温度、pH值对Nisin抑菌活性的影响

研究了温度、pH值对Nisin抑菌活性的影响。结果表明:温度、pH会显著影响Nisin活性,在酸性条件下,Nisin对温度较稳定,随着pH值的增加,温度越高,Nisin活性下降越显著,pH6和7时,121℃、20min高温后Nisin活性完全丧失。同时,放置温度和时间对Nisin活性也有显著影响,放置温度越高、时间越长,Nisin活性下降越显著。     

Nisin抑菌作用的研究

采用琼脂扩散法测定温度和pH值分别作用和联合作用对Nisin的抑菌效果的影响.结果表明,在pH<4时Nisin的稳定性较强,温度对其活性几乎无影响,随着pH值的降低,Nisin抑菌作用增强;当pH>4时,温度对其活性影响较大,随着pH值的升高,抑菌作用下降;在中、碱性条件下Nisin的活性几乎完全丧失.在相同的处理条件下,Nisin对枯草芽孢杆菌(G )的抑菌效果最好,对金黄色葡萄球菌(G )的抑菌效果也较好,但是对大肠杆菌(G-)的抑菌效果最差.     

复合有机酸保鲜剂OAA-7的抑菌特性研究

本实验以复配保鲜剂OAA-7(主要成分为抗坏血酸、柠檬酸、乳酸、丙氨酸、氯化钠、氯化钙和丙三醇)为对象,研究OAA-7抑菌谱,以及温度、pH、保存条件对其抑菌活性的影响.结果表明,OAA-7抑菌活性强、pH作用范围广,性质稳定,保质期长,在高温下也有较高的活性;对革兰氏阳性细菌、革兰氏阴性细菌以及霉菌都有抑制作用.     

不同环境因素和食品基质对Nisin抑制单增李斯特菌活性的影响

单增李斯特菌是一种人畜共患病食源性致病菌,对食品安全和人类健康存在严重的威胁。该研究以单增李斯特菌为指示菌,采用2倍梯度稀释法测定了乳酸链球菌素(Nisin)的最小抑菌浓度(minimum inhibitory concentration, MIC),并通过双层琼脂平板法探究不同环境因素以及食品基质对Nisin抑菌活性的影响。结果表明,Nisin对单增李斯特菌的MIC为250μg/mL。Nisin在100℃以内保持良好活性;温度达到121℃时,抑菌圈直径降低为11.75 mm。pH 2～10抑菌活性随着pH值的升高而降低,抑菌圈直径从14.87 mm显著降低至8.73 mm。NaCl浓度为0.2 mol/L时,对Nisin抗菌活性有显著增强作用。脱脂奶粉质量浓度达到120 g/L时,抑菌圈直径从14.62 mm显著降低至10.53 mm;卵磷脂质量浓度达到12 g/L时,抑菌圈直径从14.20 mm降低至9.10 mm;蔗糖质量浓度升高至60 g/L时,抑菌圈直径从14.77 mm减小至12.97 mm;可见,3种食品基质(脱脂奶粉、卵磷脂和蔗糖)对Nisin抑菌活性均有不利影响。上述...     

乳酸链球菌素脂质体在不同pH值条件下的稳定性及其抑菌效果

为了提高乳酸链球菌素（Nisin）的利用率,实现其长效、缓释型抑菌性能,采用薄膜-超声法制备Nisin脂质体,以大豆卵磷脂为壁材,利用傅里叶变换红外光谱分析Nisin脂质体的内部结构及不同pH值条件对Nisin脂质体稳定性及其包埋率和缓释效果的影响,比较不同pH值条件下热处理对Nisin脂质体抑菌效果的影响。结果表明：Nisin被结合在卵磷脂内部,两者通过相互作用形成的氢键结合在一起。随着体系pH值的降低,Nisin脂质体的粒径逐渐增大,颗粒规整度变差,同时包埋率降低、缓释性变差,稳定性逐渐降低。当pH值为7.0时,Nisin脂质体的包埋率（82.26%）达到最大。此外,pH 6.0时体系缓释能力最强,6 d后总释放率达到96.49%。最小抑菌浓度和最小杀菌浓度分析结果表明,Nisin脂质体的抑菌效果受pH值的影响较小,且与Nisin相比抑菌效果较弱。然而,Nisin脂质体在121 ℃、15 min灭菌处理后仍具有良好的抑菌效果,表明该体系具有热稳定性。动态杀菌曲线结果表明Nisin脂质体具有一定的持续抑菌性能。     

乳过氧化物酶的抑菌试验

分别采用分光光度法、菌体量法以及孔扩散法研究了乳过氧化物酶(LP)的抑菌作用。结果表明,LP对常见的几种食品污染菌均有一定的抑制作用,其中,LP对黄曲霉的抑制作用最显著,4μg/mL就能完全抑制其生长;在中性偏酸性环境中的抑菌活性比碱性环境的抑菌活性强;一定温度内处理不影响LP的抑菌活性;在中性条件下抑制供试革兰阴性菌、霉菌和酵母菌的能力强于Nisin,且LP和Nisin具有协同抗菌作用。     

Nisin/β-环糊精包合物的制备工艺和抑菌活性研究

为改善乳酸链球菌素(Nisin)的水溶性,采用饱和水溶液法,用β-环糊精(β-cyclodextrinβ-CD)对其进行包合。通过正交实验得到其最优条件为pH=3,摩尔比Nisin∶β-CD=1∶2,包合温度40℃,此时Nisin最优包合率达到34.46%。傅里叶变换红外光谱分析与差式扫描量热分析表明,Nisin和β-CD形成包合物,结构发生变化。在抑菌实验中,Nisin/β-CD包合物对金黄色葡萄球菌和枯草芽孢杆菌的抑菌活性与Nisin相比无显著性差异。     

南五味子提取物抑菌作用稳定性的研究

目的:研究南五味子提取物抑菌作用的稳定性。方法:以南五味子为材料,常见食品腐败细菌为供试菌种,探讨pH、温度、还原剂、紫外光等处理对南五味子提取物抑菌活性的影响。结果:在介质pH≤4时对金黄色葡萄球菌、沙门氏菌等细菌有较好的抑菌效果,pH≥5时对沙门氏菌、铜绿假单胞菌等革兰氏阴性菌没有抑菌活性;温度、紫外光、超声波、保存时间对其稳定性几乎没有影响;VC、Na2SO3、NaCl和葡萄糖对其抑菌活性具有一定的增效作用;Na+、K+、Ca2+、Mg2+和Fe3+对其抑菌活性没有或具有少许增效作用,Fe2+对南五味子提取物抑菌活性具有一定的抑制作用。结论:介质pH及Fe2+对南五味子提取物抑菌活性有显著影响,而温度、紫外光、超声波、保存时间、VC、Na2SO3、NaCl和葡萄糖及其他金属离子对其几乎没有影响。     

Spinigerin α抗菌肽的理化特性研究

本研究在对Spinigerin α抗菌肽成功的进行了克隆及表达的基础上,对Spinigerin α抗菌肽的理化性质,包括抑菌特性、温度、pH稳定性等外界条件对其抗菌活性的影响进行了进一步研究。研究结果表明:Spinigerin α抗菌肽的自身浓度、温度、及pH对其抑菌活性均有重要影响,对金黄色葡萄球菌、沙门氏菌、大肠杆菌的最小抑菌浓度分别为1.52%、3.13%、12.5%。当抗菌肽加热至60-100℃时,抗菌肽抑菌效果依然明显,当加热至121℃时,其抑菌效果开始有下降趋势。当处于pH值6.0-8.0的近中性环境中,Spinigerin α抗菌肽的抗菌活性最强。     

壳聚糖对Nisin抑菌稳定性的影响研究

研究了壳聚糖对乳酸链球菌肽（Nisin）抑菌稳定性的作用,并利用红外光谱仪和差式扫描量热仪（DSC）分析了壳聚糖对Nisin保护作用的机理。结果表明：壳聚糖可以显著提高Nisin的抑菌稳定性,在不同的温度及pH范围内,其保护效果有所差异;壳聚糖浓度在1％时效果最好;红外光谱和DSC图谱研究显示,壳聚糖能与Nisin形成氢键,稳定Nisin的空间结构,并能提高Nisin的热稳定性,从而改善了其抑菌稳定性。     

中温乳化香肠中一株优势腐败菌的分离鉴定与生物学特性

以中温乳化香肠为研究对象,对其在25 ℃贮藏过程中的优势腐败菌进行分离鉴定,并通过管碟法和酶标比浊法测定肉制品中常用的7 种防腐剂对腐败菌的抑制效果。结果表明,中温乳化香肠在25 ℃贮藏第25天时,菌落总数已超过GB 2726-2005《熟肉制品卫生标准》中规定的菌落数,从该腐败样品中分离得到1 株优势腐败菌CMRC BC-1,根据形态学、生理生化特征和16S rDNA序列比对结果,该菌株被鉴定为凝结芽孢杆菌。7 种防腐剂中,乳酸链球菌素（Nisin）对该菌株具有明显的抑菌活性,添加量为0.1 g/L时,其抑制率达到99.05%;其余6 种防腐剂除山梨酸钾外,在各自的最大添加量时对该菌株均具有一定的抑制作用。     

防腐剂复配对溶血性金黄色葡萄球菌抑菌效果研究

选择不同的防腐剂,通过药敏纸片法、最小抑菌浓度（MIC）法测定金黄色葡萄球菌对其敏感性,利用正交设计筛选最佳防腐剂组合,并对获得的最佳防腐剂组合抑菌效果进行验证。结果表明,金黄色葡萄球菌对乳酸钠、山梨酸钾不敏感,而对乳酸链球菌素（Nisin）、聚赖氨酸、尼泊金乙酯较为敏感,MIC分别为0.005、0.005和0.313mg/mL。正交试验结果表明,当Nisin、聚赖氨酸和尼泊金乙酯浓度分别为0.01、0.02、0.125mg/mL时效果最佳,可使基质中金黄色葡萄球菌降低7.64个数量级。选择这一最佳组合显示,在室温（25℃）里脊肉、牛乳中细菌数在经过4d放置后,仅仅分别增长2.78、1.86个数量级,而猕猴桃汁细菌数降低了0.73个数量级。     

Production, purification, and characterization of micrococcin GO5, a bacteriocin produced by Micrococcus sp. GO5 isolated from kimchi

Strain GO5, a bacteriocin-producing bacterium, was isolated from green onion kimchi and identified as Micrococcus sp. The bacteriocin, micrococcin GO5, displayed a broad spectrum of inhibitory activity against a variety of pathogenic and nonpathogenic microorganisms, as tested by the spot-on-lawn method; its activity spectrum was almost identical to that of nisin. Micrococcin GO5 was inactivated by trypsin (whereas nisin was not) and was completely stable at 100 degrees C for 30 min and in the pH range of 2.0 to 7.0. Micrococcin GO5 exhibited a typical mode of bactericidal activity against Micrococcus flavus ATCC 10240. It was purified to homogeneity through ammonium sulfate precipitation, ultrafiltration, and CM-Sepharose column chromatography. The molecular mass of micrococcin GO5 was estimated to be about 5.0 kDa by tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis and in situ activity assay with the indicator organism. The amino acid sequence of micrococcin GO5 lacks lanthionine and beta-methyllanthionine and is rich in hydrophobic amino acids and glycine, providing the basis for the high heat stability of this bacteriocin. The N-terminal amino acid sequence of micrococcin GO5 is Lys-Lys-Ser-Phe-Cys-Gln-Lys, and no homology to bacteriocins reported previously was observed in the amino acid composition or N-terminal amino acid sequence. Based on the physicochemical properties, small molecular size, and inhibition of Listeria monocytogenes, micrococcin GO5 has been placed with the class II bacteriocins, but its broad spectrum of activity differs from that of other bacteriocins in this class.     

国产Nisin在鲜猪肉保鲜中的应用

将国产Nisin等防腐保鲜液用于真空包装的鲜猪肉低温贮藏,对微生物、pH值、TVBN值、感观质量等指标进行评价。结果各处理组的微生物指标要优于对照,国产Nisin与其它防腐保鲜剂联合应用比单独使用效果要好。pH值呈先上升后逐渐下降的趋势。TVBN值随贮藏时间的延长而增加,但与菌落总数的变化不完全一致。国产Nisin等防腐保鲜液对鲜猪肉的感观质量无不良影响,与对照组相比,各处理组鲜肉的感观质量均好于对照。     

Release and antilisterial properties of nisin from zein capsules spray-dried at different temperatures

Nisin is an effective antimicrobial against a broad spectrum of Gram-positive bacteria. It has been proposed that reduced efficacy of nisin in foods can be improved by technologies such as encapsulation to protect it from interferences by food matrix components. The potential of spray drying, a practical technology, was studied in this work for encapsulation of nisin in zein microcapsules at four inlet temperatures between 75 and 120 °C. At 95 °C and above, no apparent loss of nisin activity was observed after spray drying. At pH 6.0, burst release of nisin was impacted by spray drying temperature more than equilibrium release, possibly due to influences on capsule structures. At pH 2.0, complete release of nisin in 30 min was observed, contrasting to limited release over 8 d at pH 8.0. Capsules produced at an inlet temperature of 105 °C showed the most sustained release of nisin at pH 6.0. For these capsules, sustained release of nisin to >80% was observed at pH 6.0 and 8.0 when NaCl was used at 0.5 mol/L. Finally, at 400 IU/mL, the encapsulated nisin demonstrated slightly improved antilisterial properties than free nisin in reduced fat (2g/100g) milk but much work is still needed to enhance the antimicrobial effectiveness.     

Identification and Partial Characterization of a Bacteriocin‐Like Inhibitory Substance (BLIS) from Lb. Bulgaricus K41 Isolated from Indigenous Yogurts

Forty‐two strains of Lactobacillus bulgaricus isolated from locally made yogurts were examined and compared for bacteriocin producing ability using spot on lawn assay which improved by taking photo and image processing. Lb. bulgaricus K41 exhibited the highest inhibition level against indicators. K41 Bacteriocin‐like inhibitory substance is sensitive to proteolytic enzymes (proteinase K, pepsin, and trypsin) but α‐amylase makes slight reduction in its activity and it is resistant to lipase. This antibacterial peptide is extremely heat‐stable (121 °C for 15 min) and remains active over a wide pH range (pH = 2 to 10); also nonionic detergents (Tween‐20, Tween‐80, and Triton X100) showed no effect on its activity. The inhibitory spectrum is against Gram‐positive bacteria (except Staphylococcus aureus) with extremely antilisterial activity and it is almost ineffective against Gram‐negative bacteria. The mode of its action was identified as bactericidal against Listeria monocytogenes. The properties of K41 bacteriocin‐like inhibitory substance add to its safety as a biopreservative produced by a generally recognized as safe (GRAS) bacterium suggesting it can be used in hurdle technology for ready‐to‐eat foods as one of the main sources of Listeria contaminations.     

Combined effect of water activity and pH on the inhibition of Escherichia coli by nisin

The Doehlert design and surface response methodology were used to study the influence of pH and water activity (aw) on Escherichia coli inhibition by nisin. Combining stress factors at levels where they are not inhibitory by themselves, a reduction of E. coli survival fraction can be achieved with lower nisin doses than in a single nisin treatment. For all the pH values assayed, a synergistic effect of aw and nisin concentration was detected, and the isoresponse lines showed the existence of an area of maximum inhibition. Factors that reduced viable cell counts by 4 to 5 log cycles were 1,000 to 1,400 IU of nisin per ml at pH 5.5 to 6.5 and a water activity of 0.97 and 0.98. The addition of different ionic and nonionic solutes to control aw suggested that the effect of aw in the inhibitory action of nisin on E. coli cells was not solute-specific. The use of the Doehlert experimental design was effective to determine the optimal combination of stress factors, as well as to point out the most important variables that affected E. coli inhibition.     

杀菌温度对乳化香肠腐败菌群的影响与靶向抑制

采用90、95、100、105、110 ℃ 5 种温度对塑料肠衣灌装的乳化香肠进行杀菌,杀菌时间均为20 min,研 究25 ℃贮藏过程中不同杀菌温度乳化香肠中腐败菌的多样性变化及菌群变化规律,并测定8 种抑菌剂对分离所得菌 株的抑制效果。结果表明：随着杀菌温度的升高,以菌落总数为指标的产品货架期越长,分离得到的腐败菌菌相也 趋于简单。经比较分类,从不同杀菌温度样品中共分离得到10 株腐败菌,根据形态学、16S rDNA菌种鉴定和生理 生化特征分析,分离得到的10 株腐败菌均为芽孢杆菌属。8 种抑菌剂对10 株腐败菌表现出不同的抑制效力,其中 乳酸链球菌素（nisin）和ε-聚赖氨酸具有普遍、明显的抑菌活性;葡萄糖酸-δ-内酯、乳酸钠和双乙酸钠对多数菌株 抑制效果良好;山梨酸钾、亚硝酸钠和脱氢乙酸钠仅选择性地对个别菌株表现出一定的抑制作用。结合不同杀菌温 度乳化香肠的腐败菌菌相分析结果,90、95、100 ℃杀菌样品可以选择Nisin和ε-聚赖氨酸作为抑菌剂;105、110 ℃ 杀菌样品可以根据生产需求选择Nisin、ε-聚赖氨酸、乳酸钠和双乙酸钠4 种抑菌剂。     

Evaluation of the Antibacterial Activity of Piperaceae Extracts and Nisin on Alicyclobacillus Acidoterrestris

Alicyclobacillus acidoterrestris is a gram‐positive aerobic bacterium. This bacterium resists pasteurization temperatures and low pH and is usually involved in the spoilage of juices and acidic drinks. The objective of this study was to evaluate the antibacterial activities of nisin and the species Piper (Piperaceae) on A. acidoterrestris. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) were determined by the broth microdilution method. The species Piper aduncum had the lowest MIC and an MBC of 15.6 μg/mL and was selected for fractionation. Six fractions were obtained, and the dichloromethane fraction (F.3) had the lowest MIC/MBC (7.81 μg/mL). The dichloromethane fraction was again fractionized, and a spectral analysis revealed that the compound was prenylated chromene (F.3.7). The checkerboard method demonstrated that the crude extract (CE) of P. aduncum plus nisin had a synergistic interaction (fractional inhibitory concentration [FIC] = 0.24). The bactericidal activity of (F.3.7) was confirmed by the time–kill curve. P. aduncum, nisin, and prenylated chromene exhibited strong antibacterial activity against the spores and vegetative cells of A. acidoterrestris. The results of this study suggest that extracts of the genus Piper may provide an alternative to the use of thermal processing for controlling A. spoilage.     

Application of nisin,CO2 and a permeabilizing agent in the preservation of refrigerated blue whiting (Micromesistius poutassou)

Gram‐negative bacteria are mainly responsible for spoilage of refrigerated fish. Nevertheless, to preserve refrigerated fresh fish no additives are permitted and only packaging as in a modified atmosphere can be used. Despite the fact that the present‐day application of nisin has been extended to dairy and meat products, its ineffectiveness against Gram‐negative bacteria complicates application to fresh fish unless combined with other additives such as chelators. With this aim, agents that increase the permeability of the membrane and facilitate the diffusion of many hydrophobic antimicrobial agents were screened for their combined activity with nisin against different genera of Gram‐negative bacteria. Quantification of the synergistic effects has shown sodium hexamethaphosphate (SMP) and ethylenediaminetetraacetic acid (EDTA) were the most effective. Further studies were done on the combined effects of nisin, SMP and CO₂ in the preservation of fresh fish. A factorial experimental design was used to determine synergism between these variables. Logarithmic values of total viable counts and total volatile bases after 12 days of storage were described by empirical equations. Analysis of the results showed a marked effect of CO₂ in decreasing both variables. Whereas CO₂ interacted positively with nisin and SMP, a non‐significant interaction was observed between nisin and SMP. It is concluded that CO₂ interacts readily with SMP, and may offer an additional advantage for CO₂‐rich atmospheres in food preservation. Copyright © 2005 Society of Chemical Industry