果酒酿造实验探索

本着“经济、简便、安全、易于操作”的基本原则,对简易酿造果酒的实验技术进行探索,从酶的角度深入分析实验原理,通过设置对照组,对果汁发酵产物CO2和酒精进行检测,以证明二氧化碳和酒精是果汁经酵母发酵后的产物。研究显示,除了训练学生制作果酒的发酵技术外．该实验还可以进一步拓展为探究性实验。     

酿酒酵母呼吸缺陷型和野生型酒精发酵特性的比较分析*

比较了酒精发酵生产菌株IFFI1300及其呼吸缺陷型突变株在酒精产量、发酵动力学、耐酒精能力及与酒精发酵相关的乙醇脱氢酶活性等方面的特性。结果表明：1)发酵终期的酒精产量,45株呼吸缺陷型的平均值与野生型没有显著性差异;但部分缺陷型的酒精产量高于野生型。2)酒精发酵动力学结果显示,呼吸缺陷型酒精产生速度略高于野生型。3)单位重量干菌体的乙醇脱氢酶活性,呼吸缺陷型高于野生型。以上结果提示：呼吸缺陷型用于酒精发酵以提高酒精产量和缩短发酵周期是有潜力的。4)单位体积发酵液的乙醇脱氢酶活性则野生型高于呼吸缺陷型,主要原因在于呼吸缺陷型的生物量明显低于野生型。5)呼吸缺陷型菌株之间的耐酒精能力差别很小,耐酒精能力的高低与酒精产量的高低没有明显的正相关性。一般的,酒精产量高的菌株耐酒精能力较强。在实验结果的基础上,对呼吸缺陷型用于酒精发酵的优越性和可行性进行了讨论。     

酵母菌和发酵条件对酒精连续发酵的影响

从多株酒精酵母菌种中筛选出Ｓ．ｃｅｒｅｖｉｓｉｎｅ ＫＧ作为加续发酵菌株,该劳动力株经耐酸驯化,提高了抵抗不利环境的能力。本论文还探讨了二氧化碳、氧气对酒精对发酵过程的影响。认为氧气是一关键性的影响因素。在另一方面,在酒精连续发酵过程中使用带有细胞循环的双罐系统,酒精生产强度达到３０．５ｇ／Ｌ．ｄ。     

信息库

1　高产乙酸的清酒酵母乙酸是酵母酒精发酵的副产物 ,果酒中乙酸浓度一般不得超过 0 .8%。清酒中的乙酸浓度一般在 5 0～ 35 0mg/L。酵母菌株和乙酸的产生和发酵产品的质量有关。但是清酒中的乙酸并不一定不好。饮用 5℃低温含乙酸的果酒有很好的滋味。感官评价表明 ,清酒的理想酸度是乙酸和乳酸的比例为一比三 ,即使乙酸浓度达到 0 .75g/L。甘油能平衡酸度 ,协调清酒的甜度和酸度。本研究从NADH脱氢酶(NDE)活性低的酵母突变株中分离到高产乙酸的清酒酵母(MHA 3)。在 10kg大米的小型清酒发酵实验中 ,MHA 3菌株产生的乙酸和乳酸分别比…     

葡萄酒中酵母菌高产甘油的研究进展

甘油是酵母菌酒精发酵过程中的副产物,甘油作为非挥发性物质,对葡萄酒的香气没有贡献,但是其黏性和甜味,可使葡萄酒具有圆润、柔滑、甘甜、肥硕、更易入口的特性,也可用于平衡酒中的酸感,增加口感复杂性,是高品质果酒的重要成分。近年来,国内外对高产甘油酵母的研究日益增多,着重于提高葡萄酒中酵母发酵生产甘油的能力。     

发酵戊糖产酒精酵母菌株的选育

介绍了一种新的发酵戊糖产酒酵母菌种筛选方法并利用该方法筛选出一株性能优良的发酵戊糖酵母蓖株Z8,该菌株性能测试结果为：产酒精能力相当于发酵戊糖理论产量的60．0％,耐酒精能力14％（V／V）,在温度高达42℃的条件下仍能正常发酵,初步鉴定该菌株为管囊酵母（Pachysolen tannophilus)。     

酵母融合菌株的构建及其特性研究

以酿酒酵母和糖化酵母为亲本,通过正交实验优化了亲本原生质体的制备,再生以及融合的最佳条件,由此获得了既具有糖化能力又可产高浓度酒精的稳定的酵母融合菌株。融合株的体积较亲株大,ＤＮＡ含量与两亲株ＤＮＡ含量之和相当,淀粉水解能力,葡萄糖发酵效率,生长速率及产酒精能力等均优于亲株     

原生质体融合构建葡萄酒降酸酵母的研究

对葡萄酒酵母1450(Chxs、Ampr)和酒酒球菌SD-2a(Chxr、Amps)的原生质体制备方法进行了研究,并采用PEG和Ca2 促融的方法进行了两菌株的跨界原生质体融合。利用放线菌酮 氨苄青霉素对融合子进行初筛,再经发酵试验复筛,从117株融合子中筛选出1株在酒精发酵的同时降解苹果酸能力强的融合子F-20,在连续传代10次后,其遗传性状稳定。融合子F-20的酒精发酵能力接近葡萄酒酵母1450,同时能够降解66%左右的苹果酸。     

酵母菌株和发酵条件对酒精连续发酵的影响

从多株酒精酵母菌种中筛选出S．cerevisiaeKG作为连续发酵菌株,该菌株经耐酸驯化,提高了抵抗不利环境的能力。本论文还探讨了二氧化碳、氧气对酒精发酵过程的影响,认为氧气最一关键性的影响因素。在另一方面,在酒精连续发酵过程中使用带有细胞循环的双罐系统,酒精生产强度达到30．5g／L·h。     

外加肌醇对嗜鞣管囊酵母发酵的酒精产量及其耐酒精能力的影响

嗜鞣管囊酵母(Pachysolen tannophilus)是可以同时发酵葡萄糖和木糖为酒精的菌种,在其生长和发酵培养基中分别添加不同浓度((0～200mg/L)的肌醇以及不同起始浓度的酒精,以考察外加肌醇对嗜鞣管囊酵母生长、产酒精能力和耐酒精能力的影响.结果 表明,添加肌醇前后,嗜鞣管囊酵母的生物量及发酵的酒精产量均有所增加.外加肌醇对嗜鞣管囊酵母生长有轻微的刺激作用,酵母生长最适肌醇浓度为150mg/L;而对酵母生长的耐酒精能力却有明显的影响, 并且,菌种在YEPD培养基中的耐酒精能力高于在YEPX培养基中的耐酒精能力.经实验测定,肌醇对嗜鞣管囊酵母产酒精能力及发酵的耐酒精能力均有显著的影响.发酵培养基中未添加起始浓度的酒精时,菌种发酵的最适肌醇浓度为100mg/L,此时生成的酒精产量为45.20g/L.当分别添加起始酒精浓度为10%和12%时,随着肌醇浓度的增加,菌种发酵生成的酒精浓度均呈上升趋势;肌醇浓度为200mg/L时,两种起始酒精浓度下,酒精的净生成量均达到最大,分别为17.18g/L和16.68g/L.     

Copper Tolerance and Biosorption of Saccharomyces cerevisiae during Alcoholic Fermentation

At high levels, copper in grape mash can inhibit yeast activity and cause stuck fermentations. Wine yeast has limited tolerance of copper and can reduce copper levels in wine during fermentation. This study aimed to understand copper tolerance of wine yeast and establish the mechanism by which yeast decreases copper in the must during fermentation. Three strains of Saccharomyces cerevisiae (lab selected strain BH8 and industrial strains AWRI R2 and Freddo) and a simple model fermentation system containing 0 to 1.50 mM Cu²⁺ were used. ICP-AES determined Cu ion concentration in the must decreasing differently by strains and initial copper levels during fermentation. Fermentation performance was heavily inhibited under copper stress, paralleled a decrease in viable cell numbers. Strain BH8 showed higher copper-tolerance than strain AWRI R2 and higher adsorption than Freddo. Yeast cell surface depression and intracellular structure deformation after copper treatment were observed by scanning electron microscopy and transmission electron microscopy; electronic differential system detected higher surface Cu and no intracellular Cu on 1.50 mM copper treated yeast cells. It is most probably that surface adsorption dominated the biosorption process of Cu²⁺ for strain BH8, with saturation being accomplished in 24 h. This study demonstrated that Saccharomyces cerevisiae strain BH8 has good tolerance and adsorption of Cu, and reduces Cu²⁺ concentrations during fermentation in simple model system mainly through surface adsorption. The results indicate that the strain selected from China’s stress-tolerant wine grape is copper tolerant and can reduce copper in must when fermenting in a copper rich simple model system, and provided information for studies on mechanisms of heavy metal stress.     

商业酵母在不同品种葡萄酒工业化生产中的定殖差异

[背景]酵母菌在葡萄酒酿造中起到重要的作用,接种商业活性干酵母(active dry yeast,ADY)进行葡萄酒酿造在国内较为普遍,然而商业酿酒酵母(Saccharomyces cerevisiae)对我国本土酵母菌资源的影响及二者竞争关系的相关报道不多.[目的]比较商业酿酒酵母在不同品种葡萄酒工业化生产中的定殖差...     

Glycerol Overproduction by Engineered Saccharomyces cerevisiae Wine Yeast Strains Leads to Substantial Changes in By-Product Formation and to a Stimulation of Fermentation Rate in Stationary Phase

Six commercial wine yeast strains and three nonindustrial strains (two laboratory strains and one haploid strain derived from a wine yeast strain) were engineered to produce large amounts of glycerol with a lower ethanol yield. Overexpression of the GPD1 gene, encoding a glycerol-3-phosphate dehydrogenase, resulted in a 1.5- to 2.5-fold increase in glycerol production and a slight decrease in ethanol formation under conditions simulating wine fermentation. All the strains overexpressing GPD1 produced a larger amount of succinate and acetate, with marked differences in the level of these compounds between industrial and nonindustrial engineered strains. Acetoin and 2,3-butanediol formation was enhanced with significant variation between strains and in relation to the level of glycerol produced. Wine strains overproducing glycerol at moderate levels (12 to 18 g/liter) reduced acetoin almost completely to 2,3-butanediol. A lower biomass concentration was attained by GPD1-overexpressing strains, probably due to high acetaldehyde production during the growth phase. Despite the reduction in cell numbers, complete sugar exhaustion was achieved during fermentation in a sugar-rich medium. Surprisingly, the engineered wine yeast strains exhibited a significant increase in the fermentation rate in the stationary phase, which reduced the time of fermentation.     

Genetic Basis of Variations in Nitrogen Source Utilization in Four Wine Commercial Yeast Strains

The capacity of wine yeast to utilize the nitrogen available in grape must directly correlates with the fermentation and growth rates of all wine yeast fermentation stages and is, thus, of critical importance for wine production. Here we precisely quantified the ability of low complexity nitrogen compounds to support fast, efficient and rapidly initiated growth of four commercially important wine strains. Nitrogen substrate abundance in grape must failed to correlate with the rate or the efficiency of nitrogen source utilization, but well predicted lag phase length. Thus, human domestication of yeast for grape must growth has had, at the most, a marginal impact on wine yeast growth rates and efficiencies, but may have left a surprising imprint on the time required to adjust metabolism from non growth to growth. Wine yeast nitrogen source utilization deviated from that of the lab strain experimentation, but also varied between wine strains. Each wine yeast lineage harbored nitrogen source utilization defects that were private to that strain. By a massive hemizygote analysis, we traced the genetic basis of the most glaring of these defects, near inability of the PDM wine strain to utilize methionine, as consequence of mutations in its ARO8, ADE5,7 and VBA3 alleles. We also identified candidate causative mutations in these genes. The methionine defect of PDM is potentially very interesting as the strain can, in some circumstances, overproduce foul tasting H₂S, a trait which likely stems from insufficient methionine catabolization. The poor adaptation of wine yeast to the grape must nitrogen environment, and the presence of defects in each lineage, open up wine strain optimization through biotechnological endeavors.     

Yeast population dynamics during the fermentation and biological aging of sherry wines

Molecular and physiological analyses were used to study the evolution of the yeast population, from alcoholic fermentation to biological aging in the process of "fino" sherry wine making. The four races of "flor" Saccharomyces cerevisiae (beticus, cheresiensis, montuliensis, and rouxii) exhibited identical restriction patterns for the region spanning the internal transcribed spacers 1 and 2 (ITS-1 and ITS-2) and the 5.8S rRNA gene, but this pattern was different, from those exhibited by non-flor S. cerevisiae strains. This flor-specific pattern was detected only after wines were fortified, never during alcoholic fermentation, and all the strains isolated from the velum exhibited the typical flor yeast pattern. By restriction fragment length polymorphism of mitochondrial DNA and karyotyping, we showed that (i) the native strain is better adapted to fermentation conditions than commercial strains; (ii) two different populations of S. cerevisiae strains are involved in the process of elaboration, of fino sherry wine, one of which is responsible for must fermentation and the other, for wine aging; and (iii) one strain was dominant in the flor population integrating the velum from sherry wines produced in González Byass wineries, although other authors have described a succession of races of flor S. cerevisiae during wine aging. Analyzing all these results together, we conclude that yeast population dynamics during biological aging is a complex phenomenon and differences between yeast populations from different wineries can be observed.     

Evaluation of Fermentation Efficiency of Yeast Strains and their Effect on Quality of Young Wines

The yeast has important role in fermentation of wine grapes and wine quality. The fermentation of wine grapes affect by efficiency of particular yeast strain, sugar content, pH, available temperature, etc. To evaluate the efficiency of yeast strains (Premier Cuvee, RS-1, RS-2, RS-3 and natural), present study was conducted on two wine grape varieties viz.; Sauvignon Blanc (White) and Cabernet Sauvignon (Red). Efficiency of yeast strains was evaluated in terms of conversion rate of sugar into alcohol. As per recorded data, strain RS-3 (Pichia kudriavzevii) was found more efficient than other strains in fermentation of Cabernet Sauvignon with efficiency of 84.4 per cent but in case of Sauvignon Blanc, the commercial culture Premier Cuevee was found superior over RS-3. The quality parameters of young wines of both the varieties were also affected by the used strains. Considering the efficiency and impact on various parameters of wines, local strain, i.e., RS-3 was found at par with commercial culture (Premier Cuvee). The RS-3 strain has potential to produce quality wines. However, studies on effects of RS-3 strain on some specific quality parameters of wines like varietal aroma compounds, flavours etc. are needed.     

贺兰山东麓优良本土酿酒酵母筛选及发酵特性分析

【背景】商业酵母的使用造成葡萄酒同质化问题严重,发掘优良本土酿酒酵母具有十分重要的意义。【目的】从168株宁夏本土酿酒酵母菌株中筛选出性能优良、具有出色葡萄酒发酵能力的菌株。【方法】基于杜氏管发酵试验和乙醇、高糖等耐受性试验分析产H2S能力及生长曲线测定的方法,筛选出发酵力好、耐受性强、低产H2S的本土酿酒酵母进行赤霞珠葡萄酒发酵试验,测定葡萄酒样基础理化指标、酚类物质和挥发性成分,探究筛选出的酿酒酵母发酵特性。【结果】初步筛选出发酵快速,能适应13%乙醇、350 g/L葡萄糖、250 mg/L SO2、pH 1.0的生存环境且低产H2S的4株本土酿酒酵母YC-E8、QTX-D17、QTX-D7、YQY-E18。菌株YC-E8产甘油能力强,所发酵酒样香气与商业酵母XR、F33最为接近,适用于赤霞珠葡萄酒的发酵。菌株QTX-D17发酵酒样中酒精、单宁、总酚和花色苷含量最高,表现出本土酿酒酵母优良的发酵特性。菌株QTX-D7所发酵酒样香气中乙酸乙酯、辛酸乙酯、1-壬醇等物质含量较高,赋予了葡萄酒香蕉味、苹果味、菠萝味、椰子味等愉悦花果香。【结论】最终筛选出3株优良本土酿酒酵母QTX-D17...     

亚麻立枯病拮抗菌的筛选、生防效果及发酵条件优化

【目的】从健康亚麻植株的根际土壤中筛选对亚麻立枯病菌具有较强抑菌作用的拮抗菌,优化其产生抑菌活性物质的发酵条件,为其生防利用奠定基础。【方法】采用稀释平板涂布法和对峙培养法进行拮抗菌的筛选;根据菌株形态学特征、生理生化特性以及16S r RNA基因序列分析对其进行鉴定;利用温室抗病实验确定其生防效果;通过单因素实验和均匀设计实验优化其发酵条件。【结果】分离筛选到一株对亚麻立枯病菌具有显著拮抗作用的细菌HXP-5,且其对另外7种植物病菌真菌均有拮抗作用;鉴定菌株HXP-5为枯草芽孢杆菌;温室抗病实验结果表明其生防效果可达71.22%;其产生抑菌活性物质的最佳发酵条件为:葡萄糖为2.3%,胰蛋白胨+酵母粉(3:1)为0.25%,Na Cl为0.18%,发酵时间为72 h,发酵温度为27°C,转速为210 r/min,250 m L摇瓶装液100 m L,接种量为1.7%。【结论】经鉴定,对亚麻立枯病病菌具拮抗作用的菌株HXP-5为枯草芽孢杆菌,且对亚麻立枯病具有较强的防治效果,发酵条件进行优化后其对亚麻立枯病病原菌显示出更强的拮抗作用。