外源过氧化氢酶对液态发酵红茶色素的影响

为得到优质速溶红茶,本研究以低档绿茶为原料,对其水提液添加外源过氧化氢酶(CAT)进行液态发酵酶促转化成红茶茶汤,探讨液态发酵工艺对红茶色素生成量的影响,结果表明:参照优质红茶色素含量标准,CAT酶促转化的最优条件为:加酶量0.25 U/m L,反应温度45℃,反应时间2 h,p H6。CAT与多酚氧化酶(PPO)存在双酶协同作用,绿茶水提液先用PPO处理后(酶添加量0.05 U/m L,温度40℃,p H5,时间1.5 h)再用CAT处理,合成红茶色素的效果比单一酶源好。      

荣昌猪不同生长阶段肌肉营养品质的变化规律

为探索荣昌猪不同生长阶段肌肉营养品质的变化规律,本研究分别选取了1(初生时)、25、50、90、150、240、300日龄等7个生长阶段的荣昌猪各15头进行肌肉水分、粗蛋白、鲜味氨基酸(天门冬氨酸、谷氨酸、丙氨酸、甘氨酸、精氨酸)、粗脂肪、必需脂肪酸(亚油酸和亚麻酸)等主要营养成分的分析。结果表明,荣昌猪肌肉水分、粗蛋白、鲜味氨基酸、粗脂肪、必需脂肪酸等重要营养物质含量均随日龄增长呈现出一定规律性的变化。初生至50日龄是荣昌猪肌肉蛋白显著增长(p<0.05)的阶段,也是鲜味氨基酸维持较高水平的时期,同时也是荣昌猪乳猪粗脂肪和必需脂肪酸含量维持较高水平的一个重要时期;50~150日龄阶段粗脂肪和必需脂肪酸含量处于较低水平;150~240日龄是荣昌猪肌粗脂肪、必需脂肪酸增长的另一个重要阶段,是荣昌猪特征香味形成的关键时期。      

肠道菌群微生态平衡与人体健康的研究进展

人体肠道微生物种类繁多且数量庞大。正常肠道菌群作为人体的天然屏障,对维持人体健康起着重要的作用。机体内外环境的变化可影响肠道菌群的结构,造成肠道菌群失衡,继而引发或加重疾病,影响人体健康。通过膳食补充益生菌和益生元,选择性地剌激和调节肠道菌群的数量和组成,保持肠道菌群的微生态平衡,是预防和治疗疾病,促进人体健康的有效措施。本文综述了国内外关于肠道菌群的组成及功能、与相关疾病及治疗的关系以及维持肠道微生态平衡的措施。      

激光填丝焊接镍基合金/304不锈钢二次相的转变机制及其对晶间腐蚀性能的影响

为了阐明激光填丝焊接镍基合金(Hastelloy C-276)/304二次相的转变机制和晶间腐蚀机制,通过EPMA和TEM对二次相进行分析;采用双环动电位再活化法(DL-EPR)对焊接接头的晶间腐蚀性能进行评价,并采用EDS对焊接接头腐蚀表面进行成分分析.实验结果表明:p相和μ相为完全共格关系,且其共格关系为[001]...     

Synthesis of Lightweight Renewable Microwave-Absorbing Bio-Polyurethane/Fe3O4 Composite Foam: Structure Analysis and Absorption Mechanism

Sustainable renewable polymer foam used as a lightweight porous skeleton for microwave absorption is a novel strategy that can effectively solve the problems of the large surface density, high additive amount, and narrow absorbing band of absorbing materials. In this article, novel renewable microwave-absorbing foams were prepared using Sapiumse biferum kernel oil-based polyurethane foam (BPUF) as porous matrix and Fe₃O₄-nanoparticles as magnetic absorbents. The microstructure and the microwave absorption performance, the structural effects on the properties, and electromagnetic mechanism of the magnetic BPUF (mBPUF) were systematically characterized and analyzed. The results show that the mBPUF displayed a porous hierarchical structure and was multi-interfacial, which provided a skeleton and matching layer for the Fe₃O₄ nanoparticles. The effective reflection loss (RL ≤ −10 dB) frequency of the mBPUF was from 4.16 GHz to 18 GHz with only 9 wt% content of Fe₃O₄ nanoparticles at a thickness of 1.5~5 mm. The surface density of the mBPUF coatings was less than 0.5 kg/cm² at a thickness of 1.8 mm. The lightweight characteristics and broadband absorption were attributed to the porous hierarchical structures and the dielectric combined with the magnetic loss effect. It indicates that the mBPUF is a prospective broadband-absorbing material in the field of lightweight stealth materials.     

Inflammatory Mechanism of Brucella Infection in Placental Trophoblast Cells

Brucellosis is a severe zoonotic infectious disease caused by the infection of the Brucella, which is widespread and causes considerable economic losses in underdeveloped areas. Brucella is a facultative intracellular bacteria whose main target cells for infection are macrophages, placental trophoblast cells and dendritic cells. The main clinical signs of Brucella infection in livestock are reproductive disorders and abortion. At present, the pathogenesis of placentitis or abortion caused by Brucella in livestock is not fully understood, and further research on the effect of Brucella on placental development is still necessary. This review will mainly introduce the research progress of Brucella infection of placental trophoblast cells as well as the inflammatory response caused by it, explaining the molecular regulation mechanism of Brucella leading to reproductive system disorders and abortion, and also to provide the scientific basis for revealing the pathogenesis and infection mechanism of Brucella.     

Comprehensive Molecular Characterization of the Mitochondrial Genome of the Takin Lungworm Varestrongylus eleguneniensis (Strongylida: Protostrongylidae)

The takin lungworm Varestrongylus eleguneniensis (Strongylida: Protostrongylidae) causes lethal bronchopneumonia and represents severe threats to captive and wild populations. However, until now there has been very limited information available concerning the molecular epidemiology and evolutionary biology of V. eleguneniensis. Mitochondrial genomes (mtDNAs) can provide resources for investigations in these areas and, therefore, can assist with the surveillance and control of this lungworm. Herein, the complete mtDNA of V. eleguneniensis was sequenced and characterized with Illumina pipeline analyses. This circular genome (13,625 bp) encoded twelve protein-coding genes (PCGs), two rRNAs, and twenty-two tRNAs, with notable levels of AT and GC skews. Comparative genomics revealed a purifying selection among PCGs, with cox1 and nad6 having the lowest and the highest evolutionary rate, respectively. Genome-wide phylogenies showed a close relationship between V. eleguneniensis and Protostrongylus rufescens in Strongylida. Single gene (PCGs or rRNAs)-based phylogenies indicated that cox1 and nad5 genes shared the same family-level topology with that inferred from genomic datasets, suggesting that both genes could be suitable genetic markers for evolutionary and phylogenetic studies of Strongylida species. This was the first mtDNA of any member of the genus Varestrongylus, and its comprehensive molecular characterization represents a new resource for systematic, population genetic and evolutionary biological studies of Varestrongylus lungworms in wildlife.