Analysis of production brewing strains of yeast by DNA fingerprinting

P. WIGHTMAN, D.E. QUAIN AND P. G. MEADEN. 1996. Production brewing strains of the yeast Saccharomyces cerevisiae were analysed by DNA fingerprinting, using a Southern blotting and hybridization procedure and employing the Tyl-15 transposon as a probe. The ability to differentiate readily between strains was very dependent on the restriction enzyme used to digest the DNA prior to Southern blotting and hybridization; the enzymes Eco RI, Pst I and Sal I were found to be particularly useful in this respect. The method was applicable to the differentiation of both ale and lager yeasts, and was sufficiently sensitive to distinguish between very closely related strains. DNA fingerprinting by this approach confirmed, for example, that a flocculent strain isolated during a production-scale fermentation with a lager yeast was genotypically different from the parent.     

P、Zn在小麦细胞内的积累、分布及交互作用的研究

报道了小麦无性系细胞在含有3个P水平(0.5、1.5、3.5mmol·L^-1)和2个Zn水平(0、60μmol·L^-1)的M.S培养液中,细胞对P、Zn的积累、分布特性及交互作用的研究.P和Zn在细胞内的积累分别随外施P、Zn浓 度的提高而提高.与缺Zn比较,加Zn处理能抑制培养7d细胞中P的含量.营养液中0.5～1.5mmol·L^-1 P能促进细胞的含Zn量,但高P处理即抑制细胞的含Zn量.小麦细胞壁固定了细胞83.9%～88.3%的P,而外施P浓度越高,则细胞壁中P分配的比例越大.在供Zn条件下,细胞壁截留了细胞中一半以上的Zn(52.0～60.5%).小麦液泡中P和Zn的含量较少,分别为2.2%～3.8%和10.6%～30%.     

Accumulation of zinc and cadmium by Cytophaga johnsonae

Passive and active accumulation of zinc and cadmium by a common soil and freshwater bacterium, Cytophaga johnsonae, was studied using a radio-tracer batch distribution technique. The effects of variation of pH (3–10), as well as of ionic strength (0.007 and 0.07 m) on passive accumulation of the metals were examined. For both zinc and cadmium, accumulation was mainly due to passive processes, such as surface adsorption and/or diffusion into the periplasm. However, at low zinc concentrations, accumulation increased when glucose was added, suggesting an active uptake; at higher zinc concentrations such uptake was not detected, probably because it was masked by the stronger sorption properties of the cell wall. Adsorption of the metals was pH dependent: at higher ionic strength, accumulation was enhanced at pH values above 7; at lower ionic strength, adsorption differed and was markedly higher, with increased accumulation between pH 5 and 8.     

Accumulation and metabolism of selenium by yeast cells

This paper examines the process of selenium bioaccumulation and selenium metabolism in yeast cells. Yeast cells can bind elements in ionic from the environment and permanently integrate them into their cellular structure. Up to now, Saccharomyces cerevisiae, Candida utilis, and Yarrowia lipolytica yeasts have been used primarily in biotechnological studies to evaluate binding of minerals. Yeast cells are able to bind selenium in the form of both organic and inorganic compounds. The process of bioaccumulation of selenium by microorganisms occurs through two mechanisms: extracellular binding by ligands of membrane assembly and intracellular accumulation associated with the transport of ions across the cytoplasmic membrane into the cell interior. During intracellular metabolism of selenium, oxidation, reduction, methylation, and selenoprotein synthesis processes are involved, as exemplified by detoxification processes that allow yeasts to survive under culture conditions involving the elevated selenium concentrations which were observed. Selenium yeasts represent probably the best absorbed form of this element. In turn, in terms of wide application, the inclusion of yeast with accumulated selenium may aid in lessening selenium deficiency in a diet.     

Transport of fructose by a proton symport in a brewing yeast

Abstract Saccharomyces cerevisiae IGC4261, a brewing strain, transported fructose and sorbose but not glucose by a high-affinity, low-capacity proton symport. The symport was not subject to glucose repression and coexisted with the facilitated diffusion system for glucose, fructose, sorbose and other sugars. Transport by the symport was accumulative. The stoichiometry was one proton per molecule of fructose. Maltose acted as a non-competitive inhibitor.     

The yeast gene MSC2, a member of the cation diffusion facilitator family, affects the cellular distribution of zinc

The sequence of the yeast gene YDR205W places it within the family of cation diffusion facilitators: membrane proteins that transport transition metals. Deletion of YDR205W was reported to result in an increase in unequal sister chromatid recombination and was named meiotic sister chromatid recombination 2 (MSC2; Thompson, D. A., and Stahl, F. W. (1999) Genetics 153, 621-641). We report here that a msc2 strain shows a phenotype of decreased viability in glycerol-ethanol media at 37 degrees C. Associated with decreased growth is an abnormal morphology typified by an increase in size of both cells and vacuoles. Addition of extracellular Zn2+ completely suppresses the morphological changes and partially suppresses the growth defect. Regardless of the concentration of Zn2+ in the media, the msc2 strain had a higher Zn2+ content than wild type cells. Zinquin staining also revealed that msc2 had a marked increase in fluorescence compared with the wild type, again reflecting an increase in intracellular Zn2+. The deletion strain accumulated excess Zn2+ in nuclei-enriched membrane fractions, and when grown at 37 degrees C in glycerol-ethanol media, it showed a decreased expression of Zn2+-regulated genes. The expression of genes regulated by either Fe2+ or Cu2+ was not affected. An epitope-tagged Msc2p was localized to the endoplasmic reticulum/nucleus. These results suggest that Msc2p affects the cellular distribution of zinc and, in particular, the zinc content of nuclei.     

Monitoring the influence of high-gravity brewing and fermentation temperature on flavour formation by analysis of gene expression levels in brewing yeast

During fermentation, the yeast Saccharomyces cerevisiae produces a broad range of aroma-active substances, which are vital for the complex flavour of beer. In order to obtain insight into the influence of high-gravity brewing and fermentation temperature on flavour formation, we analysed flavour production and the expression level of ten genes (ADH1, BAP2, BAT1, BAT2, ILV5, ATF1, ATF2, IAH1, EHT1 and EEB1) during fermentation of a lager and an ale yeast. Higher initial wort gravity increased acetate ester production, while the influence of higher fermentation temperature on aroma compound production was rather limited. In addition, there is a good correlation between flavour production and the expression level of specific genes involved in the biosynthesis of aroma compounds. We conclude that yeasts with desired amounts of esters and higher alcohols, in accordance with specific consumer preferences, may be identified based on the expression level of flavour biosynthesis genes. Moreover, these results demonstrate that the initial wort density can determine the final concentration of important volatile aroma compounds, thereby allowing beneficial adaptation of the flavour of beer.     

锌在3种乔木中的积累及其亚细胞分布和化学形态

为了探索园林木本植物对重金属锌(Zn)的积累和耐性机制,本研究以栾树(Koelreu-teria paniculata)、臭椿(Ailanthus altissima)和银杏(Ginkgo biloba)3种北京常见乔木为试验树种,通过盆栽污染模拟试验,研究不同浓度Zn处理(O、250、500、1000、2000 mg...     

啤酒生产酵母全循环新工艺的研究

以改善浅色啤酒质量,降低生产成本,提高经济效益的目的,提出一种新颖的浅色啤酒的酿造方法。采用煮－浸法糖化工工艺及５０％麦芽和５０％大米作为啤酒酿造的原料及辅料。在糖化过程中添加啤酒酵母提取物作为补充氮源,不仅使所酿造的成品啤酒色泽浅,口味淡爽,纯正,泡沫洁白细腻,持久挂杯,而且具有较显著的经济效益和社会效益。     

Detection of Pediococcus spp. in brewing yeast by a rapid immunoassay.

A membrane immunofluorescent-antibody test was developed to detect diacetyl-producing Pediococcus contaminants in brewery pitching yeast (yeast [Saccharomyces cerevisiae] slurry collected for reinoculation). Centrifugations at 11 and 5,100 x g separate yeast cells from bacteria and concentrate the bacteria, respectively. Pelleted bacteria resuspended and trapped on a black membrane filter are reacted with monoclonal antibodies specific for cell surface antigens and then with fluorescein-conjugated indicator antibodies. Whether pitching yeast is contaminated with pediococci at 0.001% is determined in less than 4 h. The sensitivity of the assay is 2 orders of magnitude below the Pediococcus detection limit of direct microscopy.     

Detection of Pediococcus spp. in brewing yeast by a rapid immunoassay.

A membrane immunofluorescent-antibody test was developed to detect diacetyl-producing Pediococcus contaminants in brewery pitching yeast (yeast [Saccharomyces cerevisiae] slurry collected for reinoculation). Centrifugations at 11 and 5,100 x g separate yeast cells from bacteria and concentrate the bacteria, respectively. Pelleted bacteria resuspended and trapped on a black membrane filter are reacted with monoclonal antibodies specific for cell surface antigens and then with fluorescein-conjugated indicator antibodies. Whether pitching yeast is contaminated with pediococci at 0.001% is determined in less than 4 h. The sensitivity of the assay is 2 orders of magnitude below the Pediococcus detection limit of direct microscopy.     

Appearance of poor-fermenting variants in brewing yeast culture.

A class of yeast variants appears after cultivation of a bottom-fermenting brewing yeast strain, IFO2003. Although IFO2003 fails to grow well above 33 degrees C, the variants can grow up to 34 degrees C. Temperature-resistance and an acquired phenotype of maltose poor-fermentation ability are strictly correlated in the bottom-fermenting brewing yeast, enabling us to develop easy estimation of the fermentation ability of the variants.     

Shochu brewing characteristics and properties of a trichothecin-resistant shochu yeast mutant

An antibiotic-resistant strain of Saccharomyces cerevisiae was isolated from shochu yeast. Three mutants were used for shochu brewing and gave higher ethanol productivities than the parent. The mutants were resistant to cycloheximide, cerulenin, trichothecin and other organic compounds such as lauric acid. In the presence of 20% (v/v) ethanol, the viability of the mutants was 87–96%, but that of the parent was 77%. Zymolyase treatment for 3 h, decreased the viability of the parent by 44% but that of the mutants only by 11–32%. Thus the higher ethanol productivity of these mutants is related to their high ethanol tolerance and resistance to various organic compounds.     

汾酒酿造车间和车间外环境中酵母菌多样性研究

为解析汾酒厂区酵母菌资源的多样性,采用分离培养方法,从汾酒酿造车间和车间外环境中的微生物中分离纯化到300株酵母菌,经26S rDNA序列比对分析,检测到酵母菌包括6科15属21种。系统发育树结果表明,汾酒酿造车间和车间外环境中的酵母菌包括担子菌门（Basidiomycota）和子囊菌门（Ascomycota）两个分支。尽管汾酒酿造车间和车间外环境中各有特异的酵母菌,但是两者都存在与白酒酿造相关的酵母菌如酿酒酵母（Saccharomyces cerevisiae）、毕赤酵母（Pichia kudriavzevii）和扣囊复膜酵母（Saccharomycopsis fibuligera）等。汾酒环境中含有丰富的酵母菌资源,可能是大曲和酒醅发酵过程中酵母菌的主要来源。这些都为进一步研究指明了方向。