不同pH值培养乳酸球菌对其发酵活力的影响

为了确定嗜热链球菌St-1最适生长pH值,研究了在不同pH值条件下培养嗜热链球菌St-1,对其活菌数、发酵活力及菌体形态学特征的影响.结果表明,当培养体系的pH值恒定在6.0时,其活菌数和发酵活力最高;对比发酵活力曲线和生长曲线表明,发酵活力最好时的活菌数并不是最高的;对比不同恒定pH值条件下培养活力最高时的嗜热链球菌St-1菌体形态特征发现,嗜热链球菌St-1的链越长,其发酵活力越低,链越短发酵活力越高.     

The effect of lactose derivatives on intestinal lactic acid bacteria

Nine strains of lactic acid bacteria were studied for growth and fermentation end products on lactulose, lactitol, and lactobionic acid. In addition, human fecal and biopsy isolates were screened for new potential by probiotic strains utilizing lactose derivatives, and one new isolate of Lactobacillus rhamnosus was enriched. The utilization of lactose derivatives and the effect on the fermentation end products were dependent on strain. Typical mixed-acid fermentations were observed with Lb. rhamnosus and Lactococcus lactis. Microbiota enriched from fecal and biopsy samples using modified MRS medium consisted mainly of enterococci and streptococci. The adhesion of tested strains to Caco-2 cells was not dependent on carbon source. The new Lb. rhamnosus strain VTT E-97800 has potential for further probiotic studies.     

酸和盐胁迫对乳酸菌活性的影响

该研究以13株食品常见乳酸菌为研究对象,考察酸和盐胁迫对其活性的影响,探究这13株乳酸菌的最适酸、盐生长条件及耐酸、耐盐能力。结果表明,适当的低盐浓度（1%、2%）对部分乳酸菌的生长有促进作用,植物乳杆菌和副干酪乳杆菌的最适盐浓度为1%,保加利亚乳杆菌和嗜酸乳杆菌的最适盐浓度为2%;盐浓度进一步增大,13株乳酸菌的生长受到抑制;盐浓度为10%时,除戊糖片球菌、乳酸乳球菌乳酸亚种、嗜热链球菌和乳酸片球菌外,其余9株菌的生长抑制率都＞95%。当pH值为5～7时,13株乳酸菌都生长良好,pH=6时,7株乳酸菌活性均最高;随着酸胁迫的增强,13株乳酸菌生长受抑制程度增大;pH为1～3时,13株乳酸菌的生长抑制率都＞90%,高盐及高酸对9株杆菌的抑制作用强于4株球菌。     

乳酸菌对酸奶保鲜作用的研究

目的比较4种具有保鲜作用的乳酸菌对酸奶中霉菌的抑制效果及在发酵和贮藏过程中对酸奶品质的影响。方法将4种乳酸菌添加到发酵乳中,比较对酸乳中霉菌的抑制作用,并对酸奶酸度、活菌数、质构和感官品质进行检测。结果按厂家推荐量和相同活菌数(2.0×10~6 CFU/m L)添加4种乳酸菌均对霉菌的生长具有抑制作用,其中,乳酸菌A和C的抑菌效果较好;按照厂家推荐量添加4种乳酸菌发现,乳酸菌A和B的添加对酸奶的发酵时间、贮藏期内的酸度、活菌数、质构和感官均无影响,而乳酸菌C和D的添加会对酸奶贮藏期内的酸度和感官产生影响。结论乳酸菌A能够有效抑制酸奶中霉菌滋生,同时不会对酸奶的品质产生影响。     

常温下市售酸奶乳酸菌数和pH值的变化研究

酸奶中活性乳酸菌的含量是评价产品对于人体营养与保健作用的重要指标,而酸奶的pH值及酸度直接影响成品的质量、风味和口感。新的酸奶国家标准(GB2746-1999)中规定产品中的乳酸菌数不得低于1×106cfu/mL,酸度应≥70°T。本试验通过对5种市售酸奶的检测及分析,得出在常温下贮藏和销售,酸奶在保质期内仍然符合国家规定的质量标准。     

直投式乳酸菌菌种传代培养初探

探讨了一次性直投式（DVS）乳酸菌菌种传代培养的可行性。并寻求最佳控制点,从而获得优良的子代发酵制,对菌种培养操作作了详尽的探索。     

乳酸菌发酵液涂膜保鲜剂对鸡蛋保鲜效果的研究

将一株具有抑菌活性的干酪乳杆菌发酵液作为涂膜保鲜剂,研究其对鸡蛋的保鲜作用。将离心后的干酪乳杆菌发酵液上清液和传统鸡蛋保鲜剂壳聚糖溶液对市售新鲜鸡蛋进行涂膜处理,以未涂膜鸡蛋作为空白对照组,4℃冰箱贮藏28d,每7d对鸡蛋减重率、蛋黄指数、浓蛋白含量、蛋白的pH和蛋壳总菌数进行测定。结果:储存28d后,对照组、壳聚糖组与乳酸菌组的鸡蛋减重率分别为6.51%、4.08%和3.95%,蛋黄指数分别为0.210、0.281和0.303,浓蛋白含量分别为16%、30%和38%,蛋白的pH值分别为9.40、9.0和8.21,乳酸菌组蛋壳总菌数明显低于对照与壳聚糖组,表明干酪乳杆菌发酵液对鸡蛋具有更好的保鲜效果。     

Effect of milk pasteurisation temperature on age-related changes in lactose metabolism,pH and the growth of non-starter lactic acid bacteria in half-fat Cheddar cheese

Half-fat Cheddar cheese (∼15%, w/w, fat) was manufactured on three occasions from milk pasteurised at 72, 77, 82 or 87 °C for 26 s, and analysed over a 270 day ripening period. Increasing milk pasteurisation temperature significantly increased the levels of moisture (from ∼45% at 72 °C to 50% at 87 °C), total lactate, and D(−)-lactate in cheese over the 270 day ripening period. Conversely, the cheese pH decreased significantly on increasing pasteurisation temperature. Increasing the pasteurisation temperature did not significantly affect the populations of starter or non-starter lactic acid bacteria during maturation. The use of higher pasteurisation temperatures would appear particularly amenable to exploitation as a means of producing high-moisture (e.g., 40–41%), short-ripened, mild-flavoured Cheddar or Cheddar-like cheeses.     

乳酸菌降胆固醇作用及其机理的研究进展

乳酸菌是一类广泛存在于人和动物体内的微生物,具有调节胃肠道健康、消除人体自由基、降低食物及人体血清中胆固醇含量等作用。文章从降胆固醇乳酸菌的筛选、乳酸菌降解胆固醇的体外研究、乳酸菌降解胆固醇在动物和人体内的研究、乳酸菌降胆固醇机理的研究和降胆固醇乳酸菌高密度培养等方面进行了论述,提出目前在研究中存在的一些问题,以期对乳酸菌的进一步开发和利用提供帮助。     

The effect of temperature on the lactic acid fermentation of rye flour

A brew (1 rye flour: 2 water) was fermented by its indigenous microflora at temperatures (T) of 10, 15, 20, 25, 30, 35 and 40°C. A direct relationship was observed between the fermentation temperature and the absolute values of the ‘b' (the t coefficient) and ‘c' (an indicator of the width of the parabola) parameters of the fitted quadratic equations: pH=a+bt+ct². Setting the first derivative of the quadratic fitted function to zero, dpH/dt=b+2ct=0, and solving for t gives the duration of the lag-phase period. When the temperature was increased from 10 to 35°C, the lag phase period (no net change in pH) of the fermentation was reduced by >sixfold from 17.8–2.9 h and the fermentation time to attain a pH of 5.0 was reduced by >13 times from 132–9.9 h. The fermentation rate (F) of rye flour within each of the three periods increased as the fermentation temperature increased up to 35°C. To predict the fermentation time to pH 5.0 at temperatures other than these examined in this study but within the range of these temperatures an exponential function, t_5.0={exp[a+(b×T_0.5)+c×exp(−T)}, was fitted. The Arrhenius plot of the acid production rate ([H⁺] h⁻¹) vs the reciprocal of the absolute temperature showed a ‘breakpoint' at 15°C; indicating that 15°C may be the minimum metabolically efficient temperature for the lactic acid fermentation of rye flour. The activation energy (E_a) was 1.4 and 16.0 cal mol⁻¹above and below the 15°C breakpoint; an additional indication that at temperatures <15°C the fermentation is less metabolically efficient.     

Modelling pH evolution and lactic acid production in the growth medium of a lactic acid bacterium: application to set a biological TTI

Time temperature integrators or indicators (TTIs) are effective tools making the continuous monitoring of the time temperature history of chilled products possible throughout the cold chain. Their correct setting is of critical importance to ensure food quality. The objective of this study was to develop a model to facilitate accurate settings of the CRYOLOG biological TTI, TRACEO. Experimental designs were used to investigate and model the effects of the temperature, the TTI inoculum size, pH, and water activity on its response time. The modelling process went through several steps addressing growth, acidification and inhibition phenomena in dynamic conditions. The model showed satisfactory results and validations in industrial conditions gave clear evidence that such a model is a valuable tool, not only to predict accurate response times of TRACEO, but also to propose precise settings to manufacture the appropriate TTI to trace a particular food according to a given time temperature scenario.     

The microflora of sourdough. XIX. The effect of temperature and dough yield on the proteolytic effect of lactic acid bacteria in sourdough

During fermentation of sour dough the flour proteins are degraded. The proteolysis depends not only on lactic acid bacteria (Lactobacillus plantarum, L. brevis ssp. lindneri, L. fructivorans) but also on the conditions of fermentation of the sour dough. An increase of temperatures between 25 degrees C and 35 degrees C causes an increase in the amino acid content. The water content of the dough (T.A. 150/T.A. 210) influences the proteolytic activity of the bacteria to a lesser degree.     

乳酸菌对精神性疾病作用的研究进展

目前我国精神性疾病的发病率呈逐年上升趋势,如何缓解精神性疾病越来越受到人们关注。研究表明,乳酸菌可通过调节肠道免疫功能、促进产生神经信号物质、调节内分泌细胞激素等多种作用机制和途径帮助维持人脑及神经系统的正常功能。临床医学研究表明,乳酸菌具有对自闭症、抑郁症、精神分裂症、焦虑症等多种精神性疾病的预防及缓解作用,使用乳酸菌辅助药物治疗已成为目前精神性疾病治疗研究热点之一。本文总结了乳酸菌对精神性疾病的有益作用及其作用机制,旨在为乳酸菌在该领域的科研和应用提供借鉴和参考。      

冻干保护剂对复合低温乳酸菌发酵剂的影响

以青藏高原牧区分离筛选出的低温乳酸菌为研究对象,以活菌数为指标,比较了4种冻干保护剂对复合低温乳酸菌发酵剂的影响,并通过正交实验优化了其中3种较优冻干保护剂的复配配方。结果表明,复合低温乳酸菌冻干保护剂的最优组合为:甘油为8m L/L,蔗糖为10%(w/v),脱脂乳为15%(w/v),以此为保护剂冻干存活率达到了90.55%。与商业发酵剂相比,低温发酵剂发酵酸乳组织状态良好,滴定酸度为92°T,感官评分为95分,活菌含量(10.3lg CFU/m L)极显著高于商业发酵酸乳(p0.01)。实验结果为制备高活力直投式低温乳酸菌发酵剂的冻干菌粉提供理论支撑,对开发低温乳酸菌发酵剂具有重要意义。     

冻干保护剂对复合低温乳酸菌发酵剂的影响

以青藏高原牧区分离筛选出的低温乳酸菌为研究对象,以活菌数为指标,比较了4种冻干保护剂对复合低温乳酸菌发酵剂的影响,并通过正交实验优化了其中3种较优冻干保护剂的复配配方。结果表明,复合低温乳酸菌冻干保护剂的最优组合为:甘油为8m L/L,蔗糖为10%(w/v),脱脂乳为15%(w/v),以此为保护剂冻干存活率达到了90.55%。与商业发酵剂相比,低温发酵剂发酵酸乳组织状态良好,滴定酸度为92°T,感官评分为95分,活菌含量(10.3lg CFU/m L)极显著高于商业发酵酸乳(p<0.01)。实验结果为制备高活力直投式低温乳酸菌发酵剂的冻干菌粉提供理论支撑,对开发低温乳酸菌发酵剂具有重要意义。      

蜂蜜对酸奶生产中乳酸菌生长和产酸能力的影响

在脱脂乳粉制成的全乳固体含量为12%(w/v) 的复原乳中,分别添加5%(w/v)的蔗糖、果糖或蜂蜜,并以不添加甜味剂的复原乳作为对照,经过70℃、15min灭菌,冷却至室温,分别接种唾液链球菌嗜热亚种、德氏乳杆菌保加利亚亚种和嗜酸乳杆菌,接种量5%(v/v),培养温度37℃,分别在培养初始和经过24h培养时取样,测定其乳酸菌活性、pH值和乳酸含量。结果表明,添加量为5%(w/v)的蜂蜜对于3种乳酸菌均没有抑制作用,是酸奶生产的合适甜味剂。     

Influence of sodium chloride, pH, and lactic acid bacteria on anaerobic lactic acid utilization during fermented cucumber spoilage

Cucumbers are preserved commercially by natural fermentations in 5% to 8% sodium chloride (NaCl) brines. Occasionally, fermented cucumbers spoil after the primary fermentation is complete. This spoilage has been characterized by decreases in lactic acid and a rise in brine pH caused by microbial instability. Objectives of this study were to determine the combined effects of NaCl and pH on fermented cucumber spoilage and to determine the ability of lactic acid bacteria (LAB) spoilage isolates to initiate lactic acid degradation in fermented cucumbers. Cucumbers fermented with 0%, 2%, 4%, and 6% NaCl were blended into slurries (FCS) and adjusted to pH 3.2, 3.8, 4.3, and 5.0 prior to centrifugation, sterile-filtration, and inoculation with spoilage organisms. Organic acids and pH were measured initially and after 3 wk, 2, 6, 12, and 18 mo anaerobic incubation at 25 °C. Anaerobic lactic acid degradation occurred in FCS at pH 3.8, 4.3, and 5.0 regardless of NaCl concentration. At pH 3.2, reduced NaCl concentrations resulted in increased susceptibility to spoilage, indicating that the pH limit for lactic acid utilization in reduced NaCl fermented cucumbers is 3.2 or lower. Over 18 mo incubation, only cucumbers fermented with 6% NaCl to pH 3.2 prevented anaerobic lactic acid degradation by spoilage bacteria. Among several LAB species isolated from fermented cucumber spoilage, Lactobacillus buchneri was unique in its ability to metabolize lactic acid in FCS with concurrent increases in acetic acid and 1,2-propanediol. Therefore, L. buchneri may be one of multiple organisms that contribute to development of fermented cucumber spoilage. PRACTICAL APPLICATION: Microbial spoilage of fermented cucumbers during bulk storage causes economic losses for producers. Current knowledge is insufficient to predict or control these losses. This study demonstrated that in the absence of oxygen, cucumbers fermented with 6% sodium chloride to pH 3.2 were not subject to spoilage. However, lactic acid was degraded by spoilage microorganisms in reduced salt, even with pH as low as 3.2. Efforts to reduce salt in commercial brining operations will need to include control measures for this increased susceptibility to spoilage. Lactobacillus buchneri was identified as a potential causative agent and could be used as a target in development of such control measures.     

罗汉果对乳酸菌生长及保存活力的影响

通过体外实验研究罗汉果对与人类关系密切的植物乳杆菌、肠膜明串珠菌、嗜热链球菌的生长及保存活力的影响.结果表明:用水煎煮法制备的罗汉果汁浓度在0.05～0.5 g/mL范围内对3种受试乳酸菌的生长及活力保存都有不同程度的促进作用.因此可考虑将罗汉果汁适当添加到含有植物乳杆菌、肠膜明串珠菌、嗜热链球菌的食品中,用以促进菌体的生长及保存活力,还可考虑利用罗汉果制微生态制剂.     

一株具有抑制麦芽糖酶活性的乳酸菌的筛选与鉴定

以抑制麦芽糖酶为目的,采用α-葡萄糖苷酶抑制剂的体外筛选模型,筛选出具有较好麦芽糖酶抑制效果的乳酸菌菌株JH28。菌株JH28的MRS发酵上清及无细胞提取物均对麦芽糖酶有抑制作用。将该菌株的无细胞提取物经透析膜（截留分子量1000Da,去离子水为透析液）透析后取透析液冻干,测定不同浓度冻干物对麦芽糖酶的抑制效果,最高抑制率可达67.19%,经计算其IC为4.12mg/mL。菌株经16SrDNA鉴定为干酪乳杆菌,具有潜在的工业应用价值。      

发酵乳中酵母菌和乳酸菌生长的相互影响

探讨了乳酸菌和酵母菌之间的相互作用。在发酵过程中,酿酒酵母对乳酸菌的生长有抑制作用。乳酸菌能促进酿酒酵母和马克思克鲁维酵母的生长。酿酒酵母和乳酸菌共同接种有利于保持产品冷藏期间活菌数的稳定,菌株之间可能存在共生作用。