Search

This study investigated high-throughput screening of inhibitors for the key enzyme CitE in the synthesis of red yeast citrinin through computer simulation. First, Alphafold 2 was used to build the homology model of CitE. and it was aligned with similar sequences to predict the ligand binding region. Subsequently, a ligand library of 20 000 compounds was constructed by searching for natural ligands and flavonoid skeleton analogues in the Arthur database. Afterwards, molecular docking of the CitE protein to the library of small molecule compounds was performed using Maestro to select potential CitE ligands. Gromacs kinetic simulation was used to evaluate the binding stability, and the binding free energy was calculated using MM/PBSA. The protein-ligand binding mode was analyzed, confirming that six small molecule ligands including quercetin, luteolin, apigenin, genistein, 5,4’-dihydroxyflavone, and fisetin had strong CitE binding activities. The results from solid and liquid state fermentation showed that the above compounds exhibited significant inhibitory activity against Monascus citrinin production. Specifically, the addition of these compounds in solid state fermentation (20 mg/28 g of dry material) resulted in a reduction of Monascus citrinin production by 42.52%, 48.81%, 32.54%, 32.57%, 21.02%, and 13.67%, respectively, while their addition in liquid state fermentation (0.1 g/L) led to a reduction by 33.77%, 15.58%, 33.33%, 62.34%, 58.87%, and 50.22%, respectively. In summary, this study is of reference significance for establishing an efficient and safe Monasucs fermentation system.

In this study, Lactobacillus paracasei FP02, a strain isolated from pickled Chinese cabbage, was tested for its capability to reduce uric acid in vitro, and its physiological and biochemical characteristics were characterized. Furthermore, the effect of this strain on the serum uric acid level of a hyperuricemic (HUA) rat model was explored. The in vitro results showed that L. paracasei FP02 degraded uric acid and its precursor substances, inosine and guanosine, by 29.10%, 67.09%, and 70.48%, respectively, and inhibited xanthine oxidase (XOD) activity by 64.20%. Simultaneously, this strain could ferment various sugars (alcohols) and exhibited good tolerance to gastric acid and bile salts. The 14-day continuous intragastric administration of freeze-dried L. paracasei FP02 powder reduced the serum uric acid concentration by 49.96% compared to the hyperuricemia model group (P < 0.001), which was established by intragastric administration of potassium oxonate combined with high dietary uric acid. After the treatment, the serum uric acid concentration approached the levels observed in the blank control group. Additionally, in the FP02 treatment group, uric acid excretion in the urine increased, and serum XOD activity was significantly inhibited (P < 0.001). Renal sections showed that renal injury was partially restored in the FP02 treatment group. This study will lay the foundation for the development of L. paracasei FP02 as a potential drug or functional food for preventing HUA.

In this study, the genomes of 19 Latilactobacillus curvatus and 40 L. sakei strains were comparatively analyzed. Average nucleic acid identity (ANI) and genome-wide colinearity indicated that the genomes of L. curvatus and L. sakei had weak nucleotide sequence homology, allowing them to be used as indicators to distinguish the two species. Pangenomes for these species were constructed, whose core gene functions were annotated. The results showed that the core genomes of L. curvatus and L. sakei were mainly involved in their basic metabolism. Analysis of individual genomes of the strains revealed that 1) both L. curvatus and L. sakei contained a wide range of genes encoding glycoside hydrolases, which are abundant genetic resources for catabolizing and metabolizing dietary fiber such as polysaccharides, lactose utilization, and lignocellulose; 2) antibiotic resistance genes were annotated in the genomes of three strains, which originate from horizontal gene transfer; 3) the unique arginine deiminase pathway of L. sakei, the serine dehydratase and guanine deaminase pathways of L. curvatus, and the glutamate decarboxylase pathway of several strains were identified, revealing that the acid tolerance mechanisms of these two species are different; and 4) genes encoding cold stress proteins were discovered, which endow the two species with good cold processing properties. Moreover, the genomes of some L. sakei strains contained gene clusters related to the biosynthesis of lactocin S and condensin. In conclusion, this study established taxonomic criteria for the two species and information on individual differences between their strains, which will provide a basis for the study of the physiological, biochemical, molecular genetic mechanisms of L. curvatus and L. sakei and their industrial applications.

Purpose: To compare the structure and antioxidant activity of arabinoxylan (AX) extracted from wheat bran of different varieties by different methods. Methods: AX was extracted from wheat bran from the cultivars ‘Bainong 207’, ‘Baihan 207’, ‘Guanmai 1’, ‘Huayu 198’ and ‘Huayu 166’ by alkali extraction, ultrasonic-assisted xylanase extraction or ultrasonic-assisted cellulase extraction, and its chemical composition, relative molecular mass, molecular structure, thermal stability and antioxidant activity were determined. Results: Among the three extraction methods, alkali extraction gave higher levels of AX yield and total sugar content, while enzymatic extraction retained polyphenols to a greater extent, which may contribute to the better antioxidant capacity of the AX-rich extract, but reduced the relative molecular mass of AX to a certain extent. The monosaccharide composition of enzymatically extracted AX was significantly different from that of alkali extracted AX, and the glycosidic linkage types in enzymatically extracted AX were more complex. Compared with ultrasonic-assisted cellulase extraction, higher AX yield and total sugar content were obtained using ultrasound-assisted xylanase, while the polyphenol content of AX obtained by ultrasound-assisted cellulase extraction was higher, and monosaccharide composition and glycosidic linkage types were also different between AXs extracted by the two enzymatic methods. In addition, the relative molecular mass, the monosaccharide composition, and the types and proportions of glycosidic linkage of AX extracted from wheat bran of different varieties were different. Conclusion: The structure and activity of AX extracted from wheat bran by alkali extraction, ultrasonic-assisted xylanase extraction and ultrasonic-assisted cellulase extraction were obviously different. Compared with alkali extraction, AX obtained by enzymatic extraction had lower yield and molecular mass, but higher polyphenol content and better antioxidant performance. Compared with ultrasound-assisted cellulase extraction, AX obtained by ultrasound-assisted xylanase extraction had higher yield and total sugar content, but lower polyphenol content. The structure of wheat bran AX varied with different extraction methods and varieties.

Intestinal tract is the major organ for digestion and absorption of food nutrients. The establishment of an effective intestinal ex vivo model is helpful to promote the development of a novel evaluation system for absorption and efficacy of food nutrients and functional active substances. Based on the intestinal crypt containing intestinal stem cells, we created an integrated set of organoid culture of different intestinal segments (including duodenum, jejunum and ileum) of mouse through optimizing the isolation method of intestinal crypt from different intestinal segment and the composition of culture medium. In addition, RT-PCR and immunofluorescence results demonstrated that the organoids derived from different segment recapitulate the structural characteristics and cell composition of corresponding intestinal tissues. These characters had high stability during in vitro repeated passage. In short, the establishment of orgnaoid culture of different intestinal segment may provide a promising ex vivo model for the evaluation of absorption and function of food nutrients in the food research field. [ABSTRACT FROM AUTHOR]

The analysis of the feedback effect of air pollution on the process of urbanization is the key to perfecting the research framework of the interaction mechanism between air pollution and urbanization, and is also an important reference for the collaborative promotion of ecological civilization construction and new urbanization. In view of this, this article used night time light data to reflect the comprehensive level of urbanization, selected the annual average PM2.5 concentration of 281 prefecture-level cities and above in China from 2013 to 2018 to measure air pollution, explored the feedback effect of air pollution on the process of urbanization and mechanism of action, and analyzed the heterogeneity on this basis. The results of the study showed that: 1 Air pollution had a significant negative feedback effect on the level of urbanization. This conclusion was still valid under a series of robustness tests and endogenous tests. 2 Urban population scale and economic development were two important mechanisms of air pollution affecting the process of urbanization. Air pollution had significant negative effects on urban population scale and economic development, and further producing negative feedback effects on urbanization through these two channels. 3 The feedback effect of air pollution on urbanization had urban heterogeneity. Air pollution had a more significant negative feedback effect on the urbanization process of northern cities, central and northeastern regions, and large and medium-sized cities; in addition, the two demonstrated a significant 'inverted U-shaped' curve relationship in the south area of the Qinling-Huaihe line, indicating that the feedback effect of air pollution on the urbanization process had nonlinear characteristics. In response to the above research conclusions, this article believes that the reduction of pollutant gas is still an effective measure to alleviate the negative feedback effect of air pollution on the urbanization process, and the intensive and efficient promotion of the urbanization process is a fundamental measure; it is essential to implement a proactive talent introduction policy and use innovation to change the extensive economic growth structure to alleviate the negative feedback effect of air pollution on urbanization. Furthermore, in the process of preventing and controlling pollution in large and medium cities, we must be alert to the development trend of air pollution in small cities. [ABSTRACT FROM AUTHOR]