Antibacterial activity of xanthorrhizol isolated from Curcuma xanthorrhiza Roxb. against foodborne pathogens

Xanthorrhizol, isolated from the ethanol extract of Curcuma xanthorrhiza Roxb., is a sesquiterpene compound with a molecular weight of 218. The aim of this study was to investigate the antibacterial activity of xanthorrhizol against foodborne pathogens. The antibacterial activity of xanthorrhizol was measured in terms of the MIC and the MBC. MICs and MBCs of xanthorrhizol against Bacillus cereus, Clostridium perfringens, Listeria monocytogenes, Staphylococcus aureus, Salmonella Typhimurium, and Vibrio parahaemolyticus were 8, 16, 8, 8, 16, 8 microg/ml and 16, 32, 16, 16, 16, 16 microg/ml, respectively. The bactericidal study, as determined by the viable cell count method, revealed that xanthorrhizol treatment at 4 x MIC reduced viable cells by at least 6 to 8 log for all six foodborne pathogens in 4 h. Xanthorrhizol maintained its antibacterial activity after thermal treatments (121 degrees C, 15 min) under various pH ranges (pH 3.0, 7.0, and 11.0). These results strongly suggest that xanthorrhizol, conferring strong antibacterial activity with thermal and pH stability, can be effectively used as a natural preservative to prevent the growth of foodborne pathogens.     

Activity of ε–Polylysine Against Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes

ABSTRACT: ε–polylysine is a homopolymer of L-lysine, an essential amino acid, with a reportedly wide antimicrobial spectrum. This study evaluated the antimicrobial activity of ε–polylysine, as compared with known preservatives and organic acids, against Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes , in culture broth. The compounds tested included ε–polylysine (0.0025% to 0.05%), sodium diacetate (0.25%), sodium lactate (3.0%), lactic acid (0.1%), and acetic acid (0.1%), alone, as well as in combination with ε– polylysine (0.0025% to 0.03%); all treatments were evaluated in tryptic soy broth supplemented with 0.6% yeast extract. Treatments were inoculated (approximately 2 log colony-forming units [CFU]/mL) with 5-strain ( E. coli O157:H7, S. Typhimurium) or 10-strain ( L. monocytogenes ) mixtures of the pathogens. Survival/growth of the inoculated bacteria was periodically monitored during incubation at 4 °C (30 d) and 24 °C (48 h). Bactericidal effects of ε–polylysine were obtained against E. coli O157:H7 and S. Typhimurium at 4 °C. At the same temperature (4 °C), ε–polylysine alone or in combination with other compounds tested inhibited growth or was bactericidal against L. monocytogenes. All 3 pathogens were inhibited by ε–polylysine at 24 °C; however, L. monocytogenes was the most sensitive and S. Typhimurium the most resistant. The antimicrobial activity of ε–polylysine against E. coli O157:H7 and S. Typhimurium was enhanced ( P < 0.05) when tested in combination with sodium diacetate or acetic acid. Combination treatments with sodium lactate resulted in loss of ε–polylysine activity by the end of the incubation period. Overall, under the conditions of this study, ε–polylysine exhibited antimicrobial effects against the 3 pathogens tested.     

Contribution of wine components to inactivation of food-borne pathogens

ABSTRACT:  Wine is a complex solution containing several components with several likely antimicrobial properties. Low pH (3.0 to 4.0), high organic acid content (titratable acidity ≥6.0 g/L tartaric acid), relatively high ethanol (10% to 15%), and potentially high total sulfur dioxide (0 to 300 ppm) may contribute to inactivation of food-borne pathogens when exposed to wine. The objective was to determine the effect of these 4 parameters on reducing populations of Escherichia coli ( E. coli ) O157:H7 and Staphylococcus aureus . A factorial design was used to test variables (pH, titratable acidity, sulfur dioxide, ethanol) in combinations of low, medium, and high levels. Suspension tests were performed to compare the efficacy of 81 treatments with controlled exposure time of 20 min. Staphylococcus aureus was significantly more resistant to wine treatment than E. coli O157:H7. Stepwise regression analysis of S. aureus inactivation revealed the ordered impact of pH, molecular sulfur dioxide, titratable acidity, and ethanol concentration. Selected analysis of E. coli inactivation revealed the importance of pH and ethanol in predicting inactivation. Total and free sulfur dioxide were not predictive of inactivation of either pathogen. Wine-based solutions may have application as surface disinfectants for food surfaces and food contact equipment. Wine destined to be used as a disinfectant could be enhanced by increasing any of the parameters tested in this study; however, lowering the pH would be the most effective and would likely enhance the efficacy of the other parameters. Additional wine components such as volatile acidity and phenolics were not evaluated but may also contribute to the antimicrobial properties of wine.     

Protein haze formation in wines revisited. The stabilising effect of organic acids

The effect on the wine protein haze potential of five organic acids commonly encountered in wines (l(+)-tartaric, l(−)-malic, citric, succinic and gluconic acids) was assessed. All five acids, tested at 20 mM, reduced dramatically the haze potential of proteins, either in wine or dissolved in water, throughout the range of pH values typical of wines (i.e., from 2.8 through 3.8). Subtle differences among the acid effects did not correlate with the number of their carboxyl groups, but were attributed to electrostatic interactions that depend upon the acid pK_a values, the protein pI values and the medium pH. These results invalidate or question the validity of all experiments on wine proteins involving wine model solutions containing organic acids. Overall, the results obtained in the present work clearly indicate that organic acids with a common occurrence in wines exhibit a stabilising effect upon the haze potential of the wine proteins.     

蔗糖癸酸酯对沙门氏菌的抗菌作用及其机理初探

本文研究了蔗糖癸酸酯对沙门氏菌的体外抗菌作用及其机理。采用肉汤稀释法测定了不同p H值下蔗糖癸酸酯对沙门氏菌的最小抑菌浓度(MIC)和最小杀菌浓度(MBC)。通过测定菌体渗漏物、SDS-聚丙烯酰胺凝胶电泳分析、扫描电镜观察、DNA结合试验等,初步研究了蔗糖癸酸酯对沙门氏菌的抗菌机理。结果表明:蔗糖癸酸酯在p H 7.0时对沙门氏菌的MIC为20 m M,在酸性条件下抗菌效果更为显著。蔗糖癸酸酯能够使菌体细胞内核酸、蛋白质和还原糖等外泄,影响细胞膜结构完整性和菌体正常形态;对菌体细胞蛋白(尤其是大分子量蛋白)的合成与积累有干扰作用;同时糖酯的亲水性头基可与DNA磷酸基团以氢键的方式结合,使DNA骨架收缩。因此,可将蔗糖癸酸酯作为兼具乳化和防腐作用的多功能食品添加剂,应用于动物源性食品的加工和储藏过程中。     

Antimicrobial Effects of Wine: Separating the Role of Polyphenols,pH, Ethanol,and Other Wine Components

Abstract: While the antimicrobial effectiveness of wine is well documented, relative contributions of the wine components to its antimicrobial activity is controversial. To separate the role of wine phenolics, ethanol, and pH from other wine constituents, the antimicrobial effects of intact wine were compared to that of phenols-stripped wine, dealcoholized wine, ethanol, and low pH applied separately and in combination, against 2 common foodborne pathogens, Salmonella enterica serovar Enteritidis and Escherichia coli. All samples were biochemically characterized with respect to their total phenolics and resveratrol content, antioxidant capacity, ethanol content, and pH. Antioxidative activity of the samples corresponded to their total phenolics content. Except for respective controls, pH and ethanol content were similar in all samples. The order of antibacterial activity of the samples was: intact wine > phenols-stripped wine > dealcoholized wine > combination of ethanol and low pH > low pH > ethanol. Separate application of ethanol or low pH showed negligible antibacterial activity while their combination showed synergistic effect. Antibacterial activity of the samples could not be related to their total phenolics and resveratrol content, antioxidant capacity, ethanol content, or pH. Our study indicates that antimicrobial activity of complex solutions such as intact wine cannot be exclusively attributed to its phenolic or nonphenolic constituents, nor can the antimicrobial activity of wine be predicted on the basis of its particular components.     

Growth and survival of foodborne pathogens in beer

This work aimed to assess the growth and survival of four foodborne pathogens (Escherichia coli O157:H7, Salmonella Typhimurium, Listeria monocytogenes, and Staphylococcus aureus) in beer. The effects of ethanol, pH, and storage temperature were investigated for the gram-negative pathogens (E. coli O157:H7 and Salmonella Typhimurium), whereas the presence of hops ensured that the gram-positive pathogens (L. monocytogenes and S. aureus) were rapidly inactivated in alcohol-free beer. The pathogens E. coli O157:H7 and Salmonella Typhimurium could not grow in the mid-strength or full-strength beers, although they could survive for more than 30 days in the mid-strength beer when held at 4°C. These pathogens grew rapidly in the alcohol-free beer; however, growth was prevented when the pH of the alcohol-free beer was lowered from the "as received" value of 4.3 to 4.0. Pathogen survival in all beers was prolonged at lowered storage temperatures.     

Antibacterial activity of propolis against Staphylococcus aureus

In the present study, antimicrobial activity of the ethanolic extract of propolis (EEP), collected at different periods (June, August, and October-November) from various regions (Taipei, Mingchien, and Fanglia) in Taiwan, against Staphylococcus aureus was investigated. The effects of cell age, incubation temperature, and pH in response to EEP were also investigated. Depending on concentration, collecting area, and time, EEP exerted various degrees of antibacterial activity against S. aureus. The minimum inhibitory concentration of EEP tested ranged from <3.75 to 60 microg/ml, while the minimum bactericidal concentration ranged between 7.5 and 120 microg/ml against S. aureus. In general, a higher antibacterial activity was noted with EEP collected in August than other months. EEP of Mingchien-6 showed the most profound antibacterial activity among the EEP samples tested. The age of a bacterial culture affected its susceptibility to EEP. Cells in the late-exponential phase were most susceptible to EEP. Higher temperature (37 degrees C) and acidic pH enhanced the antibacterial activity of EEP.     

The in vitro antibacterial activity of dietary spice and medicinal herb extracts

The in vitro antibacterial activities of a total of 46 extracts from dietary spices and medicinal herbs were investigated by agar-well diffusion method against five foodborne bacteria (Bacillus cereus, Listeria monocytogenes, Staphylococcus aureus, Escherichia coli, and Salmonella anatum). Their total phenolic contents were also evaluated. Many herb and spice extracts contained high levels of phenolics and exhibited antibacterial activity against foodborne pathogens. Gram-positive bacteria were generally more sensitive to the tested extracts than Gram-negative ones. S. aureus was the most sensitive, while E. coli was the most resistant. There were highly positive relationships (R(2)=0.73-0.93) between antibacterial activities and phenolic content of the tested extracts against each bacterium. This suggested that the antibacterial activity of the tested extracts was closely associated with their phenolic constituents.     

银杏酚酸的分离鉴定及其抗菌活性研究

本文以银杏外种皮为原料,研究了吸附树脂分离纯化银杏酚酸的方法和银杏酚酸的抗菌活性,并对其结构进行了鉴定。结果表明:非极性树脂D4020和弱极性树脂AB-8对银杏酚酸具有较好的吸附能力,银杏酚酸粗提液经两种树脂吸附,不同浓度乙醇梯度洗脱后,产物纯度可达90%,得率为0.91%,利用树脂精制银杏酚酸成本低、效率高,是一种有效的分离方法;通过LC/DAD/MS分析表明,银杏酚酸由五种异构体(C13:0,C15:1,C17:2,C15:0,C17:1)组成,其中C15:1含量最高,其次是C17:1;银杏酚酸主要抑制革兰氏阳性菌,对蜡状芽孢杆菌、枯草芽孢杆菌和金黄色葡萄球菌有很好的抑制作用,而对大肠杆菌等革兰氏阴性菌无抑制作用,酚酸的烷基侧链在抑菌中起了重要作用。     

Sensitivity of three pathogenic bacteria to Turkish cemen paste and its ingredients

Pastirma is a dry cured meat product which is pasted with cemen. This paste is prepared from ground fenugreek, garlic and red hot pepper (RHPP). In this study, the cemen mix/paste and all its ingredients were tested for their inhibitory effects on Escherichia coli, Staphylococcus aureus and Yersinia enterocolitica. All samples had a varying inhibitory effect against all the bacteria tested during 4 days of storage. Complete cemen paste showed the strongest inhibitory effect on the three pathogens compared to ingredients alone. Fenugreek and RHPP had a bacteriostatic effect while the cemen paste and garlic had a bactericidal effect. S. aureus was the most sensitive bacterium while Y. enterocolitica was the most resistant. The results of this study confirmed the protective effect of cemen paste and garlic in food preservation especially against E. coli, S. aureus and Y. enterocolitica proving safety for public health. Hence it might be concluded that cemen paste is the first hurdle to prevent bacterial contamination, and a low pH (～4.83) value would also add an additional barrier to secure safety of the product. Finally, it can be suggested that similar studies should be conducted on actual meat systems to confirm these findings.     

Effect of Chitosan Physical Form on Its Antibacterial Activity Against Pathogenic Bacteria

The antibacterial activity of chitosan (CS) nanospheres, in comparison with other physical forms, was investigated against Salmonella enterica serovar Typhimurium and Staphylococcus aureus, which are 2 foodborne harmful pathogens. Results showed that the antibacterial efficacy of CS nanospheres: (1) was superior to that displayed by CS in powder and solution form; (2) was higher against S. aureus than against Salmonella Typhimurium; and (3) was dependent on the temperature and pH of the medium depending on the strain. For S. Typhimurium, a higher activity was displayed at 37 °C, in which 99.9% of the population was eradicated independently of the pH, followed by 20 °C and 7 °C, in which acidic pH conditions favored a higher susceptibility of bacteria to the effect of CS. On the contrary, S. aureus was less susceptible to the pH and temperature conditions of the medium, and no statistical difference in the antibacterial effect was observed for pH 5.8 and 8.0 at 20 °C and 37 °C. However, at 7 °C a slightly higher activity was displayed at pH 5.8 than at 8.0.     

仙人掌提取物对常见食品污染菌的抑菌特性研究

用水和95%乙醇2种溶剂提取仙人掌的有效成分,测试了2种提取物的抑菌圈直径,对乙醇提取物的最小抑菌浓度(MIC)进行了测定,研究了温度、pH、盐、糖对抑菌活性的影响。结果表明,仙人掌95%乙醇浸提物的抑菌效果优于水浸提物;仙人掌乙醇浸提液的最小抑菌浓度分别为:大肠杆菌3.125 mg/mL,沙门氏菌、金黄色葡萄球菌、枯草芽抱杆菌、黑根霉6.25 mg/mL,桔青霉12.5 mg/mL,毕赤酵母、啤酒酵母25 mg/mL,黑曲霉50 mg/mL;提取物热稳定性好,在pH4～6的范围内具有稳定的抑菌作用,提取物与盐、糖具有良好的协同抑菌作用。     

Antibacterial effects of chitosan solution against Legionella pneumophila, Escherichia coli, and Staphylococcus aureus

Chitosan has been shown to have antibacterial activities on the growth of a wide variety of bacteria. Chitosan solution has been sold commercially for use as an antibacterial agent. Chitosan solution contains not only chitosan but also organic acids as solvents and desalted Japan Sea Proper Water (dJSPW). We aimed to clarify whether chitosan solution has antibacterial activity against bacteria invading bath water, and then to explore the causative factor among these ingredients. The antibacterial activity of full-strength chitosan solution and of 10(2)- and 10(4)-fold chitosan solution diluted with purified water was studied against Legionella pneumophila serogroups 1 (L. pneumophila SG1) and 6 (L. pneumophila SG6), Escherichia coli (E. coli), and Staphylococcus aureus (S. aureus) for 7 days at 37 degrees C. To clarify the causative factor in the antibacterial activity against E. coli, the antibacterial activities of the full-strength and diluted chitosan solutions for 24 h were examined. L. pneumophila SG1 and SG6, and E. coli could not survive in the chitosan solution or in the 10(2)-fold dilute solution for over a day at 37 degrees C. The cells of S. aureus were found to have decreased more than 2.46 log cfu/ml after 1 day of incubation, not only in the chitosan solutions, but also in phosphate buffer solution as a control. No inhibitory effect of dJSPW on the growth of the bacteria was observed. The antibacterial activity of the chitosan solution was lower compared with those of the organic acids solutions, and it increased with decreasing pH value. We observed the antibacterial activity of chitosan solution against L. pneumophila SG1 and SG6, and E. coli, suggesting it may be due to the decreased pH value derived from organic acids rather than from chitosan itself or dJSPW.     

Assessment of Oligogalacturonide from Citrus Pectin as a Potential Antibacterial Agent against Foodborne Pathogens

Foodborne diseases are an important public health problem in the world. The bacterial resistance against presently used antibiotics is becoming a public health issue; hence, the discovery of new antimicrobial agents from natural sources attracts a lot of attention. Antibacterial activities of oligogalacturonide from commercial microbial pectic enzyme (CPE) treated citrus pectin, which exhibits antioxidant and antitumor activities, against 4 foodborne pathogens including Salmonella Typhimurium, Staphylococcus aureus, Listeria monocytogenes, and Pseudomonas aeruginosa was assessed. Pectin hydrolysates from CPE hydrolysis exhibited antibacterial activities. However, no antibacterial activity of pectin was observed. Citrus oligogalacturonide from 24‐h hydrolysis exhibited bactericidal effect against all selected foodborne pathogens and displayed minimal inhibitory concentration at 37.5 μg/mL for P. aeruginosa, L. monocytogenes, and S. Typhimurium, and at 150.0 μg/mL for S. aureus.     

Antimicrobial performance of alkaline ionic fluid (GC-100X) and its ability to remove Escherichia coli O157:H7 from the surface of tomatoes

An efficacy test of GC-100X, a noncorrosive alkaline ionic fluid (pH 12) composed of free radicals and supplemented with xylitol, was carried out against six major foodborne pathogens-Staphylococcus aureus FRI 913, Salmonella enterica serovar Enteritidis ATCC 13076, S. enterica serovar Typhimurium DT104 Korean isolate, Vibrio parahaemolyticus ATCC 17803, Escherichia coli O157:H7 ATCC 43894, and Pseudomonas aeruginosa KCTC 1637-at three different temperatures (4, 25, and 36 degrees C) with or without organic load (2% yeast extract). Results revealed a more than 4-log10 (CFU/ml) reduction (1.0 x 10(4) CFU/ml reduction) against all pathogens reacted at 37 degrees C for 3 h in the absence of organic material. GC-100X solution diluted with an equal volume of distilled or standard hard water (300 ppm CaCO3) showed effective bactericidal activity, particularly against gram-negative bacteria. Washing efficacy of GC-100X solution was compared against E. coli O157:H7 on cherry tomato surfaces with those of a commercially used detergent and chlorine water (100 ppm). Viable cell counts of E. coli O157:H7 that had penetrated to the cores of tomatoes after sanitizing treatment revealed that GC-100X stock and its 5% diluted solutions had similar washing effects to 100-ppm chlorine water and were more effective than the other kitchen detergent. These results indicate that GC-100X has good bactericidal and sanitizing activities and is useful as a new sanitizer for food safety and kitchen hygiene.     

Thermal inactivation of the wine spoilage yeasts Dekkera/Brettanomyces

The heat resistance of three strains of Dekkera/Brettanomyces (Dekkera anomala PYCC 5,153, Dekkera bruxellensis PYCC 4,801 and Dekkera/Brettanomyces 093) was evaluated at different temperatures between 32.5 and 55 degrees C. Thermal inactivation tests were performed in tartrate buffer solution (pH 4.0) and in wines. In the studies employing buffer as the heating menstruum, measurable thermal inactivation began only at temperatures of 50 degrees C. When heating was performed in wine, significant inactivation begins at 35 degrees C. Subsequent thermal inactivation tests were performed in buffer at various levels of pH, ethanol concentration, and various phenolic acids. Results from experiments in buffer with added ethanol suggest that the greater heat sensitivity shown in wines can be largely attributed to ethanol, although potentiation of this effect might be due to the phenolic content, particularly from ferulic acid. In the range of pH values tested (2.5-4.5), this factor had no influence in the heat inactivation kinetics. Relevant data, in the form of D and Z values calculated in the various environments, potentially useful for the establishment of regimes of thermal control of Dekkera/Brettanomyces yeasts in wine and contaminated equipment is presented.     

沙棘叶绿体对葡萄酒中亚硫酸盐清除条件的筛选及感官品质的影响

研究沙棘叶绿体对葡萄酒中亚硫酸盐的清除效果。从中国沙棘叶片中提取叶绿体,在叶绿体浓度、pH、乙醇浓度等6个单因素基础上筛选出显著清除模拟葡萄酒中亚硫酸盐的因素,通过响应面中心组合实验优化清除反应参数,并利用优化后参数分别评价其对干型、甜型、红色、白色4种葡萄酒中亚硫酸盐的清除效果及对感官特性的影响。实验结果表明,沙棘叶绿体最佳清除条件为乙醇浓度15.00%、pH5.00、反应温度25℃,在此条件下模拟酒中亚硫酸盐清除率为55.45%,对干白、冰白、冰红和干红葡萄酒中亚硫酸盐的实际清除率分别为51.90%、46.00%、42.57%和30.14%。感官分析表明,添加沙棘叶绿体对干红葡萄酒的口感影响不大。综上所述,沙棘叶绿体可通过体外氧化反应有效降低葡萄酒中的亚硫酸盐,对干红葡萄酒的口感影响较小。     

茶槲寄生“螃蟹脚”醇提正丁醇萃取相对金黄色葡萄球菌抑菌机理的研究

本文研究了茶槲寄生“螃蟹脚”醇提各萃取相的抑菌作用及正丁醇萃取相（NVBEs）对金黄色葡萄球菌的抑菌机理。采用滤纸片扩散法测定抑菌圈直径（DIZ）的大小,对倍稀释法测定最小抑菌浓度（MIC）和最低杀菌浓度（MBC）,来评价“螃蟹脚”醇提各萃取相对金黄色葡萄球菌（S. aureus）、大肠杆菌（E. coli）、鼠伤寒沙门氏菌（S. typhimurium）、单核细胞增生李斯特菌（L. monocytogenes）4种食源性腐败菌的抑制性;通过光学显微镜和扫描电镜观察、胞膜通透性、胞壁完整性和酶活性等实验,研究了NVBEs抑菌机理。结果表明,“螃蟹脚”醇提各萃取相对S. aureus、E. coli、S. typhimurium和L. monocytogenes均有明显抑制效果,其中NVBEs抑菌活性较好,对S. aureus抑制效果最好,DIZ为9.84±0.57 mm,MIC为3.52 mg/mL,MBC为7.04 mg/mL。抑菌机理结果表明：NVBEs可增加S. aureus细胞壁及细胞膜的通透性,破坏菌体细胞结构,引起细胞内含物如核酸和蛋白质等外泄;引起遗传物质DNA的改变,使菌体细胞形态结构出现异常;影响菌体酶的代谢活动,从而抑制细菌的生长。     

Chemical composition and in vitro antimicrobial and cytotoxic activities of plum (Prunus domestica L.) wine

A moderate intake of wine is associated with a positive impact on human health owing to the effects of important biologically active components present in the wine in large amounts. The aim of this study was to examine the chemical composition and to assess antimicrobial and cytotoxic activities of fruit wines produced from three plum varieties (?a?anska rana, ?a?anska lepotica and Po?ega?a) commonly grown in Serbia as an approach to assess the quality and acceptability of these wines as a functional food. Furthermore, the activity of a series of control samples was assessed in order to determine components from the wine that are responsible for its functional properties. The plum wines produced showed considerable antimicrobial activity against six bacterial and two yeast strains used in this study. In addition to antimicrobial activity, the plum wines showed a significant cytotoxic effect (IC₅₀ < 50 µg mL^?1) on the growth of three tested cancer cell lines (Hep2c, RD and L2OB). Regarding the determined activities, ?a?anska rana plum wine achieved the best results. The results indicated that the antimicrobial activity of the plum wines was, in large part, based on the effects of the total acids and the pH value, while the contribution of ethanol and the content of the phenolic compounds were not significant. Similar conclusions were drawn regarding the cytotoxic activity of this fruit wine. The results can be seen as a contribution to the global acceptance of fruit wines as a functional food, with the accent placed on moderate consumption. An important advantage of fruit wines (in particular plum wine), compared with traditional grape wine, is their lower alcohol content. Copyright © 2016 The Institute of Brewing & Distilling