Reduced acetaldehyde production by genome shuffling of an industrial brewing yeast strain

High levels of acetaldehyde produced by yeast during fermentation can be of concern to product quality. A novel approach, based on genome shuffling, was applied to reduce the production of acetaldehyde by industrial brewing strain YS86. Four isolates with different impacts of acetaldehyde concentration were obtained from populations generated by ultraviolet irradiation and nitrosoguanidine mutagenesis. These yeast strains were then subjected to recursive pool‐wise protoplast fusion. A strain library that was likely to yield positive colonies was created by fusing the lethal protoplasts obtained from both UV irradiation and heat treatments. After two rounds of genome shuffling, a recombinant YSF2–9 strain produced less acetaldehyde than wild‐type strain YS86, by 64.5 and 66.2% in laboratory and pilot plant fermentations, respectively. The shuffled yeast strain YSF2–9 was genetically stable and may have a potential application in brewing industry for managing acetaldehyde in beer. Copyright © 2017 The Institute of Brewing & Distilling     

青岛啤酒酵母与高浓酵母筛选高浓酿造酵母融合亲株

以青岛啤酒酵母和高浓精酵母为供试菌株,筛选出生长良好的酵母,为选育具有青岛啤酒风味的高浓酵母做准备.比较了7株酵母不同糖类发酵、离子抗性、二氧化碳减重、发酵液风味品评等指标.结果表明:T1、T2和T3是传统的青岛啤酒发酵菌株,其发酵液口味符合青岛啤酒口味要求,且对Cu2+均不耐受;而G4和G6发酵减重试验和风味物质分析中的乙醛含量指标的评价均优于G5和G7菌株,且它们的发酵液的风味也接近青啤口味.因此,选择T1、T2、T3和G4、G6作100L酿造试验,进一步确定融合亲株.     

青岛啤酒酵母与高浓酵母筛选高浓酿造酵母融合亲株100L发酵分析

以青岛啤酒酵母T1、T2、T3和高浓酵母G4、G6为供试菌株,筛选生长良好的酵母,为筛选具有青岛啤酒风味的高浓酵母原生质体融合亲株做指导。比较了5株酵母菌100L发酵过程中酵母菌数量、双乙酰变化及待滤酒发酵度、酸度、α-氨基氮同化率等指标。结果表明:G4和G6酵母数量变化、双乙酰变化、发酵度和α-氨基氮同化率指标优于T1、T2和T3,青岛啤酒酵母中T1和T3除酵母凝聚性外其他指标都优于T2。因此,确定T1、T3和G4、G6为融合亲株。      

工业化酿造过程中酵母分泌蛋白酶A的规律及影响因素的研究

对啤酒工业化规模发酵过程中酵母分泌蛋白酶A的规律进行了探讨,对酵母代数及酵母贮存条件等因素对酵母分泌蛋白酶A的影响进行了研究,并对蛋白酶A活性不同的成品纯生啤酒的泡持值、泡沫活性蛋白含量及蛋白酶A活性进行了跟踪分析。结果表明:发酵过程中,蛋白酶A的活性呈上升趋势且接种酵母的蛋白酶A活性越高,与其对应的发酵液中蛋白酶A的活性越高,成品酒的泡沫稳定性越差。另外,随着酵母代数及贮存时间的增加,酵母分泌蛋白酶A的量增加。当酵母蛋白酶A活性控制在0.015U/m L以下且成品酒的初始蛋白酶A活性在15×10-5U/m L以下时,储存4个月的成品纯生啤酒的泡沫稳定性较好。      

Genetically modified industrial yeast ready for application

Tremendous progress in the genetic engineering of yeast had been achieved at the end of 20th century, including the complete genome sequence, genome-wide gene expression profiling, and whole gene disruption strains. Nevertheless, genetically modified (GM) baking, brewing, wine, and sake yeasts have not, as yet, been used commercially, although numerous industrial recombinant yeasts have been constructed. The recent progress of genetic engineering for the construction of GM yeast is reviewed and possible requirements for their application are discussed. 'Self-cloning' yeast will be the most likely candidate for the first commercial application of GM microorganisms in food and beverage industries.     

The use of atmospheric and room temperature plasma mutagenesis to create a brewing yeast with reduced acetaldehyde production

High acetaldehyde levels in beer from yeast metabolism is a major concern for brewers in China. To obtain a strain with lower acetaldehyde production, this work reports a novel approach based on atmospheric and room temperature plasma mutagenesis and high‐throughput screening using 4‐methylpyrazole + disulphiram plating. A mutant LAL‐8a with lower acetaldehyde‐producing capability was obtained. The alcohol dehydrogenase activity decreased by 54% compared with the wild‐type M14 and the aldehyde dehydrogenase activity increased by 64% of the wild‐type strain. Through domestication and fermentation in EBC tubes, the mutant LAL‐8a was shown to produce 2.2 mg/L acetaldehyde, 88.2% less than the wild‐type strain M14. In addition, the ratio of higher esters to alcohols in beer fermented by the mutant LAL‐8a (0.28) was higher than M14 (0.16). The fermentation performance of LAL‐8a was similar to that of the wild‐type M14. This work suggests strain LAL‐8a a promising option for the brewing industry. © 2018 The Institute of Brewing & Distilling     

Constructing an amylolytic brewing yeast Saccharomyces pastorianus suitable for accelerated brewing

An amylolytic brewing yeast Saccharomyces pastorianus, free of vector sequences and drug-resistance genes, was constructed by disrupting the alpha-acetolactate synthase gene and introducing the alpha-amylase gene as a selective marker. The resulting recombinant strain was able to utilize starch as the sole carbon source and its alpha-acetolactate synthase activity was lowered by 30%. Fermentation tests confirmed that the diacetyl concentration and the residual oligosaccharide were reduced by 70% and 25%, respectively, in fermented wort by the recombinant strain, while the brewing performance of the recombinant strain was retained.     

甘蔗酒酿造酵母的筛选

选择常用商业果酒酵母菌株KD、DV10、Q23、EC1118、安琪和H7Y7作为供试酵母菌株,以川蔗17为原料发酵生产甘蔗酒,通过分析发酵液中糖含量变化情况及酒精度、澄清度,比较不同菌株发酵特性,结果发现EC1118菌株发酵彻底,产酒能力最强,发酵后甘蔗酒的高级醇含量最低;H7Y7菌株发酵的甘蔗酒中酯类物质最高,为其他菌株的3～6倍;安琪酵母发酵液最易澄清,但其发酵后的甘蔗酒中甲醇含量为其他菌株的5倍以上。感官评分结果显示,不同酵母菌株发酵的甘蔗酒感官评分依次为H7Y7EC1118DV10安琪酵母Q23KD。研究结果表明,供试酵母菌株中EC1118和H7Y7更适宜用于甘蔗酒酿造。     

Construction of a brewing yeast expressing the glucoamylase gene STA1 by mating

Standard brewing yeast cannot utilize larger oligomers or dextrins, which represent about 25% of wort sugars. A brewing yeast strain that could ferment these additional sugars to ethanol would be useful for producing low‐carbohydrate diabetic or low‐calorie beers. In this study, a brewing yeast strain that secretes glucoamylase was constructed by mating. The resulting Saccharomyces cerevisiae 278/113371 yeast was MAT a/α diploid, but expressed the glucoamylase gene STA1 . At the early phase of the fermentation test in malt extract medium, the fermentation rate of the diploid STA1 strain was slower than those of both the parent strain S. cerevisiae MAFF113371 and the reference strain bottom‐fermenting yeast Weihenstephan 34/70. At the later phase of the fermentation test, however, the fermentation rate of the STA1 yeast strain was faster than those of the other strains. The concentration of ethanol in the culture supernatant of the STA1 yeast strain after the fermentation test was higher than those of the others. The concentration of all maltooligosaccharides in the culture supernatant of the STA1 yeast strain after the fermentation test was lower than those of the parent and reference strains, whereas the concentrations of flavour compounds in the culture supernatant were higher. These effects are due to the glucoamylase secreted by the constructed STA1 yeast strain. In summary, a glucoamylase‐secreting diploid yeast has been constructed by mating that will be useful for producing novel types of beer owing to its different fermentation pattern and concentrations of ethanol and flavour compounds. Copyright © 2017 The Institute of Brewing & Distilling     

超高浓酿造下抗葡萄糖阻遏啤酒酵母的筛选

根据高浓发酵下(16°P)发酵度的高低,挑选下面啤酒酵母C12作为出发菌株。经过2-去氧-D-葡萄糖的定向驯养、抗性平板分离初筛以及复筛验证等步骤,筛选出一株抗葡萄糖阻遏效应的菌株CM23。将该菌株在18°P麦汁15℃条件下进行3L的EBC小型啤酒发酵实验并测定发酵指标。结果表明:与出发菌株相比,CM23的降糖速度提高了37%,达到1.8°P/d,真正发酵度达到66%,且双乙酰还原能力以及啤酒中主要风味物质含量基本不变。CM23是一株具有工业应用前景的啤酒超高浓酿造酵母菌株。     

高压蒸汽提取啤酒废酵母还原型谷胱甘肽的工艺优化

为了得到高压蒸汽提取废酵母中还原型谷胱甘肽的最佳工艺条件,利用Box-Behnken的中心组合设计及响应面法（RSM）探讨了表压、提取时间、液料比和提取次数四因素的优化组合。通过建立二次回归模型,确定其最佳提取工艺条件为:表压1.1MPa,提取时间15min,液料比10∶1,提取次数1次,在此条件下得率最大为4.63mg/g。结果表明高压蒸汽提取技术是提高啤酒废酵母还原型谷胱甘肽得率的有效途径之一。      

低产乙醛啤酒酵母的定向驯化筛选

为降低啤酒中乙醛含量,采用紫外线对1株啤酒工业生产菌株MI4进行诱变,经双硫仑平板初筛、乙醛培养基驯化复筛,获得了1株低产乙醛的啤酒酵母D-A-14。与出发菌株MI4相比,采用该突变株酿制的啤酒中乙醛含量为2.86 mg/L,降低了76%;且高级醇总量降低而酯含量升高,风味更加协调。这表明筛选得到的低乙醛突变株适于啤酒工业生产。     

还原型谷胱甘肽在果酒酿造中的应用

谷胱甘肽是一种广泛存在于生物细胞中的活性三肽,分为还原型谷胱甘肽（GSH）和氧化型谷胱甘肽（GSSG）两种,但绝大部 分是以GSH的形式存在的。 由于GSH具有重要的生理功能,所以它被广泛用于食品加工领域,可以起到增加食品营养价值和强化食品 风味的作用。 文章综述了外源GSH的添加对果酒品质特性的影响,讨论了GSH在果酒酿造中扮演的抗氧化、抑制褐变、改善果酒风味 以及促进苹果酸-乳酸发酵的作用,同时阐述了富集谷胱甘肽非活性干酵母制剂（g-IDY）在果酒中的应用现状,为GSH作为一种添加 剂应用于果酒酿造提供了理论依据。     

海红果酒酵母筛选及其发酵工艺的响应面法优化

选取8种活性干酵母对海红果酒进行了发酵实验,以残糖和酒精度为考量参数,筛选出适于海红果酒酿造的最优菌株。在单因素实验的基础上,选取发酵温度、接种量、发酵时间为影响因子,以残糖为响应值,应用中心组合Box-Behnken实验设计构建二次回归方程的数学模型,进行了响应面分析。结果表明,Z2酵母是海红果酒酿造的最优菌株,优化后的海红果酒发酵工艺条件为:发酵温度为23℃;接种量为0.25g/L;发酵时间为35d,在此条件下,发酵所得的海红果酒残糖量为5g/L,且果香浓郁,酒体丰满。      

一株低产高级醇酵母菌在苹果酒酿造中的应用

目的 优化一株低产高级醇酵母菌发酵苹果酒的工艺条件。方法 采用一株低产高级醇的果酒酵母, 以红富士苹果为原料, 通过单因素试验和正交试验, 对影响苹果酒发酵的工艺参数进行优化。结果 最佳苹果酒酿造工艺为: 酵母液接种量5%, 果汁糖度18%, 发酵温度22 ℃; 经验证和对比, 该工艺条件有效控制了高级醇的含量, 比果酒酵母产的高级醇低, 为72 mg/100 mL。结论 本文对低醇苹果酒的酿造具有一定的指导意义。     

Optimised quantification of the antiyeast activity of different barley malts towards a lager brewing yeast strain

The brewing of beer involves two major biological systems, namely malted barley (malt) and yeast. Both malt and yeast show natural variation and assessing the impact of differing malts on yeast performance is important in the optimisation of the brewing process. Currently, the brewing industry uses well-established tests to assess malt quality, but these frequently fail to predict malt-associated problem fermentations, such as incomplete fermentations, premature yeast flocculation (PYF) and gushing of the final beer product. Antimicrobial compounds, and in particular antiyeast compounds in malt, may be one of the unknown and unmeasured malt factors leading to problem fermentations. In this study, the adaptation of antimicrobial assays for the determination of antiyeast activity in malt is described. Our adapted assay was able to detect differing antiyeast activities in nine malt samples. For this sample set, malts associated with PYF during fermentation and gushing activity in beer showed high antiyeast activity. Both PYF and gushing are malt quality issues associated with fungal infection of barley in the field which may result in elevated antimicrobial activity in the barley grain. Also, two more malts that passed the normal quality control tests were also observed to have high antiyeast activity and such malts must be considered as suspect. Based on our results, this assay is a useful measure of malt quality as it quantifies the antiyeast activity in malt which may adversely impact on brewery fermentation.     

Lachancea thermotolerans as an alternative yeast for the production of beer

The ability of Lachancea thermotolerans strains to ferment brewer's wort has been investigated. Initial fermentations with three L. thermotolerans strains compared the use of maltose and maltotriose, as well as production of glycerol and lactic acid and pH evolution over the course of the fermentation. The most promising strain was subsequently tested for additional traits important for beer production, including pitching rate, generational capacity, foam stability, hop tolerance, vicinal diketone production, oxygen requirement and flocculation. These tests suggest that L. thermotolerans may be a good choice for producing sour beers in a single fermentation step without the use of lactic acid bacteria. Copyright © 2016 The Institute of Brewing & Distilling     

Construction of proteinase A deficient transformant of industrial brewing yeast

Yeast proteinase A is detrimental to beer foam. The proteinase A deficient transformant of industrial brewing yeast, WZ65/a, was constructed using PCR-mediated gene disruption, and the transformant was verified to be genetically stable. The PCR analysis showed that PEP4 gene coding for proteinase A in the WZ65/a was disrupted. No matter in the yeast cells or in the fermenting liquor of WZ65/a, proteinase A activity could not be detected. Analysis of the main charicteristics indexes of beer also showed that proteinase A activity and foam performance in the beer brewed with WZ65/a were better than that of the host strain, WZ65.     

枸杞酒酿造技术及香气分析研究进展

近年人们对于保健养生日益重视,枸杞酒因其独特营养功能优势而为消费者广泛关注。该文就枸杞酒发展现状,酿造技术包括酿酒原料选择、外源酶添加、成分调整、酵母菌筛选和选育、发酵温度、陈酿、澄清方法等,以及枸杞酒香气分析研究进展展开论述,提出了目前存在的问题,并展望其未来发展,旨在为枸杞深加工产业助力,为枸杞酒产品开发与推广提供参考。