具有优良发酵特性德氏乳杆菌保加利亚亚种的筛选及其益生特性

本研究对10株实验室保存的德氏乳杆菌保加利亚亚种产酸能力,产黏能力,产香能力和贮藏期稳定性进行测定,并通过测定乳酸菌对抗生素的耐药性、抑菌能力、β-半乳糖苷酶(β-Gal)活性、α-半乳糖苷酶(α-Gal)活性和乳酸脱氢酶(LDH)活性探究菌株的益生特性.单菌株发酵实验结果表明:菌株KSDB-1凝乳时间短(6.3 h)...     

具有优良发酵特性的德氏乳杆菌保加利亚亚种的筛选

对分离自青海、云南及蒙古国等地区的酸牦牛奶、酸山羊奶、乳饼、酸马奶、酸驼奶和酸山羊黄牛混合奶中的22株德氏乳杆菌保加利亚亚种(Lactobacillus delbeueckii subsp.bulgaricus)进行了筛选,通过对其发酵牛乳的发酵时间,pH值,滴定酸度,黏度,游离氨基氮和脱水收缩性等发酵特性进行分析,筛选出IMAU20094等7株具有优良发酵特性的试验菌,适于进一步应用研究.     

德氏乳杆菌保加利亚亚种发酵乳风味成分分析

本实验采用同时蒸馏萃取- 气谱- 质谱(SDE-GC-MS)联用技术对5 株德氏乳杆菌保加利亚亚种L.b-01、L.b-3、L.b-MYC、L.b-SP1.1 和L.b-M01A 发酵乳中风味物质进行了定性和定量测定,经分析分别有13、19、11、9、12 种成分为发酵乳的风味物质,共涉及酸类化合物、酯类化合物、醇类化合物、羰基化合物、芳环和杂环化合物6 大类、22 种物质。除L.b-M01A 菌产乙醇、乙酸含量较高外,其他各菌株间未发现存在明显的代谢差异。     

优良保加利亚乳杆菌菌株的筛选及增殖培养

以24株德氏乳杆菌保加利亚亚种菌株为材料,通过发酵特性分析,包括产酸、产粘、后酸化及发酵风味质地等感官特性,从中筛选出具有优良发酵特性的菌株L3,LB和M28.并对LB菌株的增殖培养基进行了初步探讨,为酸奶发酵剂的开发奠定一定基础.     

德氏乳杆菌保加利亚亚种耐酸机制

德氏乳杆菌保加利亚亚种是最具经济价值的乳酸菌之一,其耐酸能力是影响其发酵性能和发挥益生功效的关键因素。本文就该菌的耐酸能力调节进行阐述。     

优选保加利亚乳杆菌发酵特性的测定

对实验室研究较为成熟的4株保加利亚乳杆菌进行发酵产酸、后酸化测定,同时对单菌株发酵、与嗜热链球菌组合发酵制备的酸奶进行质构测定和感官评价,旨为菌株开发成直投式酸奶发酵提供基础。     

中温发酵乳菌株筛选及其发酵特性分析

采用德氏乳杆菌保加利亚亚种、唾液链球菌嗜热亚种和肠膜明串珠菌混合发酵制备中温(35℃)发酵酸乳制品。根据发酵乳的感官品质、黏度及持水力分析,筛选出菌株德氏乳杆菌保加利亚亚种L2、唾液链球菌嗜热亚种S8、肠膜明串珠菌乳脂亚种M4为发酵剂优组合,其最适宜的接种比例为33︰60︰7。此发酵剂35℃发酵5 h得到的中温发酵乳的感官品质和持水力优于普通发酵乳。三菌混合发酵对上述菌种的生长都有一定的促进作用,但发酵后期M4的生长受到一定抑制。三菌混合发酵乳中酸度主要是L2和S8发酵作用的结果。     

德氏乳杆菌保加利亚亚种发酵对牛乳中β-酪蛋白抗原性的影响

复原脱脂牛乳经德氏乳杆菌保加利亚亚种发酵至凝乳,然后在4℃下冷藏5 d。用间接竞争ELISA法测定了其中β-酪蛋白(β-CN)的抗原残留量,并且对发酵样品的蛋白水解程度与滴定酸度进行了分析。结果表明,复原脱脂乳经90～95℃处理5 min后,β-CN的抗原残留量为60.25%,发酵过程中其抗原残留量持续下降,凝乳时下降到55.46%,而冷藏1 d后降到了最低值54.03%,随后又缓慢上升,冷藏3 d后为55.87%,继续冷藏至5 d,β-CN的抗原残留量基本没有变化,维持在55.5%与55.9%之间。因此采用德氏乳杆菌保加利亚亚种发酵能够在一定程度上降低牛乳中β-CN的抗原性,但是在冷藏5 d的过程中其抗原性又有一定程度的升高。     

德氏乳杆菌保加利亚亚种发酵对牛乳中β-酪蛋白抗原性的影响

复原脱脂牛乳经德氏乳杆菌保加利亚亚种发酵至凝乳,然后在4℃下冷藏5d.用间接竞争ELISA法测定了其中β-酪蛋白(β-CN)的抗原残留量,并且对发酵样品的蛋白水解程度与滴定酸度进行了分析.结果表明,复原脱脂乳经90～95℃处理5min后,β-CN的抗原残留量为60.25％,发酵过程中其抗原残留量持续下降,凝乳时下降到55.46％,而冷藏1d后降到了最低值54.03％,随后又缓慢上升,冷藏3d后为55.87％,继续冷藏至5d,β-CN的抗原残留量基本没有变化,维持在55.5％与55.9％之间.因此采用德氏乳杆菌保加利亚亚种发酵能够在一定程度上降低牛乳中β-CN的抗原性,但是在冷藏5d的过程中其抗原性又有一定程度的升高.     

具有良好风味德氏乳杆菌保加利亚亚种的筛选及其产香性能分析

风味是评价酸奶发酵剂及其产品的重要指标之一。该文以科汉森公司提供的商业发酵剂为对照组,以分离自传统发酵乳制品中具有良好发酵特性的6株德氏乳杆菌保加利亚亚种为试验菌株,从中筛选出1株具有良好风味的菌株。采用固相微萃取(solid phase micro-extraction, SPME)和GC-MS技术测定牛乳发酵终点时的挥发性风味化合物,从中筛选出1株与对照组中的挥发性风味物质的种类和相对含量相似度较高的菌株,并继续分析该菌株在牛乳发酵和贮藏期间所产风味物质的动态变化情况。德氏乳杆菌保加利亚亚种MGA17-6在牛乳发酵和贮藏期间产生的主要风味化合物包括酸类、醛类、酮类、酯类、醇类等,其中一些重要的化合物如乙酸、乙醛、庚醛、乙偶姻、1-庚醇等对发酵乳的风味产生重要的影响。筛选出1株具有良好风味的德氏乳杆菌保加利亚亚种MGA17-6。     

Productions and monomer compositions of exopolysaccharides by Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus strains isolated from traditional home-made yoghurts and raw milk

In this study, a total of forty‐five strains of lactobacilli and streptococci were determined exopolysaccharide (EPS) production in skim milk and Man Rogosa and Sharpe (MRS)/M17 medium, viscosity and proteolytic activity. The exopolysaccharide production by lactobacilli strains during growth in MRS medium was twenty‐one to 211 mg L^?1, while in skim milk was to thirty‐six to 315 mg L^?1. The EPS production by streptococci strains during growth in M17 medium was sixteen to 114 mg L^?1, while in skim milk was to twenty‐four to 140 mg L^?1. The EPS production of strains was lower in MRS/M17 medium than skim milk. Results showed that it was not clear correlation between the viscosity and EPS production of some strains. All strains were shown proteolytic activity. Positive correlations between exopolysaccharide production and proteolytic activity in skim milk were found some strains of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus. These results indicated that the high exocellular protease‐producing strains can produce high EPS in skim milk. The monomer compositions of the EPSs formed by selected five strains were analysed. Mannose dominated (99–100%) on the EPS produced by L. delbrueckii subsp. bulgaricus and S. thermophilusstrains (except L. delbrueckii subsp. bulgaricus 22) in skim milk and MRS/M17 medium. Besides, the EPSs of strains in skim milk contained small amount of lactose.     

Identification and functional characterization of Lactobacillus strains isolated from milk and Gioddu,a traditional Sardinian fermented milk

Raw milk from Sardinian cows and sheep, and sheep's milk yoghurt (Gioddu), are food products that are poorly characterized in terms of the presence of mesophilic Lactobacillus strains, and may be good sources from which to isolate novel bacterial strains. Sixteen Lactobacillus strains were identified by genotypic and phenotypic methods from samples of sheep's milk (n=7), fermented sheep's milk (n=7) and one sample of cows’ milk. These strains were further characterized for the presence of functional traits useful for probiotic applications, such as resistance to simulated gastric acid, resistance to bile salts, and adhesion of two different cell lines (Caco-2 and MIM/PPK). Moreover, selected aspects correlated with safety (antimicrobial susceptibility and presence of plasmids) and ecological roles (ability to produce biofilms and bacteriocin-like substances) were tested. All but 1 of the 16 strains were unambiguously allotted to three species, L. paracasei (5 strains), L. plantarum (8 strains), and L. reuteri (2 strains). Many of the strains exhibited characteristics suggesting that they would survive in the gastrointestinal tract and also had the capability to attach to various cells. Greater variability was observed for the other traits analyzed. These data suggest that Sardinian artisan dairy products are interesting sources for the isolation of bacterial strains with characteristic and differentiated functional traits.     

补料分批法高密度培养德氏乳杆菌保加利亚亚种S-1

将补料分批培养法与化学中和法相结合,对乳酸菌进行高密度培养。通过流加不同组分配比的补料液,发现碳源(葡萄糖)和氮源是乳酸菌增殖的限制性底物,并在此基础上确定了补料液的最优碳氮比为5︰7.5(体积比)。通过5 L自控发酵罐的批式补糖实验,对恒速流加、葡萄糖反馈流加和指数流加等3种补糖模式的发酵进程进行了比较。结果表明,3种补料模式都可以使菌体浓度出现不同程度的增加,葡萄糖反馈流加由于保持了发酵过程中较低的残糖浓度,获得了较高的菌体密度,菌体干重达到3.889 g/L,较分批培养提高43.8%。     

Antioxidant activity of Lactobacillus plantarum strains isolated from traditional Chinese fermented foods

Eleven Lactobacillus plantarum strains isolated from traditional Chinese fermented foods were investigated for their in vitro scavenging activity against hydroxyl and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radicals, and their resistance to hydrogen peroxide. L. plantarum C88 at a dose of 10(10) CFU/ml showed the highest hydroxyl radical and DPPH scavenging activities, with inhibition rates of 44.31% and 53.05%, respectively. Resistance of intact cells to hydrogen peroxide was also found in all strains. L. plantarum C88 was the most resistant strain against hydrogen peroxide. When L. plantarum C88 was administered to senescent mice suffering oxidative stress induced by d-galactose, the serum superoxide dismutase activity, the glutathione peroxidase activity and the total antioxidant capacity in liver increased significantly, while the level of malondialdehyde in liver decreased significantly. L. plantarum C88 isolated from traditional Chinese fermented dairy tofu could be considered as a potential antioxidant to be applied in functional foods.     

德氏乳杆菌保加利亚亚种高密度培养的研究初探

用响应面(RSM)方法和正交试验对Lactobacillus delbeueckii subsp.bulgaricus S-1的培养基和分批培养条件进行了优化,为补料分批高密度培养提供基础.首先用一次回归正交试验对培养基组分葡萄糖、蛋白胨、牛肉膏、酵母膏、K2HPO4、柠檬酸铵、乙酸钠对细胞生长的影响进行评价,并找出主要影响因子为牛肉膏、柠檬酸铵、酵母膏,皆为正效应,其他组分影响不显著;第二步用最陡爬坡路径逼近最大响应区域;然后用中心组合设计确定主要影响因子的最佳浓度,最后对细胞分批培养的条件进行了优化.应用优化的培养基,在温度41℃,起始pH值6.8,接种量7%,培养时间12h的培养条件下,OD值为2.136,最高活菌数为2.1×109cfu/mL.     

Potential probiotic characteristics of Lactobacillus and Enterococcus strains isolated from traditional dadih fermented milk against pathogen intestinal colonization

Traditional fermented buffalo milk in Indonesia (dadih) has been believed to have a beneficial impact on human health, which could be related to the properties of the lactic acid bacteria (LAB) involved in its fermentation process. In previous studies, it was discovered that strains of dadih lactic isolates possessed some beneficial properties in vitro. In the present study, the adhesion capacity of specific LAB isolates from dadih to intestinal mucus was analyzed. Further, the ability to inhibit model human pathogens and displace them from mucus was assessed. The adhesion of tested LAB strains was strain-dependent and varied from 1.4 to 9.8%. The most adhesive Lactobacillus plantarum strain was IS-10506, with 9.8% adhesion. The competition assay between dadih LAB isolates and pathogens showed that a 2-h preincubation with L. plantarum at 37 degrees C significantly reduced pathogen adhesion to mucus. All tested LAB strains displaced and inhibited pathogen adhesion, but the results were strain-specific and dependent on time and pathogen strains. In general, L. plantarum IS-10506 showed the best ability against pathogen adhesion.