乳铁素B的抗菌活性及其影响因素

乳铁素B是牛乳铁蛋白经胃蛋白酶酶解后得到的最重要的抗菌肽，具有较强抗菌活性．研究表明，乳铁素B对大肠杆菌的最小抑菌质量浓度为0．5mg／mL，对金黄色葡萄球菌的最小抑菌浓度为0．4mg／mL；葡萄糖、蔗糖、麦芽糖、牛血清白蛋白(BSA)、尿素、硫酸铵在0～10mg／mL，乳糖、可溶性淀粉在0～4mg／mL，的质量浓度范围内，对乳铁素B的抗菌活性影响不大；当NaCl或KCl的浓度为25～100mmol／L，MgCl2或CaCl2的浓度为1．0～5．0mmol／L时，乳铁素B的抗菌活性就会大大降低；随着缓冲盐浓度和有机酸浓度(25～100mmol／L)的增大，乳铁素B的抗菌活性呈下降趋势，且在微碱性环境下乳铁素B表现出较强的抗菌活力．     

常用防腐剂对牛乳铁蛋白抗菌活性的影响

乳铁蛋白的抗菌活性常受到其他共存成分的影响。本文研究了常用防腐剂对乳铁蛋白抗菌活性的影响。在研究过程中,以大肠杆菌为实验菌株,进行了实验研究。研究表明,在牛肉膏蛋白胨培养基中,pH6.0,菌浓为106CFU/ml的条件下,乳铁蛋白对大肠杆菌的最小抑菌质量浓度为3mg/ml;苯甲酸钠、山梨酸钾、乳酸链球菌素、对羟基苯甲酸等分别与乳铁蛋白共同作用时,对乳铁蛋白的抗菌活性都有明显的影响。其中,山梨酸钾和苯甲酸钠减弱了乳铁蛋白的抗菌活性,乳酸链球菌素和对羟基苯甲酸丁酯加强了乳铁蛋白的抗菌活性。     

牛乳铁蛋白抗菌活性及其影响因素的研究

乳铁蛋白具有广谱的抗菌性 ,它通过直接性的“铁剥夺”和间接性的“膜渗透”2种机制发挥抗菌作用。文中开展了牛乳铁蛋白抗菌活性的研究 ,研究表明 ,牛乳铁蛋白对大肠杆菌的最小抑菌浓度为 2mg/mL ,对金黄色葡萄球菌的最小抑菌浓度为 1 6mg/mL。葡萄糖、蔗糖、麦芽糖、牛血清白蛋白 (BSA)、尿素、硫酸铵在 0～ 1 0mg/mL ,乳糖、可溶性淀粉在 0～ 4mg/mL ,酪蛋白在 0～ 1 2mg/mL的质量浓度范围内 ,对牛乳铁蛋白的抗菌活性影响不大。当NaCl或KCl的浓度为2 5～ 1 0 0mmol/L ,MgCl2 或CaCl2 的浓度为 1 0～ 5 0mmol/L时 ,牛乳铁蛋白的抗菌活性就会大大降低。随着缓冲盐浓度和有机酸浓度 (2 5～ 1 0 0mmol/L)的增大 ,牛乳铁蛋白的抗菌活性呈下降趋势 ,且在微碱性pH环境下牛乳铁蛋白表现出较强的抗菌活力。     

牛乳铁蛋白抗菌活性的研究

研究表明,牛乳铁蛋白对大肠杆菌的最小抑菌浓度为2mg/mL,对金黄色葡萄球菌的最小抑菌浓度为1.6mg/mL;牛乳铁蛋白与溶菌酶联合作用能增强其抗菌效果;葡萄糖、蔗糖、麦芽糖、牛血清白蛋白(BSA)素、硫酸铵在0～10mg/、尿mL,乳糖、可溶性淀粉在0～4mg/mL,酪蛋白在0～1.2mg/mL的质量浓度范围内,对牛乳铁蛋白的抗菌活性影响不大;当NaCl或KCl的浓度为25～100mmol/L,MgCl2或CaCl2的浓度为1.0～5.0mmol/L时,牛乳铁蛋白的抗菌活性就会大大降低;随着缓冲盐浓度和有机酸浓度(25～100mmol/L)的增大,牛乳铁蛋白的抗菌活性呈下降趋势,且在微碱性pH环境下牛乳铁蛋白表现出较强的抗菌活力;在巴氏杀菌温度范围内,加热对牛乳铁蛋白抗菌活性影响不大,过高的温度(90～120℃)会使牛乳铁蛋白变性,从而使其抗菌活性大大下降。     

乳铁蛋白和乳铁素的抗菌活性比较

牛乳铁蛋白是从牛乳中提取出来的一种铁结合性糖蛋白，牛乳铁素是从牛乳铁蛋白N-端水解下来的25个氨摹酸残荩。它们具有多种乍物学功能，其中的广谱抗菌性尤为引人注目。本实验以牛初乳中提取的乳铁蛋白及其水解产物乳铁素为研究对象，选取大肠杆菌为实验菌株，进行铁饱和乳铁蛋白和缺铁性乳铁蛋白、乳铁素对大肠杆菌生长抑制的比较研究。研究结果表明：铁饱和乳铁蛋白、缺铁性乳铁蛋白和乳铁索的最小抑菌浓度分别为6mg／ml、3mg／ml和15μg／ml，乳铁素的最小杀菌浓度为30μg／ml。乳铁蛋白水解后，经纯化获得的乳铁素，其抗菌能力较缺铁性乳铁蛋白增加200倍，较铁饱和乳铁蛋白增加400倍。     

平贝总碱体外抗菌活性研究

探讨平贝总碱的体外抑菌活性.采用纸片扩散法和琼脂平板稀释法测定平贝总碱对常见致病菌的体外抗菌活性及最低抑菌浓度(MIC).平贝总碱对金黄色葡萄球菌、大肠杆菌、克雷伯氏肺炎杆菌、铜绿色假单胞杆菌皆有抗菌作用,对克雷伯氏肺炎杆菌的最低抑菌浓度为2.5mg/ml;对金黄色葡萄球菌、大肠杆菌、铜绿色假单胞杆菌的最低抑菌浓度为5mg/mL.     

ε-聚赖氨酸抑菌性能研究

分别采用分光光度法、菌体量法以及孔扩散法研究了ε-聚赖氨酸对细菌和真菌的抑菌活性及ε-聚赖氨酸浓度、pH值和温度对其抑菌活性的影响。结果表明,ε-聚赖氨酸对金黄色葡萄球菌、大肠杆菌、黄曲霉、枯草芽孢杆菌、酿酒酵母、保加利亚乳杆菌等6种供试微生物均有一定的抑制作用,对大肠杆菌、金黄色葡萄球菌、保加利亚乳杆菌抑制效果较好,对黄曲霉较差;对各种菌的最小抑菌浓度(MIC)为大肠杆菌、金黄色葡萄球菌、保加利亚乳杆菌12.5 mg/L;枯草芽孢杆菌25 mg/L;酿酒酵母800 mg/L;黄曲霉1 600 mg/L。ε-聚赖氨酸的抑菌活性随其浓度的增加而增强,热稳定性非常好,能耐100℃的高温,在pH5～8抑菌活性最强,与甘氨酸、Nisin都有协同增效的作用。     

乳铁蛋白及乳铁素对嗜酸乳杆菌生长影响的研究

本实验主要针对乳铁蛋白和乳铁素对嗜酸乳杆菌的生长影响进行研究。结果表明,在37℃恒温培养下,添加一定浓度的乳铁蛋白或乳铁素,可促进嗜酸乳杆菌生长繁殖。乳铁蛋白的最适添加浓度为2.5mg/ml,乳铁素的最适添加浓度为0.15mg/ml,培养26h后活菌数分别达到6.7×108CFU/ml和8.0×108CFU/ml。     

酶解牛乳铁蛋白制备乳铁素 B的酶解条件研究

乳铁素B是牛乳铁蛋白经胃蛋白酶酶解后所得到的最重要的抗菌肽，乳铁蛋白酶解生成乳铁素后抗菌活性大大增强。通过正交试验确立了牛乳铁蛋白酶解制备乳铁素B的最佳条件，指出在底物质量浓度为50g／L，酶与底物质量浓度比为1：30(质量比)，酶解时间为60min时所得的乳铁素质量浓度及活性较好。     

半乳糖基甘油月桂酸单酯的抑菌活性和稳定性

研究半乳糖基甘油月桂酸单酯对食品中几种常见腐败菌的抑菌作用及其稳定性。方法：采用倍比稀释法测定半乳糖基甘油月桂酸单酯对5 种细菌和3 种真菌的最小抑菌浓度（minimum inhibitory concentration,MIC）。同时以大肠杆菌和蜡样芽孢杆菌为指示菌,研究pH值、温度、紫外线照射及NaCl质量分数对半乳糖基甘油月桂酸单酯抑菌稳定性的影响。结果：半乳糖基甘油月桂酸单酯对大肠杆菌、蜡样芽孢杆菌等5 种细菌具有较好的抑菌活性,而对黄曲霉、黑曲霉和酿酒酵母等真菌的抑制效果不明显或无抑制效果。半乳糖基甘油月桂酸单酯对荧光假单胞菌的MIC为0.078 mg/mL,对大肠杆菌、枯草芽孢杆菌、蜡样芽孢杆菌和金黄色葡萄球菌的MIC均为0.156 mg/mL。半乳糖基甘油月桂酸单酯在pH 5～8范围内具有较好的抑菌活性,经温度和紫外线照射处理后,抑菌活性有微弱下降,随着NaCl质量分数的增加,其抑菌活性显著下降。     

Enhancement of the activity of novobiocin against Escherichia coli by lactoferrin

The activity of novobiocin against Escherichia coli ATCC 25922 and three E. coli strains that were isolated from cases of bovine mastitis was determined in timekill studies in the presence of bovine lactoferrin. Lactoferrin alone did not affect the growth of any of the strains of E. coli. A combination of 1.0 mg/ml of lactoferrin and novobiocin at 1/16x minimum inhibitory concentration (MIC) was bactericidal for E. coli ATCC 25922. When the concentration was increased to 3.0 mg/ml of lactoferrin, novobiocin was bactericidal at 1/64x MIC. Among the mastitis strains tested, 6789 and 6806 were more susceptible to killing by novobiocin than was strain 6800. Strains 6789 and 6806 were killed when treated with novobiocin concentrations of 2, 1/2, and 1/4x MIC. When these strains were also treated with lactoferrin at 3.0 mg/ml, there was a bacteriostatic effect at novobiocin concentrations of 1/8 and 1/16x MIC for strains 6789 and 6800. Strain 6806 appeared to be more susceptible to the combination of lactoferrin and novobiocin as was evidenced by a bactericidal effect over the 24-h testing period. The combination treatment with cephapirin and lactoferrin showed that there was a synergistic bactericidal effect against all of the E. coli strains tested. These studies indicate that lactoferrin can potentiate the activity of antibiotics against Gram-negative bacteria.     

Antimicrobial properties of pepsin-digested lactoferrin added to carrot juice and filtrates of carrot juice

The objective of this study was to determine the antimicrobial activity of pepsin-digested lactoferrin added to carrot juice and filtrates prepared from carrot juice. Lactoferrin isolated from raw skim milk was digested by pepsin for 4 h at pH 3. The digest of lactoferrin was lyophilized, and the antimicrobial activity of the digests was determined in peptone-yeast-glucose broth, carrot juice, permeate from carrot juice, and the dialysate of carrot juice permeate using Escherichia coli (American Type Culture Collection strain 35343) as the test organism. Growth of E. coli and the inhibitory effect of the peptide were greater in peptone-yeast-glucose broth at pH 7 than at pH 4. The peptic digest of lactoferrin did not have antimicrobial properties in carrot juice at concentrations of less than 10 mg/ml of juice. Carrot juice was filtered through a membrane with a molecular weight rejection of 10,000 or 500 Da, and the permeate was dialyzed against distilled water. Growth of E. coli was delayed in the filtrate by 5 mg but not by 1 mg of the peptic digest of lactoferrin per ml of filtrate. Bacterial counts of the control and experimental samples were not significantly different after 24 h of incubation. The peptic digest of lactoferrin at a concentration of 5 mg of digest per ml of dialysate was bacteriostatic toward E. coli after 24 h of incubation at 23 degrees C. Dialysis of permeate caused a percentage reduction in cation concentration in the permeate ranging from 69.23% (Co) to 99.32% (Na). The antimicrobial activity of lactoferrin added to carrot juice was probably inhibited by cations.     

普洱茶与绿茶提取物体外抑菌效应的研究

采用滤纸片扩散法分别研究不同浓度的普洱茶和绿茶提取物对李斯特氏菌(L. monocytogenes)、猪粪链球菌(S. faecalis)、大肠杆菌(E. coli)、鼠伤寒沙门氏菌(S. typhimurium)、金黄色葡萄球菌(S. aureus)和炭疽杆菌(B. anthracis)6 株食源性微生物和致病菌的抑制效果及其最小抑菌浓度(MIC)。结果表明：普洱茶提取物在1%～7%(m/V)范围内对李斯特氏菌(L. monocytogenes)有较强的抑制作用,其MIC 为0.07mg/ml,在5%～7% 范围内对所有供试菌种均有抑制作用,对炭疽杆菌的抑制效果最好。绿茶提取物在1%～2%(m/V)范围内仅对李斯特氏菌(L. monocytogenes)有抑制作用,其MIC 为0.09mg/ml,在3% 时仅对炭疽杆菌(B. anthracis)无抑制作用,在4%～7% 范围内对所有供试菌种都有抑制作用,对猪粪链球菌抑制效果最好。     

桑叶活性成分的抑菌作用及稳定性研究

以桑叶为原料,提取多糖、黄酮、生物碱三种活性成分,采用牛津杯法测定活性成分抑菌效果,并研究桑叶黄酮对供试菌的最小抑制浓度（MIC）及抑菌稳定性。结果表明,桑叶多糖对供试菌无抑制作用;桑叶生物碱对大肠杆菌、金黄色葡萄球菌具有抑制作用,抑菌圈直径分别为9.8 mm、13.7 mm;桑叶黄酮对供试菌的抑制效果较好,对金黄色葡萄球菌、大肠杆菌、灰葡萄孢和扩展青霉的最小抑菌浓度分别为5.09 mg/mL、10.18 mg/mL、20.35 mg/mL、20.35 mg/mL;桑叶黄酮在热（40～100 ℃）、紫外照射及酸性（pH 5～7）条件下均有良好的抑菌稳定性。     

酶联免疫法测定牛初乳中乳铁蛋白含量

应用酶联免疫法制定牛初乳中乳铁蛋白的含量,最小检出量为０．５ｎｇ／ｍｌＬＦ,浅性范围为０．８ｎｇ／ｍｌ至１００ｎｇ／ｍｌ。标准曲线性方程为Ｙ＝－２２．７２Ｘ＋２１．３８,相关系数γ为０．９９６。结果较为理想,这种对ＬＦ的检测方法在国内未见报道。     

Inactivation of escherichia coli O157:H7 in cattle drinking water by sodium caprylate

Escherichia coli O157:H7 is an important foodborne pathogen. Cattle serve as one of the major reservoirs of E. coli O157:H7, excreting the pathogen in feces. Environmental persistence of E. coli O157:H7 is critical in its epidemiology on farms, and the pathogen has been isolated from cattle water troughs. Thus, there is a need for an effective method for killing E. coli O157:H7 in cattle drinking water. In this study, the efficacy of sodium caprylate for killing E. coli O157:H7 in cattle drinking water was investigated. A four-strain mixture of E. coli O157:H7 was inoculated (6.0 log CFU/ml) into 100-ml samples of well water containing 0, 75, 100, or 120 mM sodium caprylate. Water samples containing 1% (wt/vol) bovine feces or feed also were included. The samples were incubated at 21 or 8 degrees C for 21 days. Water samples were analyzed for viable E. coli O157:H7 on days 0, 1, 3, 5, and 7 and weekly thereafter. Triplicate samples of each treatment and control were included, and the study was repeated twice. The magnitude of E. coli O157:H7 inactivation in water significantly increased (P < 0.01) with increases in caprylate concentration and storage temperature. At 120 mM, sodium caprylate completely inactivated E. coli O157:H7 in all the samples after 1 to 20 days, depending on the treatments. The presence of feces or feed also had a significant effect (P < 0.01) on the antibacterial property of caprylate; the presence of feces decreased the antibacterial effect, whereas addition of feed enhanced the effect. These results indicate that sodium caprylate is effective in killing E. coli O157:H7 in cattle drinking water, but detailed cattle palatability studies of water containing caprylate are necessary.     

桦褐孔菌多酚抑菌活性分析研究

为减少辅料糠壳给酒体带来的邪杂味，研究箭竹作为辅料酿造小曲酒的工艺。分别考察箭竹的粉碎大小、加量、小曲种类、入窖温度对箭竹小曲酒的影响。结果表明，约7.0 mm长、3.0 mm宽的箭竹适合作小曲固态酿酒辅料，箭竹使用前清蒸1 h，加量为7%，选用泸州某小曲，入窖温度为24 ℃。通过理化分析及感官评定表明在该优化条件下，出酒率为47%以上，总酸含量为685.3 mg/L，总酯含量为1 071.5 mg/L，达到优级白酒标准；小曲酒酒体清香纯正，柔和谐调、醇甜爽净，除具有乙酸乙酯为主体的复合香气外，还带有箭竹独有的清香味。