植物乳杆菌天然质粒分类

为建立植物乳杆菌天然质粒分类方法,以质粒复制起始蛋白(replication initiation protein,Rep)作为分类标记,通过系统进化树分析方法,将植物乳杆菌53个编码Rep天然质粒划分为6个质粒类型,包括5个质粒家族和1个新的复制类型质粒,之后进一步提出了每个质粒家族特有的骨干序列,最终建立了一种简单、有效的植物乳杆菌天然质粒的分类方法和标准。与以往质粒功能和不相容性分类方法相比较,本方法具有较好的实用性和通用性。     

一株植物乳杆菌的分离鉴定及其隐蔽质粒的序列分析

从传统发酵乳制品中分离到1 株乳酸杆菌,经API 50 CH 细菌鉴定系统和16S rRNA 基因序列分析后鉴定为植物乳杆菌。分析该菌的质粒图谱后发现该菌携带多个质粒,将其中的小质粒pLD1 测序,结果显示该质粒的大小为2112bp,碱基G+C 含量为37.8%,只编码1 个复制蛋白,其中有1 个17bp 的序列重复了13 次。BLAST 发现该质粒同pLP2000 等的同源性在95% 以上,其中复制蛋白同其他质粒存在一些氨基酸差异。pLD1 质粒序列的GenBank 登陆号为NC_012220,并且它可用于构建良好的乳杆菌基因工程载体。     

乳杆菌属天然质粒研究进展

天然质粒在乳杆菌属多个菌种中已被发现,它们携带了许多重要生理功能和胁迫因子抗性基因,对乳杆菌遗传、代谢、进化等生物学研究具有重要意义。本文概述乳杆菌属天然质粒的生物学特征、分布和主要功能,重点对乳杆菌属天然质粒的复制类型与调控机制的研究进展进行综述,最后对乳杆菌质粒的未来研究方向进行探讨,希望可以为相关研究人员提供有益的参考与借鉴。     

短乳杆菌的研究和应用进展

短乳杆菌是乳酸菌中乳杆菌属的重要菌种。研究和报道表明,短乳杆菌具有高产酸能力和解毒、抑菌、提高机体免疫能力等多种功能特性,已被逐渐应用于食品和医药生产中。     

泡菜中乳杆菌的快速检出和乳杆菌质粒资源的初步调查

乳杆菌(Lactobacillus)的质粒不仅决定了乳杆菌的某些性状,还应用于乳杆菌克隆表达载体的构建,是一种珍贵的遗传信息资源。为了调查中国泡菜中的乳杆菌质粒资源,采集了52份中国泡菜样品,采用乳杆菌PCR快速检出技术检出其中的乳杆菌,并用16s rDNA测序验证检出结果,然后提取检出乳杆菌菌株的质粒。结果检出1株清酒乳杆菌(Lactobacillus sakei)和18株植物乳杆菌(Lactobacillus plantarum),乳杆菌检出率为36.5%。检出含质粒的乳杆菌菌株11株,琼脂糖电泳显示有9种质粒谱型,乳杆菌质粒检出率为21.2%,质粒谱型检出率为17.3%。调查结果提示,中国泡菜中蕴藏丰富的乳杆菌质粒资源,值得进行更大规模的调查和研究。     

泡菜发酵专用短乳杆菌的高密度培养

为了实现泡菜发酵专用短乳杆菌H3的高密度细胞培养,考察了培养基成分、培养条件、中和剂以及补料策略对菌体活菌数的影响。结果表明:菌体适宜培养基配方为葡萄糖25 g/L,酵母粉15 g/L,柠檬酸1.53 g/L,柠檬酸钠18.58 g/L,VB620 mg/L,Mg SO4·7H2O 0.58 g/L,Mn SO4·5H2O 0.25 g/L,Tween-80 1 g/L,在培养过程中使用20%柠檬酸钠调节培养液p H值6.8~6.3、培养温度30℃、装液量40 m L/250 m L三角瓶,适宜补料培养方式为培养10 h和20 h时各补加4%的碳氮源(碳氮比为5∶3)。培养结束时培养液中短乳杆菌活菌数可达1.27×1010CFU/m L,为未优化前的7.5倍,是目前已报道的最高活菌数水平,为实现泡菜发酵专用的短乳杆菌发酵剂的工业化生产奠定基础。     

益生乳杆菌质粒抗生素抗性基因与其耐药性的相关性探讨

采用K-B药敏纸片法检测了5株具有潜在益生乳杆菌的耐药性,通过质粒消除,分析了菌株质粒与耐药性之间的联系,应用PCR确定了质粒决定的耐药基因。5株乳杆菌对万古霉素、多粘菌素B以及链霉素等7种抗生素普遍表现出抗性,但主要对四环素敏感。采用SDS与SDS-高温两种方法消除戊糖乳杆菌CH8的质粒后,菌株CH8表现出头孢噻吩和氯霉素敏感性。设计β-内酰胺类抗性基因blr、ECP-1569和nps-1以及氯霉素抗性基因cmlA、cat和cmlA1的引物进行PCR,与目的产物测序比对表明,戊糖乳杆菌CH8的质粒上含有β-内酰胺类抗性基因blr,该基因与其头孢噻吩抗性有关。该研究为探讨乳酸菌的抗药基因转移性提供了前期基础,有助于益生乳杆菌安全性评价体系的建立与完善。      

短乳杆菌的培养条件及高密度培养研究

对实验室自制泡菜中分离到的短乳杆菌进行生长特性研究,并采用响应面分析对影响短乳杆菌增殖的发酵培养基进行优化.首先采用PB实验筛选影响短乳杆菌增殖的显著因素,利用最陡爬坡实验逼近最大增殖区域,最后应用中心组和设计和响应面分析确定短乳杆菌高密度培养的最佳优化培养基成分为(%W/V):MRS基础培养基、乳糖0.2、大豆蛋白0.53、番茄汁0.4、胡萝卜汁1.04、醋酸钠0.05、碳酸钙0.125、磷酸氢二钠0.075,乳酸菌高密度培养活菌数可达5.21×109cfu/mL.     

乳杆菌噬菌体基因组学研究进展

随着乳杆菌在乳品工业中的广泛应用,噬菌体污染对终产品造成的严重威胁日益增加。目前,噬菌体相关研究已从最初的形态学进入到了分子水平。许多噬菌体的全基因组测序工作已经完成。基因组研究有助于揭示噬菌体侵染宿主的机制,能挖掘其关键功能基因。本文基于乳杆菌噬菌体的基因组信息对主要乳杆菌噬菌体基因组的特征、功能基因组及比较基因组进行了分析和概述,为进一步研究噬菌体提供理论依据。     

短乳杆菌发酵对红枣汁品质的影响

该研究利用短乳杆菌(Lactobacillus brevis,LB)发酵红枣汁,生产具有功能性成分的γ-氨基丁酸(γ-aminobutyric acid,GABA)作为膳食补充剂。通过分析发酵过程中红枣汁的营养成分和抑菌性能动态变化,探究发酵对红枣汁品质的影响。结果表明,在添加质量浓度5 g/L的L-谷氨酸、接种8%的短乳杆菌、发酵时间为60 h时产生的GABA量最大,为288. 04μg/m L;在发酵72 h过程中总酚含量、DPPH和ABTS自由基清除率均呈现先增加后降低的趋势,总酸含量和发酵液的抑菌性能呈现上升趋势;红枣汁经短乳杆菌发酵后不仅可以提供益生菌,还可以提供许多有益健康的营养物质,因此经短乳杆菌发酵后红枣汁的品质明显优于发酵前。该实验的研究结果可为开发富含GABA的功能性红枣汁饮料提供理论依据。     

Lactobacillus brevis W5-17产生1,3-丙二醇的条件研究

从酸败果酒中分离到1株可同时利用葡萄糖和甘油产生1,3-丙二醇的乳杆菌,经鉴定为Lactobacillus brevis。当葡萄糖∶甘油为0.05mol/L∶0.1mol/L时,厌氧发酵70h,1,3-丙二醇产量为11.2mmol/L,生成速率为0.16mmol/(L.h),甘油的转化率为0.30mol/mol,甘油脱水酶活性为0.84U/mL,1,3-丙二醇氧化还原酶活性为3.80U/mL,该研究为过量生产1,3-丙二醇的乳酸菌工程菌株改造奠定了基础。     

Influence of Lactobacillus brevis on metabolite changes in bacteria-fermented sufu

Sufu is a form of food derived from traditional Chinese fermented soybean. It has a unique flavor and contains abundant nutrients. With demands for healthy food on the rise, a higher level of sufu functionality is required. In fermentation of soybean-derived products, lactic acid bacteria (LAB) are widely used as an adjunct culture, which provides health benefits and enhances flavor of food. Among LAB, Lactobacillus brevis has the potential to generate γ-aminobutyric acid (GABA), which is well-known for its physiological functions. In this study, L. brevis was added to bacteria-fermented sufu to evaluate its impacts on sufu quality. Sufu was produced via co-inoculation with Bacillus subtilis and L. brevis (group A sufu) or a single inoculation with B. subtilis (group B sufu). Metabolite changes in the two groups during fermentation were investigated and physicochemical changes were observed. The results indicated that the addition of L. brevis increased the concentration of GABA and decreased the concentrations of histamine and serotonin. The concentrations of volatile compounds, such as esters and acids, especially 2-methyl-butanoic acid ethyl ester, as well as the concentrations of phenylethyl alcohol and 3-methyl-butanol were significantly higher in group A. Inoculation of L. brevis changed the metabolite profile of sufu and improved its functionality and safety of edibility. The current study explored the potential of applying L. brevis to the manufacture of bacteria-fermented sufu.     

消毒处理对表皮葡萄球菌和短乳杆菌的杀菌研究

为了保证真空包装的萝卜干的品质,试验通过在培养基中添加不同浓度的过氧化氢、次氯酸钠和臭氧水对从“胖袋”的萝卜干中分离出的表皮葡萄球菌和短乳杆菌分别进行了消毒处理.并且研究了温度对萝卜干品质的影响.结果显示:50 mg/kg的过氧化氢、350 mg/kg的次氯酸钠、通臭氧2.5h就可以完全杀灭表皮葡萄球菌.250 mg/kg的过氧化氢、通臭氧2h可以完全杀灭短乳杆菌,但次氯酸钠对短乳杆菌的杀菌效果较差.85℃处理萝卜干5 min后有较好的杀菌效果,但是萝卜干的品质遭到严重破坏.     

Detection of Beer‐spoilage Lactobacillus brevis strains by Reduction of Resazurin

Lactobacillus brevis is the most common beer‐spoilage bacteria found in breweries. Due to its high prevalence and biodiversity, it is necessary to differentiate between the strains based on their hop tolerance. Forcing tests are often conducted for different types of beer, which can vary in cereal base, fermentation type, ethanol‐ and hop content. These conventional tests are considered to be the safest way to determine the ability of a given strain to cause beer‐spoilage, but they are very time consuming and costly. Since NADH₂ is used as cofactor by many cellular dehydrogenases, this study used the reduced form of intracellular nicotinamide adenine dinucleotide (NADH₂) as an indicator for microbial metabolic activity and thus ability to spoil beer, in order to reduce the time required to conduct the forcing tests for beer production. Beer‐spoiling L. brevis strains were detected among other strains in beer samples within two days (of sampling).     

Production of proteinaceous antifungal substances from Lactobacillus brevis NCDC 02

Forty standard Lactobacillus cultures were checked for their antifungal properties against nine standard fungi. Yeasts were found to be more resistant than moulds. Lactobacillus brevis NCDC 02 was selected for further studies due to the maximum antifungal activity and proteinaceous nature of antifungal substance production. The optimum production of antifungal substances was at 37°C for 48 h and at the initial pH of 6–7 of the medium. The antifungal substances were heat- and pH-stable. The antifungal substances were found to be hydrophobic and their molecular weight was found to be more than 1 kDa and less than 5 kDa.     

短乳杆菌AR247的抗氧化成分及其抗衰老作用

对短乳杆菌AR247的抗氧化成分及其对D-半乳糖致衰老小鼠的保护作用进行研究。通过分级萃取等试验得知,短乳杆菌AR247的抗氧化成分多为水溶性组分和胞内组分。通过皮下注射D-半乳糖【150 mg/(kg·d)】6周后,建造衰老模型,然后灌胃6周1.0×10^9 CFU/mL(1 mL/100 g)的短乳杆菌AR247。结束后测定血清、肝脏和脑中的抗氧化水平,如过氧化氢酶(CAT)、超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GSH-Px)活力和谷胱甘肽(GSH)、丙二醛(MDA)的含量。同时测定小鼠血清中的白介素2(IL-2)、肿瘤坏死因子α(TNF-α)含量。结果表明:短乳杆菌AR247能延缓D-半乳糖引起的衰老,如恢复体重和脑指数至正常水平,使小鼠的CAT、SOD、GSH-Px活性升高(P<0.05),GSH含量升高(P<0.05),MDA含量降低(P<0.05),其中肝脏MDA含量降至正常的66.13%。与模型组相比,免疫水平提高(P<0.05),IL-2含量提高至正常组的104.50%。短乳杆菌AR247具有抗氧化和延缓衰老作用,其体内抗氧化的作用机制可能与改善机体的抗氧化功能和增强免疫功能有关。