High gravity primary continuous beer fermentation using flocculent yeast biomass

The current work assessed a new immobilized cell reactor system throughout a long‐term (54 days) continuous primary fermentation of lager‐type wort of high specific gravity. The experiment was performed in a 4 L airlift bioreactor and immobilization of biomass was attained solely by flocculation. Despite the constant liquid agitation and washout of biomass, up to 53 g dry wt/L of yeast remained immobilized in the system. Two types of beer were produced without interrupting the reactor, based on two types of wort: a Pilsener type with high specific gravity of 15.6 ± 0.3°P; and a dark lager wort with specific gravity of 14.4 ± 0.03°P. Even during the inlet of high gravity wort, the desired attenuation was achieved without the need for either recirculation or an auxiliary second stage bioreactor. The specific saccharide consumption rate was kept around 7.9 ± 0.4 g/L/h and ethanol productivity oscillated at 3.36 ± 0.2 g/L/h for nearly a month. During this period the volumetric productivity of the current bioreactor reached 1.6 L beer/L/day. The green beers produced from the Pilsener and dark lager worts met the standards of regular finished primary beer fermentation. The productivity of diacetyl through the entire experiment could be correlated to the free amino nitrogen consumption rate. Copyright © 2014 The Institute of Brewing & Distilling     

Carrier‐free,continuous primary beer fermentation

Developing a sustainable continuous fermentation reactor is one of the most ambitious tasks in brewing science, but it could bring great benefits regarding volumetric productivity to modern breweries. Immobilized cell technology is often applied to reach the large densities of yeast needed in a continuous fermentation process. However, the financial cost associated with the use of carriers for yeast immobilization is one of the major drawbacks in the technology. This work suggests that yeast flocculation could address biomass immobilization in a gas‐lift reactor for the continuous primary fermentation of beer. Nearly 25 g dry wt L^?1 of yeast was flocculated in the reactor before interruption of the fermentation. Stable sugar consumption and ethanol production (4.5% alcohol by volume) from an 11°P wort was evidenced. The key esters and higher alcohols measured in the young beer met the standards of a finished primary beer fermentation. Copyright © 2014 The Institute of Brewing & Distilling     

泡沫陶瓷固定化酵母细胞啤酒连续主发酵工艺

采用泡沫陶瓷固定化酵母细胞,并对其应用于啤酒连续主发酵进行了实验研究,获取了优化的工艺条件:发酵温度16℃,稀释率0.044h-1。在此工艺条件下,实际测得浓度降低为7.09%,嫩啤酒双乙酰含量为0.144mg/L。嫩啤酒主要理化指标的测定结果表明:采用固定化酵母细胞啤酒主发酵工艺不会对啤酒质量造成影响。     

连续发酵啤酒风味的研究

研究了工艺因素，连续时间，发酵方式等对连续发酵啤酒风味的影响，结果发现，在本连续发酵系统中，稀释率D选择0．5d^-1，温度T选择13℃，对形成良好的风味物质更为粗利，当连续时间由15d延长至90d后，只有3－甲基丁醇超过了风味阈值20％，乙酸乙酯的差异是造成连续发酵啤酒和分批发酵啤酒风味不同的主要原因。     

优良酵母菌连续混合发酵赤霞珠葡萄酒的研究

通过对新疆赤霞珠葡萄自然发酵过程中分离鉴定的7株酵母菌的SO2、酒精、高糖、酸性及温度耐受性能进行发酵研究,获得了葡萄酒最适发酵菌株Y6和Y19,以工业菌株D-254为参照进行连续混合发酵试验,确定其最佳生产工艺为前期添加菌株Y6,发酵温度20℃,发酵时间54h;后期添加菌株Y19,发酵温度25℃,发酵时间120h,酵母总添加量为0.08%,添加比例Y6/Y19为1∶3。     

利用固定化酵母进行黄酒主发酵的初步研究

该文以海藻酸钙凝胶为固定化载体,从酵母浓度、海藻酸钠浓度、氯化钙浓度3方面来探究黄酒主发酵阶段的最佳固定化条件,确定了酵母浓度为109个/mL,海藻酸钠浓度为2.0%,氯化钙浓度为4%。同时将其与传统游离酵母的发酵曲线进行对比,并且在实验室条件下连续进行了12次固定化酵母发酵,结果显示主发酵结束时酒样的酒精度在7.4%vol左右(与游离发酵结果类似),稳定性较为理想。     

天然固定化酵母载体在果酒中的发酵试验研究

采用海藻酸钠、甘蔗渣、玉米芯、干红枣4种材料作为酵母菌的固定化载体在香蕉果酒中进行发酵试验,结果表明,无论从载体的制备、酵母的连续发酵能力以及酒液的感官品质,天然甘蔗渣载体均具有其优越性,为果酒生产提供高效优质的酵母固定化载体.     

啤酒发酵过程中酸类物质的变化与酵母活力关系的研究

研究了发酵过程中部分有机酸、脂肪酸含量的变化趋势与酵母活力的关系，以及使用不同代数的酵母对发酵液有机酸和脂肪酸含量、组成的影响；并且对比了不同使用代数酵母泥离心液和发酵液相应有机酸、脂肪酸含量的差值，以及差值与酵母活力的关系。     

Effect of immobilised cell concentration on beer quality in continuous fermentation

Abstract

We studied the influence of immobilised yeasts on fermentation parameters and beer quality using a continuous gas‐lift bioreactor system with Saccharomyces warum entrapped in calcium pectate beads. The higher the amount of biomass, the shorter the fermentation time. At an immobilised biomass volume to wort ratio of 0.35:1 (v/v), productivity began to fall and the specific rate of saccharide utilisation decreased. The optimum level for productivity and beer quality was obtained at the ratio of 0.27:1 (v/v) biocatalyst volume to the wort volume. Beer with suitable flavour, low level of diacetyl (less than 0.1 mg/1) and an optimum ratio of the higher alcohols to esters content (4.53:1) has been produced with a residence time of 13.16 h and maximum specific rate of saccharide utilisation of I.106 g/g.h. Except for higher nitrogen and lower amyl alcohols contents, the parameters characterising the beer quality produced in this bioreactor were close to the parameter values of classically produced beer.     

发酵环境变化对酵母生长和成品啤酒的影响

啤酒发酵是一个复杂的生物和物质转化过程,在整个酿造过程中,从原料粉碎到开始发酵直至发酵结束降温冷贮,环境变量因素很多,会影响啤酒酵母生长,从而影响成品啤酒中的挥发性风味物质和啤酒品质。该文重点总结介绍麦汁浓度、接种率、发酵温度、压力变量对发酵过程的影响,旨在为解决啤酒酿造过程可能出现的问题提供一些思路,从而提高啤酒质量。     

Identification of bottom-fermenting yeast genes expressed during lager beer fermentation

It has been proposed that bottom-fermenting yeast strains of Saccharomyces pastorianus possess at least two types of genomes. Sequences of genes of one genome [S. cerevisiae (Sc)-type] have been found to be highly homologous (more than 90% identity) to S. cerevisiae S288C sequences, while those of the other [Lager (Lg)-type] are less so. To identify and discriminate Lg-type from Sc-type genes expressed during lager beer fermentation, normalized cDNA libraries were constructed and analysed. From approximately 22 000 ESTs, 3892 Sc-type and 2695 Lg-type ORFs were identified. Expression patterns of Sc- and Lg-type genes did not correlate with particular cell functions in KEGG classification system. Moreover, 405 independent clones were isolated that have no significant homology with sequences in the S288C database, suggesting that they include the bottom-fermenting yeast-specific (BFY) genes. Most of BFY genes have significant homology with the S. bayanus genome.     

果酒发酵酵母菌株的发酵性能初探

针对一株用于猕猴桃及橙子果酒发酵皆较优的酿酒酵母GJ-JS1,初步探索其各项发酵特性,对其发酵条件筛选得到：初始糖度0.115g/mL,初始pH值应控制在2.8~3.4之间为宜,发酵初始菌浓度2.32×104个/mL。对GJ-JS1进行耐受实验得到：该菌株发酵时间最好控制在24h~36h内,发酵pH值不低于3.2,综合分析得发酵酸度以pH3.2~3.4为宜。酒精度可控制于6%vol左右,糖浓度不高于200g/L,有利于菌株生长。     

固定化酵母应用于酵母工序大生产试验研究

介绍了固定化酵母应用于酵母工序大生产的试验过程。结果表明，酒固定化酵母具有传统酵母的发酵能力，其含酒精高于传统酵母0．05％加．1％；以麦芽、玉米为混合原料的发酵周期为40h-50h，以瓜干为原料的发酵周期为45h-50h，产酒精能力8%-11％。并提出了该技术的优点和不足之处。     

利用酵母发酵芦荟汁饮料的研究

以芦荟为原料，利用酵母菌发酵芦荟汁成为低酵度的饮料。对加入防腐剂H2SO3后不同的接种时间，加入糖量和不同酵母菌种等因素对发酵产品质量作了初步探讨，确定了发酵芦荟汁饮料的工艺参数。     

啤酒固定化连续后发酵中两种载体性能的研究

使用山毛榉木片和多孔陶瓷作为固定酵母的载体,对这两种载体在固定化连续后发酵中的固定化效果以及生产的啤酒的各项指标进行比较和研究。结果表明,与多孔陶瓷相比,山毛榉木片固定化酵母的量、达到饱和时速率分别高出31.2%、45.4%,且牢固程度较优。分别以山毛榉木片与多孔陶瓷作为载体,后酵生产的啤酒中双乙酰含量差异显著(p<0.05),其余指标差异不显著(p>0.05)。风味物质中,乙醛、甲酸乙酯、乙酸乙酯、正丙醇、异丁醇、乙酸异戊酯、异戊醇的差异显著(p<0.05),其余风味物质的差异不显著(p>0.05)。氨基酸含量中,酪氨酸、亮氨酸的含量差异不显著(p>0.05),其余氨基酸含量差异性显著(p<0.05)。      

酸乳发酵中优良共生酵母菌的筛选

为了筛选酸乳发酵中与保加利亚乳杆菌优良共生的酵母菌。以保加利亚乳杆菌单菌发酵酸乳为对照,将前期从新疆、西藏和青海等地区传统自制乳制品中分离的27株酵母菌株分别和保加利亚乳杆菌混菌发酵制备酸乳,通过比较凝乳时间、感官特性、质地特性、后酸度、粘度、持水力、乙醛和双乙酰含量等特征,筛选酸乳发酵中与保加利亚乳杆菌优良共生的酵母菌株;基于26S D1/D2区和ITS1序列鉴定菌株。结果显示:27株酵母菌株均没有明显促进凝乳作用,9株菌混菌发酵酸乳在感官评价得分较高(80分以上),其中菌株\     

HPLC-ELSD法同时测定酵母发酵液中的多元醇

建立高效液相色谱-蒸发光散射检测器法（HPLC-ELSD）测定酵母菌株发酵液中多元醇含量的方法。采用Agilent Hi-plexCa色谱柱（7.7 mm×300 mm,8 μm）,以纯水为流动相,流速0.5 mL/min,蒸发光散射检测器（ELSD）为检测器;柱温为70 ℃,进样量为4 μL。结果表明,5种多元醇在0.8～6.0 mg/mL质量浓度范围内与峰面积呈良好的线性关系（相关系数R均≥0.996）;精密度实验结果相对标准偏差（RSD）均＜5%,平均回收率为96.73%～100.46%,表明该方法灵敏度高,重现性良好,准确度高,可用于发酵液中5种多元醇的检测。以酱香型白酒酿造过程中大曲和酒醅分离的酵母为研究对象,运用该方法在酵母发酵液中检测到5种多元醇。     

响应面法优化啤酒酵母抽提工艺条件的研究

以啤酒酵母为原料,通过单因素试验在自溶时间、温度、pH值及助溶剂等因素中确定对酵母自溶影响最为关键的因素,然后根据Box-Benhnken的中心组合试验设计原则,选取对酵母抽提影响较大的3个因素:自溶时间、自溶温度和pH值进行实验和响应面分析,得出啤酒酵母抽提的最佳工艺条件:在NaCl添加量为3%的条件下,自溶时间18.5h、自溶温度56.8℃和pH6.03,在此条件下酵母抽提液中氨基氮含量可达0.44g/100mL。     

啤酒酵母突变株发酵性能比较及随机扩增多态DNA分析

对9株啤酒酵母菌种及经过诱变获得的突变株进行了发酵试验，比较了不同菌株的发酵能力、产高级醇能力、双乙酰还原能力以及菌株稳定性。同时利用随机引物对不同啤酒酵母株的基因组DNA进行了随机扩增多态DNA（RAPD）分析，比较不同突变株之间基因组的分子差异。结果表明：不同酵母发酵14d后外观发酵度在72．3％-76．8％，其中酵母YZB具有较高的发酵能力，最终发酵产物的高级醇含量最低，双乙酰峰值最低为0．36mg／L，而酵母Y1110最终发酵产物的高级醇含量最低为67．4mg／L，但双乙酰峰值达0．41mg／L，后酵结束后这2株酵母的双乙酰均可降至0．1mg／L以下。菌株稳定性实验结果表明，在传代7次以后和第1代的主要性能没有明显变化。利用随机引物OPG-5对不同酵母的基因组进行RAPD分析，酵母Y1110、YZB和YZD可以通过特异的扩增谱带区别于其它菌株，该结果为啤酒酵母特异的分子标记奠定了基础。     

碱性和支链氨基酸对啤酒高浓酿造酵母发酵性能的影响

研究分别考察添加三种碱性氨基酸：精氨酸（Arg）、赖氨酸（Lys）、组氨酸（His）与支链氨基酸：缬氨酸（Val）、亮氨酸（Leu）、异亮氨酸（Ile）对24 °P高浓酿造过程中酵母发酵性能及啤酒风味的影响。结果表明,六种氨基酸的添加可促进酵母生长并提高活细胞率,显著提高麦汁发酵度及乙醇产量。其中,添加Val、Leu与Arg的高浓麦汁发酵性能较好,与对照组相比,发酵结束时总CO2失质量分别为92.4 g/L、92.7 g/L与91.2 g/L;发酵度极显著提高（P＜0.01）,分别为83.65%、82.95%和82.93%;乙醇产量极显著提高（P＜0.01）,分别为11.97%（V/V）、11.90%（V/V）和11.83%（V/V）。添加Arg可显著提高酵母总细胞数（1.64×108 cells/mL）（P＜0.05）,His、Val与Leu的添加对风味物质影响较大,可提高啤酒的醇酯比,其中,Val的添加可显著提高异丁醇含量（P＜0.05）,降低总酯含量;Leu的添加则可同时提高异戊醇及乙酸异戊酯的含量。