Preparation and characterization of agar/silver nanoparticles composite films with antimicrobial activity

Composite films with silver nanoparticles (AgNPs), obtained by reduction of AgNO₃ using an environmentally friendly method (combined reduction of AgNO₃ by trisodium citrate solution and heating), and agar as a polymer matrix and a capping agent were prepared by solvent casting method. The surface color of the resulting agar/AgNPs films exhibited the characteristic plasmonic effect of the silver nanoparticles, and the characteristic properties of the composite films were greatly influenced by changing the concentration of AgNPs added. Significant increase in water vapor barrier properties and surface hydrophobicity were observed with increase in the concentration of AgNPs without reduction in the mechanical strength. In addition, the agar/AgNPs films loaded with more than 1 wt% of silver nanoparticles exhibited strong antimicrobial activity against both Gram-positive (Listeria monocytogenes) and Gram-negative (Escherichia coli O157:H7) bacterial pathogens.     

Antimicrobial silver-montmorillonite nanoparticles to prolong the shelf life of fresh fruit salad

In this work, silver-montmorillonite (Ag-MMT) antimicrobial nanoparticles have been obtained by allowing silver ions from nitrate solutions to replace the Na⁺ of natural montmorillonite and then to be reduced by a thermal treatment. Ag-MMT were used as active antimicrobial compounds to improve the shelf life of fresh fruit salad. In order to assess their influence on product shelf life, sensorial and microbiological quality has been monitored during the storage. The microbiological quality was determined by monitoring the principal spoilage microorganisms (mesophilic and psychrotrophic bacteria, coliforms, lactic acid bacteria, yeasts and molds). Additionally, the evolution of sensorial quality was assessed by monitoring color, odor, firmness and product overall quality. The Ag-MMT nanoparticles seemed to be effective in inhibiting microbial growth, above all at the highest tested concentration. Consequently, the sensorial quality of samples stored in the active packaging appeared to be better preserved. Thus, experimental results showed that a significant shelf life prolongation of fresh fruit salad can be obtained by a straightforward new packaging system.     

桉叶精油气相扩散抑菌活性及抑菌成分研究

通过测定桉叶精油在气相、液相和固相扩散方式下对供试菌的抑菌圈大小和最低抑菌浓度(MIC),探讨桉叶精油气相扩散抑菌效果,并结合气相色谱-质谱(GC-MS)和顶空固相微萃取(SPME)/GC-MS技术,对比分析气态桉叶精油的抑菌成分。结果表明:桉叶精油通过气相扩散方式抑菌也具有明显抑菌效力,对供试菌的MIC值范围为0.045~0.36mg/mL,显著低于液相MIC值(4.5~18.0 mg/mL)和固相MIC值(4.5~18.0 mg/mL);对大肠杆菌、金黄色葡萄球菌抑制作用较好,对黑曲霉抑制作用稍差;气态桉叶精油与桉叶精油的主要成分无显著差别,均以萜烯类和醇类物质为主,萜烯类物质相对含量的升高导致抑菌活性变强;气态桉叶精油的抑菌活性与α-蒎烯、右旋柠檬烯、3-蒈烯、异松油烯和月桂烯等物质有关。     

Synthesis and characterization of nanosilver-silicone hydrogel composites for inhibition of bacteria growth

Purpose

Nanosilver-silicone hydrogel (NAgSiH) composites for contact lenses were synthesized to asses the antimicrobial effects.

乙二胺四乙酸二钠抑菌性研究

惭二胺四乙酸二钠是一种优秀的络合剂。本介绍了它的结构、性状、质量标准及功能,并对其抑菌特性进行了研究,同时讨论了与山梨酸钾的防腐协同作用。     

乳酸菌抗菌肽抗菌机理的研究进展——乳酸菌抗菌肽抗菌机理

乳酸菌抗茵肽是乳酸菌代谢过程产生的一类具有活性的多肽或蛋白质物质,可抑制或杀死食品中的病原茵或腐败菌。近几年,乳酸茵对其他细菌的拮抗作用的机理研究得最多的是乳酸菌抗茵肽,在食品行业中具有广泛的应用前景,这是由于乳酸茵抗茵肽被认为是一种“天然”的食品添加剂而容易被接受。对乳酸菌抗菌肽作用机理的研究可为其在食品安全生产加工业中的应用奠定了基础。本文综述了乳酸菌抗茵肽的分类及作用机制的最新研究进展。     

荷叶提取液的抑菌特性研究

为研究荷叶提取液对大肠杆菌的抑制特性,进行了不同提取液浓度、培养基pH值、热处理、环境离子浓度、作用时间对荷叶提取液抑菌作用影响的试验。结果表明:荷叶提取液对大肠杆菌的最低抑菌浓度(MIC)为0.125g/mL;抑菌pH值范围6～9;对高温处理较稳定;钠离子和镁离子的浓度对抑菌效果的影响不大;提取液与菌悬液作用3h可抑制大肠干菌的生长,从而说明荷叶提取液对大肠杆菌有较好的抑菌效果,且受环境条件的影响较小,为荷叶天然食品防腐剂的开发提供了理论基础。     

中式灌肠生产中壳聚糖的抑菌效果研究

目的：研究壳聚糖在中式灌肠生产中的抑菌效果；方法：采用中性蛋白酶水解方法制备出不同黏均分子量的壳聚糖，添加到灌肠中，测定不同保存天数时的细菌总数和感观变化；结果：添加0．2％壳聚糖的灌肠在室温条件下的保质期提高2d以上，风味比其他添加量要好，且在同样添加量的条件下，黏均分子量低的壳聚糖比黏均分子量高的壳聚糖抑菌效果更好。     

鲢鱼鱼精蛋白抗菌活性的研究

本文测试了鲢鱼鱼精蛋白的抗菌谱,研究了pH值、温度、金属离子、蛋白酶对鲢鱼鱼精蛋白抗菌活性的影响,考察了鲢鱼鱼精蛋白与甘氨酸、醋酸钠的复配效果,还对鲢鱼鱼精蛋白的抗菌方式作了初步探讨。     

香辛料精油抑菌作用及其在肉制品中的应用

香辛料精油的研究已成为目前国内外香辛料研究的热点问题。本文介绍了香辛料精油的主要成分,抑菌活性成分,在肉制品中的应用及国内外研究进展。     

Antimicrobial activity of nobiletin and tangeretin against Pseudomonas

The inhibitory activities of two polymethoxylated flavone (PMFs) monomers (nobiletin and tangeretin) have been investigated against Pseudomonas fluorescens and Pseudomonas aeruginosain vitro. The effects on cell morphology, the release of cell constituents, the synthesis of proteins and the activities of key dehydrogenase were examined to elucidate their antibacterial mechanism. The concentration of transaminase and reducing sugar in bacterial solutions increased significantly when treated with nobiletin and tangeretin. Electron microscopy showed that the structure of the bacterial cells was destroyed and accompanied with induced cells plasmolysis. Nobiletin and tangeretin also inhibited the activities of succinate dehydrogenase (SDH) and malate dehydrogenase (MDH), and reduced proteins synthesis in bacterial cells. It is proposed that nobiletin and tangeretin destroyed the permeability of the cell membrane, with release of the cell constituents, leading to metabolic dysfunction, inhibition of protein synthesis, and eventually to cell pyknosis and death.     

Volatile constituents of propolis from various regions of Greece – Antimicrobial activity

The volatiles of five samples of Greek propolis from various geographic origin (A–E) were analyzed by capillary gas chromatography, using flame ionization GC and mass spectrometric detection. Ninety-four components were identified from the oils. The major components from each sample were found to be: junipene (11.7%), α-pinene (7.9%), manoyl oxide (7.1%) (sample A), α-pinene (45.8%), trans-β-terpineol (6.6%) (sample B), α-pinene (17.7%), α-eudesmol (12.1%), n-decanal (6.2%), guaiol (5.0%) (sample C), α-pinene (18.2%), δ-cadinene (8.4%) and α-muurolene (5.0%) (sample D), α-pinene (10.9%), n-decanal (10.3%), cedrol (6.3%), n-nonanal (5.4%), and manool (5.2%) (sample E). The total profile of the volatile constituents of all samples reveals the predominance of terpenoids, especially of α-pinene. The in vitro antimicrobial activity of the volatiles from all five studied samples against six bacteria and three fungi is also assayed and reported.     

Antimicrobial activity of enterococci strains isolated from white cheese

Twelve strains of enterococci isolated from white cheese samples obtained from different regions of Turkey were screened for their antimicrobial activity against some Gram-positive and Gram-negative food-borne pathogens and contaminating bacteria, also against themselves and some other lactic acid bacteria (LAB), including some species of lactococci, lactobacilli and Leuconostoc . Antimicrobial activity was confirmed for all 12 strains, including six Enterococcus faecium , two Enterococcus faecalis and four Enterococcus durans . Antimicrobial agents produced by these enterococci exhibited a spectrum of activity, which is mainly directed against food-borne pathogens, specially Listeria monocytogenes and Bacillus cereus and some other Bacillus spp. and also some enterococci. Tested LAB was insensitive to inhibitory agents produced by them.     

Antimicrobial and anti-biofilm effects of probiotic Lactobacillus plantarum KU200656 isolated from kimchi

Food Science and Biotechnology - The probiotic properties and anti-pathogenic effects of Lactobacillus plantarum KU200656 (KU200656) isolated from Korean fermented kimchi against Staphylococcus...     

Antimicrobial activity and bioactive compounds of Portuguese wild edible mushrooms methanolic extracts

The antimicrobial properties of phenolic extracts of Portuguese wild edible mushroom species (Lactarius deliciosus, Sarcodon imbricatus and Tricholoma portentosum) against pathogens were investigated. The minimal inhibitory concentrations (MICs) were evaluated for the entire mushroom, the cap and the stipe, separately; the portion of the mushroom used proved to be influenced in the results obtained, which are directly correlated with the content of total phenols and flavonoids in the extracts. The growth of Gram-positive bacteria (Bacillus cereus, B. subtilis,) was well inhibited by these mushrooms, while Escherichia coli (Gram-negative bacteria) was resistant. The study on the antifungal effect of these mushrooms revealed that Candida albicans and Cryptococcus neoformans were differently inhibited for the mushrooms used.     

芦荟提取物抑菌作用的研究

用芦荟提取物对几种常见的微生物进行抑菌活性测定,结果表明芦荟提取物能有效地抑制细菌的生长,对供试菌的最低抑菌浓度金黄色葡萄球菌为１０％,沙门氏菌为８％,大肠杆菌为９％,产气肠杆菌９％,枯草杆菌１１％,芦荟提取物能耐受高温短时的热处理。     

显齿蛇葡萄提取物抗菌作用的研究

目的:筛选显齿蛇葡萄抗菌成分,测定其抗菌效果,为其作为食品天然防腐剂提供依据。方法:选用常见食品污染菌作为供试菌,用回流、真空浓缩干燥等方法提取成分,用扩散法、稀释法等测定其抗菌力。结果表明,显齿蛇葡萄不同极性溶剂提取物对各类菌均表现明显的抗菌效果,且随着二氢杨梅素浓度的提高,抗菌效果增强。结论:显齿蛇葡萄抗菌成分丰富,抗菌谱广,二氢杨梅素是主要的抗菌成分。     

Antimicrobial activity of buckwheat starch films containing zinc oxide nanoparticles against Listeria monocytogenes on mushrooms

Buckwheat starch (BS) films containing zinc oxide nanoparticles (ZnO‐N; 0%, 1.5%, 3% and 4.5%) were prepared, and their physical, optical and antimicrobial properties were examined. As ZnO‐N content increased from 0% to 4.5%, TS increased from 14.99 to 19.09 MPa and E decreased from 25.60% to 20.65%. In addition, L* and a* values decreased, whereas b*, ΔE and opacity increased. Regarding antimicrobial activity, the BS/ZnO‐N films had the reductions of 2.96–3.74 log CFU mL^?1 against Listeria monocytogenes after 8 h based on viable cell count assay. The BS film containing 3% ZnO‐N, an optimal concentration chosen in this study, was applied to fresh‐cut mushroom packaging, and the film exhibited antimicrobial activity against L. monocytogenes, resulting in a reduction of 0.86 log CFU g^?1 after 6 days of storage. Thus, these results indicate that the BS/ZnO‐N film can be used as a biodegradable packaging material.     

Antimicrobial activity of nanosilver-coated socks fabrics against foot pathogens

Nanotechnology can be used in engineering-desired textile attributes, such as fabric softness and durability in fibres, yarns and fabrics. Nanocoating the surface of socks is one approach to the production of highly active surfaces with UV blocking, antimicrobial and self-cleaning properties. Synthesis of silver nanoparticles in this project was carried out chemically by wet reduction method (Ag-chem) and biologically by using neem (Azadirachta indica) leaves (Ag-neem). The formation of silver nanoparticles was monitored by UV–visible spectroscopy, which revealed the surface plasmon resonance peak at 420?nm for Ag-chem and 430?nm for Ag-neem, and transmission electron microscopy, which showed nanoparticles of various shapes and sizes (～5–50?nm). Quantification of the prepared silver nanoparticles was done by atomic absorption spectroscopy, which revealed 0.044?M Ag⁺ and 0.042?M Ag⁺ ions in Ag-chem and Ag-neem, respectively. Coating of the socks fabrics (nylon and cotton) was carried out by exposing these fabrics to the prepared nanoparticle solutions on a gyratory shaker overnight. Antimicrobial activity of the Ag-chem and Ag-neem was carried out by performing minimum inhibitory concentration (MIC) and disc diffusion test against Sarcina lutea, an odour-producing organism, Klebsiella pnuemoniae, Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus and Candida albicans, organisms causing foot infections. P. aeruginosa and S. lutea were found to be most sensitive to either of the above preparations. Ag-chem was found to be more effective than Ag-neem. Nylon and cotton socks fabrics were coated with each of the above preparations. The antibacterial efficacy of the nanosilver-finished fabrics was checked by zone inhibition test, antibacterial test and wash fastness test. In both cases, coated nylon fabrics showed better antimicrobial activity than coated cotton fabrics. S. lutea and K. pneumoniae showed greater zones of inhibition than the other test organisms. Nylon fabric coated with Ag-chem and Ag-neem gave maximum reduction in viable count of all test organisms as compared to cotton fabrics. Higher reduction in the viable count of all test organisms was observed with Ag-chem-coated nylon fabrics. Thus, coating of the nylon socks fabric with silver nanoparticles can be used as an effective way to combat foot-borne pathogens and thereby reducing discomforts like foot odour, perspiration, complications due to diabetes, athlete’s foot, etc.