定向驯化筛选耐毒酵母

通过向五种驯化培养基中逐渐增加抑制剂,经过23d的连续驯化后,找到一株适用于纤维素水解液发酵生产乙醇的耐毒酵母。耐毒酵母和原始菌株在含有乙酸3.2g/L,糠醛0.8g/L,甲酸0.4g/L的培养基中生长时,耐毒酵母的乙醇产率为0.428g/g,达到理论值的85.6%,而原始菌株产率为0.246g/g,仅达到理论值的52.8%。耐毒酵母经连续传代5次,其产乙醇性能基本保持稳定。与原始菌株相比,耐毒酵母展现了良好的耐毒性状和高效利用葡萄糖发酵产生乙醇的能力。      

定向驯化筛选耐毒酵母

通过向五种驯化培养基中逐渐增加抑制剂,经过23d的连续驯化后,找到一株适用于纤维素水解液发酵生产乙醇的耐毒酵母。耐毒酵母和原始菌株在含有乙酸3.2g/L,糠醛0.8g/L,甲酸0.4g/L的培养基中生长时,耐毒酵母的乙醇产率为0.428g/g,达到理论值的85.6%,而原始菌株产率为0.246g/g,仅达到理论值的52.8%。耐毒酵母经连续传代5次,其产乙醇性能基本保持稳定。与原始菌株相比,耐毒酵母展现了良好的耐毒性状和高效利用葡萄糖发酵产生乙醇的能力。     

耐高温高产酒精酵母菌的筛选鉴定及特性研究

为了筛选耐高温产酒精酵母菌,以贵州省茅台镇酱香型酒厂的第四轮次酒醅为实验材料,采用平板划线分离法筛选出37株酵母菌,从37株酵母菌中通过热致死温度、TTC染色法获得1株耐高温且高产酒精的J18菌株,对其在最高发酵温度的耐乙醇、耐酸、耐糖及发酵力进行了研究。结果表明：J18菌株的最高发酵温度为44℃,耐乙醇浓度18%vol,最适生长pH值为5.5;最适生长葡萄糖浓度为35%,最适发酵条件下发酵力为4.881 g/100 mL。对该菌株进行形态学鉴定和26S rDNA测序,确定该菌株为酿酒酵母（Saccharomyces cerevisiae）。     

多样品耐高温产乙醇酵母的筛选及生长特性研究

从未经蒸煮的压滤酒糟、蒸煮酒糟、菜园土壤以及家用面头等4种样品中,经菌种富集、纯化、耐酒精和耐高温的驯化以及发酵产气和产乙醇能力的比较,选育出一株耐性优良的高产菌株LZ2.该菌株的最低乙醇致死浓度为22%(v/v),37～40℃生长良好,在10°麦汁的初步发酵研究中,40℃条件下发酵5d,最终乙醇浓度为5.21%(v/v),发酵液中残还原糖和总糖浓度分别为12.751mg/mL和32.758mg/mL.该菌的成功选育为酵母菌实际利用稻草粉的同步糖化发酵提供了菌种来源.     

黄酒生产用酵母的分离与筛选

从5种不同的黄酒酒药中分离出了10株酵母菌,并观察了它们的细胞形态和群体形态特征.通过对10株酵母比较发现,1号酵母和8号酵母在发酵能力、抗高温能力、耐乙醇能力及凝聚性等方面优于其它酵母,从而筛选出两株性能优良的黄酒生产酵母菌株.     

白酒酒曲中9株酵母菌的分离与特性研究

从本地白酒酒曲中成功分离出9株酵母菌,依次命名为Y-1～Y-9。比较了这9个菌株的生理生化特性、耐高温能力和耐酒精能力等特性。结果表明:分离的9株酵母菌上述特性差别较大,其中,Y-4各方面均表现突出,该菌株能利用木糖在内的多种糖源,在45℃下生长良好,能耐14%的酒精度。对橘子汁为原料进行的发酵实验表明,上述菌株均能以橘子汁为原料生产酒精,其中,Y-4发酵能力最强,发酵84h后,CO2失重为12.913g。综上所述,Y-4是一株极具潜力的燃料乙醇生产工程菌株。     

白酒酒曲中9株酵母菌的分离与特性研究

从本地白酒酒曲中成功分离出9株酵母菌,依次命名为Y-1～Y-9。比较了这9个菌株的生理生化特性、耐高温能力和耐酒精能力等特性。结果表明:分离的9株酵母菌上述特性差别较大,其中,Y-4各方面均表现突出,该菌株能利用木糖在内的多种糖源,在45℃下生长良好,能耐14%的酒精度。对橘子汁为原料进行的发酵实验表明,上述菌株均能以橘子汁为原料生产酒精,其中,Y-4发酵能力最强,发酵84h后,CO2失重为12.913g。综上所述,Y-4是一株极具潜力的燃料乙醇生产工程菌株。      

人参果自然发酵醪中酵母菌种筛选及其发酵性能

为筛选适合甘肃河西走廊特产人参果酒精发酵的优良酵母菌株,以人参果自然发酵醪为原料,通过镜检等方法从分离纯化的20株酵母菌中进一步筛选得到11株发酵性能良好的酵母菌,分别命名为TY8、TY5、TY6、Y3、Y4、Y5、LY3、LY1、Y1、Y2、TY2。以葡萄酒活性干酵母作为对照菌株,通过酵母发酵力比较、耐乙醇能力、耐SO2能力、理化指标分析及感官评价,筛选出1株适于人参果果酒发酵的酿酒酵母TY8。以此菌株发酵生产的人参果果酒香气特征明显,酒体澄清透明,具有人参果果酒典型风味。     

枣酒酵母菌的驯化研究

为获得优良的枣酒生产用的酵母菌,以酵母菌ZJ16为出发菌株,对其耐酒精能力和耐高糖能力进行驯化,最终获得的菌株ZJ16-8-6可以耐36Brix的高糖,在酒精度为24%时仍能正常发酵,并确定了该菌株发酵的最佳初始糖度为20Brix。最终酿制出酒精含量为9.9%、残糖为2.9Brix、pH为3.3,呈琥珀色,清澈透亮,枣香浓郁的枣酒。     

发酵木糖产乙醇菌种筛选及应用

采用传统的菌种筛选方法,对样品进行了发酵木糖生产酒精的酵母菌的筛选,得到一株能够发酵木糖生产酒精的酵母菌,经初步鉴定为假丝酵母菌.其在木糖含量2%、30℃、100r/min的条件下发酵,酒精产量达到3.10g/L,基本达到了一般野生酵母的水平.再利用其发酵麦糟水解液,乙醇产量最高为4.24g/L.结果表明,Y-4T-1具有抵抗麦糟水解液中的乙酸、糠醛、羟甲基糠醛等抑制物生长的能力,为发酵麦糟生产酒精的进一步研究提供了菌种支持,为生物质燃料生产燃料乙醇的研究提供了新的思路.     

Identification of <Emphasis Type="Italic">Zygosaccharomyces mellis</Emphasis> strains in stored honey and their stress tolerance

To screen yeast with high sugar tolerance and evaluate their stress tolerance, six yeast strains were selected from 17 stored honey samples. The species were identified through 26S rRNA sequencing. Their stress tolerance was determined via the Durham fermentation method and ethanol production ability was determined via flask fermentation. The results demonstrated that all the six strains were Zygosaccharomyces mellis. Their sugar, ethanol, and acid tolerance ranges were 500–700 g/L, 10–12% (v/v), and pH 2.5–4.5, respectively. The SO₂ tolerance was 250 mg/L. Among the six strains, 6-7431 had the best stress tolerance with sugar tolerance of 700 g/L, ethanol tolerance of 12% (v/v), and acid tolerance of pH 2.5. Furthermore, the strain of 6-7431 had the highest percentage of ethanol production at the same initial sugar content as the other strains. Therefore, the selected six yeast strains would be promising fermentation yeasts for wine-making, ethanol production, or other fermentation purposes.     

酿酒活性干酵母生理特性的研究

建立一种酿酒活性干酵母生理活性的简易评价方法,比较并筛选一株适合以木薯粉水解液发酵发酵生产燃料酒精的活性干酵母。优化2株酿酒活性干酵母的活化条件、生长温度和生长pH值,以木薯粉水解液为发酵液,在最适生长条件下比较两株酵母的生长曲线、发酵强度、耐糖能力、耐温能力和耐酒精能力。选择酿酒活性干酵母Ⅰ作为木薯粉水解液发酵酵母,该酵母在前36h发酵强度高于1g(/L.h),36h后发酵强度迅速下降;耐糖能力为20%,耐受温度是55℃以及耐酒精浓度是7%。     

白酒酿造酒醅与周边土壤中酵母菌多样性及东方伊萨酵母发酵特性比较

采用平板分离法,从白云边酒厂酒醅和周边土壤中分离获得120株酵母菌,采用26S rDNA D1/D2序列分析,比较2种环境中酵母菌的多样性,并测定不同来源的东方伊萨酵母（Issatchenkia orientalis）菌株耐酸、耐温和乙醇耐受性及发酵产物乙醇和乙酸乙酯含量差异。结果表明,来自酒醅和土壤中的酵母菌多样性差异较大,土壤、酒醅中热带假丝酵母（Candida tropicalis）、盔形毕赤酵母（Pichia manshurica）分别占优势。I. orientalis在土壤和酒醅中均比较丰富,其耐酸、耐高温和高温下耐乙醇能力有差异,且来源酒醅的菌株在耐受性方面较来源土壤菌株有一定优势,来源酒醅I. orientalis菌株发酵产乙醇和乙酸乙酯含量显著高于来源土壤菌株。该研究结果将有助于揭示参入白酒发酵的菌种来源和I. orientalis优良菌株的选育。     

酵母耐性评价方法的比较

酿造酵母对发酵中所形成胁迫的耐受能力是乙醇工业生产中酵母菌株所应具备的重要特性。为了筛选和评价具有胁迫耐受能力的乙醇发酵生产酵母菌株,需要建立通用的实验方法。文中通过比较耐性生长曲线、点滴试验和杜氏管产气3种方法,来评价4株酿造酵母的耐渗性能、耐乙醇性能及耐温性能。结果表明,评价体系下4株酵母耐渗性与耐温性体现了相似的趋势;在耐乙醇性能评价试验中,点滴试验评价与耐性生长曲线评价结果拟合度较高,而杜氏管产气作为酵母耐性评价的方法实验中未能得到很好的规律,其可靠性有待商榷。     

CAMBRIDGE PRIZE LECTURE IMPROVING YEAST FERMENTATION PERFORMANCE

A number of factors affecting yeast fermentation performance have been investigated. These include the mode of substrate feeding, nutrient supplementation, temperature, osmotic pressure, oxygen, intracellular ethanol accumulation, and yeast ethanol tolerance. Nutrient supplementation was observed to play a key role in yeast fermentations employing high gravity media and at high temperatures. Furthermore, complete attenuation of high gravity wort (25°P) could be achieved by optimizing the yeast pitching rate, fermentation temperature, and level of wort oxygenation. Genetic manipulation techniques, such as spheroplast fusion, were successfully employed to obtain ethanol and osmotolerant yeast strains. In addition, a number of stable 2-deoxy-D-glucose resistant mutants, isolated from brewing and non-brewing yeast strains, were observed to rapidly utilize maltose and maltotriose in the presence of high concentrations of glucose. Fermentation and ethanol production rates were increased in these strains. Therefore, employing strategies of optimized fermentation conditions and strain development have resulted in improvements in yeast fermentation performance.     

Sake yeast strains have difficulty in entering a quiescent state after cell growth cessation

Sake yeast strains produce a high concentration of ethanol during sake brewing compared to laboratory yeast strains. As ethanol fermentation by yeast cells continues even after cell growth stops, analysis of the physiological state of the stationary phase cells is very important for understanding the mechanism of producing higher concentrations of ethanol. We compared the physiological characteristics of stationary phase cells of both sake and laboratory yeast strains in an aerobic batch culture and under sake brewing conditions. We unexpectedly found that sake yeast cells in the stationary phase had a lower buoyant density and stress tolerance than did the laboratory yeast cells under both experimental conditions. These results suggest that it is difficult for sake yeast cells to enter a quiescent state after cell growth has stopped, which may be one reason for the higher fermentation rate of sake yeast compared to laboratory yeast strains.     

Overexpression of vacuolar H+‐ATPase‐related genes in bottom‐fermenting yeast enhances ethanol tolerance and fermentation rates during high‐gravity fermentation

Vacuolar H⁺‐ATPase (V‐ATPase) is thought to play a role in stress tolerance. In this study it was found that bottom‐fermenting yeast strains, in which the V‐ATPase‐related genes DBF2, VMA41/CYS4/NHS5 and RAV2 were overexpressed, exhibited stronger ethanol tolerance than the parent strain and showed increased fermentation rates in a high‐sugar medium simulating high‐gravity fermentation. Among the strains examined, the DBF2‐overexpressing bottom‐fermenting yeast strain exhibited the highest ethanol tolerance and fermentation rate in YPM20 medium. Using this strain, high‐gravity fermentation was performed by adding sugar to the wort, which led to increased fermentation rates and yeast viability compared with the parent strain. These findings indicate that V‐ATPase is a stress target in high‐gravity fermentation and suggests that enhancing the V‐ATPase activity increases the ethanol tolerance of bottom‐fermenting yeast, thereby improving the fermentation rate and cell viability under high‐gravity conditions. Copyright © 2012 The Institute of Brewing & Distilling     

96孔板高通量选育产乙醇酵母

以巴斯德毕赤酵母(Pichia pastoris),安琪酵母(Angel yeast),酿酒酵母(Sacchro-myces cerevisiae)等4株菌为出发菌株,经过紫外诱变,96孔板高通量筛选出60株,复筛选出4株.最大乙醇产量提高到76.6g/L,糖醇转化率达到了0.488g/g.对上述4株菌进行耐乙醇性能驯化,发酵耐乙醇能力达到15%.     

Isolation and Characterisation of Sri Lankan Yeast Germplasm and Its Evaluation for Alcohol Production

Use of inferior yeast cultures represents one of the reasons for low fermentation efficiencies in Sri Lankan alcohol distilleries that use sugarcane molasses. The present study isolated and characterised yeast strains found in natural environments in Sri Lanka and evaluated their performance under laboratory conditions in an effort to select superior strains for industrial fermentations. Yeasts were characterised based on morphological and physiological features such as sugar fermentation and nitrate assimilation. Ethanol production, alcohol tolerance and growth rate of the most promising strains were monitored following laboratory fermentations of molasses. Over a thousand yeast cultures were collected and screened for fermentative activity and a total of 83 yeast isolates were characterised as higher ethanol producers. Most of these belonged to the genus Saccharomyces. Certain strains produced over 10% (v/v) alcohol in molasses media during 72 h laboratory fermentations. Only two strains, SL‐SRI‐C‐102 and 111, showed an appreciable fermentation efficiency of about 90%. The latter strain produced the highest level of ethanol, 11% (v/v) within a 48 h fermentation and exhibited improved alcohol tolerance when compared with the baker's yeast strains currently used in Sri Lankan alcohol distilleries. This study highlights the benefits of exploiting indigenous yeasts for industrial fermentation processes.