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636 results on '"Xu Zheng-Hong"'

157. The tale of a versatile enzyme: Molecular insights into keratinase for its industrial dissemination

Author

Su, Chang, Gong, Jin-Song, Qin, Jiufu, Li, Heng, Li, Hui, Xu, Zheng-Hong, Shi, Jin-Song, Su, Chang, Gong, Jin-Song, Qin, Jiufu, Li, Heng, Li, Hui, Xu, Zheng-Hong, and Shi, Jin-Song

Abstract

Keratinases are unique among proteolytic enzymes for their ability to degrade recalcitrant insoluble proteins, and they are of critical importance in keratin waste management. Over the past few decades, researchers have focused on discovering keratinase producers, as well as producing and characterizing keratinases. The application potential of keratinases has been investigated in the feed, fertilizer, leathering, detergent, cosmetic, and medical industries. However, the commercial availability of keratinases is still limited due to poor productivity and properties, such as thermostability, storage stability and resistance to organic reagents. Advances in molecular biotechnology have provided powerful tools for enhancing the production and functional properties of keratinase. This critical review systematically summarizes the application potential of keratinase, and in particular certain newly discovered catalytic capabilities. Furthermore, we provide comprehensive insight into mechanistic and molecular aspects of keratinases including analysis of gene sequences and protein structures. In addition, development and current advances in protein engineering of keratinases are summarized and discussed, revealing that the engineering of protein domains such as signal peptides and pro-peptides has become an important strategy to increase production of keratinases. Finally, prospects for further development are also proposed, indicating that advanced protein engineering technologies will lead to improved and additional commercial keratinases for various industrial applications.

Published
2020

177. Changes in physicochemical characteristics and metabolites in the fermentation of goji juice by Lactiplantibacillus plantarum.

Author

Xie, Han, Gao, Pengyan, Lu, Zhen-Ming, Wang, Fang-Zhou, Chai, Li-Juan, Shi, Jin-Song, Zhang, Hui-Ling, Geng, Yan, Zhang, Xiao-Juan, and Xu, Zheng-Hong

Subjects
ORGANIC acids, FERMENTATION, MULTIVARIATE analysis, METABOLITES, UMAMI (Taste), AMINO acids, TRYPTOPHAN
Abstract

Untargeted and targeted metabolomics based on LC-MS/MS was applied here to investigate the changes in metabolites following Lactiplantibacillus plantarum (L. plantarum) fermentation of goji juice. The changes in physicochemical characteristics, free amino acid and organic acid levels were quantified. Total phenols, total flavonoids, and antioxidant activity were increased after these L. plantarum fermentation. 31 primary metabolites were screened out by comparison between two groups using multivariate statistical analysis. L. plantarum consumed reducing sugar and most varieties of amino acids. Gamma amino butyric acid (GABA) and phenylacetaldehyde were significantly accumulated via precursor of glutamate and phenylalanine, respectively. Indole-3-lactic acid (ILA) was the characteristic secondary metabolite after fermentation. There were 6.25 and 4.19 mg/L ILA accumulated after LP-D and LP-F fermentation, respectively, whereas it was not detected in goji juice. The accumulation of tyrosol was strain-dependent. Part of the bitter-taste amino acids, including l -methinoine, l -phenylalanine and tryptophan, were converted into their corresponding acetyl-derivatives, which represented umami or kokumi taste. Overall, fermentation by L. plantarum strains altered the metabolite profile and increased the levels of several biologically active substances of goji juice. These results deepen the understanding of L. plantarum metabolism, and the bioconversion associated with flavor and bioactive compounds unraveled here can be used as references in other plant-based materials for LAB fermentation. [ABSTRACT FROM AUTHOR]

Published
2023
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178. Comparative genomics of Clostridium tyrobutyricumreveals signatures of environment-specific adaptation and metabolic potentials

Author

Fang, Guan-Yu, Chai, Li-Juan, Lu, Zhen-Ming, Zhang, Xiao-Juan, Xu, Hong-Yu, Wang, Song-Tao, Shen, Cai-Hong, Shi, Jin-Song, and Xu, Zheng-Hong

Abstract

Clostridium tyrobutyricumis a promising microbial host for the anaerobic production of bio-based chemicals, especially butyric acid. However, the limited genetic traits of C. tyrobutyricumresulted in its constrained applicability in the food industry due to the absence of publicly available data. We performed a comparative genomic analysis of 13 C. tyrobutyricumstrains isolated from different habitats to investigate the adaptation mechanisms and metabolic potentials of the C. tyrobutyricumstrains isolated from fermentation environments (FE). The results showed that the genetic diversity of FE- associated C. tyrobutyricumstrains was higher than that of strains isolated from non-fermentation environments (NFE). Based on evaluating safety-related genes, FE-associated strains were likely non-pathogenic to humans or animals. Many environmental adaptation-related genes involved in energy production and conversion, phosphotransferase system (PTS), etc., were significantly enriched in FE-associated strains, which was conducive to their survival in the corresponding habitats. The analysis of carbohydrate-active enzymes revealed that the CAZyme categories of glycoside hydrolases (GHs) and carbohydrate esterases (CEs) were found to be significantly enriched in FE-associated strains, which was beneficial for carbohydrate utilization (including starch, cellulose, etc.). Fermentation experiments revealed that strains isolated from the Chinese liquor fermentation environment were capable of decomposing carbohydrates and producing organic acids. Collectively, this study provided insights into the genomic features of C. tyrobutyricumand the theoretical basis for further use, research, and development of these strains.

Published
2024
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179. Deciphering the effects of different types of high-temperature Daqu on the fermentation process and flavor profiles of sauce-flavor Baijiu

Author

Shi, Wei, Chai, Li-Juan, Zhao, Han, Song, Ya-Ning, Mei, Jun-Lan, He, Yang-Xue, Lu, Zhen-Ming, Zhang, Xiao-Juan, Yang, Bo, Wang, Song-Tao, Shen, Cai-Hong, and Xu, Zheng-Hong

Abstract

The fermentation of sauce-flavor Baijiu requires high-temperature Daqu as the starter, which is classified into three types: white, yellow, and black. Recent studies highlighted the variability of the microbiota and metabolome profiles of these three types of Daqu, however, what functions they precisely provide in the sauce-flavor Baijiu brewing process remains unclear. In this study, white, yellow, and black Daqu in five different proportions were utilized as starters in field-scale Baijiu fermentation, with the control group lacking Daqu inoculation. Fermented grains inoculated with 100% white Daqu (47.7°C) had the highest temperature during stacking fermentation, while 100% black Daqu and control groups were lower than 45°C. Lactic acid (12.6-22.0 mg/g) was the most abundant organic acid, followed by acetic acid (0.7-5.0 mg/g). qPCR analysis revealed that bacterial biomass decreased during fermentation, while fungal biomass increased. A comparison with the control revealed that Daqu contributed high-temperature resistant microorganisms to the stacking fermentation process, primarily Kroppenstedtia, Virgibacillus, Byssochlamys, Thermoascus, and Thermomyces. Meanwhile, stacking fermentation promoted the enrichment of Acetobacter, Kazachstania, and Leiothecium. Mantel test and co-occurrence network analysis revealed that utilizing different fermentation starters could vary the biotic and abiotic factors that drive microbial community succession. We investigated the flavor of Baijiu further, and found that fermentation with white Daqu enhanced the accumulation of ethyl acetate, isoamyl alcohol, and isobutanol, whereas black Daqu increased the accumulation of ethyl lactate, lactic acid, and furfural. This study contributes to the rational usage of different types of Daqu in the manufacturing of Baijiu.

Published
2024
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180. Mining and Expression of a Metagenome-Derived Keratinase Responsible for Biosynthesis of Silver Nanoparticles

Author

Tao, Li-Yan, Gong, Jin-Song, Su, Chang, Jiang, Min, Li, Heng, Li, Hui, Lu, Zhen-Ming, Xu, Zheng-Hong, and Shi, Jin-Song

Abstract

A keratinase gene kerBvwas mined from soil metagenomes. The open reading frame consisted of 1149 bp and potentially encoded a protein of 382 amino acid residues. It shared the same active site with several reported typical keratinases via analysis of the amino acid sequence. The keratinase was successfully expressed in B. subtilisWB600 with pMA5 expression vector. The maximum activity of 164.8 U/mL in the fermentation supernatant was observed after incubating for 30 h in Terrifc Broth (TB) medium. The keratinase exhibited outstanding resistance to metal ions and was surfactant-stable. Additionally, the enzyme displayed broad substrate specificity especially toward insoluble substrate feather meal because of its disulfide bond-reducing activity. Furthermore, the reducing power of the recombinant keratinase was investigated. It showed that the protein exhibited a relatively high reducing power, which was subsequently used in the biosynthesis of silver nanoparticles (AgNPs). The biosynthesized AgNPs were characterized by ultraviolet–visible (UV–vis) spectroscopy, dynamic light scattering (DLS), transmission electron microscope (TEM), as well as Fourier transform infrared spectroscopy (FTIR) and displayed obvious antibacterial activities toward Escherichia coli.

Published
2024
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188. The Processing of the Degraded Medical Digital Image's Image Enhancement

Author

Xu Zheng-hong, Zhang Zhen-xi, He Qing-hang, and Li Zheng

Subjects
Computer science, Image quality, business.industry, ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION, Image processing, Edge enhancement, Digital image, Clipping (photography), Image noise, Median filter, Computer vision, Artificial intelligence, business, Image restoration
Abstract

Image's noise, edge and contrast are the important factors that influence image's quality. If a method of image enhancement is solely applied to the degraded medical digital image, image's quality is improved in part, if a combined method of image enhancement is applied to the degraded medical digital image, it can increase the image's quality greatly.

Published
2007

191. Nitrile-converting enzymes as a tool to improve biocatalysis in organic synthesis: recent insights and promises.

Author

Gong, Jin-Song, Shi, Jin-Song, Lu, Zhen-Ming, Li, Heng, Zhou, Zhe-Min, and Xu, Zheng-Hong

Subjects
ORGANIC synthesis, BIOCATALYSIS, NITRILASES, BIOCONVERSION, AGRICULTURAL chemicals
Abstract

Nitrile-converting enzymes, including nitrilase and nitrile hydratase (NHase), have received increasing attention from researchers of industrial biocatalysis because of their critical role as a tool in organic synthesis of carboxylic acids and amides from nitriles. To date, these bioconversion approaches are considered as one of the most potential industrial processes using resting cells or purified enzymes as catalysts for production of food additives, pharmaceutical, and agrochemical precursors. This review focuses on the distribution and catalytic mechanism research of nitrile-converting enzymes in recent years. Molecular biology aspects to improve the biocatalytic performance of microbial nitrilase and NHase are demonstrated. The process developments of microbial nitrilase and NHase for organic synthesis are also discussed. [ABSTRACT FROM AUTHOR]

Published
2017
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192. Average Over Depth During Optical Mapping of Cardiac Propagation

Author

Jin Yin-bin, Xu Zheng-hong, Zhang Zhen-xi, and Wang Jing

Subjects
Physics, Surface (mathematics), Membrane potential, Optics, business.industry, Optical mapping, Optical decay, business, Constant (mathematics), Fluorescence, Molecular physics, Signal, Transmembrane protein
Abstract

High-resolution optical mapping with voltage-sensitive dyes has become a powerful tool to depict complex propagation patterns of cardiac transmembrane potentials. Many studies have proved that this optical signal obtained from tissue surface is the response of the transmembrane potential averaged upon depth rather than only surface. In order to investigate the differential between the two transmembrane potentials, in this paper, we simulated cardiac propagation using Luo-Rudy (L-R) model and calculated the transmembrane potentials average over depth by an optical decay constant from 0.0 mm to 3.0mm. Our results suggest that the transmembrane potentials weighted average over depth is different from that on the tissue surface, the discrepancy between them depends on the depth of the fluorescence emission of the tissue. If only top layer of tissue (< 1.0mm) contributes the fluorescence, optical mapping is an almost accurate representation of surface activation dynamics

Published
2005
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