THE EFFECT OF OSMOTIC PRESSURE ON THE PRODUCTION AND EXCRETION OF ETHANOL AND GLYCEROL BY A BREWING YEAST STRAIN*

When the cells of a lager brewing yeast Saccharomyces uvarum (carlsbergensis) were grown in minimal media containing sucrose and a non-metabolized sugar sorbitol, significant levels of intracellular ethanol were obtained. Intracellular ethanol concentration decreased as the osmotic pressure of the medium was lowered and the proportion of extracellular ethanol increased. A reduction in cell viability occurred when there were high levels of intracellular ethanol. The total amount of glycerol produced increased with increased osmotic pressure, but glycerol diffused out of the cells faster than ethanol.     

共混改性改善高低黏度PET并列复合纤维性能的研究

选取高黏度PET、低黏度PET添加PBT的混合物作为并列纺丝的两种组分进行复合纺丝,并对其可纺性进行研究;采用与不经改性的高低黏度PET并列复合纤维的力学性能对比进行研究。结果表明,高黏度PET/(低黏度PET混合PBT)并列复合纺丝具有良好的可纺性及后加工性能,纺制的复合纤维具有较好的力学性能及自卷曲性能。     

SUGAR UTILIZATION BY A BREWING YEAST IN RELATION TO THE GROWTH AND MAINTENANCE PHASES OF METABOLISM

In batch fermentations, carried out using a range of conditions, the specific rate of sugar utilization is shown to decline throughout. When yeast mass is increasing, the yield coefficient relating carbohydrate utilization to mass production remains approximately constant and the declining specific fermentation rate parallels declining specific growth rate. When mass production ceases, maintenance of the yeast population requires only a low rate of sugar utilization. Attenuation associated with maintenance phase activity is relatively insignificant compared with that associated with growth.     

THE METABOLISM OF PUTRESCINE,SPERMIDINE AND SPERMINE BY YEAST IN RELATION TO THE AVAILABILITY OF MAGNESIUM

During the lag period immediately after inoculation of yeast into a defined salts medium rapid changes in the internal concentrations of the oligoamines occurred when the medium was deficient in magnesium or high in calcium. Pronunced changes in the oligoamine content of yeast also occurred after inoculation into a range of worts and the extent of the effect appeared to depend on the magnesium content of the wort. The amount of magnesium in all the worts was much higher than was found to be saturating in a minimal medium and it therefore seems that the magnesium in worts is not freely available to the yeast cells. Putrescine was the only oligoamine found in wort and was present at about 1 mg/litre. The putrescine concentration in the wort always increased during fermentation and the period of most rapid increase corresponded to the period of decline in the internal oligoamine pools.