乳杆菌体外降解胆固醇特性研究

以实验室自主分离纯化的鼠李糖乳杆菌zxr01、嗜酸乳杆菌zrx02、植物乳杆菌zrx03, 3株乳杆菌体外降解胆固醇的特性以及不同金属阳离子对其影响进行了研究。嗜酸乳杆菌、鼠李糖乳杆菌、植物乳杆菌体外胆固醇降解率分别为28.87%、25.61%、20.39%；当pH为3时，3株乳杆菌耐酸性分别为：52.77%、52.57%、59.82%;牛胆盐浓度为0.3%时胆盐耐受性为28.65%、27.40%、26.04%；嗜酸乳杆菌在氯仿中的疏水性最好，达到了19.88%，静置24 h后，嗜酸乳杆菌和植物乳杆菌的自凝聚力都达到了80%以上且3株乳杆菌产生白色沉淀说明能产生胆盐水解酶，在Ca2+浓度为0.02 N时，嗜酸乳杆菌的胆固醇降解率为35.4%和降解效果65.43μg/u。结果显示3株乳杆菌均能在体外降解胆固醇，嗜酸乳杆菌的降解胆固醇的能力要优于其它两株乳杆菌，添加浓度为0.02 N的Ca2+可以促进嗜酸乳杆菌胆固醇降解率和降解效力。本研究结果可为进一步研究胆固醇降解提供了试验依据，为开发降胆固醇食品提供材料。     

嗜酸乳杆菌生理特性的研究

本文以实验室保藏的一株嗜酸乳杆菌为研究对象，研究了该菌的生理特性，包括生长曲线的测定，渗透压对菌体生长的影响，耐胆盐性，同化胆固醇及抑菌能力。结果表明，嗜酸乳杆菌为革兰氏阳性菌，培养16h是最佳收获期，最高可耐受浓度为6％的NaCl，菌体在0．5％的胆盐溶液中放置0．5h后存活率为80％，胆固醇同化率为57．06％，对大肠杆菌、金黄色葡萄球菌有明显的拮抗作用。     

一株自主分离嗜酸乳杆菌的功能性研究

针对一株自主分离保存的嗜酸乳杆菌MF204(CGMCC No.2122)的益生特性,抑菌、降血脂以及提高免疫力等功能进行了研究.结果表明,嗜酸乳杆菌MF204能耐受胆盐、模拟人工胃液和肠液;体外抑菌效果明显,对多种致病菌均有抑制作用:体外对胆固醇平均脱除率达65.64%;对降低高脂大鼠血清胆固醇有一定疗效;对试验小鼠的特异性免疫力均有所提高.表明嗜酸乳杆菌MF204是一株具有较强功能性的益生菌株.     

高效降胆固醇乳酸菌的筛选

研究了25株嗜酸乳杆菌在MRS-CHOL培养基中对胆固醇的降解量,降胆固醇的能力,以及对酸、胆盐的耐受性。实验表明:所有实验菌株均有降解培养物中胆固醇的能力,其中有6株实验菌对培养物中胆固醇的降解率大于40%,这6株菌对胆固醇的脱除效力也较高,同时对这6株菌的耐酸、耐胆盐,以及对胆固醇的脱除能力进行了比较,筛选出降胆固醇能力较强同时对酸和胆盐耐受性较强的嗜酸乳杆菌1株。     

嗜酸乳杆菌优良菌株筛选及其生物学性状的研究

对嗜酸乳杆菌6个菌株的产酸力、胆盐抗性、生物量及同化胆固醇性状进行了测定、比较,从中筛选出LA－1、LA－3两株。其产酸力可达209．5°T,胆盐抗性为0．50%的胆盐浓度,能够同化60%－80%的胆固醇,可较好地用于制备微生态活菌制剂。     

植物乳杆菌ST-Ⅲ菌株降胆固醇影响因素的研究

研究发现植物乳杆菌ST-Ⅲ菌株降低胆固醇作用受胆盐和胆固醇影响.在培养基中添加不同的胆盐,能增加ST-Ⅲ菌株降胆固醇能力,依次为牛磺胆酸钠>牛胆盐>胆酸,当牛胆盐的添加浓度为3.0g/L时,降胆固醇率达到最高值38.57%;在培养基中添加不同来源和不同浓度的胆固醇,ST-Ⅲ菌株均具有降低作用,但降低能力有差异,依次为羊血清>鸡蛋黄>卵磷脂-胆固醇胶束溶液,且降低能力受胆固醇的浓度影响较大,当浓度低于0.5mg/mL时,降胆固醇率可维持在40%左右,高于0.5mg/mL时,降胆固醇效果则显著降低;降胆固醇量在胆固醇浓度为1.0mg/mL时达到最高值307μg/mL,这可能是高浓度胆固醇抑制ST-Ⅲ菌株的生长所致.     

蓝莓汁及其提取物对嗜酸乳杆菌NCFM体外生长的影响

蓝莓汁、蓝莓花青素和蓝莓多糖对嗜酸乳杆菌NCFM(Lactobacillus acidophilus NCFM)体外生长影响表明,24 h培养期间,添加蓝莓汁会促进嗜酸乳杆菌NCFM的生长,蓝莓汁添加量低于70％时,随蓝莓汁添加量的增加益生茵NCFM的细胞活茵数上升;当蓝莓汁添加体积分数高于70％时,促进菌株NCFM生长的作用趋于稳定;当添加量达到100％时,促进益生菌NCFM生长的作用开始减弱.添加单一蓝莓花青素对嗜酸乳杆茵NCFM的生长无明显作用;蓝莓多糖添加量为100 mg/L时能较好的促进菌株NCFM的生长,37 ℃培养24 h,细胞活菌数可达到8.323× 108 mL-1.目前的工作表明,在发酵乳中添加适当浓度的蓝莓能促进益生茵数量的增殖.     

嗜酸乳杆菌生物抗性的研究

选择一株嗜酸乳杆菌优良菌株为研究对象,用平板菌落计数法测定嗜酸乳杆菌在各因素的作用下的存活率来研究其耐酸、耐渗透压、耐胆盐能力以及模拟人体肠胃环境研究胃酸、食盐、胆盐对嗜酸乳杆菌的综合影响;从实验结果得出嗜酸乳杆菌具有一定的抗性能力。     

混料设计法应用于多菌种发酵制备大豆凝胶蛋白

采用保加利亚乳杆菌、嗜热链球菌、嗜酸乳杆菌及其混合菌对大豆分离蛋白进行发酵,应用流变仪和质构仪等手段进行分析,结果表明混合菌的发酵产酸性能和对大豆分离蛋白体系凝胶性质影响优于单一菌.在单因素试验的基础上,采用混料设计对混合菌发酵大豆分离蛋白制备凝胶的发酵条件和混合菌配比进行优化.最优发酵工艺条件为:大豆分离蛋白质量分数12％,葡萄糖添加量5％,40℃发酵4.8h,4℃冷藏12h.改变混合菌的配比可得到不同性能的大豆分离蛋白凝胶,当保加利亚乳杆菌添加量1.27％、嗜酸乳杆菌添加量0.37％时,可得到凝胶强度为145.98 g的高强度凝胶;当保加利亚乳杆菌添加量0.48％、嗜热链球菌添加量0.99％、嗜酸乳杆菌添加量0.14％,可得到持水率为87.28％的高持水率凝胶.     

具有高抗胃肠道胁迫嗜酸乳杆菌的筛选及对肠炎小鼠的治疗作用

目的:从三株嗜酸乳杆菌中筛选出具有高抗胃肠道胁迫特性的嗜酸乳杆菌并研究其对溃疡性结肠炎小鼠的治疗效果。方法:人工模拟人体消化道胃液、肠液和胆盐环境,设置不同浓度梯度,研究三株嗜酸乳杆菌进入人体后对在消化道胃液、肠液和胆盐环境中的存活率,从而反映嗜酸乳杆菌对人体消化道胃液、肠液和胆盐环境的抵抗力。然后以筛选出的具有高抗胃肠道胁迫能力的嗜酸乳杆菌为研究对象,让处理组小鼠自由饮用3%葡聚糖硫酸钠盐(DSS)溶液7 d,以人工诱发的溃疡性结肠炎(UC)小鼠为动物模型,观察此株高性能的嗜酸乳杆菌CGMCC10436的抗溃疡性结肠炎潜力。结果表明,嗜酸乳杆菌CGMCC10436在模拟胃酸pH2.5~4.5时,其活菌数大于10~7CFU/mL,并且在3 h时没有下降的趋势;在模拟肠液中2h时,嗜酸乳杆菌CGMCC10436活菌数有所上升;并且嗜酸乳杆菌CGMCC10436在胆盐浓度为4g/kg时,3 h时其活菌数大于1×107CFU/mL。嗜酸乳杆菌CGMCC10436发挥较好的抗溃疡性结肠炎功效的剂量为3×108CFU,能够改善溃疡性结肠炎小鼠表观状况,修复溃疡性结肠炎小鼠肠粘膜损伤,增强溃疡性结肠炎小鼠的免疫调节。     

Assimilation of cholesterol and probiotic characterisation of yeast strains isolated from raw milk and fermented foods

In this study, cholesterol assimilation ratios and some probiotic characteristics of yeasts were investigated. For this purpose, yeasts were isolated from milk and foods that were naturally fermented and not containing starter culture. In vitro cholesterol assimilation properties were determined in media. The Cholesterol assimilation by yeast strains ranged between 1.36 and 73.33%. Twenty‐one yeast strains showing high assimilation percentage were selected, and their acid tolerance, bile tolerance, bile salt deconjugation activity and survival in simulated gastrointestinal conditions were investigated. Among the strains assessed, 12 of them showed probiotic characteristics.     

干酪乳杆菌KM-16的筛选及其降胆固醇活性研究

从西藏传统发酵乳(西藏灵菇)中分离筛选到1株高效降胆固醇乳酸菌KM-16。应用VITEK-32全自动微生物分析系统鉴定该菌为干酪乳杆菌(Lactobacilluscasei)。在液体培养基中KM-16乳酸菌对降胆固醇达51.8%。用KM-166灌胃高脂血症模型小鼠研究其对血清总胆固醇(TC)、甘油三酯(TG)、高密度脂蛋白(HDL-C)的影响。结果表明,灌胃14d后,实验组小鼠血清中TC、TG浓度较对照组显著降低(P<0.01),同时HDL-C浓度有所增加,动脉硬化指数(AI)低于对照的水平。     

自然发酵肉制品中乳酸菌的体外降胆固醇特性

为筛选出具有高效降胆固醇作用的乳酸菌,以自然发酵肉制品中分离出的13株乳酸菌为实验对象,采用邻苯二甲醛法对其体外降胆固醇能力进行测定,并对其中2株菌（M12、M23）的作用机理进行初步探讨。结果表明,2株菌均通过同化吸收和共沉淀作用协同降低培养基中的胆固醇;添加0.3 g/100 mL胆盐可极显著增加菌体对胆固醇的去除作用（P＜0.01）,去除率分别为56.05%和58.49%;添加胆固醇和胆盐均可显著提高菌株经超声波处理后的存活率（P＜0.05）,存活率分别为32.09%和37.93%;2株菌的热灭活菌体和休眠菌体也具有一定的胆固醇去除能力,且休眠菌体的去除率高于热灭活菌体。经16S rRNA序列分析,菌株M12为弯曲乳杆菌（Lactobacillus curvatus）,菌株M23为戊糖片球菌（Pediococcus pentosaceus）。     

Selection of potential probiotic lactobacilli for cholesterol-lowering properties and their effect on cholesterol metabolism in rats fed a high-lipid diet

The objectives of this study were to screen probiotic characteristics of lactobacilli isolated from traditionally homemade koumiss products in Xinjiang and Inner Mongolia of China, and to determine and compare the effect of the Lactobacillus strains in vivo on lipid metabolism in rats fed with a high-lipid diet. Three out of 68 strains of Lactobacillus isolated from the koumiss were screened for bile-salt resistance, acid tolerance, and different hypocholesterolemic properties. The cholesterol-lowering effects of the 3 screened strains were estimated in rats fed a high-lipid diet by determination of serum lipids, liver, and fecal cholesterol, fecal total bile acids, and short-chain fatty acids. After a 4-wk feeding period, in comparison with the control group, the groups LIP-1 and MG9-2 had a significant reduction in serum total cholesterol, triglyceride and low-density lipoprotein cholesterol, and significantly increased high-density lipoprotein, the group E7301 had similar effects on serum lipids, but the change was not significant. The groups LIP-1, MG9-2 and E7301 had a significant reduction in liver cholesterol content and an increase in fecal cholesterol content compared with the control group. Total bile acid excretion was significantly higher in rats fed MG9-2 than the other groups. Rats fed diets containing lactic acid bacteria strains had significantly higher propionic acid and butyric acid concentrations in the feces compared with the control. Results indicated that the 3 screened Lactobacillus strains were able to lower cholesterol in vitro, and reduce cholesterol effectively in vivo. The mechanisms behind the hypocholesterolemic effect of 3 strains are likely to be diverse and will need further investigation.     

Mechanisms of cholesterol removal by lactobacilli under conditions that mimic the human gastrointestinal tract

Five strains of lactobacilli were studied for their ability to remove cholesterol in vitro under conditions that mimic the human gastrointestinal tract. The highest assimilation of cholesterol was observed in media supplemented with oxgall and the lowest in the presence of taurocholic acid. Scanning electron micrographs showed that cholesterol was adhered to the cellular surface of lactobacilli cells. Resting and dead cells were able to remove cholesterol although in small amounts. Additionally, inhibition of cholesterol micelles formation was observed in the presence of bile salts. All strains were able to deconjugate bile salts, where higher deconjugation was observed in the presence of sodium glycocholate compared with other bile salts studied. All strains also exhibited bile salt hydrolase activity and most strains showed higher substrate specificity towards glycine-conjugated bile than towards taurine-conjugated bile. The results indicated that lactobacilli could remove cholesterol in vitro via various mechanisms, and may exert such hypocholesterolaemic effects in vivo.     

三株植物乳杆菌降胆固醇机理的研究

测定了已筛选出的具有较高胆固醇去除能力和胆盐水解酶活性的3株植物乳杆菌(KLDS6.0330,KLDS6.0333,KLDS6.0335)的胆固醇同化作用,胆汁盐的去结合作用和胆固醇共沉淀作用。这3株植物乳杆菌能够同化较多的胆固醇(﹥43μg/mL);所有的菌株都表现出了对甘氨胆酸钠和牛磺胆酸钠的去结合作用,与牛磺胆酸钠相比,甘氨胆酸钠的去结合能够释放较多的胆酸;所有菌株都表现出了胆固醇与甘氨胆酸钠和牛磺胆酸钠去结合释放胆酸的共沉淀,与牛磺胆酸钠相比,甘氨胆酸钠去结合产生的胆酸表现出了与较多的胆固醇共沉淀;随着pH值的下降,解聚态的胆汁酸与胆固醇的共沉淀量增加,结合态胆盐与胆固醇的共沉淀量较少。结果表明这3株植物乳杆菌在体外可以通过3种机制去除胆固醇。     

Use of bacterial strains antagonistic to Escherichia coli for biocontrol of spinach: A field trial

To counteract global food safety hazards related to raw consumption of ready-to-eat leafy vegetables, a method to improve bacterial status using antagonistic bacteria was studied under field conditions. This is the first study to identify potential Escherichia coli antagonists from the native microbiota on leafy green vegetables and evaluate their effect in an industrial field production setting. Bacterial strains were isolated from different types of leafy green vegetables and selected upon their effect against E. coli in vitro, and out of 295 tested bacterial strains, 37 showed an antagonistic effect. Four of those antagonistic strains were coated in separate treatments onto spinach seeds and planted in the field. Both seeds and plants were analyzed by Illumina MiSeq next generation sequencing (NGS), and it was seen that the microbiota of the plants contained lower relative abundance of plant and human pathogenic genera. Higher β-diversity was observed for the samples treated with Bacillus coagulans LMG P-32205 and B. coagulans LMG P-32206 compared to control, indicating that those strains have induced substantial changes in the native microbiota of the leaves. A reduction of Escherichia-Shigella was seen for two of the isolates (Pseudomonas cedrina LMG P-32207 and Pseudomonas punonenis LMG P-32204) as the seeds developed into plants. Seeds inoculated with two of the strains (B. coagulans LMG P-32205 and B. coagulans LMG P-32206) had increased levels of Lactobacillaceae, and treatment with B. coagulans LMG P-32206 resulted in lower levels of Pantoea (from 31.4 to 12.2%).These results encourage the usage of bacterial antagonists as part of a global solution to reduce the risk of human pathogens on leafy green vegetables.     

Acid and bile tolerance and cholesterol removal ability of lactobacilli strains

Eleven strains of lactobacilli were studied for their acid and bile tolerance. Possible mechanisms of cholesterol removal by strains of lactobacilli were examined. Cholesterol assimilation as determined by the difference in cholesterol content in the medium before and after the incubation period showed that all lactobacilli strains were able to assimilate cholesterol at varying levels ranging from 12.03 to 32.25 microg/mL. Cholesterol removal was associated with growth of cultures. Binding of cholesterol to lactobacilli cells was determined using growing, heat-killed, and resting cells in phosphate buffer. Cholesterol removed by dead and resting cells ranged from 0.79 to 3.82 mg/g of dry weight compared with growing cells, which ranged from 4.53 to 16.03 mg/g of dry weight. Fatty acid methyl esters, as quantified using gas chromatography, showed changes in lipid profiles in cells grown in the presence of cholesterol compared with those grown without cholesterol. Fatty acid profiles, especially of hexadecanoic, octadecanoic, total saturated, and unsaturated acids suggested that cholesterol from the medium was incorporated into the cellular membrane. These findings suggest that strains of lactobacilli could remove cholesterol via various mechanisms and may be promising candidates for use as a dietary adjunct to lower serum cholesterol in vivo.     

Homemade traditional cheeses for the isolation of probiotic Enterococcus faecium strains

One hundred twenty-two strains of Enterococcus faecium isolated from Tafí Cheese, a homemade traditional cheese of the highlands in the province of Tucumán, Argentina, were evaluated for their potential application as starter cultures in the manufacture of this traditional cheese. Eleven of the 122 strains showing limited delays in growth in oxgall were selected for the study of bile salts hydrolase activity (BSH), cholesterol reduction, antimicrobial activity, and virulence determinants. Nine strains were able to remove cholesterol in in vitro assays, a property that was closely related to the bile salt hydrolase activity. Only two strains produced active bacteriocins against Listeria strains although genetic evidence for the bacteriocin structural gene was found in six other enterococci strains. No virulence factors were detected in any of the 11 selected strains of enterococci.     

Biotransformation of hop derived compounds by Brettanomyces yeast strains

Several hop derived compounds in wort are known to be converted by yeast during fermentation, influencing the overall perception of the beer. A deeper understanding of such metabolic processes during fermentation is needed to achieve better control of the outcome. Here, the interaction between hop derived compounds and the yeast genera Brettanomyces was studied. Several Brettanomyces strains with different genomic backgrounds were selected, focusing on two traits: beta-glucosidase activity and nitrate assimilation. The role of three beta-glucosidases present in Brettanomyces bruxellensis and Brettanomyces anomalus and their impact on the final monoterpene alcohol profile was analysed. The beta-glucosidase activity was highly strain dependent, with B. anomalus CRL-49 exhibiting the highest conversion. Such activity could not be related to the release of aglycones from hops during fermentation, as a substantial part of such activity was intracellular. Nevertheless, the reduction of geraniol to β-citronellol was remarkably efficient for all Brettanomyces strains during fermentation, and it is suggested that two oxidoreductases BbHye2 and BbHye3 may have an influence. Moreover, the transfer of nitrate from hops to wort and its further assimilation by Brettanomyces species was analysed. The amount of nitrate in wort proved to be linearly proportional to the contact time of the hops with the wort. The level of nitrate assimilation by yeast was shown to be dependent on the nitrate assimilation cluster (YNR, YNI, YNT). Hence, the desired yeast strains may be selected according to the genetic make-up. © 2020 The Authors. Journal of the Institute of Brewing published by John Wiley & Sons Ltd on behalf of The Institute of Brewing & Distilling