乳酸菌胞外多糖对结肠癌HT-29细胞增殖的影响

从15株大连工业大学大连市益生菌功能研究重点实验室保藏植物乳杆菌中筛选出对人结肠癌细胞HT-29抑制率最高的乳杆菌胞外多糖,对其进行分离纯化并研究多糖对HT-29细胞增殖的影响。通过苯酚硫酸法测定15种乳酸菌胞外多糖产量、3-(4,5-二甲基吡啶-2-基)-5-(3-羧基甲氧基苯基)-2-(4-磺苯基)-2H-四唑[3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium,MTS]测定不同浓度的粗多糖对HT-29细胞的抑制率,最终筛选出高产胞外多糖、对HT-29细胞增殖抑制率高的菌株Lactobacillus plantarum12所产胞外多糖,其胞外多糖的糖含量为54%、蛋白含量为3.6%。对其胞外多糖进行DEAE-Sepharose Fast Flow离子柱和Sepharose CL-6B凝胶柱的分离纯化,得到中性多糖组分EPS12-1和酸性多糖组分EPS12-2,2个多糖组分的糖含量分别为31.82%和35.21%,通过MTS法测定L. plantarum12菌所产粗多糖、多糖组分EPS12-1和EPS12-2分别在50、100、250、500μg/mL浓度时对HT-29细胞的抑制率,发现多糖浓度为250μg/mL时,对HT-29细胞增殖达到了最佳抑制效果,抑制率分别为27.58%、7.11%、12.00%。当多糖浓度为250μg/mL时,HT-29细胞凋亡率、活性氧(reactive oxygen species,ROS)水平、caspase 8活性,均处在较高水平。L. plantarum12胞外多糖通过增加ROS酶活和激活caspase 8来抑制HT-29增殖。     

Lactobacillus plantarum-12菌株胞外多糖培养条件优化及功能特性研究

某些乳杆菌属细菌所产胞外多糖具有一些重要的益生功能。本研究优化菌株Lactobacillus plantarum-12培养基碳源、培养温度和时间,以增加该菌株胞外多糖表达量,并通过细胞增殖检测试剂盒(MTS Cell Proliferation Colorimetric Assay Kit,MTS)和末端脱氧核苷酸转移酶介导的d UTP缺口末端标记测定法(Terminal deoxynucleotidyltransferase mediated d UTP nick end labeling,TUNEL)研究其胞外多糖对HT-29细胞增殖的抑制作用以及诱导细胞凋亡作用,并研究胞外多糖清除DPPH自由基的能力以评价其潜在的抗氧化能力。结果表明,乳杆菌菌株生物合成EPS最佳条件为:MRS培养基中碳源为40 g/L蔗糖、培养温度30℃、培养时间48 h时,L.plantarum-12 EPS产量为50 mg/L;随着胞外多糖(Exopolysaccharides,EPS)作用浓度的增加,对HT-29细胞的抑制率增大,当EPS浓度为500μg/mL时HT-29细胞凋亡数可达50.3个,显著高于其它3个浓度(p0.05);L.plantarum-12 EPS的DPPH自由基清除率也随EPS作用浓度的增加而增大,在0.5 mg/mL时高达49.13%。L.plantarum-12 EPS的分子结构及其益生功能还有待进一步研究。     

植物乳杆菌35对大肠杆菌在肠上皮细胞HT-29上黏附及刺激产生促炎细胞因子的影响

本论文采用肠上皮细胞模型HT-29细胞系研究8株植物乳杆菌在HT-29细胞上的黏附性,并研究黏附性较强的菌株及其胞外多糖(Exopoly Saccharides,EPS)抑制大肠杆菌(E.coli ATCC25922)在HT-29细胞上黏附及刺激HT-29细胞产生炎性因子的作用。结果表明8株植物乳杆菌在HT-29细胞上的黏附性差异较大:黏附性最强的植物乳杆菌35通过取代、竞争和排阻方式抑制大肠杆菌在HT-29细胞上黏附,抑制黏附率分别为30%、33%和59%,其EPS在作用浓度为500μg/mL时对大肠杆菌的抑制黏附率为32%。植物乳杆菌35可抑制大肠杆菌刺激HT-29细胞产生IL-8,通过取代、竞争、排阻方式抑制大肠杆菌刺激HT-29细胞产生IL-8,抑制率分别为3%、28%和40%;其EPS抑制大肠杆菌刺激HT-29细胞产生IL-8具有浓度效应,浓度为500μg/mL时抑制率最高,为50%。而对于IL-10表达量的影响均不显著。结果表明植物乳杆菌35具有抑制大肠杆菌引起肠炎的潜在益生功能。     

Lactobacillus plantarum-12胞外多糖抑制志贺氏菌生物膜形成的研究

研究菌株Lactobacillus plantarum-12胞外多糖(Exopolysaccharides,EPS)对6种致病菌(Escherichia coli,Staphyloccocus aureus,Salmonella,Listeria monocytogenes,Vibrio Parahaemolyticus,Shigella flexneri)生物膜形成的抑制作用,结果显示L.plantarum-12 EPS对于6种致病菌生物膜形成均有不同程度的抑制效果,对S.flexneri生物膜形成的抑制效果最佳,在2 mg/mL多糖的影响下抑制率达到53.77%,且EPS对S.flexneri已形成的生物膜也具有清除作用,清除率最高可达61.2%:在多糖的影响下S.flexneri在玻片上的黏附及聚集受到了明显抑制。6种致病菌菌体疏水性在L.plantarum-12 EPS作用下都有不同程度的降低,其中S.flexneri菌体疏水性下降了90%,S.flexneri的疏水性随着EPS浓度升高而逐渐降低;在4 mg/mL EPS的作用下,S.flexneri菌体的自聚性降低了30%。L.plantarum-12 EPS处理S.flexneri生物膜,可使环丙沙星及左氧氟沙星S.flexneri的最小生物膜清除浓度从256μg/mL降至64μg/mL,显著提高了环丙沙星及左氧氟沙星的药效。而且,L.plantarum-12 EPS能够抑制S.flexneri胞外多聚物基质中多糖的分泌量。试验结果表明,Lactobacillus plantarum-12 EPS通过降低S.flexneri疏水性,自聚性及胞外多聚物中多糖的表达量的方式抑制了S.flexneri生物膜的形成。     

藏灵菇源干酪乳杆菌KL1胞外多糖抑制人结肠癌细胞增殖的研究

分离纯化藏灵菇源干酪乳杆菌KL1胞外多糖(EPS),研究EPS纯品对HCT-8人结肠癌细胞的增殖抑制和诱导细胞凋亡作用。利用Sepharose CL-6B凝胶柱探讨干酪乳杆菌KL1菌株EPS粗品的纯化条件,应用紫外全波长扫描及苯酚-硫酸法鉴定EPS纯度;采用CCK-8法和Annexin V-FITC细胞凋亡检测试剂盒研究EPS对HCT-8人结肠癌细胞的增殖抑制和凋亡作用。结果表明:在0.02～0.12mol/L磷酸盐缓冲液梯度洗脱、流速3mL/min、样品上样质量浓度15.0mg/mL、样品上样量2.0mL的纯化条件下获得EPSa和EPSb两个单一组分的胞外多糖,其纯度分别为91.67%和82.86%。EPSa处理HCT-8人结肠癌细胞体外实验发现,EPSa对HCT-8细胞的增殖有抑制作用,以及诱导细胞凋亡的发生,且细胞生长抑制率呈时间-剂量依赖性。提示藏灵菇源干酪乳杆菌KL1菌株的EPSa有抑制结肠癌细胞增殖的生物活性。     

乳杆菌胞外多糖抗氧化活性研究

从本实验室保藏的8株产胞外多糖的乳杆菌:干酪乳杆菌-Y3,干酪乳杆菌-Y4,干酪乳杆菌-Y16,植物乳杆菌-Y41,植物乳杆菌-Y42,植物乳杆菌-Y44,干酪乳杆菌-Y35,鼠李糖乳杆菌LGG中,筛选出1株产抗氧化活性多糖的菌株,评价其抗氧化性并分析其结构。采用酸沉醇提法从8株乳杆菌的MRS培养液中提取胞外多糖,并用苯酚硫酸法和考马斯亮蓝法测定粗多糖和蛋白含量,同时测定胞外多糖的1,1-二苯基-2-三硝基苯肼自由基(DPPH)清除率、2,2’-连氮基-双-(3-乙基苯并二氢噻唑啉-6-磺酸)自由基(ABTS)清除率、羟自由基(·OH)清除率、铁离子还原力(FRAP)、氧自由基吸收能力(ORAC)及对ABAP氧化损伤HT-29细胞的保护作用,以评价8株菌胞外多糖抗氧化活性。通过主成分分析法得到产高抗氧化活性胞外多糖的菌株为Y42。进一步研究发现:随着菌株Y42胞外多糖作用浓度的降低,对ABAP氧化损伤HT-29细胞的保护作用降低,然而都显著高于氧化损伤组(P0.05)。菌株Y42胞外多糖显著上调HT-29细胞过氧化物酶和超氧化物歧化酶的表达量(P0.05),HT-29细胞内谷胱甘肽过氧化物酶活性也显著高于氧化组(P0.05)。菌株Y42胞外多糖由中性多糖和酸性多糖组成,其单糖组成为甘露糖、葡萄糖醛酸、氨基葡萄糖、氨基半乳糖、半乳糖,它们的物质的量比为11.30∶3.51∶10.64∶7.53∶7.19。红外光谱扫描显示菌株Y42胞外多糖具有典型的特征吸收峰,属于吡喃糖环的骨架模式。     

Lactobacillus casei HS4胞外多糖对发酵乳组织结构和流变特性的影响

研究干酪乳杆菌（Lactobacillus casei）HS4所产乳酸菌胞外多糖（exopolysaccharide,EPS）及其对发酵乳微观结构和流变性的影响。通过Sephadex G-50柱纯化得到两种类型的EPS,分别命名为HS4-1-EPS和HS4-2-EPS。HS4-1-EPS主要由葡萄糖组成,峰面积为0.940。HS4-2-EPS主要由葡萄糖和甘露糖组成,峰面积比为0.3830.364。红外光谱结果显示,HS4-1-EPS和HS4-2-EPS均为杂多糖。分别采用干酪乳杆菌HS4、嗜热链球菌-保加利亚乳杆菌（11）复合菌株以及复合菌株添加纯化EPS制成的不同发酵乳作为样品,通过测定流变特性及微观结构观察,研究补充纯化EPS和原位EPS对发酵乳流变特性及微观结构的影响。结果显示,其在4 ℃贮存期间显示出不同的流变特性及微观结构。基于扫描电镜下样品的微观结构,可以推知,EPS的类型和空间阻挡效应与发酵乳的流变性质相关。     

益生菌制剂对抗生素诱导腹泻模型小鼠肠道菌群的恢复

本论文采用肠上皮细胞模型HT-29细胞系研究8株植物乳杆菌在HT-29细胞上的黏附性,并研究黏附性较强的菌株及其胞外多糖（ExopolySaccharides,EPS）抑制大肠杆菌(E?coliATCC25922)在HT-29细胞上黏附及刺激HT-29细胞产生炎性因子的作用。结果表明8株植物乳杆菌在HT-29细胞上的黏附性差异较大：黏附性最强的植物乳杆菌35通过取代、竞争和排阻方式抑制大肠杆菌在HT-29细胞上黏附,抑制黏附率分别为30%、33%和59%,其EPS在作用浓度为500 μg/mL时对大肠杆菌的抑制黏附率为32%。植物乳杆菌35可抑制大肠杆菌刺激HT-29细胞产生IL-8,通过取代、竞争、排阻方式抑制大肠杆菌刺激HT-29细胞产生IL-8,抑制率分别为3%、28%和40%;其EPS抑制大肠杆菌刺激HT-29细胞产生IL-8具有浓度效应,浓度为500 μg/mL时抑制率最高,为50%。而对于IL-10表达量的影响均不显著。结果表明植物乳杆菌35具有抑制大肠杆菌引起肠炎的潜在益生功能。     

Lactobacillus casei HS4胞外多糖对发酵乳组织结构和流变特性的影响（英文）

研究干酪乳杆菌(Lactobacillus casei)HS4所产乳酸菌胞外多糖(exopolysaccharide,EPS)及其对发酵乳微观结构和流变性的影响。通过Sephadex G-50柱纯化得到两种类型的EPS,分别命名为HS4-1-EPS和HS4-2-EPS。HS4-1-EPS主要由葡萄糖组成,峰面积为0.940。HS4-2-EPS主要由葡萄糖和甘露糖组成,峰面积比为0.3830.364。红外光谱结果显示,HS4-1-EPS和HS4-2-EPS均为杂多糖。分别采用干酪乳杆菌HS4、嗜热链球菌-保加利亚乳杆菌(1:1)复合菌株以及复合菌株添加纯化EPS制成的不同发酵乳作为样品,通过测定流变特性及微观结构观察,研究补充纯化EPS和原位EPS对发酵乳流变特性及微观结构的影响。结果显示,其在4℃贮存期间显示出不同的流变特性及微观结构。基于扫描电镜下样品的微观结构,可以推知,EPS的类型和空间阻挡效应与发酵乳的流变性质相关。     

植物乳杆菌NMGL2胞外多糖对其生长特征及发酵乳加工特性的影响

将不同添加量的植物乳杆菌（Lactobacillus plantarum）NMGL2胞外多糖（EPS）与菌株NMGL2混合培养,考察EPS对菌株NMGL2生长、形态和稳定性的影响,并将其应用于菌株NMGL2发酵乳加工中,研究其对发酵乳加工特性的影响。结果表明,EPS能促进菌株NMGL2的生长,EPS添加量为4%的效果最佳,培养24 h后,活菌数达4.3×109 CFU/mL;扫描电镜观察发现添加EPS后菌体之间出现黏连现象,细胞形态发生不规则变化,并且EPS附着于菌体表面,降低了体系Zeta电位及稳定性。菌株NMGL2发酵过程中,EPS对菌株NMGL2的产酸及发酵乳的内聚性无显著影响（P＞0.05）,但能显著提高发酵乳样品的弹性和黏性、降低其流动性和硬度（P＜0.05）。因此,植物乳杆菌NMGL2 EPS能够有效改善发酵乳加工特性,为产EPS植物乳杆菌在发酵乳制品中的应用提供技术依据。     

Factors influencing autoaggregation and aggregation of Lactobacillus delbrueckii subsp. bulgaricus isolated from handmade yogurt

Of 26 Lactobacillus delbrueckii subsp. bulgaricus strains isolated from yogurt, strains B2 and 22, which produce low levels (28 and 21 mg liter(-1), respectively) of extracellular polysaccharides (EPSs), and strains B3 and G12, which produce high EPS levels (211 and 175 mg liter(-1), respectively), were selected for further study. The two high EPS-producing strains showed a significant autoaggregation and coaggregation ability with Escherichia coli ATCC 11230 (P < 0.05). Moreover, the effect of bile was evaluated on autoaggregation and hydrophobicity. Autoaggregation and hydrophobicity of these L. delbrueckii subsp. bulgaricus strains decreased after treatment with bile. Only the high EPS-producing L. delbrueckii subsp. bulgaricus strain B3 showed greater autoaggregation (80%) and hydrophobicity (86%) than the other strains after bile treatment. When these strains were assessed for the inhibition of E. coli ATCC 11230 in coculture, L. delbrueckii subsp. bulgaricus B3 completely inhibited E. coli during 24 and 48 h of incubation. This investigation showed that a high EPS production and coaggregation ability may be important in the selection of probiotic strains.     

Exopolysaccharides produced by probiotic strains modify the adhesion of probiotics and enteropathogens to human intestinal mucus

Exopolysaccharides (EPSs) are exocellular polymers present in the surface of many bacteria, including Lactobacillus and Bifidobacterium. The genome sequence of several strains revealed the presence of EPS-encoding genes. However, the physiological role that EPSs play in the bacterial ecology still remains uncertain. In this study, we have assessed the effect of EPSs produced by Lactobacillus rhamnosus GG, Bifidobacterium longum NB667, and Bifidobacterium animalis IPLA-R1 on the adhesion of probiotic and enteropathogen strains to human intestinal mucus. The EPS fraction GG had no significant effect on the adhesion of L. rhamnosus GG and B. animalis IPLA-R1. However, the EPS fractions NB667 and IPLA-R1 significantly reduced the adherence of both probiotic strains. In contrast, the three EPS fractions increased the adhesion of Enterobacter sakazakii ATCC 29544 and Escherichia coli NCTC 8603. Higher adherence of Salmonella enterica serovar Typhimurium ATCC 29631 and Clostridium difficile ATCC 9689 was detected in the presence of the EPS fractions GG and NB667. In general, these effects were obtained at EPS concentrations of up to 5 mg/ml, and they were EPS dose dependent. The competitive exclusion of probiotics in the presence of EPS could suggest the involvement of these biopolymers in the adhesion to mucus. The increase in the adherence of enteropathogens could be explained if components of the pathogen surface are able to bind to specific EPSs and the bound EPSs are able to adhere to mucus. To the best of our knowledge, this is the first work reporting the effect of EPSs from probiotics on bacterial adhesion properties.     

植物乳杆菌胞外多糖的分离纯化及其乳化特性

在脱脂乳中分别培养植物乳杆菌菌株YW11和菌株SKT109,经三氯乙酸除蛋白、离心、乙醇沉淀、透析、冷冻干燥得到胞外多糖粗品,再经DEAE-Sepharose Fast Flow离子交换柱和Sepharose CL-6B凝胶柱纯化,得到两种胞外多糖纯品。利用气相色谱法分析此两种多糖的单糖组成,并采用KBr压片法观察红外光谱,利用动态光散射方法测定多糖的流体力学半径（Rh）。结果显示：YW11胞外多糖的单糖组成为葡萄糖、半乳糖,其物质的量比为3.45∶1,流体力学半径为69.20 nm;SKT109胞外多糖的单糖组成为葡萄糖、半乳糖,其物质的量比为1.43∶1,流体力学半径为41.74 nm;YW11胞外多糖的乳化能力强于SKT109胞外多糖,但前者的乳化稳定性略低;两种胞外多糖分别与其他乳化剂之间具有一定的协同作用,乳化颗粒的半径主要集中在1～2 μm之间。本研究获得的植物乳杆菌胞外多糖在食品加工中具有潜在的应用前景。     

产胞外多糖植物乳杆菌的筛选及粗多糖的活性研究

通过观察乳酸菌菌落拉丝状况并测定其胞外多糖（exopolysaccharide,EPS）的产量,筛选出1 株所产EPS黏性好、产量高的乳酸菌AR307,经鉴定为植物乳杆菌。为得到更多的胞外多糖,对植物乳杆菌AR307的发酵条件进行优化,确定其在发酵温度32 ℃、发酵时间20 h条件下的产糖量为389 mg/L。在体外实验中,所得胞外多糖具有抑制HT-29肿瘤细胞活性、降低血糖水平的作用。     

东北传统发酵食品中高抗氧化活性植物乳杆菌的筛选及体外耐受性分析

为了获得高抗氧化活性植物乳杆菌,从东北传统发酵食品辣椒酱、臭豆腐、粘面子中筛选出75株植物乳杆菌。将75株植物乳杆菌分为无细胞上清液、完整细胞、无细胞提取物三个组分,以DPPH和ABTS+自由基清除率为指标对菌株进行筛选,分析不同指标间的相关性,并评价菌株耐酸、耐胆盐能力及对抗生素的敏感性。结果表明,23株菌株表现出较好的抗氧化活性,无细胞上清液对DPPH和ABTS自由基清除率均大于90%,完整细胞和无细胞提取物对这两种自由基清除率均大于30%。植物乳杆菌的三个组分在清除DPPH自由基中存在相关性,无细胞上清液在DPPH和ABTS+两种评价方法上存在极显著相关性。其中有5株植物乳杆菌(D2、H8、L20、L11和A2)在pH2.0环境中存活率均大于59%,在0.3%胆盐中的存活率均大于93%,对7种抗生素敏感性较强。因此,这5株植物乳杆菌对于开发抗氧化作用的功能食品具有潜在的应用价值。     

副干酪乳杆菌胞外多糖抗氧化活性分析

为评价干酪乳杆菌生物合成胞外多糖(exopolysaccharides,EPS)抗氧化活性,本文分离纯化高产胞外多糖的三株副干酪乳杆菌(3号、5号和7号)的胞外多糖,并对其DPPH·、·OH和O₂-清除率分别进行测定,评价其体外抗氧化活性。通过分析EPS对H₂O₂诱导氧化损伤293T细胞的保护作用,评价其胞内抗氧化活性。结果表明,当EPS浓度为400 μg/mL时,其DPPH·、·OH和O₂-的清除率最高,分别为8.87%(5号)、88.94%(7号)和34.55%(7号),其中对·OH清除能力高于抗坏血酸(65.87%),且三株菌株之间没有明显差异。3号副干酪乳杆菌所产EPS显著提高超氧化物歧化酶(SOD)活性、总抗氧化能力(T-AOC)活性并抑制了丙二醛(MDA)的生成(P<0.05),且与多糖浓度呈正相关。因此,3株副干酪乳杆菌胞外多糖具有良好的抗氧化活性,作为天然抗氧化剂具有良好的应用潜力。     

Isolation and identification of exopolysaccharide producer lactic acid bacteria from Turkish yogurt

Lactic acid bacteria (LAB) were isolated from traditional yogurt samples and genotypic characterization of these isolates revealed the presence of 21 distinct LAB strains belonging to Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus thermophilus, Leuconostoc mesenteroides, and Lactobacillus plantarum as new LAB strains. Determination of the exopolysaccharide (EPS) production characteristics of the selected strains of each species revealed that all strains possessed at least one gene required for both homopolymeric‐ and heteropolymeric‐type EPS production. Structural analysis of the EPSs showed that L. delbrueckii subsp. bulgaricus Y39 and S. thermophilus Y102 produced heteropolymeric EPS containing glucose and galactose, whereas Leuc. mesenteroides Y35 and L. plantarum Y36 produced homopolymeric glucan‐type EPS. The level of EPS production in these strains was found to be in a similar range. These strains with EPS production characteristics are good candidates for future studies as new LAB for yogurt production.

Practical applications

Recent trends in yogurt production technology have led to an increased use of ropy starter cultures in yogurt production due to the technological roles of exopolysacharides (EPS) produced by these cultures. The main role of EPS in yogurt production is to improve the textural properties of yogurt as an in situ produced natural polymer. In addition to the yogurt starter cultures, use of adjunct cultures during production of yogurt is also of special interest to enhance the technological and nutritional characteristics of yogurt. Therefore, in this study, potential yogurt starter and adjunct cultures from traditional yogurt samples with EPS production characteristics were isolated. From these isolates, Lactobacillus delbrueckii subsp. bulgaricus Y39 and Streptococcus thermophilus Y102 produced heteropolymeric EPS containing glucose and galactose, whereas Leuconostoc mesenteroides Y35 and Lactobacillus plantarum Y36 produced homopolymeric glucan.     

Functional Properties of Lactic Acid Bacteria Isolated from Romanian Fermented Vegetables

A total of 139 lactic acid bacterium (LAB) strains isolated from Romanian traditionally fermented vegetables were screened for the ability to produce exopolysaccharides and for their antagonistic activity against a set of nine LAB strains, three Bacillus strains, and four Gram-negative bacteria. Eighty-five of the tested strains showed a variable antimicrobial activity against Listeria monocytogenes ATCC 1911, 35 of the strains showed a limited inhibition zone against Escherichia coli ATCC25922, and 26 strains against Salmonella enterica ATCC 14024, while 19 strains showed inhibition against one or all three Bacillus strains used as indicators. None of the tested strains showed an antimicrobial activity against Staphylococcus aureus ATCC 25923. Several strains showed antibacterial activity against more than one indicator strain. For instance, Lactobacillus plantarum 307, Lactobacillus brevis 308, and Lactobacillus plantarum/pentosus 358 were active against five of the indicator strains used, while other 23 LAB were active against three indicator strains. In the case of two strains, namely Leuconostoc citreum 344 and Lactobacillus brevis 183, the activity was maintained after neutralizing the pH of the cell-free supernatant likely due to the production of bacteriocins. The gel permeation chromatography-based screening revealed seven EPS-producing LAB strains. Two of the positive strains, namely Leuconostoc citreum 177 and Leuconostoc citreum 52, have been shown to produce large amounts of EPS, of about 20 g/L. All isolated EPS have a high molecular mass, of above 1400 KDa, and a monomer composition dominated by the presence of glucose.     

1株抑制乳房炎病原菌乳杆菌的筛选、鉴定及其抑菌机理研究

为了研究乳酸菌对牛乳房炎病原菌的抑制作用,降低牛乳房炎所造成的经济损失。本实验以大肠杆菌ATCC25922、金黄色葡萄球菌ATCC25923、无乳链球菌ATCC14556作为指示菌,综合抑菌试验和黏附试验从8株乳杆菌中筛选抑菌效果较好的菌株。结果表明,乳杆菌KLDS1.0344对指示菌的抑制作用比其他乳杆菌的作用更明显,最大抑菌直径为15.4 mm,经过对16S rDNA鉴定,发现KLDS1.0344为植物乳杆菌,同时,对抑菌机理的初步研究表明,其代谢过程中产生的乳酸和细菌素类物质对抑制三种指示菌发挥主要作用,而且这些抑菌活性物质在酸性条件下才具有更强的抑菌活力。     

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.