Inhibitory Effect of Fusarium Mycotoxins on Growth of Brewing Yeasts. 1 Zearalenone and Fumonisin B1*

The Fusarium mycotoxins zearalenone (ZEA) and fumonisin B₁ (FB₁) added to the growth medium in low and high concentrations, were investigated as a possible cause of inhibition of growth of Saccharomyces cerevisiae lager and ale strains. Toxic effects were assessed by measurement of dry weight or growth relative to controls, cell number, viability and conductance changes of the growth medium using indirect and direct methods. The Fusarium mycotoxins studied affected growth on brewing yeasts, but the inhibitory effect was dependent on concentration. Low concentrations (0.1–2 μg/ml) had no significant effect on growth compared to controls. Although high concentrations of both mycotoxins strongly affected growth, the inhibitory effect depended on toxin concentration and type, yeast strain, length of incubation and method used to assess growth. The lowest concentrations of mycotoxin causing significant inhibition on growth of these brewing yeasts were 50 μg/ml ZEA for both yeast strains, and 10 μg/ml FB₁ for the lager strain and 50 μg/ml for the ale strain.     

Isolation and Characterization of Shochu Yeasts with Superior Brewing Ability from Shochu Mashes

Seven yeasts with superior ability in terms of alcohol fermentation and aromatic ingredient generation were isolated from 272 wild yeasts obtained from shochu mashes of shochu breweries. These seven yeasts were examined for their fermentation ability with rice and sweet potato using small scale of fermentation tests. Moreover, their thermotolerance was evaluated by growth tests and fermentation tests with barley koji. Among the isolated seven yeasts, the shochu yeast “MF062” was superior in the characteristics of fast fermentation, high alcohol production, aromatic ingredient generation and thermotolerance. It was named the “Heisei Miyazaki Yeast”. From the results of analyses of physiological and genetic characteristics of MF062, it was shown to be a Saccharomyces cerevisiae, but it showed different characteristics from the industrial yeasts used in shochu production. Using a sweet potato shochu brewing test, with 60 kg of raw materials and yeast MF062, it was confirmed that a high alcohol production yield and a high quality shochu could be obtained.     

耐盐酱油酵母生长特性分析

对耐盐酱油酵母菌的生长曲线和其生长过程中培养基中还原糖消耗和乙醇生成量变化进行了研究。实验结果表明：食盐的添加对4种酵母菌的生长都有比较明显的影响，尤其是CanV酵母。还原糖含量下降和乙醇含量的增加与各酵母菌的生长阶段相关，迟滞期阶段还原糖含量下降和乙醇含量的增加比较平缓，对数生长期和稳定期阶段，还原糖含量下降和乙醇含量的增加速度最大，衰亡期阶段还原糖含量和乙醇含量相对稳定。     

Advanced Method for Measuring Proteinase A in Beer and Application to Brewing*

Proteinase A, excreted from yeast cells into beer during fermentation in the brewing process, has been shown to degrade foam-active proteins and to decrease foam stability. In order to improve the measurement of this enzyme in beer, a new fluorescent peptide, MOCAc-Ala-Pro-Ala-Lys-Phe-Phe-Arg-Leu-Lys (Dnp)-NH₂, was synthesised and applied to the accurate and rapid estimation of proteinase A in commercial beer and fermenting wort. This novel substrate is several hundred times more sensitive to proteinase A than other previously reported synthetic substrates or native protein substrates. The concentration of proteinase A in beer is closely related to foam stability and proteinase A activity was found to increase gradually during fermentation. The concentration of proteinase A excreted from yeast cells is also closely related to the vitality of pitching yeast cells. This new method was successfully applied to the evaluation of yeast vitality and the development of optimum yeast handling procedures.     

菌种选育技术在葡萄酒酿造中的应用与发展

介绍了酿酒酵母菌研究的基础和选育酿酒酵母的主要考虑因素,分析了各种菌种选育技术的优缺点,对国内外该领域的研究进展状况及各种育种方法的实际应用进行了综述,对我国未来葡萄酒酿酒酵母的选育及应用进行了展望。     

Microbiological Analyses of Dry and Slurry Yeasts for Brewing

Classical microbiological methods in association with molecular methods (DNA amplification, Temperature Gradient Gel Electrophoresis (TGGE) and Denaturing Gradient Gel Electrophoresis (DGGE) were used. These methods, developed to rapidly analyze microbial communities on the basis of sequence‐specific separation of DNA amplicons, allowed the detection of DNA differences in the amplicons tested and the identification of the strains analyzed by the comparison of unknown sequences with sequences of known species. TGGE allowed the comparison of the different Saccharomyces cerevisiae strains used in brewing while DGGE allowed the identification of lactic acid bacteria (LAB) in beer. These methods are a reliable tool for fast comparison of strains of Saccharomyces cerevisiae collected from different craft breweries where they were used as starters to check the presence of possible yeast contaminants in the brewing process and for rapid LAB identification.     

不同代数啤酒酵母对啤酒风味的影响

对不同代数4株啤酒酵母的发酵性能及其对啤酒风味物质的影响展开了研究。通过研究发现,随着酵母的不断传代,酵母的遗传稳定性会发生相应的变化。一般而言,二、三代酵母活性较高,产风味物质的量较为协调。     

不同干酵母对香蕉果酒酿造的影响

比较4种干酵母对香蕉果酒的发酵特性和品质的影响。绘制不同干酵母在发酵过程中的生长曲线和酒精、残糖变化曲线,并对比不同干酵母在高糖度和高浓度SO2香蕉汁中的发酵能力。原酒陈酿180d后,进行感官评定并测定其杂醇油的含量。结果表明,安琪葡萄酒活性干酵母发酵过程中酒精度增加速度与残糖下降速度均较快,在高浓度SO2和高糖度条件下发酵能力较好;不同干酵母发酵的酒中杂醇油生成量不同;用安琪干酵母酿造果酒感官评分最高。安琪葡萄酒活性干酵母发酵速度较快,所得产品感官品质好,是香蕉酒酿造的良好选择。     

野生酵母及其对啤酒生产的影响

讨论了啤酒生产常见野生酵母的种类及其对啤酒生产和质量的影响,并提出了野生酵母的检验和消除方法。     

Yeasts isolated from New Zealand vineyards and wineries

Background and Aims: The yeast flora from a range of New Zealand commercial wineries was surveyed to estimate the incidence of yeast species in grape juice. Methods and Results: Molecular analysis of the internal transcribed spacer region was performed for 1279 yeast colonies isolated from 17 different fresh grape juices sampled in eight New Zealand wineries between 2003 and 2009. The 17 juices contained at least 25 different species of yeast from nine genera. Microsatellite fingerprinting of Saccharomyces cerevisiae showed that some strains were identical to known commercial yeast varieties, but we also found evidence for local populations of S. cerevisiae common to individual wineries or regions. Five genotypes from Central Otago, New Zealand, were very closely related to a single sequenced strain derived from Chile, which in turn is related to European wine isolates. Conclusions: The yeast flora found in New Zealand grape juices is broadly similar to that found in wineries elsewhere around the world. Genotyping of S. cerevisiae suggests recent dispersal of both commercial and non-commercial yeast strains from Europe to New Zealand. Significance of the Study: These data are consistent with two human-mediated modes for the international dispersal of S. cerevisiae: one via the escape of strains traded commercially, and another via long distance dispersal of non-commercial strains.     

Effect of Initial PH on Growth Characteristics and Fermentation Properties of Saccharomyces cerevisiae

As the core microorganism of wine making, Saccharomyces cerevisiae encounter low pH stress at the beginning of fermentation. Effect of initial pH (4.50, 3.00, 2.75, 2.50) on growth and fermentation performance of 3 S. cerevisiae strains Freddo, BH8, Nº.7303, different tolerance at low pH, chosen from 12 strains, was studied. The values of yeast growth (OD₆₀₀, colony forming units, cell dry weight), fermentation efficiency (accumulated mass loss, change of total sugar concentration), and fermentation products (ethanol, glycerol, acetic acid, and l ‐succinic acid) at different pH stress were measured. The results showed that the initial pH of must was a vital factor influencing yeast growth and alcoholic fermentation. Among the 3 strains, strain Freddo and BH8 were more tolerant than Nº.7303, so they were affected slighter than the latter. Among the 4 pH values, all the 3 strains showed adaptation even at pH 2.50; pH 2.75 and 2.50 had more vital effect on yeast growth and fermentation products in contrast with pH 4.50 and 3.00. In general, low initial pH showed the properties of prolonging yeast lag phase, affecting accumulated mass loss, changing the consumption rate of total sugar, increasing final content of acetic acid and glycerol, and decreasing final content of ethanol and l ‐ succinic acid, except some special cases. Based on this study, the effect of low pH on wine products would be better understood and the tolerance mechanism of low pH of S. cerevisiae could be better explored in future.     

酵母菌株对低浓度啤酒酿造的影响

啤酒酵母BY - 1,BY - 2 ,BY - 3和BY - 4分别接入 6°P、7°P、8°P麦汁中 ,10℃发酵。监控发酵过程中的酸度、pH值、酒精度 ,并对过滤啤酒进行感官品评。相同麦汁浓度下 ,4株酵母的发酵液酸度、pH、酒精度值无较大差异。发酵后 6°P麦汁pH值下降约 1.5 ,7°P、8°P麦汁下降约 1.2。发酵 6°P、7°P和 8°P麦汁时 ,BY - 2酵母所酿啤酒风味最佳。     

Contribution by Saccharomyces cerevisiae Yeasts to Fermentation and Flavour Compounds in Wines from cv. Kalecik karasi Grape

The effect of indigenous and commercial S. cerevisiae yeasts on fermentation and flavour compounds of wines was examined in pasteurised grape juice. The flavour compounds were analysed and identified by GC‐FID and GC‐MS, respectively and in general, the amounts of these volatiles were increased by the use of both indigenous and commercial yeasts. The levels of isoamyl alcohol, isoamyl acetate, ethyl octanoate and ethyl deconoate exceeded flavour thresholds. All grape juices were fermented to dryness. Selected yeasts produced higher ethanol concentrations compared to spontaneous fermentations.     

酵母可同化氮含量对低产硫化氢酿酒酵母发酵特性的影响

该研究以3株本土低产硫化氢酿酒酵母（Saccharomyces cerevisiae）41y5、182y12和174y1为研究对象,研究酵母可同化氮（YAN）的质量浓度对其发酵特性的影响,并对不同菌株各指标间的相关性进行分析。结果表明,随着初始YAN质量浓度的升高,酵母的生物量越大,发酵周期越短;发酵后模拟酒的挥发酸含量和pH值升高;初始YAN质量浓度对菌株产H2S的影响不同。初始YAN质量浓度与CO2平均释放速率、挥发酸含量、pH值呈极显著正相关（P＜0.01）,与最大生物量呈显著正相关（P＜0.05）,与H2S释放量无显著相关性（P＞0.05）,且在发酵过程中H2S的释放量与发酵后模拟酒的pH值存在显著的正相关（P＜0.05）。与酿酒酵母41y5和182y12相比,酿酒酵母174y1在4个初始YAN质量浓度下,生物量均最高,发酵周期均最短,发酵性能优良。     

The Effect of Pitching Rate on Fermentation and Flavour Compounds in High Gravity Brewing

The effect of pitching rate on fermentation and production of flavour compounds was studied in high gravity wort using a lager yeast. Fermentation performance was followed by monitoring the total sugar content and yeast growth. Volatile compounds were evaluated by analysing higher alcohols, esters and carbonyl compounds at the end of fermentation. Faster fermentation rates and higher yeast counts were observed with the higher pitching levels. Lower amounts of 2‐ and 3‐methyl‐1‐butanols and higher levels of 2‐methyl‐1‐propanol were found at the increased pitching rates. The concentration of isoamyl acetate was reduced with an increased pitching rate. Higher amounts of diacetyl and 2,3‐pentanedione were obtained at the lower pitching levels.     

酒精发酵副产物对酵母菌生物的影响

探讨了乙酸、乳酸、焦糖色素及糠醛酒精发酵副产物对酵母菌生长和酒精发酵的影响。在酵母基本培养基中,加入乙酸、乳酸、焦糖色素及糠醋的量分别为0.1%、0.1%、2.0%和0.2%时,酵母细胞数减少50％。而在酵母基本培养基中同时添加乙酸、乳酸、焦糖色素及糠醛时,对酵母菌生长的抑制强度高达70％。酒精发酵的原料出酒率仅为正常发酵的50％。     

PFK2, ISP42, ERG2 and RAD14 are located on the right arm of chromosome XIII

An 11 kb yeast DNA insertion isolated from a genomic library by complementation of a phosphofructokinase-deficient strain was used as a source for a partial sequence analysis. Four genes were shown to reside on this fragment, namely PFK2, ISP42, ERG2 and RAD14. PFK2 was mapped previously to the right arm of chromosome XIII, locating the latter three genes to the same chromosome.     

The complete sequence of K3B, a 7.9 kb fragment between PGK1 and CRY1 on chromosome III, reveals the presence of seven open reading frames.

We have determined the nucleotide sequence of a segment from chromosome III of Saccharomyces cerevisiae extending over 7.9 kb between the PGK1 and CRY1 loci. The fragment contains seven open reading frames, YCR241, YCR242, YCR243, YCR244, YCR245, YCR246 and YCR247, of more than 70 codons. The study of the effects of a global disruption of YCR242, YCR243, YCR244, YCR245 and YCR247 shows that they are not essential for growth and division.     

Altered Patterns of Maltose and Glucose Fermentation by Brewing and Wine Yeasts Influenced by the Complexity of Nitrogen Source

Maltose and glucose fermentations by industrial brewing and wine yeasts strains were strongly affected by the structural complexity of the nitrogen source. In this study, four Saccharomyces cerevisiae strains, two brewing and two wine yeasts, were grown in a medium containing maltose or glucose supplemented with a nitrogen source varying from a single ammonium salt (ammonium sulfate) to free amino acids (casamino acids) and peptides (peptone). Diauxie was observed at low sugar concentration for brewing and wine strains, independent of nitrogen supplementation, and the type of sugar. At high sugar concentrations altered patterns of sugar fermentation were observed, and biomass accumulation and ethanol production depended on the nature of the nitrogen source and were different for brewing and wine strains. In maltose, high biomass production was observed under peptone and casamino acids for the brewing and wine strains, however efficient maltose utilization and high ethanol production was only observed in the presence of casamino acids for one brewing and one wine strain studied. Conversely, peptone and casamino acids induced higher biomass and ethanol production for the two other brewing and wine strains studied. With glucose, in general, peptone induced higher fermentation performance for all strains, and one brewing and wine strain produced the same amount of ethanol with peptone and casamino acids supplementation. Ammonium salts always induced poor yeast performance. The results described in this paper suggest that the complex nitrogen composition of the cultivation medium may create conditions resembling those responsible for inducing sluggish/stuck fermentation, and indicate that the kind and concentration of sugar, the complexity of nitrogen source and the yeast genetic background influence optimal industrial yeast fermentation performance.