Microbiological safety of kinema, a fermented soya bean food

Kinema is a fermented soya bean food of Nepal and the hilly regions of North-eastern States of India. Generally, the fermentation is dominated by Bacillus spp. that often cause alkalinity and desirable stickiness in the product. The present study was undertaken in a limited number of commercial (market) kinema samples to test for the presence of foodborne pathogens and their properties. Bacillus cereus was present in numbers exceeding 10⁴ cfu/g product in five of the tested 15 market samples. Enterobacteriaceae and coliform bacteria exceeded 10⁵ cfu/g in 10 of the 15 samples. Escherichia coli exceeding 10⁵ cfu/g was found in two samples. Staphylococcus aureus was not detected in any of the tested samples. Of 31 isolated typical and atypical strains of B. cereus, 18 representative strains were tested qualitatively for the ability to produce diarrhoeal type enterotoxin (BCET) using an Oxoid BCET-RPLA test kit. Overall, BCET was formed by 12 strains in BHIG (brain heart infusion broth +1% glucose), by seven strains on sterilized cooked rice, and by five strains on sterilized cooked soya beans. Semi-quantitative tests on BCET revealed that levels exceeding 256 ng/g soya beans, produced by single pure culture inoculation with the isolated B. cereus strains, were reduced to ≤ 8 ng/g by frying kinema in oil, a common procedure when making kinema curry. It was also shown in a mixed pure culture experiment that a kinema strain B. Subtilis DK-W1, is able to suppress growth and BCET formation by a selected toxin producing strain (BC7-5) of B. cereus. It is concluded that the traditional way of making kinema and its culinary use in curries is safe. However, for novel applications of kinema, safety precautions are advisable.     

Investigation of the Anti-Methicillin-Resistant Staphylococcus aureus Activity of (+)-Tanikolide- and (+)-Malyngolide-Based Analogues Prepared by Asymmetric Synthesis

Herein, we report antibacterial and antifungal evaluation of a series of previously prepared (+)-tanikolide analogues. One analogue, (4S,6S)-4-methyltanikolide, displayed promising anti-methicillin-resistant Staphylococcus aureus activity with a MIC of 12.5 µg/mL. Based on the antimicrobial properties of the structurally related (−)-malyngolide, two further analogues (4S,6S)-4-methylmalyngolide and (4R,6S)-4-methylmalyngolide bearing a shortened n-nonyl alkyl side chain were prepared in the present study using a ZrCl₄-catalysed deprotection/cyclisation as the key step in their asymmetric synthesis. When these were tested for activity against anti-methicillin-resistant Staphylococcus aureus, the MIC increased to 50 µg/mL.     

液体消毒洗涤剂的研制

研制了具有消毒杀菌、洗涤去污双重功效的液体消毒洗涤剂 ,测定了其对金黄色葡萄球菌的杀灭效果。结果表明 ,消毒洗涤剂的杀菌效果随其浓度的增加 ,作用时间的延长而提高 ;戊二醛浓度为 2 0 0× 10 -6时 ,与金黄色葡萄球菌作用 5min ,杀灭率可达 99.99%。将消毒洗涤剂在室温下放置半年 ,戊二醛分解率为 17.3 1%     

The Antimicrobial Peptide 1018-K6 Interacts Distinctly with Eukaryotic and Bacterial Membranes,the Basis of Its Specificity and Bactericidal Activity

Since penicillin was discovered, antibiotics have been critical in the fight against infections. However, antibiotic misuse has led to drug resistance, which now constitutes a serious health problem. In this context, antimicrobial peptides (AMPs) constitute a natural group of short proteins, varying in structure and length, that act against certain types of bacterial pathogens. The antimicrobial peptide 1018-K6 (VRLIVKVRIWRR- NH2) has significant bactericidal and antibiofilm activity against Listeria monocytogenes isolates, and against different strains and serotypes of Salmonella. Here, the mechanism of action of 1018-K6 was explored further to understand the peptide–membrane interactions relevant to its activity, and to define their determinants. We combined studies with model synthetic membranes (liposomes) and model biological membranes, assessing the absorption maximum and the quenching of 1018-K6 fluorescence in aqueous and lipid environments, the self-quenching of carboxyfluorescein, as well as performing lipid sedimentation assays. The data obtained reflect the differential interactions of the 1018-K6 peptide with eukaryotic and prokaryotic membranes, and the specific interactions and mechanisms of action in the three prokaryotic species studied: Salmonella Typhimurium^2GN, Escherichia coli^3GN, and Staphylococcus aureus^3GP. The AMP 1018-K6 is a candidate to prevent (food preservation) or treat (antibiotic use) infections caused by certain pathogenic bacteria, especially some that are resistant to current antibiotics.     

混合菌种发酵生产低酸度川味香肠的加工工艺

将植物乳杆菌、戊糖片球菌和葡萄球菌接种到川味香肠中,采用单因素实验和正交实验对低酸度川味香肠的加工工艺进行优化。结果表明,发酵期最佳工艺条件为:发酵温度20℃,发酵时间12h,葡萄糖添加量0.10%,发酵相对湿度75%;成熟期最佳工艺条件为:成熟温度13℃,成熟时间4d,成熟相对湿度60%。最终得到低酸度的川味香肠p H5.50,感官评分为92分,产品酸味适中,麻辣爽口,具有传统四川香肠的特有风味。      

一株耐甲氧西林金黄色葡萄球菌噬菌体qdsa002的分离鉴定及其生理学性质研究

为探究耐甲氧西林金黄色葡萄球菌的生物防治方法,从青岛市团岛污水处理厂采集到的污水中分离得到了一株噬菌体qdsa002。借助噬菌斑形态、酶切、电镜等技术对其进行了分类鉴定。研究了其最佳感染复数、一步生长曲线、p H稳定性和热稳定性等生理学特征。结果表明,qdsa002核酸属于线型双链DNA,具有正多面体的头部及较长的尾部,qdsa002头部直径约47 nm,尾长约120 nm,属肌尾噬菌体科。生理学特征研究结果表明,qdsa002在双层平板上能形成清晰透亮的噬菌斑。最佳感染复数为0.001,潜伏期40 min,爆发期180 min。在p H为5~9范围内能够保持良好的生理活性。在温度不高于50℃条件下裂解性能良好。该噬菌体可用于防治MRSA感染的生物制剂。      

肉桂精油对成团泛菌和腐生葡萄球菌的抑菌活性及其机理

本文利用滤纸片法和二倍稀释法分别测定了肉桂精油对成团泛菌及腐生葡萄球菌的抑菌圈直径、最小抑菌浓度(MIC)以及最小杀菌浓度(MBC)来评估肉桂精油对其的抑菌活性,通过扫描电镜、透射电镜探究肉桂精油对成团泛菌和腐生葡萄球菌的形态影响,以及通过测定细胞膜的通透性、细胞膜的完整性和膜电位来共同阐释肉桂精油对两种菌活性抑制的机理。结果表明肉桂精油对成团泛菌和腐生葡萄球菌的生长均有较强的抑制作用,且对腐生葡萄球菌的抑菌作用明显强于成团泛菌的抑制作用;肉桂精油改变细胞的形态、增加膜的通透性、破坏了膜的完整性、并造成了细胞内容物的泄露、膜电位的降低,从而导致细菌的死亡。      

金黄色葡萄球菌在猪肉上的生长以及新型肠毒素基因sek的表达

目的:研究金黄色葡萄球菌在猪肉上的生长以及新型肠毒素sek的时序性表达。方法:将实验室保存的三株携带sek基因的金黄色葡萄球菌SA005、SA008和SAB0分别接种于无菌猪肉上37℃静置培养至120 h,每隔12 h取样进行细菌计数以及p H测定,同时收集不同时间点的菌体提取RNA,利用实时荧光定量PCR监测细菌生长过程中sek的相对表达量。结果:三株菌株在猪肉上生长36 h以后进入稳定期,48 h肉上已经出现肉眼可见的金黄色葡萄球菌菌体聚集,120 h肉粒变得粘稠并有黏液渗出;猪肉p H在细菌生长的36 h前变化不大,在120 h已逐渐上升到p H8.85~9.14;三株金黄色葡萄球菌sek的表达量在细菌生长的对数期有一次高表达,随后表达量下降,在生长的稳定后期表达量再次升高,其中,SA005的sek基因在细菌的生长过程中表达量明显高于SA008和SAB0(p<0.01)。结论:三株金黄色葡萄球菌在猪肉上生长,肠毒素sek基因持续表达但相对表达量因菌株而存在差异,sek基因在转录水平上的高表达将会带来食品安全的潜在威胁。      

化妆品中金黄色葡萄球菌焦磷酸测序检测方法的研究

本研究采用焦磷酸测序法对nuc基因的保守片断进行测序,分别对36株金黄色葡萄球菌和30株非金黄色葡萄球菌进行了特异性和复现性实验,并在化妆品中进行了方法验证,建立了化妆品中鉴定金黄色葡萄球菌的焦磷酸测序法,结果表明,本方法具有准确、快速的特点,可满足金黄色葡萄球菌的高通量鉴定的需求。      

不同制备条件对SpA分子印迹聚合微球聚合效果的影响

本文用金黄色葡萄球菌蛋白A(SpA)作为模板,以丙烯酰胺为功能单体,利用反相悬浮聚合法合成了SpA分子印迹聚合微球.通过扫描电镜观测不同条件下聚合微球的聚合效果,研究不同制备条件对SpA分子印迹聚合微球聚合效果的影响,从而筛选制备聚合微球最佳工艺;并检测了制备的分子印迹聚合物对SpA的吸附性能.结果表明,反相悬浮聚合法合成SpA分子印迹微球的最佳工艺条件为:分散剂乙基纤维素(EC)加入量0.20 g/100 mL(甲苯);甲苯与水的比例10:3;交联度10%;引发剂加入方式为缓慢滴加;反应温度50℃.反相悬浮聚合法制备的SpA分子印迹聚合微球对SpA的吸附量:6.956×10-3μmol/g.