广谱、高效抑菌作用乳酸菌的选育

本对从自然发酵辣椒中分离出的66株乳酸菌的抑菌特性进行了研究，结果发现66株乳酸菌中仅有28株对指示菌表现出抑菌活性，从这28株中选育出了三株具有广谱、高效抑菌作用乳酸菌，对这三株乳酸菌的抑菌成分进行了研究，最后发现起抑菌作用的物质是细菌素。     

广谱高效抑菌作用乳酸菌的选育

对从自然发酵辣椒中分离出的66株乳酸菌的抑菌特性进行了研究，结果发现66株乳酸菌中仅有28株对指示菌表现出抑菌活性，从这28株中选育出了三株具有广谱、高效抑菌作用乳酸菌，对这三株乳酸菌的抑菌成分进行了研究，最后发现起抑菌作用的物质是细菌素。     

产细菌素乳酸菌的选育及其抑菌特性的研究

采用牛津杯琼脂扩散法,从实验室保存的乳酸菌中筛选到具有较高抑菌活性的菌株嗜酸乳杆菌A、戊糖片球菌M和戊糖片球菌T,它们产生的抑菌物质经排除酸、过氧化氢后,仍具有抑菌活性,然而经蛋白酶处理后其抑菌活性明显下降,确定其抑菌物质为细菌素,进一步的抑菌实验表明,3株菌所产细菌素具有较宽的抑菌谱,适宜用作生物型防腐剂。     

金属离子与乳酸菌素对沙门氏菌的协同抑菌作用

通过检测唾液乳杆菌O2A发酵上清液及其所产乳酸菌素对沙门氏菌的抑菌活性,考察金属离子对乳酸菌素抑菌活性的协同作用及其机理。结果表明,单独的乳酸菌素和乳酸菌素-金属离子复配均对沙门氏菌有较好的抑菌效果;不同抑菌剂对沙门氏菌处理18 h后,细菌的生长曲线发生较大变化,且Zn2+(30 mmol/L)-乳酸菌素、Zn2+(30 mmol/L)-发酵上清液的抑菌效果较佳。扫描电子显微镜和透射电子显微镜结果表明,与标准沙门氏菌菌株相比,处理组的菌株细胞完整性均受到不同程度的破坏,破坏程度最严重的Zn2+(30 mmol/L)-乳酸菌素处理组,其抑菌机理可能是破坏细胞结构的完整性,使菌体细胞壁和细胞膜受到损伤,从而抑制细菌生长甚至杀死细菌。     

产细菌素乳酸菌的鉴定及其特性研究

从婴儿粪便中分离获得能够产生抑菌活性物质的乳酸菌,通过排除有机酸、过氧化氢的干扰试验,该菌发酵上清液仍有明显的抑菌活性;通过蛋白酶K和胰蛋白酶试验,证明该菌株产生的抑菌活性物质具有蛋白质性质,是一种细菌素.初步提纯该细菌素,其抑菌活性较适pH范围为2～4,120℃热处理30 min后仍有70%的抑菌活性.经Trcine-SDS-PAGE试验分析该细菌素分子质量为4kDa.抑菌谱测定结果表明,该细菌素不仅对革兰氏阳性菌(单增李斯特氏菌、枯草芽孢杆菌、金黄色葡萄球菌等)有抑制作用,而且还抑制革兰氏阴性菌(大肠杆菌、沙门氏菌、恶臭假单胞菌、福氏志贺氏菌等),具有广谱的抑菌作用.通过菌落形态、生理生化特性试验和16S rRNA基因序列分析,鉴定该乳酸菌为植物乳杆菌,命名为Lactobacillus plantarum ZJ317.     

乳酸菌细菌素抑菌特性及在食品中的应用研究进展

乳酸菌细菌素是细菌在核糖体上合成的具有抗菌活性的多肽类物质,这些细菌素能杀灭或抑制引起食品腐败的细菌的繁殖,可作为天然的食品防腐剂在食品中应用。该文综述了乳酸菌细菌素的分类、国内外研究现状、抑菌特性及应用等方面的最新研究进展,并对乳酸菌细菌素未来研究趋势进行简要分析,对乳酸菌细菌素在食品中的应用有一定参考价值。     

产广谱细菌素乳酸菌的筛选

从四川传统发酵食品、市售酸奶、自制泡菜、香肠中分离出267株乳酸菌,采用平板挖井法从中筛选了64株对大肠杆菌、金黄色葡萄球菌、藤黄微球菌、铜绿假单胞杆菌、枯草芽孢杆菌有抑制作用的广谱抑菌性乳酸菌菌株,再对这些乳酸菌采用牛津杯抑菌实验,排除酸、过氧化氢干扰后,部分菌株的发酵上清液仍有很强的抑菌作用;进行胰蛋白酶、木瓜蛋白酶处理后,发酵上清液抑菌活性降低,因而确定产生的抑菌物质为蛋白质类细菌素。     

乳酸菌对酸乳中霉菌的抑制作用研究

以酸乳中的腐败霉菌为指示菌,采用双层平板拮抗法对28株乳酸菌进行了抗霉菌筛选,得到了9株抗性菌株,分别属于戊糖乳杆菌(Lactobacillus pentosus)、乳酸乳球菌乳酸亚种(Lactococcus lactis subsp)以及植物乳杆菌(Lactobacillus plantarum)。对戊糖乳杆菌(Lactobacillus pentosus)ZJ28在不同培养条件下的抑菌能力进行了研究。结果表明,L.pentosus ZJ28在37℃下,恒温培养26~50 h,pH值为4.5或5.5时抗霉菌活性最好。     

乳酸菌细菌素的高效表达方法研究

乳酸菌细菌素作为天然的生物防腐剂,因其高效、无毒等特点而备受关注,但目前只有乳酸链球菌素实现了工业化生产。乳酸菌细菌素产量低是限制其大规模生产的瓶颈之一。从高产菌株筛选、发酵条件调控、基因工程技术、诱导调控和胁迫刺激应答5个方面,综述了提高乳酸菌细菌素产量的方法,期望为提高乳酸菌细菌素产量的研究提供新思路。     

生物保鲜乳酸菌的筛选及其细菌素特性研究

利用牛津杯法从传统泡菜和腊肠中分离的80株乳酸菌中筛选出10株具有较高抑菌活性的乳酸菌.通过排除酸性产物有机酸、过氧化氢干扰及抑菌谱试验,LAB5和LAB55仍表现广谱的抑菌活性;2菌株发酵上清液经蛋白酶K、木瓜蛋白酶和胰蛋白酶处理后抑菌活性均有降低,其中LAB5对木瓜蛋白酶敏感,因此可以初步判定这2株乳酸菌产生的抑菌物质为细菌素.2种细菌素具有良好的热稳定性,pH值越低抑菌能力越强;2株菌表现良好的产酸能力,经生理生化和16S rDNA鉴定为植物乳杆菌.     

乳酸菌的固定化方法及其发酵特性的研究

对乳酸菌固定化工艺参数及发酵特性进行了研究,结果表明,乳酸菌包埋法固定最佳工艺条件为:海藻酸钠的浓度为2%,菌体的稀释比例为1:1,CaCl2溶液的浓度为1.5%,菌种的固定化温度为42℃。固定化菌种胶珠含菌量为4.59×109个/g。固定化乳酸菌产酸和耐酸能力强,菌种活力得到保持,具有持久和可重复利用的特点。     

乳酸菌发酵混合乳研究

着重探讨乳酸菌发酵不同比例的混合乳（牛乳和豆乳）的产酸和凝乳工艺条件．结果表明：对豆乳∶牛乳＝２∶１的混合乳中添加１．０％葡萄糖，３．０％蔗糖和２．０％海藻酸钠，接种５％活化的嗜热链球菌和保加利亚杆菌，在４２℃培养６ｈ可获得具有清新的乳酸发酵风味、无豆腥、有乳香、酸味爽口、凝乳良好、口感细腻的混合酸乳     

乳酸发酵鲜菇汁技术研究

以鲜菇汁为原料，经乳酸发酵而制成鲜菇汁发酵饮料，通过对接种量、发酵时间、乳粉量、糖酸比进行试验．从而确定最佳工艺参数为：接种量3％，乳粉量5％，发酵时间3．75h，蔗糖12％，柠檬酸0．04％。     

THE ACTION OF NISIN ON BEER SPOILAGE LACTIC ACID BACTERIA

Within one minute of adding nisin to suspensions of Lactobacilli clumping of cells was observed. This happened with all the strains assayed, irrespective of their sensitivity or resistance to nisin. There was, however, no evidence of cell lysis. Two different assays for cell viability were used to show that the vast majority of cells of sensitive strains were killed within one minute of contact with nisin. The time needed to kill all the cells depended on the concentrations of both nisin and cells. One strain was more resistant and only 50–60% of the cells died within one minute of nisin addition . Using an ATP-bioluminescence assay it was shown that the addition of nisin to both Lactobacilli and Pediococci caused a rapid fall in intracellular ATP levels, which was reflected in a simultaneous appearance of ATP in the extracellular medium. Actively growing cells lost ATP more rapidly than did those in stationary phase. The amount of intracellular ATP lost was affected both by the concentration of nisin used and the sensitivity of the bacteria. It appears that an initial effect of nisin is to make the cell membrane ‘leaky’ as happens with many antibiotics, yeast killer factors (zymocins), colicins, and other gram-positive bacteriocins .     

嗜热菌合成乳酸的研究

从467株原始菌株保藏物中筛选获得了产乳酸的嗜热菌29株.进一步复筛确定19株为产乳酸水平较高的嗜热菌,且均为Bacillus coagulans.采用高效液相色谱法对19株Bacillus coagulans的主要发酵产物进行分析.55℃下发酵54h,总乳酸产量最高的为74.80 g/L,最低的为49.55 g/L.选择总乳酸产量较高的四株菌和产物中杂酸最少的一株菌作为进一步研究的菌株,分析所形成乳酸光学构型发现,5株菌所产L-乳酸的光学纯度均在98%以上,同时皆形成少量D-乳酸.     

INHIBITION OF BEER-SPOILAGE LACTIC ACID BACTERIA BY NISIN

149 strains of bacteria, mostly brewery contaminants able to spoil wort or beer, and 12 brewing strains of yeast (8 ale and 4 lager strains) have been screened using a well-test assay for sensitivity to the food preservative, Nisin (E234), Nisin inhibited growth of 92% of the gram-positive strains, predominantly lactic acid bacteria of the genera Lactobacillus and Pediococcus. In contrast, all 32 gram-negative strains tested, except 3 Flavobacter strains, were Nisin-resistant; in addition none of the brewing yeasts showed Nisin-sensitivity. Therefore. Nisin has potential applications in preventing spoilage of worts or beers by lactic acid bacteria.     

VARIATIONS AMONGST BEERS AND LACTIC ACID BACTERIA RELATING TO BEER SPOILAGE

The ability of lactic acid bacteria to grow in beer has been studied using 31 beers, 13 strains of Lactobacillus and 3 strains of Pediococcus isolated from wort or beer. In 3 beers all the micro-organisms were able to grow, in 5 beers none of them developed and diverse results were obtained with the remaining 23 beers. Resistance of the beers to spoilage was not correlated with values of pH, specific gravity, total or free amino nitrogen, individual or total fermentable sugars, colour or levels of sulphur dioxide. Resistant beers became sensitive after certain filtration treatments and after heating at 80° for 15 minutes, but not after treatment at 60°. Resistance to spoilage is tentatively attributed to the presence of a yeast metabolite which is heat-labile. The lactic acid bacteria varied in their ability to grow in beer but those possessing a broad range of biochemical abilities had the greater propensity to cause spoilage.     

乳酸菌基础培养基比较研究

研究了脱脂乳中性蛋白酶的最适酶解条件，并以保加利亚乳杆菌和嗜热链球菌为混合发酵菌种，对MRS、脱脂乳和脱脂乳酶解液3种基础培养基进行了比较研究。结果表明：（1）脱脂乳中性蛋白酶的适宜酶解条件为：加酶量5000U／g蛋白质，在pH=7．0，50℃下酶解2h；（2）脱脂乳酶解液是保加利亚乳杆菌和嗜热链球菌混合菌种较好的基础培养基，其冻干发酵剂的质量和数量均优于脱脂乳培养基。以脱脂乳酶解液为基础培养基制备的冻干发酵剂的活菌数达到3．5×10^11cfu／g，冻干发酵剂的重量是脱脂乳的1．93倍。     

冷藏鲜肉中腐败乳酸菌的分离及鉴定

利用稀释平板法从冷藏3 d的肉样品中共分离出60株疑似乳酸菌菌株,经过2次划线分离,然后进行革兰氏染色、镜栓、过氧化氢酶试验、明胶液化试验、硝酸盐还原试验和H2S检验,得到36株乳酸菌.将分离出的这36株乳酸菌,经过形态学和生理生化鉴定,确定他们属于5大类,即清酒乳杆菌,13株;马里乳杆菌,8株;消化乳杆菌,7株;口乳杆菌,4株;未知乳杆菌,4株.