly distinguish tea products with different price levels and varying storage years. With the advantages of ease of use, high portability and flexibility, e-nose will be widely expanded and applied in refined processing and the development of flavored foods.

Rutin, γ-Aminobutyric Acid, Gallic Acid, and Caffeine Negatively Affect the Sweet-Mellow Taste of Congou Black Tea Infusions

The sweet-mellow taste sensation is a unique and typical feature of premium congou black tea infusions. To explore the key taste-active compounds that influence the sweet-mellow taste, a sensory and molecular characterization was performed on thirty-three congou black tea infusions presenting different taste qualities, including the sweet-mellow, mellow-pure, or less-mellow taste. An integrated application of quantitative analysis of 48 taste-active compounds, taste contribution analysis, and further validation by taste supplementation experiments, combined with human sensory evaluation revealed that caffeine, γ-aminobutyric acid, rutin, succinic acid, citric acid, and gallic acid negatively affect the sweet-mellow taste, whereas glucose, sucrose, and ornithine positively contribute to the sweet-mellow taste of congou black tea infusions. Particularly, rutin, γ-aminobutyric acid, gallic acid, and caffeine, which impart the major inhibitory effect to the manifestation of the sweet-mellow taste, were identified as the key influencing components through stepwise screening and validation experiments. A modest level of these compounds was found to be favorable for the development and manifestation of the sweet-mellow taste. These compounds might potentially serve as the regulatory targets for oriented-manufacturing of high-quality sweet-mellow congou black tea.

Methylene blue attenuates renal ischemia-reperfusion injury by negative regulation of NLRP3 signaling pathway

OBJECTIVE

To investigate the effect of methylene blue (MB) on renal ischemia-reperfusion (IR) injury in mice and its possible relevant mechanisms.

MATERIALS AND METHODS

A total of 30 male C57/BL6 mice aged 4 months old were randomly divided into the following three groups: Sham group (n=10), IR group (n=10), and MB group (n=10). Mice in MB group were treated with gavage continuously using methylene blue solution (dosage: 25 mg·kg-1·d-1) until they were 7 months old. Mice in the other two groups were administrated with the same amount of normal saline for gavage. After that, the abdomen of mice in Sham group was opened and closed, and bilateral renal pedicles of mice in IR group and MB group were occluded using a micro-artery clamp for 45 min for modeling. After modeling, the renal tissues and blood samples of mice were taken for detection. The levels of serum creatinine (Scr), blood urea nitrogen (BUN), and malondialdehyde (MDA), and activity of superoxide dismutase (SOD) in mice in each experimental group were detected and statistically analyzed, respectively. The degree of renal tubular necrosis in renal tissues of mice was observed under an optical microscope. Enzyme-linked immunosorbent assay (ELISA) was used to detect the levels of inflammatory factors [interleukin-1β (IL-1β), IL-18, IL-10 and transforming growth factor-β1 (TGF-β1)] in renal tissues of mice in each experimental group, followed by relevant statistical analyses. The expressions of relevant proteins [NACHT, LRR, and PYD domains-containing protein 3 (NLRP3), nuclear factor-κB (NF-κB), caspase-1, pro-IL-1β, and IL-1β] in renal tissues of mice in each experimental group were detected via Western blotting, and the gray value of each band was detected for statistical analysis.

RESULTS

It was found in this experimental study that Scr and BUN levels in MB group were significantly lower than those in IR group, and the differences were statistically significant (p<0.05). Compared with that in IR group, the degree of renal tubular necrosis in MB group was significantly alleviated, and the difference was statistically significant (p<0.05). Compared with those in IR group, the levels of inflammatory factors (IL-1β and IL-18) in MB group were significantly decreased, but the levels of IL-10 and TGF-β1 in MB group were significantly increased, and the differences were statistically significant (p<0.05). Compared with those in IR group, the activity of SOD in MB group was increased significantly, but the level of MDA was decreased, and the differences were statistically significant (p<0.05). The protein expressions of NLRP3, NF-κB, caspase-1, and pro-IL-1β in MB group were decreased compared with those in IR group, but the expression of IL-1β in MB group was increased, and the differences were statistically significant (p<0.05).

CONCLUSIONS

We showed that methylene blue can alleviate the apoptosis and inflammatory response induced by renal IR injury in mice, and its relevant mechanism may be related to the fact that methylene blue can negatively regulate NLRP3 signaling pathway.

Trehalose Production Using Recombinant Trehalose Synthase in Bacillus subtilis by Integrating Fermentation and Biocatalysis

Trehalose, a stable nonreducing disaccharide, protects biomolecules against environmental stress. However, trehalose production using secretory trehalose synthase (TreS) by Bacillus subtilis has not been well studied. In this study, a mutant TreS was successfully secreted and expressed in B. subtilis WB800N. The extracellular enzyme activity of TreS regulated by the P₄₃ promoter and SP_PhoD signal peptide in recombinant B. subtilis WB800N reached 23080.6 ± 1119.4 U/L in a 5-L fermenter after optimizing the culture medium, while xpF, skfA, lytC, and sdpC were knocked out. To reduce maltose consumption, malP and amyE corresponding to maltose transporters were further deleted. To simplify the trehalose production process, we invented a fermentation-coupling biocatalysis process involving recombinant bacteria fermentation to secrete TreS and simultaneous conversion of maltose to trehalose by TreS and found that the conversion rate of maltose to trehalose reached 75.5%, suggesting that this is an efficient strategy for large-scale trehalose production using recombinant B. subtilis.

Normal human skin is superior to monkey oesophagus substrate for detection of circulating BP180-NC16A-specific IgG antibodies in bullous pemphigoid

BACKGROUND

Bullous pemphigoid (BP) is the most common autoimmune subepidermal blistering skin disease. Two antigens have been identified as targets of circulating autoantibodies (autoAbs) - BP180 and BP230 - with BP180 being a critical transmembrane adhesion protein of basal keratinocytes of the epidermis. The noncollagenous domain 16A (NC16A) of BP180 is the immunodominant epitope in patients with BP, and anti-BP180-NC16A IgG antibodies (Abs) correlate to disease activity. Routine serological testing and follow-up of BP relies on indirect immunofluorescence (IIF) of serum Abs, commonly performed on monkey oesophagus (ME), and/or enzyme-linked immunosorbent assay (ELISA) testing on recombinantly produced fragments of BP180 and BP230 (BP180-NC16A, BP230-C/N).

OBJECTIVES

To determine if NC16A epitopes are well represented on ME substrate.

METHODS

Sera from different BP cohorts were tested by IIF on ME and normal human skin (NHS). To confirm findings, affinity-purified anti-BP180-NC16A/BP230 polyclonal Abs and recombinant anti-BP180-NC16A/BP230 monoclonal antibodies (mAbs) were used.

RESULTS

For sensitive detection of BP180-NC16A-specific IgG Abs, sections of NHS are superior to the widely used ME. Confirmation comes from polyclonal affinity-purified anti-BP180-NC16A/BP230 Abs, and by mAbs cloned from a patient with active BP.

CONCLUSIONS

Use of NHS is preferable over ME in routine IIF testing for BP. These results are of clinical relevance because anti-BP180-NC16A IgG titres are correlated to disease activity and detecting them reliably is important for screening, diagnosis and follow-up of patients with BP.