The antibacterial activity of LI-F type peptide against methicillin-resistant Staphylococcus aureus (MRSA) in vitro and inhibition of infections in murine scalded epidermis

Applied Microbiology and Biotechnology - LI-F type peptides are a family of cyclic lipodepsipeptide antibiotics isolated from Paenibacillus polymyxa and display potent activities against positive...     

Production of arabitol from enzymatic hydrolysate of soybean flour by Debaryomyces hansenii fermentation

Arabitol is a low-calorie sugar alcohol with anti-cariogenic properties. Enzymatic hydrolysate of soybean flour is a new renewable biorefinery feedstock containing hexose, pentose, and organic nitrogen sources. Arabitol production by Debaryomyces hansenii using soybean flour hydrolysate was investigated. Effects of medium composition, operating conditions, and culture stage (growing or stationary phase) were studied. Production was also compared at different culture volumes to understand the effect of dissolved oxygen concentration (DO). Main factors examined for medium composition effects were the carbon to nitrogen concentration ratio (C/N), inorganic (ammonium) to organic nitrogen ratio (I/O-N), and sugar composition. Arabitol yield increased with increasing C/N ratio and a high I/O-N (0.8–1.0), suggesting higher yield at stationary phase of low pH (3.5–4.5). Catabolite repression was observed, with the following order of consumption: glucose > fructose > galactose > xylose > arabinose. Arabitol production also favored hexoses and, among hexoses, glucose. DO condition was of critical importance to arabitol production and cell metabolism. The yeast consumed pentoses (xylose and arabinose) only at more favorable DO conditions. Finally, arabitol was produced in fermentors using mixed hydrolysates of soy flour and hulls. The process gave an arabitol yield of 54%, volumetric productivity of 0.90 g/L-h, and specific productivity of 0.031 g/g-h.

     

A novel de novo mutation of ACTG1 in two sporadic non-syndromic hearing loss cases

正Dear Editor,Actins are a family of essential cytoskeletal proteins involved in nearly all cellular processes(Lambrechts et al.,2004).Of the six human genes that encode actins,only ACTG1and ACTB are ubiquitously expressed.ACTG1(OMIM#604717),which is linked to the DFNA20/26 locus,was     

Stable Formamidinium‐Based Perovskite Solar Cells via In Situ Grain Encapsulation

Formamidinium (FA)‐based lead iodide perovskites have emerged as the most promising light‐absorber materials in the prevailing perovskite solar cells (PSCs). However, they suffer from the phase‐instability issue in the ambient atmosphere, which is holding back the realization of the full potential of FA‐based PSCs in the context of high efficiency and stability. Herein, the tetraethylorthosilicate hydrolysis process is integrated with the solution crystallization of FA‐based perovskites, forming a new film structure with individual perovskite grains encapsulated by amorphous silica layers that are in situ formed at the nanoscale. The silica not only protects perovskite grains from the degradation but also enhances the charge‐carrier dynamics of perovskite films. The underlying mechanism is discussed using a joint experiment‐theory approach. Through this in situ grain encapsulation method, PSCs show an efficiency close to 20% with an impressive 97% retention after 1000‐h storage under ambient conditions.     

基于PAT的PCV2 VLPs生产过程优化与控制研究

昆虫细胞-杆状病毒载体表达系统(baculovirus expression vector system,BEVS)是病毒样颗粒亚单位疫苗(virus like particles,VLPs)的理想生产平台。动物细胞培养过程分析技术(process analytical technology,PAT)研究的重点在于更多地获取与细胞生理状态相关的过程参数,以及实现过程敏感参数的在线表征和过程控制关键时间节点的在线判定,从而指导过程优化和控制。通过昆虫Sf9细胞的分批和补料悬浮培养,发现细胞代谢活性与在线特征频率(fc)之间存在相关性。以fc作为细胞代谢活性的在线指征,在细胞代谢活性下降之前补料,使得Sf9细胞在代谢活性明显增强的基础上,最高活细胞密度提高1.75倍。通过分批培养与补料分批培养过程细胞生理特性参数的相关性分析,发现比电容增长速率(με)与培养体系S-期细胞比例之间存在相关性,με作为细胞增殖活性状态的在线指征参数,可以作为最佳接毒时间的判定依据。此外,研究还发现在线检测参数电容(ε)与最高疫苗产量之间存在相关性,可以作为疫苗最佳收获时间的在线表征参数。以在线fc值作为补料时间指征,以在线με值作为病毒感染时间指征,以在线ε值作为病毒收获时间指征,实现了猪圆环病毒2型(PCV2)VLPs的高效生产。相比于批培养,基于PAT的生产工艺疫苗单位体积产量提高76%,生产周期缩短了24h,为PCV2病毒样颗粒亚单位疫苗大规模生产提供了一种新的高效生产模式。     

Bioactivity‐Guided Isolation of Anti‐Inflammatory Constituents of the Rare Mushroom Calvatia nipponica in LPS‐Stimulated RAW264.7 Macrophages

Calvatia species, generally known as puffball mushrooms, are used both as sources of food and as traditional medicine. Among the Calvatia genus, Calvatia nipponica (Agaricaceae) is one of the rarest species. Using bioassay‐guided fractionation based on anti‐inflammatory effects, five alkaloids ( 1 – 5 ), two phenolics ( 6 and 7 ), and a fatty acid methyl ester ( 8 ) were isolated from the fruiting bodies of C. nipponica. Compound 8 was identified from C. nipponica for the first time, and all isolates ( 1 – 8 ) were tested for inhibition of nitric oxide (NO) production in lipopolysaccharide (LPS)‐stimulated RAW264.7 macrophages. Compound 7 showed mild inhibition while compound 8 significantly inhibited NO production with an IC₅₀ value of 27.50 ± 0.08 μm . The mechanism of NO inhibition of compound 7 was simulated by molecular docking analysis against nitric oxide synthase (iNOS), which revealed the interactions of 7 with the key amino acid residue and the heme in the active site. With the most potent inhibition against LPS‐induced inflammation, compound 8 was further investigated with respect to its mechanism of action, and the activity was found to be mediated through the inhibition of iNOS and COX‐2 expression.     

Electrochemical CO2 Reduction with Atomic Iron‐Dispersed on Nitrogen‐Doped Graphene

Electrochemical reduction of CO₂ provides an opportunity to reach a carbon‐neutral energy recycling regime, in which CO₂ emissions from fuel use are collected and converted back to fuels. The reduction of CO₂ to CO is the first step toward the synthesis of more complex carbon‐based fuels and chemicals. Therefore, understanding this step is crucial for the development of high‐performance electrocatalyst for CO₂ conversion to higher order products such as hydrocarbons. Here, atomic iron dispersed on nitrogen‐doped graphene (Fe/NG) is synthesized as an efficient electrocatalyst for CO₂ reduction to CO. Fe/NG has a low reduction overpotential with high Faradic efficiency up to 80%. The existence of nitrogen‐confined atomic Fe moieties on the nitrogen‐doped graphene layer is confirmed by aberration‐corrected high‐angle annular dark‐field scanning transmission electron microscopy and X‐ray absorption fine structure analysis. The Fe/NG catalysts provide an ideal platform for comparative studies of the effect of the catalytic center on the electrocatalytic performance. The CO₂ reduction reaction mechanism on atomic Fe surrounded by four N atoms (Fe–N₄) embedded in nitrogen‐doped graphene is further investigated through density functional theory calculations, revealing a possible promotional effect of nitrogen doping on graphene.