酿酒醇母的保存（第一部分胞内海藻糖含量的作用）

这里所描述的结果指出，事实上酵母胞内海藻糖含量与不利生理条件下细胞的存活并无密切关系。可以看出：一方面海藻糖在营养缺乏时充当糖原，另一方面其他参数如酵母菌株，保护剂的选择，预培养基的组成，预培养过程中细胞运动和通气情况，预培养菌龄等对成功保存有很重要的影响。

酿酒酵母和粟酒裂殖酵母细胞增殖对Ca^(2+)依赖性的比较研究

同样实验条件下Ca^(2+)对S.cerevisiae的增殖没有影响,但能明显促进S.pombe的增殖;Ca^(2+)螯合剂EGTA对S.cerevisiae的增殖没有明显抑制作用,但对S.pombe的增殖有显著的抑制作用,回加Ca^(2+)能够有效消除EGTA的抑制作用;而非特异性螯合剂EDTA虽然对两类酵母细胞的增殖都有抑制作用,但Ca^(2+)却不能消除EDTA的抑制作用,这样就直接指明了两类酵母对胞外Ca^(2+)的依赖性是不一样的。由于S.cerevisiae细胞的增殖速率比S.pombe细胞要快近3倍,且与转化细胞或肿瘤细胞具有类似的细胞增殖不依赖于胞外Ca^(2+)的特性,说明研究胞外Ca^(2+)对这两类酵母细胞增殖不同作用效应的机制,对搞清细胞周期失控与细胞转化之间的关系有重要的意义。

酿酒酵母的衍生物对断奶仔猪腹泻的影响

试验旨在探讨在断奶仔猪的教槽料或母猪日粮中添加啤酒酵母所产的酵母衍生物（YD）对仔猪断奶后腹泻（PWD）和生长性能的影响。30头母猪及其仔猪随机分为3个处理组，分别为PSP组（断奶前l周在母猪日粮中添加YD1．5g·kg^-1仔猪2周龄开始向其教槽料中添加YD3和2g·kg^-1直到断奶后2周和5周结束）、PP组（仔猪教槽料中添加YD3和2g．kg^-1）和C组（对照组，不添加YD）。在断奶后（4周龄）1～3d，对各组仔猪进行大肠杆菌侵染试验（对照组采用plaeebo对照试剂），测定各组仔猪的生长性能。对仔猪进行粪便一致性评分（FCS）发现，其受断奶、YD处理以及大肠杆菌处理之间的相互作用。对照组仔猪的FCS值低于大肠杆菌处理组和PSP、PP处理组仔猪。在断奶后2-6d，与对照组相比，PSP和P1）处理组仔猪出现腹泻的风险较低（FCS〉3，P=0．014，P=0．001），placebo和大肠杆菌处理的PP组的仔猪也取得了相同的结果（P=0．010，P=0．038），而PSP处理组的仔猪仅与大肠杆菌处理的对照组仔猪之间存在差异（P=0．030），大肠杆菌处理的PP组仔猪粪便中的溶血性大肠杆菌显著低于对照组（尸=0．026）。placebo处理的PP组仔猪首次出现腹泻的时间较PSP和对照组显著推迟（P=0．048andP=0．017）。YD对仔猪和母猪的特异性抗体滴定度无显著影响。在断奶后的3周，PP组的仔猪腹泻发生的几率低于PSP组和对照组（P=0．078）。各组间仔猪的平均日增重无显著差异，但PSP组仔猪在断奶后0-5周的肉料比（G：F）极显著提高（P〈0．01）。总之，在仔猪断奶前2周和断奶后的教槽料中添加YD可降低4周龄断奶仔猪惠仔猪腹泻的可能性向母猪日粮中添加YD也可能会降低大肠杆菌的致病性，但是与对照组相比会增加肉料比。，

Improve Ethanol Yield Through Minimizing Glycerol Yield in Ethanol Fermentation of Saccharomyces cerevisiae

In ethanol fermentation of Saccharomyces cerevisiae （S. cerevisiae）, glycerol is one of the main by-products. The purpose of this investigation was to increase ethanol yield through minimizing glycerol yield by using mutants in which FPS1 encoding a channel protein that mediates glycerol export and GPD2 encoding one of glycerol-3-phosphate dehydrogenase were knocked-out using one-step gene replacement. GLT1 and GLN1 that encode glutamate synthase and glutamine synth.etase, respectively,were overexpressed using two-step gene replacment in fpsl△gpd2△ mutant.The fermentation properties of ZAL69（fpsl△：：LEU2 gpd2△：：URA3） and ZAL808 （fps1△：：LEU2 gpd2△：：URA3 PPGK1-GLT1 PPGK1-GLN1） under microaerobic conditions were investigated and compared with those of wild type（DC124）. Consumption of glucose, yield of ethanol, yield of glycerol, acetic acid, and pyruvic acid were monitored. Compared with wild type, the ethanol yield of ZAL69 and ZAL808 were improved by. 13.17% and 6.66 %, respectively, whereas glycerol yield decreased by 37.4 % and 41.7 %. Meanwhile, acetic acia yield and pyruvic acid yield aecreasea aramatlcally comparea to wild type. Our results indicate that FPS1 and GPD2 deletion of S. cerevisiae resulted in reduced glycerol yield and increased ethanol yield, but simultaneous overexpression of GLT1 and GLN1 infps1△gpd2△ mutant did not have a higher ethanol yield thanfps1△gpd2△ mutant.

Effect of Propanoic Acid on Ethanol Fermentation by Saccharomyces cerevisiae in an Ethanol-Methane Coupled Fermentation Process

Propanoic acid accumulated in an ethanol-methane coupled fermentation process affects the ethanol fermentation by Saccharomyces cerevisiae. The effects of propanoic acid on ethanol production were examined in cassava mash under different pH conditions. Final ethanol concentrations increased when undissociated propanoic acid was <30.0 mmol·L-1 . Propanoic acid, however, stimulated ethanol production, as much as 7.6% under proper conditions, but ethanol fermentation was completely inhibited when undissociated acid was >53.2 mmol·L-1 . Therefore, the potential inhibitory effect of propanoic acid on ethanol fermentation may be avoided by controlling the undissociated acid concentrations through elevated medium pH. Biomass and glycerol production decreased with propanoic acid in the medium, partly contributing to increased ethanol concentration.

Relationship between Ethanol and 2-phenylethanol Stress Tolerance and Fatty Acid Compositions of Saccharomyces cerevisiae

In the present study, we investigated of the ethanol （Eth）, 2-phenylethanol （2-PE） and ethanol/2-phenylethanol （Eth/2-PE） stress tolerance and established relationship between stress tolerance and fatty acid compositions of wine yeast strain S. cerevisiae UCM Y-524 in relation to different cultivation factors. Changes in cell membrane fatty acid profiles studied under different temperature and media. The active oxygenation, semi-aerobic cultivation supplemented Tween 80 conditions were used in different combinations. The concentrations of 2-PE and Eth, the fatty acids methyl esters （FAMES） in the media were measured by GC-MS analyses. 2-PE, Eth, FAMES were identified by NIST02 MS database at the 2-PE and Eth standard solution （Merck, Germany）, bacterial FAMES standard （Supelco）. Palmitoleic and oleic acid were dominated for S. cerevisiae UCM Y-524. The unsaturated/saturated fatty acid （UFA/SFA） ratio was higher than five for S. cerevisiae UCM Y-524 at 14 ~C in simple medium and about more than three for other conditions. It has been found that yeast cells grown in the presence of the 2-PE, Eth and Eth/2-PE appear to increase the amount of unsaturated fatty acids, especially oleic acid, in cellular lipids especially under active oxygenation supplemented with Tween 80. S. cerevisiae UCM Y-524 has a higher tolerance under 2-PE, Eth and Eth/2-PE stress at 28 ~C in a simple medium under aerobic conditions. A higher concentration of unsaturated fatty acids in the membrane S. cerevisiae UCM Y-524 and a lower temperature under aerobic conditions, has been considered to have a positive influence on the excretion of 2-phenylethanol.

Recent advances in metabolic engineering of microorganisms for production of tyrosol and its derivatives

Tyrosol is a natural phenolic compound with antioxidant,anti-inflammatory and other biological activities,serving as an important precursor of high-value products such as hydroxytyrosol and salidroside.Therefore,the green and efficient biosynthesis of tyrosol and its derivatives has become a research hotspot in recent years.Building cell factories by metabolic engineering of microorganisms is a potential industrial production way,which has low costs and environmental friendliness.This paper introduces the biosynthesis pathway of tyrosol and presents the key regulated nodes in the de novo synthesis of tyrosol in Escherichia coli and Saccharomyces cerevisiae.In addition,this paper reviews the recent advances in metabolic engineering for the production of hydroxytyrosol and salidroside.This review can provide a reference for engineering the strains for the high-yield production of tyrosol and its derivatives.