Biodiversity of Secondary Metabolites Compounds Isolated from Phylum Actinobacteria and Its Therapeutic Applications

The current review aims to summarise the biodiversity and biosynthesis of novel secondary metabolites compounds, of the phylum Actinobacteria and the diverse range of secondary metabolites produced that vary depending on its ecological environments they inhabit. Actinobacteria creates a wide range of bioactive substances that can be of great value to public health and the pharmaceutical industry. The literature analysis process for this review was conducted using the VOSviewer software tool to visualise the bibliometric networks of the most relevant databases from the Scopus database in the period between 2010 and 22 March 2021. Screening and exploring the available literature relating to the extreme environments and ecosystems that Actinobacteria inhabit aims to identify new strains of this major microorganism class, producing unique novel bioactive compounds. The knowledge gained from these studies is intended to encourage scientists in the natural product discovery field to identify and characterise novel strains containing various bioactive gene clusters with potential clinical applications. It is evident that Actinobacteria adapted to survive in extreme environments represent an important source of a wide range of bioactive compounds. Actinobacteria have a large number of secondary metabolite biosynthetic gene clusters. They can synthesise thousands of subordinate metabolites with different biological actions such as anti-bacterial, anti-parasitic, anti-fungal, anti-virus, anti-cancer and growth-promoting compounds. These are highly significant economically due to their potential applications in the food, nutrition and health industries and thus support our communities’ well-being.     

Effects of Green Tea Powder,Pomegranate Peel Powder,Epicatechin and Punicalagin Additives on Antimicrobial,Antioxidant Potential and Quality Properties of Raw Meatballs

Alternative technologies, which have been developed in order to meet the consumers’ demand for nourishing and healthy meat and meat products, are followed by the food industry. In the present study, it was determined, using the HPLC method, that green tea contains a high level of epicatechin (EP) under optimal conditions and that pomegranate peel contains a high level of punicalagin (PN). Green tea, pomegranate peel, EP and PN were added to meatballs at different concentrations in eight groups. The antioxidant capacities of extracts were measured. The antimicrobial activity was examined for 72 h using three different food pathogens. The highest level of antimicrobial activity was achieved in the 1% punicalagin group, whereas the minimum inhibition concentration (L. monocytogenes, S. typhimurium) was found to be 1.87 mg/mL. A statistically significant decrease was found in FFA, POV and TBARS levels of meatballs on different days of storage (p < 0.05). When compared to the control group, the bioactive compounds preserved the microbiological and chemical properties of meatballs during storage at +4 °C (14 days). It was concluded that the extracts with high EP and PN concentrations can be used as bio-preservative agents for meat and meat products.     

抗革兰氏阴性菌耐格霉素的形式合成

耐格霉素是具有抗革兰氏阴性菌活性的天然产物.以廉价易得的3-羰基-4-氯丁酸乙酯为原料,以八步29%的总收率实现了耐格霉素的形式合成.该工作改进了文献的合成路线,利用生物催化不对称还原高立体选择性引入C-5位的手性羟基,并将危险的叠氮引入反应放在合成后期,降低合成路线的操作风险.分子中C-3位的仲碳胺基手性中心通过Ellamn试剂介导的不对称Mannich反应构建.该路线易于放大,有望为构建耐格霉素类似物分子库以及高通量药物筛选奠定基础.     

Development of an impedimetric immunosensor based on electropolymerized polytyramine films for the direct detection of Salmonella typhimurium in pure cultures of type strains and inoculated real samples

The development of a faradic impedimetric immunosensor based on electropolymerized polytyramine (Ptyr) films for the detection of S. typhimurium in milk is described for the first time. Polyclonal anti-Salmonella was cross-linked, in the presence of glutaraldehyde vapors, on Ptyr-modified gold electrodes. The dielectric behaviour of Ptyr films was evaluated with capacitance measurements, while their stability in neutral aqueous solutions was examined with impedimetric measurements. The effect of the concentration of tyramine in the forming solution on both the sensitivity and the dynamic range of the resulted immunosensors was also investigated. The alteration of the interfacial features of the electrodes due to different modification or recognition steps, was measured by faradic electrochemical impedance spectroscopy in the presence of a hexacyanoferrate(II)/(III) redox couple. At samples containing a low initial concentration of 10 cfu mL⁻¹S. typhimurium, that actually defines the LOD of the immunosensors, signal changes of 33% and 88% were achieved after 3 and 10 h incubation, respectively. To achieve the working simplicity expected by a biosensor, immunoreaction was performed directly in cultures. This resulted in the elimination of various centrifugation and washing steps, which are used for the isolation of bacteria cells from the culture, thus making the proposed immunosensors promising candidates for on-site applications. Finally, the proposed immunosensors were successfully used for the detection of S. typhimurium in experimentally inoculated milk samples.     

Electrochemical Detection of Pathogenic Bacteria—Recent Strategies,Advances and Challenges

Bacterial infections represent one of the leading causes of mortality worldwide, nevertheless the design and development of rapid, cost‐efficient and reliable detection methods for pathogens remains challenging. In recent years, electrochemical sensing methods have gained increasing attention for the detection of pathogenic bacteria, due to their increasingly competitive sensitivity. However, combining sensitivity with cost efficiency, high selectivity and a facile working procedure in a portable device is difficult. The presented review provides a summary of biosensing strategies for bacteria, published since 2015, by covering significant achievements towards custom‐designed portable point‐of‐care devices. Herein, the direct chemical recognition of bacteria via enzyme activity or secretion products, as well as their detection at various electrode surfaces and materials, such as nanomaterials, indium tin oxide or paper‐based immunosensors, is discussed. Furthermore, newly established hyphenated sensing principles, incorporated into lab‐on‐a‐chip and microfluidic devices, are presented and remaining technical challenges and limitations are considered.     

万古霉素在食源性致病菌检测中的应用

食源性致病菌污染是引起食品安全的主要因素之一,对人类健康构成了严重威胁。万古霉素作为一种对革兰氏阳性菌具有特异性识别功能的小分子,能够修饰在磁性纳米粒子表面,使粒子获得靶向目标菌的能力,结合其他检测方法,可以实现分离检测革兰氏阳性菌的目的。本文对万古霉素功能化的磁珠在革兰氏阳性菌分离检测的研究进展进行了介绍,分析了万古霉素不同修饰方式和检测方法对其检测效果的影响,并对各种方法的检测结果进行了分析比较,最后,提出了万古霉素在食源性致病菌检测中存在的问题,并对其未来应用进行了展望。     

Antimicrobial flavonoids isolated from Indian medicinal plant Scutellaria oblonga inhibit biofilms formed by common food pathogens

Scutellaria oblonga Benth., a hitherto phytochemically unexplored Indian medicinal folklore plant was extracted with acetone and subjected to chromatography to yield nine flavonoids, for the first time from this plant. Antimicrobial assays were performed against 11 foodborne pathogens, and three molecules (Techtochrysin, Negletein and Quercitin-3-glucoside) depicted significant activity. These molecules were assessed for their rate of antibacterial action using time–kill curves which depicted complete inhibition of most of the bacteria within 12–16 h. The significant biofilm-reducing capability exhibited by these three molecules formed a significant finding of the current study. In most of the experiments, a 90–95% reduction in biofilms was observed. Thus, flavonoids as natural molecules from S. oblonga could be further researched to be used as potent antimicrobial and antibiofilm agents.     

基于金属有机骨架材料的生物传感器在食源性致病菌或毒素检测中的应用

食源性致病菌或其产生的毒素污染的食物会给人体健康带来严重威胁,并造成巨大的经济损失。近年来,金属有机骨架材料(MOFs)作为一种新型的多孔晶体材料,因其具有大的表面积、高的孔隙率等特点,受到人们的广泛关注。将MOFs与生物传感器结合用于食源性致病菌或毒素的检测引起了研究者的兴趣。基于此,本文介绍了MOFs用于生物传感器的优势,概述了MOFs在不同的电化学和光学生物传感器的应用,综述了基于MOFs的生物传感器在致病菌或毒素的研究进展,讨论了基于MOFs的生物传感器在致病菌或毒素所面临的挑战和展望。