Effects of growth with ethanol on fermentation and membrane fluidity of Saccharomyces cerevisiae

Saccharomyces cerevisiae HSc was grown with ethanol at concentrations up to 10% (v/v). The immediate effects of additions of externally added ethanol on CO₂ production and O₂ consumption of washed organisms were studied by stopped-flow membrane inlet quadrupole mass spectrometry. Fermentative activities of organisms grown with ethanol (0–5% v/v) showed similar sensitivities to inhibition by ethanol, whereas those grown with 10% (v/v) ethanol had become protected and were markedly less sensitive. The fluidity of subcellular membrane fractions was measured by determination of the temperature dependence of the rotational order parameter of the spin label 5-doxyl stearic acid (free radical) by electron spin resonance. Mitochondria prepared from yeasts grown with 0, 7 and 9% (v/v) ethanol showed similar overall fluidity, although differences in temperature-dependent behaviour indicate altered lipid composition or lateral phase separations. On the other hand the microsomal fraction from organisms grown with 9% ethanol showed a remarkable increase in fluidity. These data suggest that the protective effects of growth with ethanol near the limit of tolerance on fermentative activities may arise from altered plasma membrane fluidity properties.     

工业发酵的生物学属性对发酵过程最优控制的制约与对策

从工业发酵过程计算机控制的历史和现状出发，探讨了工业发酵过程的生物学属性对发酵过程最优化控制的制约，以及解决这个难题的对策。在论证了工业发酵具有明显的生物学属性的基础上，阐明了发酵的生物学原理及其在发酵过程最优化控制中应用的重要性。     

Mathematical modelling of the alcoholic fermentation of glucose by Zymomonas mobilis mobilis

The kinetics of alcoholic fermentation of a strain of Zymomonas mobilis, isolated from sugarcane juice, has been studied with the objective of determining the constansts of a non-structured mathematical model that represents the fermentation process. Assays in batch and in continuous culture have been carried out with different initial concentrations of glucose. The final concentrations of glucose, ethanol and biomass were determined. The following kinetic parameters were obtained: μ_max, 0·5 h^?1; K_s, 4·64 g dm^?3; P_max, 106 g dm^?3; Y_x/s, 0·0265 g g^?1; m, 1·4 g g^?1 h^?1; α, 17·38 g g^?1; β, 0·69 g g^?1 h^?1.     

EM发酵饲料中主要微生物类群的动态变化

对EM发酵饲料中乳酸杆菌、酵母菌、大肠菌群、腐败菌等微生物类群的动态变化进行了研究。结果表明 :饲料经EM发酵后 ,乳酸杆菌大量增加 ,发酵第4天达到最大值(9.5×108CFU·g-1 饲料) ,大肠菌群与腐败菌被明显抑制。并认为细菌总数与酵母菌数量不能作为评价EM发酵饲料质量好坏的指标。     

细菌纤维素合成过程中的影响因素

研究了接种量、pH值、培养液深度、培养液表面积和发酵时间等因素对形成细菌纤维素膜的产量、厚度及比表面积的影响。结果表明:接种量在7%、初始pH值在5～6范围内细菌纤维素的产量最大;厚度主要取决于发酵时间和初始pH值;培养液表面积对单位面积细菌纤维素产量有比较大的影响;膜的比表面积与发酵时间的长短无关。     

高效液相色谱法测定柠檬酸的含量

建立了一种准确对发酵液中柠檬酸含量测定的仪器方法,在检测范围6-16 mg/mL之间成线性,R=0.999 7,RSD为±0.8%-1.2%(n=6),最低检测浓度为0.02 mg/mL.此方法简单、灵敏、重现性好,避免了由于化学转化所引起的测定误差,以及发酵液中色素的影响.     

提高发酵过程乙醇分离效率的新型反应器

设计了一种新型的带侧臂循环的气升式反应器,该反应器可以有效地把真空闪蒸发酵和汽提发酵2项技术结合起来。实验结果表明,与单独的汽提和闪蒸过程相比,利用此反应器进行同步汽提闪蒸操作,大大提高了乙醇的移出效率,从而进一步提高了发酵强度。     

嗜单宁管囊酵母木糖酒精发酵的研究

综合利用丰富、廉价且可再生的农作物秸秆资源生产酒精的研究已经渐渐成为全球范围的热点之一。文章研究了嗜单宁管囊酵母木糖酒精发酵的发酵性能,分离、筛选、驯化培养出一株高效木糖酒精发酵菌株 g-13,在最适条件下其木糖酒精发酵的转化率为 0.446 g/g(酒精/消耗的糖),为发酵秸秆纤维水解液中的戊糖生产燃料酒精提供菌种支持。     

高黏度头孢菌素C发酵液的超滤研究

利用新型的板式超滤系统对高黏度头孢菌素C发酵液进行了澄清实验研究,通过实验数据与现有系统的运行数据对比,该系统基本解决了目前国内头孢菌素C发酵液超滤提纯中存在的主要过滤问题.     

Ethanol production from raw starch by a recombinant yeast having saccharification and fermentation activities

In order to develop a method for converting raw starch into ethanol efficiently, direct fermentation of ozonized raw starch using a recombinant yeast was investigated. Ozonolysis was carried out as a pretreatment to convert raw starch into ethanol rapidly and efficiently, and then the effect of the ozone degradation conditions on the degree of polymerization and the amount of amylose in a raw starch was determined. Since the degree of polymerization was low and the amount of amylose was high, raw starch treated with an ozone concentration of 40 gm^?3 and an ozonation time of 30 min was the material chosen for alcohol fermentation. Though the recombinant yeast could not convert the untreated raw starch, it converted the soluble starch and the ozonized raw starch at a comparatively high yield into ethanol. About 56% of the ozonized raw starch decomposed, and the ethanol concentration obtained from the ozonized raw starch was markedly greater than that obtained from untreated raw starch. The dynamic behavior of cell growth, substrate degradation, and ethanol production was examined in a continuous culture under various dilution rates, and the optimal dilution rate, ie 0.15 h^?1, was determined for maximizing the ethanol productivity (amount of ethanol produced per unit time). © 2002 Society of Chemical Industry