外源诱导及共培养对植物乳杆菌J23合成细菌素Lac-B23的影响研究

目的 研究外源诱导物及共培养对植物乳杆菌J23合成细菌素Lac-B23的影响,提高细菌素产量。方法 利用双层琼脂牛津杯扩散法测定细菌素活性,通过单因素实验、自诱导和共培养验证实验探究外源诱导物及共培养对细菌素J23产量的影响。结果 当初始pH为7、37℃培养12 h,细菌素Lac-B23的产量达到最大值,为2560 AU/mL。甘油和丙酮酸基本不影响细菌素Lac-B23的合成;但酪氨酸、苯丙氨酸、精氨酸、谷氨酰胺和亮氨酸则能促进细菌素Lac-B23的产量。此外,自我诱导研究发现植物乳杆菌J23发酵培养基中含有可以诱导细菌素Lac-B23合成的信号分子。一定浓度范围内,植物乳杆菌J23与单增生李斯特菌或金黄色葡萄球菌共培养时可以提高细菌素Lac-B23的产量。然而,诱导菌的灭活菌体和无细胞上清液并不能提高细菌Lac-B23的产量。结论 环境诱导因素对细菌素的合成有较大影响。初始pH、发酵温度、培养时间、酪氨酸、苯丙氨酸、精氨酸、谷氨酰胺和亮氨酸可以作为诱导因子,提高细菌素Lac-B23的产量。此外,共培养诱导分子没有分泌到培养基中,可能需要活的诱导细菌来诱导细菌素Lac-B22的合成。     

绿原酸与Ⅲ型细菌素复配对鸡肉中假单胞菌的抑菌机制

荧光假单胞菌是引起冷鲜鸡肉腐败变质的优势腐败菌,可降解肉品中的蛋白质、脂肪等物质,产生多种 腐败代谢产物,进而使肉类食品风味和品质发生劣变。采用体外抑菌实验研究绿原酸（chlorogenic acid,CA）、 Ⅲ型细菌素Helveticin-M及二者复配对荧光假单胞菌的抑菌效果;通过扫描电子显微镜观察不同处理对荧光假单 胞菌外部形态结构的影响,通过激光共聚焦显微镜观察、测定胞外ATP含量、胞外蛋白和核酸外渗,研究CA或 Helveticin-M对指示菌细胞膜渗透性的影响。结果表明：与CA或Helveticin-M单独作用相比,二者复配后抑菌作用 显著增强（P＜0.05）;绿原酸与Helveticin-M复配处理可显著破坏荧光假单胞菌形态,增强细胞膜渗透性,加剧胞 内物质外泄,最终加速荧光假单胞菌死亡。     

Characterisation of Antimicrobial Producing Lactic Acid Bacteria from Malted Barley

Thirty‐three putative inhibitor‐producing lactic acid bacteria (LAB) were isolated from malted barley based on their ability to inhibit growth of two indicator strains. Eleven of the inhibitor‐producing LAB produced an antimicrobial activity which was active across a wide pH range, relatively insensitive to heat treatment while sensitive to treatment with proteolytic enzymes indicating that the inhibitory compounds are proteinaceous in nature and therefore bacteriocin‐like inhibitory substances. Ten of these eleven malt isolates were observed to secrete the inhibitory compounds into the cell‐free supernatant with optimal production occurring in the late exponential growth phase. The inhibitory spectra of these isolates included various Gram‐positive bacteria among which a variety of beer‐spoiling bacteria.     

干酪乳杆菌细菌素的抗菌机制分析

目的：分析和预测干酪乳杆菌细菌素基因及其编码蛋白的分子结构和理化性质,明确细菌素的抗菌机制。方法：利用生物信息学软件进行细菌素编码蛋白的结构预测和功能分析,采用氨基酸定点突变技术对预测的氨基酸位点进行点突变,检测突变体的抗菌活性。结果：干酪乳杆菌细菌素（LacA和LacB）属于热稳定、分泌信号肽的跨膜蛋白,LacA蛋白存在典型的抗菌结构域GxxxG,构建LacA蛋白中第40位V和第57位I的突变载体,两个位点中任何一个发生突变都明显影响细菌素的抗菌活性。结论：推测V40和I57是干酪乳杆菌细菌素发挥抑菌活性的关键氨基酸位点,为今后探索干酪乳杆菌细菌素（class IIb）抗菌机制提供理论依据。     

乳酸菌细菌素和超高压联合处理对低温切片火腿的防腐保鲜效果

为了揭示乳酸菌细菌素和超高压联合处理对低温切片火腿的防腐保鲜效果,并探讨乳酸菌细菌素和超高压联合处理在低温肉制品防腐保鲜应用中的可行性,在不添加任何化学防腐剂的情况下,分别以乳酸菌细菌素(enterocin LM-2)添加量320AU/g、600MPa超高压处理5min以及两者联合处理低温切片火腿,考察联合处理对样品中微生物数量、理化指标以及感官特性的影响。结果表明：enterocin LM-2和超高压技术的联合使用可明显延长低温切片火腿的货架期,有效减少贮藏过程中挥发性盐基氮的生成及脂肪氧化,并保持产品原有色泽、气味、质构等感官特性。综合微生物和理化特性分析结果,联合处理组的防腐效果最好,可将低温切片火腿的货架期延长至100d。     

Characterization of a Bacteriocin from Lactobacillus plantarum Strain LR/14

A rhizospheric isolate of a lactic acid bacterium, identified as Lactobacillus plantarum strain LR/14, was characterized to produce a bacteriocin. A supernatant from 20h culture growth was used as the source of bacteriocin. The antimicrobial compound showed remarkable stability at high temperatures (100°C for 30 min and 121°C for 15 min under 15 psi pressure) and to the presence of organic solvents, detergents and surfactants. It was also active in the pH regime of pH 2.0–6.0. Moreover, the compound was stable under different storage temperatures as tested up to 24 months. While antimicrobial function was not lost by catalase or β-glycerophosphate treatment, the same was sensitive to a number of proteolytic enzymes. The crude preparation inhibited not only related strains but also other gram-positive and gram-negative bacteria, such as Staphylococcus aureus, Listeria monocytogenes and urogenic E. coli. Bacteriocinogenic activity co-migrated as a single protein band on tricine-SDS-PAGE with molecular mass of ～3.6 kDa.     

产细菌素乳酸菌的筛选及其发酵特性

从传统发酵制品中分离出60株乳酸菌,在排除有机酸及过氧化氢的干扰后,从中筛选出抑菌活性较高的菌株P-319,经常规生理生化实验,鉴定该菌株为短乳杆菌.其发酵上清液经胰蛋白酶和木瓜蛋白酶处理后抑菌活性丧失;对其抑菌谱的测定表明,其能抑制革兰氏阳性菌和革兰氏阴性菌的生长,但对霉菌和酵母菌没有任何抑制作用.产细菌素的发酵过程测定结果表明,该菌株在MRS培养基中30 ℃培养24 h时,抑菌活性达到最高.     

Lactobacillus J23发酵合成抗菌肽Bac-J23培养条件的优化研究

研究了培养条件(接种量、发酵温度、初始pH)对LactobacillusJ23发酵合成广谱抗菌肽Bac-J23的影响,并采用响应面法进行了优化。结果表明,Lactobacillus-J23生产Bac-J23体现出温度、pH梯度和接种剂量依赖性,响应面优化结果表明最适温度和pH分别为36.8℃和5.2,接种量阈值为2.13×104cfu/mL。     

Comparative Study on Antibacterial Effect of Pediocin ACCEL and Nisin Against Fluorescencestained Listeria monocytogenes BCRC 14845

ABSTRACT: Effects of pediocin ACCEL (Class IIa, pediocin-like bacteriocins) and nisin on carboxyfluorescein diacetate (cFDA) -stained Listeria monocytogenes BCRC 14845 was carried out. Decrease of fluorescence intensity in stained cells and increase in efflux were observed with the increase in bacteriocin concentrations up to 12.5 μg/mL. No further decreases in fluorescence intensity and cell numbers were obtained when the concentration of bacteriocins was over 12.5μg/mL. The leakage of efflux was further confirmed by the release of intracel-lular ultraviolet-absorbing substances. Comparing the leaking time of fluorescence, the intensity of cFDA in nisin-treated cells within 1 min incubation was almost comparable to that in pediocin-treated samples after 40 min incubation. Considering the leakage of cFDA, UV-absorbing substances, changes in cell numbers during incubation of cFDA-stained cells, and restoration ability, nisin seemed to reveal mainly bacteriostatic effect and partially bactericidal effect on L. monocytogenes and to cause easier-to-repair membrane damage. However, pediocin ACCEL appeared to have both bacteriostatic and bactericidal effects on L. monocytogenes and to cause more difficult-to-repair membrane damage.     

产细菌素乳酸菌的筛选及对农家干酪保质期的影响

从实验室保存的7 株乳酸菌中,经分离纯化,以金黄色葡萄球菌为指示菌,筛选获得1 株高产细菌素的菌株KLDS 1.0338,排除有机酸和过氧化氢的干扰以及蛋白酶敏感性实验,确定抑菌作用是由细菌素产生的。通过菌株形态学分析,生理生化及16S rDNA分析鉴定菌株KLDS 1.0338为干酪乳杆菌ATCC 334。进一步利用该菌株制作农家干酪,考察4 ℃贮藏期间干酪的变化,添加KLDS 1.0338干酪乳杆菌的实验组抑菌活性显著大于未添加KLDS 1.0338干酪乳杆菌组（P＜0.01）,实验组的pH值下降平缓,可以有效延长农家干酪的货架期,并保持产品原有的色泽、风味、质构等感官特性。