4 种乳酸菌体外抗氧化能力的比较研究

通过抗脂质过氧化、清除DPPH自由基、清除超氧阴离子自由基(O2－ ·)、还原力、清除羟自由基实验对发酵乳杆菌、乳酸乳球菌、嗜酸乳杆菌和瑞士乳杆菌4种乳酸菌发酵上清液和胞内提取物的抗氧化能力进行研究。结果表明：4种乳酸菌的具有不同的抗氧化能力,其中瑞士乳杆菌的羟自由基清除能力、DPPH自由基清除能力和还原能力相对较高,乳酸乳球菌和嗜酸乳杆菌清除O2－ ·能力相对较强,发酵乳杆菌抗脂质过氧化能力为最强。实验还初步研究乳酸菌的抗氧化机理,显示乳酸菌存在SOD和GSH-Px,这可能与乳酸菌的抗氧化作用有一定相关性。     

5种不同益生菌发酵南瓜浆的发酵性能及抗氧化活性研究

目的 比较分析5种益生菌发酵南瓜浆的品质和抗氧化活性, 为筛选发酵南瓜浆的优良菌株奠定基础。方法 利用植物乳杆菌、嗜酸乳杆菌、戊糖乳杆菌、保加利亚乳杆菌和嗜热链球菌5种不同益生菌发酵南瓜浆, 比较分析发酵过程中活菌数、pH、总酸含量、还原糖含量、总酚含量、1,1-二苯基-2-三硝基苯肼[1,1-diphenyl-2-picrylhydrazyl radical 2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl, DPPH]自由基清除率能力和2,2’-联氮-双-(3-乙基苯并噻唑啉-6-磺酸)[2,2’-azino-bis(3-ethylbenzthiazo-line-6-sulfonic acid), ABTS]自由基清除能力。结果 嗜热链球菌和植物乳杆菌适应南瓜浆发酵体系能力最强, 发酵结束后, 植物乳杆菌发酵南瓜浆活菌数含量最高, 达9.89 lgCFU/mL, 较发酵前提高了100倍; 5种益生菌均能产酸, 其中植物乳杆菌产酸能力最强, 对碳源的代谢能力也最强, 植物乳杆菌、嗜热链球菌发酵后南瓜浆多酚含量增加最显著(P<0.05)。抗氧化实验显示, 植物乳杆菌和嗜热链球菌具有较好的抗氧化能力。结论 植物乳杆菌和嗜热链球菌更适合发酵南瓜浆。     

基于特征风味定向筛选酸奶用乳酸菌

针对国内酸奶发酵剂成本高,菌剂被国外垄断的问题。本实验基于特征风味物质乙醛和双乙酰,从市售酸奶产品和菌剂中定向筛选出高风味物质含量菌株,经复配和感官评定,得到适合生产菌株。实验共分离鉴定出58株乳酸菌,包括嗜酸乳杆菌(9株)、鼠李糖乳杆菌(2株)、德氏乳杆菌(4株)、嗜热链球菌(39株)、乳酸乳球菌乳酸亚种/乳酸乳球菌(4株)。产乙醛能力呈现出德氏乳杆菌嗜热链球菌乳酸乳球菌嗜酸乳杆菌鼠李糖乳杆菌,最高达到25.57μg/g。产双乙酰能力呈现出鼠李糖乳杆菌嗜酸乳杆菌嗜热链球菌乳酸乳球菌德氏乳杆菌,最高达到3.57μg/g。德氏乳杆菌和鼠李糖乳杆菌产酸能力较强。菌株复配后大多风味物质含量提高,在一定条件下,呈现出乙醛/双乙酰比例越高,乙醛含量越高,感官风味越好。     

新疆传统乳品中乳酸菌的抗氧化能力

实验用菌为从新疆传统乳制品酸奶和干酪中分离出的7株乳酸菌,分别是乳酸片球菌(Pediococcus acidilactici)1株、植物乳杆菌(Lactobacillus plantarum)3株、耐久肠球菌(Enterococcus durans)1株、魏斯氏菌(Weissella cibaria)1株和面包乳杆菌(Lactobacillus panis)1株。对其清除DPPH自由基、超氧阴离子自由基、羟自由基、还原能力以及亚铁离子螯合能力进行了研究。结果表明:7株乳酸菌具有不同的抗氧化能力,其中植物乳杆菌亚铁离子螯合能力最强,乳酸片球菌超氧阴离子自由基清除能力相对较高,魏斯氏菌的DPPH自由基清除能力较强,面包乳杆菌的羟自由基清除能力和还原能力最强。     

从藏灵菇中筛选高抗氧化能力乳酸菌

藏灵菇中含有丰富的乳酸菌种,其发酵乳具有较高的抗氧化能力。为得到具有高抗氧化能力的菌株,从14份藏灵菇样品中分离出了80株乳酸菌,其中包括30株开菲尔乳杆菌、9株植物乳杆菌、7株保加利亚乳杆菌、3株干酪乳杆菌、5株假肠膜明串珠菌、26株耐久肠球菌。该文从中选出了36株乳酸菌进行4种抗氧化活性测定:DPPH自由基的清除能力、超氧阴离子的清除能力、还原能力、抗脂质过氧化能力,发现完整细胞组M23、M31、M14、M22,破碎细胞组M30、M22、M14、M30有较高抗氧化活性,并测定了8株抗氧化能力优良的菌株发酵乳的抗氧化能力,发现完整细胞组抗氧化能力较高的4株菌,其发酵乳抗氧化能力也较高。     

不同益生菌发酵乳ACEI活性比较

测定了6株德氏乳杆菌保加利亚亚种、6株嗜热链球菌、6株鼠李糖乳杆菌、4株双歧杆菌和天然发酵剂Kefir发酵产物的ACEI活性。结果显示,发酵产物的ACEI活性呈现种属和菌株差异性,发酵和贮藏条件对ACEI活性具有显著影响,菌株发酵结束后经冷藏,ACEI活性均有不同程度的下降。德氏乳杆菌保加利亚亚种Lb9菌株在发酵6h时的ACEI活性为60%,发酵产物在冷藏24h和48h后,ACEI活性分别为55.72%和49.64%。嗜热链球菌Stnh16菌株发酵6h时的ACEI活性显著高于其他嗜热链球菌菌株,为52.73%,冷藏24h和48h后,ACEI活性分别为48.82%和42.58%。鼠李糖乳杆菌在发酵18h时的ACEI活性最高,其中F菌株为83.19%,R26为72.72%,LV108菌株为69.44%,但是冷藏24h和48h后,ACEI活性LV108菌株显著高于其他菌株,ACEI活性分别为66.19%和62.91%,显示其适宜用作生产降血压益生菌发酵乳的发酵剂。双歧杆菌不同菌株中,H4在发酵24h时ACEI活性最高,为46.55%。Kefir在发酵24h时,其ACEI活性最弱,仅为15.23%。该研究为筛选降血压益生菌发酵乳的发酵剂及发酵乳生产提供了参考。     

益生菌发酵乳模拟胃肠液环境下抗氧化活性

为间接评价益生菌发酵乳在人体内的抗氧化活性,分别采用嗜热链球菌（Streptococcus thermophilus）、德氏乳杆菌保加利亚亚种（Lactobacillus delbrueckii subsp. bulgaricus）、动物双歧杆菌（Bifidobacterium）BB12及嗜酸乳杆菌（Lactobacillus acidophilus）制备SL、SL+BB12、SL+LA三种发酵乳,并对其冷藏过程中模拟胃肠液环境下对ABTS、DPPH自由基的清除能力进行了测定。结果表明,三种发酵乳随冷藏时间的延长其抗氧化活性都逐渐降低,添加菌种BB12和LA的发酵乳抗氧化活性下降的幅度小于SL发酵乳,在相同的冷藏时间下模拟胃肠液环境后抗氧化活性都较原发酵乳降低,但添加益生菌BB12和LA发酵乳在模拟胃肠液环境下抗氧化活性高于SL发酵乳,其中BB12高于LA。SL、SL+BB、SL+LA发酵乳冷藏7 d时对ABTS自由基最大清除率分别为46.21%、58.54%、51.99%,对DPPH自由基最大清除率分别为42.17%、53.34%、49.48%。     

益生菌发酵蓝莓花色苷的代谢规律

选用嗜热链球菌、两岐双歧杆菌、植物乳杆菌进行纯种发酵含有蓝莓花色苷提取液的培养液,考察了益生菌发酵过程中活菌数、体外抗氧化性、有机酸、单体花色苷和酚酸等组分的变化情况。结果表明,发酵48 h后,三种益生菌的活菌数均增至8.0 lg CFU/mL左右,两岐双歧杆菌的活菌数最高(P<0.05),发酵后不同菌株发酵样的ABTS⁺·清除能力显著提升(P<0.05),其中两岐双歧杆菌发酵样品抗氧化能力最强(P<0.05);但植物乳杆菌发酵样品中乳酸含量最高(P<0.05);发酵过程中单体花色苷含量呈下降趋势,两岐双歧杆菌发酵样品花色苷组分与其它两株菌发酵的样品差异较大;绿原酸、对香豆酸和咖啡酸的含量总体呈现下降趋势,而没食子酸、丁香酸和阿魏酸含量呈上升趋势,主成分分析图中三株益生菌发酵样的分布差异较大。以上结果为进一步解释益生菌发酵代谢花色苷的机理提供了参考。     

5种乳酸菌及其灭活态体外抗氧化能力的比较研究

以总抗氧化活性(T-AOC)、总超氧化物歧化酶(T-SOD)活力、羟自由基清除率(OH~-·)、超氧阴离子清除率(O~-_2·)、还原活性为测定指标,对5株乳酸菌灭活前后发酵上清液、完整细胞悬液、胞内提取物的抗氧化能力进行比较研究,并筛出抗氧化能力相对较强的3株乳酸菌进行复配。结果表明:5种乳酸菌灭活前后的发酵上清液、完整细胞悬液、胞内提取物具有不同的抗氧化能力,其中嗜酸乳杆菌灭活前和灭活后的发酵上清液的总抗氧化活性最好,分别为45.9、35.0 U/mL。菊糖芽孢乳杆菌未灭活的发酵上清液的超氧阴离子自由基清除率较强为21.03%。嗜热链球菌的灭活胞内提取物的总超氧化物歧化酶活力最强为456.7 U/mL,其未灭活的胞内提取物的羟自由基清除率最强为79.26%。唾液乳杆菌的灭活发酵上清液的还原活性最强。复配结果表明,灭活完整细胞悬液的超氧阴离子清除率(O~-_2·)较单一菌株强;菊糖芽孢乳杆菌和嗜酸乳杆菌复配后灭活完整细胞悬液的羟自由基清除率(OH~-·)最强,为82.40%;而菌株复配后的总抗氧化活性(T-AOC)、总超氧化物歧化酶(T-SOD)活力与单菌差异不显著。不同乳酸菌菌株的抗氧化能力存在差异,且其发挥抗氧化作用的活性物质存在的部位也因菌株不同而具有较大的差异性。     

桂圆酵素制备及其抗氧化性研究

桂圆酵素以桂圆水提液为发酵底物,选择益生菌为发酵菌种进行制备。以胞外多糖含量为评价指标,对发酵工艺进行研究,通过单因素试验和正交试验确定最佳发酵工艺条件:发酵底物浓度9%、接种量9%、菌种比例(保加利亚乳杆菌:嗜热链球菌:嗜酸乳杆菌:青春双歧杆菌=1:1:1:2)、发酵时间8 d,在此条件下制备的桂圆酵素原液胞外多糖含量达1.1086 mg/m L。抗氧化性研究结果表明,桂圆酵素原液具有DPPH自由基清除能力、羟基自由基清除能力及超氧阴离子自由基清除能力,具有一定的抗氧化活性。     

发酵乳球菌菌株的PCR鉴定

对9株发酵乳球菌标准菌株进行MRS固体平板培养基划线分离和镜检观察,采用特异性PCR对其进行鉴定,划线分离得到11株菌;依据各菌种代谢酶编码基因序列差异设计菌种特异性PCR引物,进行PCR扩增,将其在菌株水平上鉴定为9株菌(6株乳酸乳球菌、2株嗜热链球菌和1株无乳链球菌)。实验还获得了2个乳酸乳球菌的种特异性PCR引物LclamyLF-R和LclmapA2F-R、2个嗜热链球菌的种特异性PCR引物SttglgPF-R和SttamyLF-R以及可能是标准菌株AS1.1936的株特异性的PCR引物LclamyYF-R。     

Antioxidative activities of soymilk fermented with lactic acid bacteria and bifidobacteria

To further the goal of developing a probiotic dietary adjunct using soymilk, soymilk is fermented with lactic acid bacteria (Lactobacillus acidophilus CCRC 14079 or Streptococcus thermophilus CCRC 14085) and bifidobacteria (Bifidobacterium infantis CCRC 14633 or Bifidobacterium longum B6) individually, and in conjunction. We investigate several antioxidative activities including the inhibition of ascorbate autoxidation, the scavenging effect of superoxide anion radicals and hydrogen peroxide, and the reducing activity exerted by different varieties of fermented soymilks. In addition, the effect of spray-drying and freeze-drying on changes in antioxidative activity is examined. We find that in fermented soymilk both the inhibition of ascorbate autoxidation, and the reducing activity and scavenging effect of superoxide anion radicals varied with the starters used, but nevertheless are significantly higher than those found in unfermented soymilk. In general, antioxidative activity in soymilk fermented with lactic acid bacteria and bifidobacteria simultaneously is significantly higher (P < 0.05) than that fermented with either individually. Moreover, antioxidative activity increases as the fermentation period is extended. However, unfermented soymilk shows an H2O2-scavenging effect, while there is no scavenging effect except for the accumulation of H2O2 in fermented soymilk. Finally, we find that freeze-drying causes a significantly lesser (P < 0.05) reduction in the antioxidative activity of soymilk than does spray-drying. Irrespective of the drying method and the starters used for fermentation. The antioxidative activity of fermented soymilk reduces after drying yet remains higher than that of dried unfermented soymilk.     

Probiotics down-regulate flaA sigma28 promoter in Campylobacter jejuni

Lactobacilli and bifidobacteria are important members of the gastrointestinal microflora of humans and animals and are thought to have positive effects on human health. Therefore, there is an increasing interest in using these microorganisms as probiotics to be incorporated into either fermented dairy products or tablets. However, convincing scientific data that support claims of their health benefits are scarce. The effect of cell-free extracts of milk fermented by 10 probiotic bacteria (five Bifidobacterium strains and five Lactobacillus strains) on the expression of the flaA gene of Campylobacter jejuni was assessed using a fusion between the flaA sigma28 promoter and a promoterless luxCDABE cassette carried on the plasmid pRYluxCDABE, which resulted in strains with quantifiable luminescence linked to flaA sigma28 promoter activity. Cell-free extracts of milk fermented by all of the tested probiotic strains inhibited the growth of the C. jejuni and down-regulatedflaA sigma28 promoter activity. Two nonprobiotic lactic acid bacterial strains, Lactococcus lactis and Streptococcus thermophilus, were less inhibitory.     

Inhibition of Clostridium tyrobutyricum by bacteriocin-like substances produced by lactic acid bacteria

Lactic acid bacteria were selected for their inhibitory activity against Clostridium tyrobutyricum under conditions that eliminate the effects of lactic acid and hydrogen peroxide. Four strains were isolated belonging to the species Lactococcus lactis ssp. lactis. The sensitivity of the inhibitory substances to pronase and trypsine indicates that they are proteins or peptides different from nisin. Their resistance to phospholipase D indicates that they are also different from lactostrepcin. The inhibitory substances are produced during the exponential phase of growth. Their activity is bactericidal and directed toward some strains of Clostridium tyrobutyricum, Lactobacillus helveticus, and Streptococcus thermophilus, but strains used as dairy starters, Lactobacillus lactis, Streptococcus thermophilus, and Propionibacterium shermanii, are not all affected by the inhibition.     

发酵乳球菌菌株的分离鉴定

对9株发酵乳球菌菌株进行MRS固体平板培养基划线分离和形态学比较观察，井采用生化试验和RAPD对其进行鉴定。划线分离得到11株菌：通过菌体常规磷钨酸负染色标本的透射电镜观察，描述了各菌体的大小、形状以及裂殖方式；依据各菌种生化代谢差异设计生化试验．得到了2个发酵型，将其鉴定为2个菌群（乳酸乳球菌乳酸亚种和嗜热链球菌）；20个随机引物的RAPD筛选得到了9个不同的基因型．将其鉴定为9株细菌。     

水牛乳中可培养乳酸菌多样性分析

采用传统分离培养方法,从三品杂交生水牛奶混合样品中,分离出105株乳酸菌,通过形态、生理生化、API细菌鉴定系统及16S rDNA基因序列分析方法对各菌株属种进行鉴定。16S rRNA序列分析结果显示,105株菌共分为5个属8个种,呈现较为丰富的乳酸菌多样性,具体数量分布为乳酸乳球菌21株,植物乳杆菌19株,格氏乳球菌17株,乳明串珠菌13株,食窦魏斯氏菌11株,肠膜明串珠菌8株,类肠膜魏斯氏菌6株,嗜热链球菌5株,糊精乳杆菌5株。由此可知,水牛乳中可培养乳酸菌优势菌群的主次关系为：乳酸乳球菌（Lactococcus lactis）＞植物乳杆菌（Lactobacillus plantaru）＞格氏乳球菌（Lactococcus garvieae）＞乳明串珠菌（Leuconostoc lactis）＞食窦魏斯氏菌（Weissella cibaria）,此为后续开发水牛乳中优势乳酸菌资源提供了良好的理论基础。     

藏灵菇中高产胞外多糖乳酸菌的筛选及其发酵性能的研究

本研究采用高通量筛选技术和苯酚-硫酸法获得高产胞外多糖的乳酸菌菌株，并对其发酵性能和酸奶品质进行测试。筛选的八株菌均具有高产胞外多糖和良好的发酵性能。其菌种鉴定结果是：菌株KTx、 KL1、J1为干酪乳杆菌（Lactobacillus casei），菌株Tx为嗜热链球菌（Streptococcus thermophilus），菌株KS4、J4、Pl、P5为乳酸乳球菌乳酸亚种（Lactococcus lactis subsp．1actis），其中嗜热链球菌Tx制备发酵剂的粘度最高，凝乳时间最短，感官综合评分最高，可利用此菌株进一步开发研制具有良好稳定性的功能性酸奶。     

利用16S rDNA序列及tuf-RFLP鉴定蒙古国发酵乳中的乳酸菌

运用16S rDNA序列分析和tuf-RFLP技术对采于蒙古国扎布汗省的25份发酵乳样中分离出的110株乳酸菌进行鉴定。首先将分离的110株乳酸菌的16S rRNA基因进行扩增,测序并构建系统发育树,初步鉴定为41株嗜热链球菌,40株瑞士乳杆菌,11株德氏乳杆菌保加利亚亚种,2株发酵乳杆菌,1株乳明串珠菌,2株肠膜明串肠膜亚种,1株乳酸乳球乳酸亚种和12株属于干酪族的菌株。由于干酪乳杆菌族的16S rDNA序列差异很小,故采用tuf-RFLP技术对这12株进行了进一步的验证,通过分离菌株与模式菌株tuf-RFLP图谱的比较分析,结果表明这12株菌均为干酪乳杆菌。     

Screening of lactic acid bacteria for bile salt hydrolase activity

Bile salt hydrolysis is an important metabolic reaction in the bile salt metabolism of mammals. This reaction has a facilitating effect for bile salt excretion but can also be involved in various illnesses. In recent years interest has increased to use bile salt hydrolysis to influence the cholesterol metabolism of humans and farm animals. To understand the distribution and range of bile salt hydrolase activity in lactic acid bacteria, we screened more than 300 strains of the genera Bifidobacterium and Lactobacillus and the species Lactococcus lactis, Leuconostoc mesenteroides, and Streptococcus thermophilus. Results obtained for 273 strains showed that bile salt hydrolase activity is common in Bifidobacterium and Lactobacillus but absent in L. lactis, Leu. mesenteroides, and S. thermophilus. Nearly all bifidobacteria species and strains have bile salt hydrolase activity, whereas this activity can only be found in selected species of lactobacilli. A strong correlation can be observed between the habitat of a genus or species and the presence of bile salt hydrolase activity. Most often bile salt hydrolase activity is found in strains that have been isolated from the intestines or from feces from mammals--an environment rich in conjugated and unconjugated bile acids. Strains and species from other habitats like milk or vegetables--environments from which bile salts are absent--do normally not have bile salt hydrolase activity. In two independent assays, we established that bile salt hydrolase activity in bifidobacteria is, in general, much higher than in lactobacilli.     

Lithium chloride-sodium propionate agar for the enumeration of bifidobacteria in fermented dairy products.

Lithium chloride-sodium propionate agar has been developed for the enumeration of bifidobacteria in fermented dairy products. The medium contains lithium chloride and sodium propionate to inhibit the growth of other lactic acid bacteria. Pure cultures of bifidobacteria, lactobacilli, and streptococci were tested for growth in this medium. With one exception, all bifidobacteria were able to grow in this medium and in a nonselective agar with a difference not exceeding .4 log units. However, none of the lactobacilli tested and only one strain each of Streptococcus salivarius ssp. thermophilus and Lactococcus lactis ssp. cremoris grew in lithium chloride-sodium propionate agar. In those cases, the numbers of colonies were lower in lithium chloride-sodium propionate agar by 1.26 and 2.51 log units, respectively, compared with a nonselective agar. Bifidobacteria were also selectively isolated from all fermented milks and cheeses analyzed.