西藏灵菇来源酵母菌发酵面团菌株筛选与培养条件优化

从西藏灵菇中分离得到16株酵母菌,测定这16株酵母菌发酵面团的性能,结果表明,菌株Y15发酵力较好,即发酵力17.6mL/(g.h)。菌株Y15发酵的面包色泽呈金黄色,外形饱满,不塌陷,口感酥软,咀嚼时有弹性。对菌株Y15的发酵培养条件进行优化,其最佳发酵条件是:温度20℃,转速180r/min,培养时间16～18h;生理生化鉴定结果表明Y15与木篮假丝酵母相似度为80.2%。     

西藏灵菇颗粒中菌种的分离鉴定

从西藏灵菇颗粒中分离出TK-B1、TK-B2、TK-B3、TK-B4、TK-B5 5株细菌及TK-F1、TK-F2、TK-F3 3株酵母菌,利用形态学观察、生理生化实验及细菌的16S r DNA同源性鉴定、真菌的26/28S r DNA同源性鉴定,经过同源性比对及系统发育树分析,5株细菌分别是乳酸乳球菌乳酸亚种、开菲尔乳杆菌、芽孢杆菌、冲绳醋酸菌、东方醋酸菌,3株酵母菌分别是单孢酿酒酵母、单孢酵母、东方伊萨酵母。其中的冲绳醋酸菌是首次在西藏灵菇颗粒中分离出来。     

西藏灵菇菌的菌相菌学的研究

通过对西藏灵菇菌的菌体及灵菇发酵乳的宏观形态和显微形态的观察,对菌体的主体组成菌进行分离、纯化及生理生化鉴定.确定了西藏灵菇菌为以耐热可鲁维酵母、亚罗可鲁维酵母为主体真菌;以乳酸杆菌、嗜酸乳杆菌短乳杆菌和乳酸链球菌等乳酸菌为主体细菌构成的块状共生菌系.其以酵母假丝和营养体构成菌块中心,有乳酸菌分布在菌块外周部分,共同完成复杂的牛乳发酵分解过程.     

西藏灵菇发酵乳中优势菌群的分离鉴定

通过对西藏灵菇菌块的电镜扫描观察和发酵乳液中微生物的分离、纯化及生理生化鉴定,确定了西藏灵菇发酵乳中的优势菌群为乳酸球菌、乳酸杆菌、酵母菌和醋酸菌。其中乳球菌归为5个种属,分别为粪肠球菌、坚强肠球菌、乳酸乳球菌乳脂亚种、假肠膜明串珠菌、类肠膜明串珠菌;乳杆菌归为3个种属,分别为短乳杆菌、干酪乳杆菌、嗜酸乳杆菌;酵母菌归为4个属,分别为酵母属、酒香酵母属、假丝酵母属、类酵母属;醋酸菌鉴定为恶臭醋杆菌。     

西藏灵菇牛乳发酵液中的菌相与物质变化

研究了西藏灵菇菌牛乳发酵液中菌相、乳糖含量、酸度、乙醇产量的变化规律,探讨了菌相变化与发酵液中各物质间的关系,结果表明,发酵前18h,发酵液中的乳球菌数最多,其次依次为乳杆菌、明串珠菌、醋酸菌和酵母菌;发酵18 h后乳球菌数迅速下降;发酵21 h时明串珠菌和酵母菌数开始下降;发酵24 h后醋酸菌开始减少;在整个发酵过程中乳杆菌数一直在不断增长.菌相的变化不仅与各菌种的生理特性有关,还与培养基中的营养物质含量和酸度有关.     

西藏灵菇在天然基质中发酵的研究

采用天然物质作为西藏灵菇的培养基,研究西藏灵菇在这些培养基中的增殖情况并测定各发酵指标,研究表明：番茄：生菜：牛奶=1：1：1（体积比）的培养基为西藏灵菇菌体培养的最佳培养基;番茄：胡萝卜：牛奶=1：1：1（体积比）的培养基为西藏灵菇的最佳发酵培养基。     

西藏灵菇酸奶发酵过程中部分营养物质的转化

根据国家标准检测方法,对西藏灵菇发酵奶发酵过程中的主要营养成分变化进行初步的探索,为进一步研究其营养特性、保健功能和生产转化提供理论依据.通过检测,标准条件下西藏灵菇发酵奶的发酵过程中主要时间阶段的蛋白质、脂肪、乳糖、乙醇(均为质量分数)的变化结果表明:蛋白质、脂肪和乳糖的质量分数随发酵时间延长而下降,发酵终点的蛋白质为2.55%;脂肪为2.55%,乳糖为3.46%,均符合国家标准对酸奶制品的要求.而乙醇在发酵过程中随发酵时间的延长而上升,发酵终点时的质量分数为3.096%.     

藏灵菇源酸奶复合菌发酵剂对肠道菌群平衡的作用

目的:探讨藏灵菇源酸奶复合菌发酵剂对实验性高胆固醇血症大鼠调节肠道菌群平衡的作用.方法:根据大鼠血清总胆固醇水平分组.高脂模型组和试验Ⅰ、Ⅱ组饲喂高脂饲料,对照组饲喂基础饲料;试验Ⅰ组灌胃脱脂酸奶复合菌发酵剂,试验Ⅱ组灌胃全脂酸奶复合菌发酵剂,对照组和模型组给予蒸馏水,连续8周.结果:对照组大鼠的粪便中乳杆菌、肠杆菌和产气荚膜梭菌的活菌数量处于平稳状态;4周后高脂模型组大鼠的粪便中乳杆菌的活菌数量极显著低于对照组(p＜0.01),而6周后肠杆菌和产气荚膜梭菌的活菌数量极显著高于对照组(p＜0.01);试验Ⅰ组和试验Ⅱ组大鼠粪便中乳杆菌的活菌数量分别在4周和6周开始极显著高于高脂模型组(p＜0.01),而肠杆菌和产气荚膜梭菌的活菌数量极显著低于高脂模型组(p＜0.01);试验Ⅰ组调节肠道菌群平衡效果优于试验Ⅱ组.结论:藏灵菇源酸奶复合菌发酵剂能够促进高胆固醇血症大鼠肠道有益菌的生长,并抑制有害菌的繁殖,具有明显调节肠道菌群平衡作用.     

藏灵菇源酸奶复合菌发酵剂对大鼠肝脏胆固醇的作用

目的:探讨藏灵菇源酸奶复合菌发酵剂对实验性高胆固醇血症大鼠降肝脏胆固醇的作用。方法:根据大鼠血清总胆固醇(TC)水平分组,高脂模型组和试验Ⅰ、Ⅱ组饲喂高脂饲料,对照组饲喂基础饲料。试验Ⅰ组灌胃脱脂酸奶复合菌发酵剂,试验Ⅱ组灌胃全脂酸奶复合菌发酵剂,对照组和模型组给予蒸馏水,连续8周。结果:藏灵菇源酸奶复合菌发酵剂对大鼠的体重、心重、心系数、肾重和肾系数无影响,而对肝重和肝系数有极显著的降低作用(p0.01);试验Ⅰ组和Ⅱ组大鼠抗动脉硬化指数(AAI)极显著高于高脂模型组(p0.01),而动脉硬化指数(AI)分别极显著低于高脂模型组(p0.01);试验Ⅰ组和试验Ⅱ组与高脂模型组相比,对高胆固醇血症大鼠肝脏的TC、TG含量有极显著的降低功效(P0.01),而对HDL-C含量有极显著的升高作用(P0.01);试验Ⅰ组的降胆固醇效果优于试验Ⅱ组。结论:藏灵菇源酸奶复合菌发酵剂对实验性高胆固醇血症大鼠有显著的降肝脏胆固醇作用及抗动脉粥样硬化效果,并对肝脏有保护作用。     

藏灵菇源酸奶复合菌发酵剂对大鼠脂质过氧化的影响

目的:探讨藏灵菇源酸奶复合菌发酵剂对实验性高胆固醇血症大鼠的抗氧化相关酶及脂质过氧化产物丙二醛(MDA)的影响。方法:采用预防性大鼠脂质代谢紊乱模型,将试验大鼠分成基础对照组、高脂模型组、试验Ⅰ组和试验Ⅱ组。其中高脂模型组和试验组饲喂高脂饲料,试验Ⅰ组灌胃脱脂酸奶复合菌发酵剂,试验Ⅱ组灌胃全脂酸奶复合菌发酵剂。结果:试验Ⅰ组和试验Ⅱ组与高脂模型组相比,可极显著(p0.01)地降低高胆固醇血症大鼠血清和肝组织中的MDA含量。试验Ⅰ组大鼠的SOD、GSH-PX和T-AOC活性极显著(p0.01)升高。试验组肝组织切片脂滴堆积量比模型组减少,病理检查结果表明有明显的保肝作用。试验Ⅰ组的抗氧化活性、抑制肝硬化及脂肪肝效果优于试验Ⅱ组。结论:藏灵菇源酸奶复合菌发酵剂具有较强的抗氧化和预防动脉粥样硬化作用。     

酸乳发酵菌的分离及酸乳发酵工艺的研究

采用选择培养基对酸乳发酵菌种分离、筛选出优良酸乳生产菌株，并用生理生化指标对其进行鉴定。初步鉴定为嗜热链球菌和保加利亚杆菌。并采用2种混合发酵实验，结果表明：接种量4％、发酵时间5h，2种菌种比例为2：l，发酵酿制的酸乳质量较佳。     

冷冻干燥酸奶发酵剂中菌体细胞的收集

冷冻干燥酸奶发酵剂的使用避免了因微生物工业技术力量不足而造成的菌种质量不佳等问题.高浓度菌体细胞的收集是其生产的关键步骤.综合采用超滤法、缓冲盐法、流加碱中和法、离心法浓缩菌体,优选工艺路线,为规模化生产奠定基础.     

传统甜酒曲的模糊综合评价及优势丝状真菌的分离鉴定

对实验室采集的12种传统甜酒曲进行模糊综合评价。选择外观形态、水分含量、糖化力、液化力和发酵力5个评价因子建立评价模型,将甜酒曲分为3类,一类曲模糊评价值小于1.4,二类曲模糊评价值为1.4¹.6,三类曲模糊评价值大于1.6。按照此标准,Q2、Q7、Q9、Q11、Q12为第1等级甜酒曲,Q1、Q8、Q 10为第2等级甜酒曲,Q3、Q4、Q5、Q6为第3等级甜酒曲。通过酿酒试验和感官评定验证,结果表明模糊综合评价法适用于传统甜酒曲的品质评价。并对第1等级甜酒曲中的优势丝状真菌进行分离鉴定,经形态学分类和18S rDNA序列的分子生物学特性综合鉴定为4类:M1为米根霉(Rhizopus oryzae),M2为灰色小克银汉霉(Cunninghamella polymorpha),M3为黑曲霉(Aspergillus niger),M4为卷枝毛霉(Mucor circinelloides)。     

新型酸奶发酵剂的研制

研究了制备酸奶发酵剂的菌种按不同比例配合所形成的新型发酵剂的特性。通过对专用酸奶菌种StreptococcilsSalirarussubsp.cremoris和Lactobacillusdelbrueekiisubsp.bugaricus的原有研究筛选出的4种组合基础之上,对菌种SE1-2进行活化、扩培、保存并与以上2菌种以不同比例形成新的组合,经过研究筛选出1种最优比例用于酸奶生产,结果效果良好、风味独特。最终认为Lactobacillusdelbrueekiisubsp.bugaricus∶StreptococcilsSalirarussubsp.cremoris∶SE1-2为1∶8∶2是最佳比例。     

Detection and identification of yeasts in natural whey starter for Parmigiano Reggiano cheese-making

The yeast populations of natural whey starter (NWS) samples from dairies of PDO Parmigiano Reggiano cheese production area were enumerated and characterised. Yeasts were detected with an average value higher than 3 log cfu mL⁻¹ and in a case study we highlighted the correlation between the yeast growth and incorrect management of NWS fermentation. Isolated strains showed the typical Kluyveromyces marxianus PCR-RFLP pattern and D1/D2 sequences obtained displayed similarity values ranging from 99% to 100% for the same species. RAPD-PCR fingerprinting revealed 14 biotypes. The ability of several strains to grow at 52 °C demonstrates that the yeasts may be perfectly integrated into the ecosystem of NWS. This work confirms that yeasts are part of the NWS secondary microbiota, composed by wild strains with relevant biotechnological interest.     

半工业化生产酸奶与直投式发酵剂的性能评定

应用直投式发酵剂,以半工业化生产的方式制作酸奶,测定了酸奶的多种品质指标,评定了发酵剂的生产性能。车间处理鲜牛奶,投菌后测定发酵剂在0～7 h的产酸趋势,并分别以5、6 h和7 h为发酵终止时间,比较3种发酵时间所得酸奶在4℃冷藏期间的品质。发酵剂活力恢复较快,且发酵终止时间易于控制;酸奶在4℃贮藏前期酸度有略微增加,后期稳定;酸奶品质以发酵7 h为最佳,贮藏期间有略微变化。综合评定结果表明,直投式发酵剂的性能优良,在后续自主研发发酵剂的实验中可以作为参考对象。     

Effect of spray drying temperature of yoghurt on the survival of starter cultures, moisture content and sensoric properties of yoghurt powder

A synergistic set of the strains Lactobacillus delbrueckii subsp. bulgaricus 151 and Streptococcus thermophilus MK-10 was preserved with the method of spray drying. Studies were performed on the effect of outlet air temperature in range of 60-80 degrees C upon the survival of yoghurt cultures, as well as the moisture content and sensoric properties of yoghurt powder. Survival of yoghurt cultures was the highest at 60 and 65 degrees C, but excessive moisture (10.2%) of yoghurt powder had a negative effect on its texture. Moisture content of the powder was low at 80 degrees C (4.4%), unfortunately sensoric faults appeared at this temperature, and survival of bacteria cultures decreased considerably. Temperatures within the range 70-75 degrees C ensured satisfactory survival of yoghurt cultures (L. delbrueckii subsp. bulgaricus--13.7-15.8%; S. thermophilus--51.6-54.7%), maintained proportion of the strains (L:S--1:3), satisfactory moisutre content (5.1-6.3%), and good sensoric properties of yoghurt powder.     

Synthesis and utilisation of folate by yoghurt starter cultures and probiotic bacteria

Thirty-two bacterial isolates from species commonly used in yoghurts and fermented milks were examined for their ability to synthesise or utilise folate during fermentation of skim milk. The organisms examined included the traditional yoghurt starter cultures, Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus, and probiotic lactobacilli, bifidobacteria, and Enterococcus faecium. Folate was synthesised by S. thermophilus, bifidobacteria, and E. faecium. S. thermophilus was the dominant producer, elevating folate levels in skim milk from 11.5 ng g⁻¹ to between 40 and 50 ng g⁻¹. Generally, lactobacilli depleted the available folate in the skim milk. Fermentations with mixed cultures showed that folate production and utilisation by the cultures was additive. Fermentations using a combination of Bifidobacterium animalis and S. thermophilus resulted in a six-fold increase in folate concentration. Although increased folate levels in yoghurts and fermented milks are possible through judicious selection of inoculum species, the folate levels remain relatively low in terms of recommended daily allowance.     

发酵剂的筛选及其对搅拌型酸奶理化特性的影响

通过调查单菌株发酵特性、球菌/杆菌比例的选择、菌株复配后的性能,得到了4组优化的发酵剂配方。在不添加任何增稠剂的条件下,其发酵的酸奶在28d货架期内质构、后酸化程度表现优异且稳定。此外,为了预测酸奶货架期后酸化程度的强弱,比较了15组28d储存期实验与加速实验中所得的pH值及其变化趋势。结果表明,加速试验中趋于定值时的pH值可以作为判断后酸化程度强弱的先行指标。     

Differentiation of Streptococcus thermophilus strains in commercial Direct Vat Set yoghurt starter

Based on inhibition of acid production, 100 individual colonies of Streptococcus thermophilus isolated from commercial Direct Vat Set yoghurt starter DVS-M were typed into 2 groups of sensitive and insensitive to phage φ001, which was isolated from the lysis culture of the turbidity test. The ratio between the sensitive and insensitive isolates in DVS-M was calculated at 3:2. Whole-cell protein profile (WCPP) and randomly amplified polymorphic DNA (RAPD) analysis showed that both WCPP and RAPD patterns between sensitive and insensitive isolates were distinct, whereas isolates with the same sensitivity or insensitivity shared common WCPP and RAPD patterns. It suggested that all the sensitive isolates belong to one S. thermophilus strain and all the insensitive isolates belong to another one. This study revealed that DVS-M yoghurt starter consists of 2 S. thermophilus strains with different phage sensitivity.