食品中金黄色葡萄球菌、单增李斯特氏菌和副溶血性弧菌的MPCR法检测

为快速检测食品中的金黄色葡萄球菌(SA)、单增李斯特氏菌(LM)和副溶血性弧菌(VP),根据各菌的相关基因设计引物,分别扩增金黄色葡萄球菌的耐热核酸酶基因-nuc、单增李斯特氏菌溶血素O上的hlyA基因和副溶血性弧菌的热稳定直接溶血素基因-tdh,建立一种MPCR快速检测食品中致病菌的方法,结果表明,三条特异性扩增片段分别为279bp、 243bp和202bp,经DNA测序证明其序列与模板被扩增片段一致.该方法具有良好的灵敏性和特异性.     

非生物性因素对乳酸链球菌素抗菌活性的影响

为了研究乳酸链球菌素(nisin)的抗菌活性,采用金黄色葡萄球菌为实验培养菌种,分别研究了不同的酸溶液(乙酸、硝酸、盐酸、柠檬酸)、不同的金属离子(Zn2+、K+、Fe3+、Cu2+)、不同的离子强度(以Na+的离子强度:0、0.2、0.4、0.6、0.8mol/L)和不同的pH值(4.0、4.5、5.0、5.5、6.0)等非生物性因素对Nisin抗菌活性的影响。实验结果表明,乙酸对Nisin的抗菌活性的提高效果最佳;加入金属离子会提高Nisin的抗菌活性,其中K+的促进作用最强;离子强度的增加对Nisin的抗菌活性有很大的提高;Nisin在pH4.0的酸性环境中抗菌活性最好。     

壳聚糖对金黄色葡萄球菌抑菌活性的研究

研究了壳聚糖对金黄色葡萄球菌抑菌活性,考察了不同壳聚糖浓度、pH值、金属离子、醋酸浓度对壳聚糖抑制金黄色葡萄球菌活性的影响,并以壳聚糖浓度、pH值、醋酸浓度为因素进行正交试验,确定了壳聚糖对金黄色葡萄球菌抑菌活性的最优条件。实验结果表明,壳聚糖对金黄色葡萄球菌的抑制能力随其浓度的升高而增强;壳聚糖溶于浓度为2%的醋酸溶液时,培养基pH控制在6.0时壳聚糖的抑菌活性最强;金属离子在一定程度上降低了壳聚糖的抑菌活性;这3个因素对壳聚糖的抑菌活性的影响程度为壳聚糖浓度pH值醋酸浓度。     

抗耐甲氧西林金黄色葡萄球菌菌株的筛选、鉴定及其活性物质初步研究

从海南红树林土壤分离筛选抗耐甲氧西林金黄色葡萄球菌（MRSA）菌株,通过形态学观察、生理生化试验及分子生物学进行菌种鉴定。采用不同培养基优选抑菌活性物质生成条件;以有机溶剂萃取抑菌活性物质,采用气相色谱-质谱（GC-MS）分析抑菌物质化学成分,采用微量稀释法测定最低抑菌浓度与最低杀菌浓度。结果表明,筛选得到一株抗MRSA菌株,编号为NEL-002,被鉴定为萎缩芽孢杆菌（Bacillus atrophaeus）。菌株NEL-002采用LB液体培养基得到发酵液经石油醚萃取粗提物抗MRSA菌活性最强,且在40～80 ℃、pH在5～10较稳定,对多种蛋白酶不敏感;最低抑菌质量浓度为62.5 μg/mL,最低杀菌质量浓度为500 μg/mL。GC-MS鉴定出抗菌活性物质为十甲基环戊硅氧烷、十二甲基环六硅氧烷及邻苯二甲酸二丁酯。     

2011~2019年吉林省米面制品中食源性致病菌监测分析

目的 了解米面制品中食源性致病菌的污染情况,为米面制品食物中毒的原因和影响因素提供线索。方法 根据《国家食源性疾病监测工作手册》对2011—2019年吉林省九个地(市)级所采集到的米面制品食品样本中蜡样芽孢杆菌、金黄色葡萄球菌、单增李斯特菌进行检测。结果 2011—2019年共检测米面制品3967份,其中阳性菌株313株,总检出率为7.89%,2015年检出率最高(14.68%)；蜡样芽孢杆菌在白山市检出率最高(44.44%),金黄色葡萄球菌在白城市检出率最高(44.44%),单增李斯特菌在白山市检出率最高(6.21%)；餐饮服务环节总阳性检出率为9.72%,流通环节总阳性检出率为5.38%；蜡样芽孢杆菌在炒的米面制品中检出率最高(43.42%),金黄色葡萄球菌在速冻面米生制中检出率最高,单增李斯特菌也是在速冻面米制品中检出率最高(14.29%)。结论 吉林省各地市米面食品污染的情况普遍存在,白山市最严重,但是近年来污染情况正在逐步好转速,餐饮服务环节需加强管理,小吃店,零售加工店和百货商场应该给予更严格的把控,速冻米面制品生制污染相对严重,需给予重视。     

Physico-chemical and film-forming properties of bovine-hide and tuna-skin gelatin: A comparative study

A bovine-hide gelatin and a tuna-skin gelatin, both characterized on the basis of their amino acid composition and molecular weight distribution, were used to prepare edible films by casting with glycerol and sorbitol added as plasticizers. The molecular weight distribution of the tuna-skin gelatin exhibited appreciably higher quantities of β-components (covalently linked α-chain dimers), whereas bovine-hide gelatin showed a certain degradation of α₁-chains being indicative of a greater proteolysis. Intrinsic differences in the gelatin attributes affected in diverse manner some of the physical properties of the films. Thus, water vapour permeability was higher in the bovine-hide gelatin film, whereas deformability was considerably higher (10 times higher) in the tuna-skin gelatin film. In contrast, breaking force and water solubility were basically unaffected by gelatin origin. Analysis of the thermal properties revealed both films to be wholly amorphous with similar glass transition temperature values thanks to the plasticizing effects of the glycerol and sorbitol and the low moisture contents.     

Characterization of the Effect of Sprouting or Solid-State Bioprocessing by Dietary Fungus on the Antibacterial Activity of Soybean Extracts Against Listeria monocytogenes

Listeria monocytogenes is one of the most severe food-borne bacterial infections causing Listeriosis. As L. monocytogenes can survive harsh adverse conditions - such as low pH, high NaCl, and refrigeration temperatures - as well as resist current antimicrobial measures such as the use of disinfectants and antibiotics, there is a need for alternative anti-Listeria strategies. In the search for new antimicrobial agents, much recent research has focused on the potential of dietary phenolic compounds. In this study, soybean extracts enriched for phenolic content via dark-germination sprouting or solid-state bioprocessing by the dietary fungus Rhizopus oligosporus or Lentinus edodes were investigated for in vitro antibacterial activity against L. monocytogenes.L. monocytogenes growth was inhibited most effectively by R. oligosporus bioprocessed soybean extracts, which showed anti-Listeria activity at total phenolic concentrations as low as 10 µg 100 µL^-1. In both sprouted soybean extract and L. edodes-bioprocessed soybean extract the anti-Listeria activity was not observed until at least 200 µg total phenolic content 100 µL^-1 was used. Anti-Listeria activity by soybean extract was associated with phenolic mobilization but not with antioxidant activity. Further, R. oligosporus bioprocessed soybean extracts were shown to inhibit the growth of L. monocytogenes in fish and meat systems at refrigeration temperatures. The potential involvement of mobilization of antimicrobial versus non-antimicrobial phenolics during sprouting and solid-state bioprocessing was hypothesized and discussed.     

乳酸菌细菌素Durancin GL对单增李斯特菌的抗菌活性及机制

单增李斯特菌广泛分布于肉类、禽类、蛋类、乳制品及蔬菜中,且适应能力强,即使在4 ℃的冷藏环境下仍可生长繁殖,是食品中主要的食源性致病菌之一。乳酸菌细菌素Durancin GL是由干酪中肠球菌产生的一种新型细菌素,对单增李斯特菌具有靶向抑制作用。本实验研究了Durancin GL对单增李斯特菌的抗菌活性及作用机制。通过最小抑菌浓度和抑菌动力学实验检测Durancin GL对单增李斯特菌的抑制作用,结合监测胞内物质泄漏、菌体存活情况以及形态学分析,探讨Durancin GL对单增李斯特菌的抑菌机制。Durancin GL对单增李斯特菌最小抑菌浓度为（2.5±0.4）mg/L,可引起李斯特菌细胞质泄漏,增加细胞外液电导率,导致菌体细胞死亡,从而发挥其抑菌活性。     

Applicability of bacteriocin‐producing Lactobacillus plantarum,Enterococcus faecium and Lactococcus lactis ssp. lactis as adjunct starter in Minas Frescal cheesemaking

The antimicrobial and technological characteristics of three bacteriocinogenic cultures used as adjunct starters in Minas Frescal cheese were investigated. The cheeses were manufactured with 1% commercial lactic starter and 0.5%Lactococcus lactis ssp. lactis ATCC 11454, Lactobacillus plantarum ALC 01 or Enterococcus faecium FAIR‐E 198. The cheeses were then artificially inoculated with Listeria monocytogenes Scott A, Staphylococcus aureus ATCC 27154 and Bacillus cereus K1‐B041 and stored for 21 days at 8°C. The results show that there was no significant difference in the counts of L. monocytogenes and S. aureus between the cheeses made with added bacteriocinogenic cultures and the control cheese. On the other hand, B. cereus exhibited susceptibility to Lb. plantarum ALC 01 and E. faecium FAIR‐E 198 from the seventh day of storage. However, these cultures increased the proteolysis of the Minas Frescal cheese.     

明胶添加量对兔皮明胶膜特性与结构的影响

从兔皮中提取明胶制备明胶膜,通过测定不同明胶添加量下膜的机械性能、水蒸气透过率、亚基组成和结构,探究明胶添加量对明胶膜特性与结构的影响。结果表明随着明胶添加量的增加,明胶膜体系内网络空间结构变大,从而膜的厚度增加。力学结果显示,明胶添加量为4 g/100 m L（w/v）时,明胶膜抗拉强度最高（p<0.05）;明胶添加量为6 g/100 m L（w/v）时,明胶膜断裂伸长率最低（p<0.05）。水蒸气透过率结果表明随着明胶添加量的增加,水蒸气透过率呈现上升趋势。凝胶电泳结果显示,明胶添加量为4 g/100 m L（w/v）时,低分子量的蛋白组分产生更多交联,形成蛋白质-蛋白质交联的结构,此浓度下明胶膜的抗拉强度最大。FT-IR分析表明:当明胶添加量增加至4 g/100 m L（w/v）时,酰胺A带向高波数移动,说明肽链上的N-H基团并没有与甘油的-OH基团相互反应,而是明胶分子的官能团之间产生更强的相互作用,形成独特的网络结构。同时,酰胺Ⅰ带曲线拟合结果也表明当明胶添加量为4 g/100 m L时,膜内稳定结构较多,明胶分子之间的相互反应达到最大化,明胶膜的稳定性和成膜性能较优。      

Mechanical, water vapor barrier and thermal properties of gelatin based edible films

Edible films are thin materials based on a biopolymer. The objectives of this work were to determine the water vapor permeability and the mechanical and thermal properties of edible films based on bovine hide and pigskin gelatins. These films were prepared with 1 g of gelatin/100 ml of water; 15–65 g sorbitol/100 g gelatin; and at natural pH. The samples were conditioned at 58% relative humidity and 22°C for 4 days before testing. The mechanical properties were determined by the puncture test and the water vapor permeability by gravimetric method at 22°C. For DSC analysis, samples were conditioned over silica gel for 3 weeks. Samples (10 mg) were heated at 5°C/min, between −150 and 150°C in a DSC TA 2010. A second scan was run after cell cooling with liquid nitrogen. As expected, the puncture force decreased and the puncture deformation and water vapor permeability increased with the sorbitol content. The origin of gelatin was important only above 25 g sorbitol/100 g gelatin. The DSC traces obtained in the first scan of samples with 15–35 g sorbitol/100 g gelatin, showed a well visible glass transition followed by a sol–gel transition. However, with the increase of sorbitol concentration, the glass transition became broader, typical of the system presenting a phase separation. The model of Couchman and Karazs for ternary system, was used to predict the Tg values as a function of sorbitol concentration.     

Antibacterial Effects and Cell Morphological Changes in Sfaphylococcus aureus Subjected to Low Ethanol Concentrations

Ethanol in low concentrations (5–10% weight) affected aerobic growth (at 37°C) of two strains of Stuphylococcus aureus. Growth inhibition in laboratory media was observed with ethanol about 6–7% weight water activities (a_w) of ～0.97. This suggested that the ethanol antibacterial effect was not only from its a_w lowering ability. Electron microscopy observations showed intense morphological modifications in cells in broth with 5% to 6.5% ethanol, and clearly indicated that cell wall changes of S. aureus was partly responsible for the antibacterial action of ethanol.     

青藏高原部分地区自由放牧与舍饲育肥牦牛食源性致病微生物污染的差异

肉中的致病微生物污染是危害人类健康的重要因素。本研究采集了青藏高原部分地区无腹泻症状的放牧型牦牛样品155份,舍饲育肥型牦牛样品122份,对其粪便及各组织中沙门氏菌、大肠菌群、金黄色葡萄球菌和单增李斯特菌进行分离,并对沙门氏菌进行血清学鉴定和抗生素药敏实验。结果发现,2种饲养方式下,牦牛组织病原微生物携带率统计学上无显著差异(P0.05),但放牧型牦牛的检出率绝对值都略高于舍饲育肥型牦牛;2种不同饲养方式的牦牛样品中分离出的沙门氏菌血清型差异较大,舍饲育肥型和放牧型牦牛肌肉中检出的血清型分别为纽波特沙门氏杆菌和肠炎沙门氏杆菌,放牧型牦牛粪便中的沙门氏菌为鼠伤寒沙门氏杆菌、肠炎沙门氏杆菌和圣保罗沙门氏菌,而舍饲育肥型牦牛仅有都柏林沙门氏菌;舍饲育肥型和放牧型牦牛源沙门氏菌对抗生素耐药性规律基本一致,对林可霉素(83.33%、81.82%)、四环素(66.67%、63.64%)和麦迪霉素(66.67%、72.73%)具有较高的耐药性。从实验结果可以得出,放牧型牦牛的微生物安全性和舍饲育肥型牦牛一致,沙门氏菌对抗生素的耐药性都较为严重。     

Antimicrobial activity of nisin incorporated in pectin and polylactic acid composite films against Listeria monocytogenes

An extruded composite food packaging film containing pectin, polylactic acids (PLAs) and nisin was developed to inhibit Listeria monocytogenes . The mechanical properties and surface structure of the film were also examined. Cells of L. monocytogenes were reduced by 2.1, 4.5 and 3.7 log units mL⁻¹ by the pectin plus PLA (pectin/PLA) film containing nisin (1000 IU mL⁻¹ of tested liquid) in Brain Heart Infusion (BHI) broth, liquid egg white and orange juice, respectively, after 48 h at 24 °C. Pectin played an important roll in embedding nisin into the film. The pectin/PLA film had a similar stiffness but lower tensile strength, elongation and fracture energy than the pure PLA film. These data suggested that nisin incorporated into the pectin/PLA film was an effective approach to reducing L. monocytogenes in a typical growth medium (e.g. BHI broth) as well as in foods (e.g. orange juice and liquid egg).     

Effect of the presence of ethyl lauroyl arginate on the technological properties of edible fish gelatin films

Physical, chemical and antimicrobial properties of fish gelatin films with different concentrations of ethyl lauroyl arginate (LAE) were studied. Optical properties of film-forming solution did not vary with increased LAE content. However, pH and surface tension increased. The incorporation of LAE into the formulation increased moisture and solubility of the films. In addition, the presence of LAE affected mechanical properties, making films stronger and more flexible; it had no effect on water vapour permeability. Finally, films with LAE significantly increased antimicrobial properties against Listeria innocua, Shewanella putrefaciens and Pseudomonas fluorescens, but not against Aeromonas hydrophila. These antimicrobial films could be used as an alternative technology for extending shelf-life of fresh fish products.     

Structural properties of films and rheology of film-forming solutions based on chitosan and chitosan-starch blend enriched with murta leaf extract

Chitosan (CH) and chitosan-corn starch (CH-CS) film-forming solutions (FFS) and films, with or without polyphenol-rich aqueous extract from murta (Ugni molinae Turcz) leaves (PEML) were prepared. The impact of the FFS type and PEML, considering pH values of the FFS, on dynamic and steady-shear behavior of FFS, interaction mechanisms of PEML with polymer chains and changes on infrared spectra of films were investigated. Mechanical properties, thickness and color from films were also evaluated.     

Assessment of film-forming potential and properties of protein and polysaccharide-based biopolymer films

This study assessed the film‐forming abilities of six types of proteins, as well as six types of polysaccharides at various concentrations (proteins: 0–16%; polysaccharides: 0–4%) and heating temperatures (60–80 °C). Biopolymer films evaluated included: sodium caseinate (SC), whey protein isolate (WPI), gelatine (G); caboxymethyl cellulose (CMC), sodium alginate (SA) and potato starch (PS). Screening trials showed that optimal film‐forming conditions were achieved using SC and G (4% and 8%), WPI (8% and 12%), PS, CMC (2% and 3%) or SA (1% and 1.5%) solutions heated to 80 °C in combination with 50% (w/w) glycerol. Films manufactured from 1.5% SA, 8% G and 3% CMC had the highest tensile strength (24.88 MPa); flexibility (89.69%)/tear strength (0.30 N) and puncture resistance (22.66 N), respectively. SC, WPI and G‐based films were more resistant to solvent than SA, CMC and PS. Film permeability to water vapour and oxygen decreased in the order: 12% WPI to 1% SA and 12% WPI to 1% SA. All films tested were impermeable to oil.     

抗菌肽zp37抑制果汁中单核细胞增生李斯特菌的活性及其作用机制

单核细胞增生李斯特菌（简称单增李斯特菌）作为一种常见的食源性致病菌,是影响果汁食用安全性的主要威胁因子。本实验设计并获得一种抗菌肽zp37,通过测定抗菌肽zp37最小抑菌浓度（minimum inhibitory concentration,MIC）,分析抗菌肽zp37处理后单增李斯特菌的生长曲线、膜电位、膜完整性、细胞微观结构、细胞聚集率、DNA结合情况以及胞内活性氧等,研究抗菌肽zp37抑制果汁中单增李斯特菌的活性及其作用机制。结果表明,抗菌肽zp37对单增李斯特菌的MIC为16μg/mL,当其质量浓度大于4MIC时,单增李斯特菌生长受到明显抑制。同时,8MIC的抗菌肽zp37处理1h能杀死绝大部分的单增李斯特菌,且在7 d贮藏期内,2MIC的抗菌肽zp37能将草莓汁、猕猴桃汁和苹果汁中的单增李斯特菌控制到检测限以下。抗菌肽zp37处理后,单增李斯特菌细胞膜离子通透性增加、膜电位消失,细胞膜完整性被破坏,细胞出现明显的凹陷变形,细胞间发生聚集。荧光标记示踪法结果显示,抗菌肽zp37同时作用于单增李斯特菌的细胞膜和细胞质。在细胞质中,当抗菌肽zp37质量浓度大于DNA质量浓度的1/4...     

双歧杆菌细菌素Bifidocin A对金黄色葡萄球菌的抑菌作用及其机制

Bifidocin A是由Bifidobacterium animalis BB04代谢合成的一种新型广谱高效细菌素。以革兰氏阳性的金黄色葡萄球菌为测试敏感菌,分析细菌素Bifidocin A的最低抑菌浓度及不同质量浓度下的抑菌效果,并从敏感菌细胞形态与结构、细胞膜的通透性、细胞膜的完整性以及细胞膜质子移动势的变化4个角度分别探讨该细菌素的抑菌作用机制。结果表明,细菌素Bifidocin A对金黄色葡萄球菌CVCC 26112的最低抑菌浓度为0.058μg/m L,抑菌活性较强且存在浓度依赖性;并初步推测其抑菌作用机制是通过耗散细胞膜质子移动势,增加细胞膜通透性,形成孔洞,进而破坏细胞膜完整性,并最终瓦解细胞。