Owens J D, Konírová L, Thomas D S
Department of Food Science and Technology, University of Reading, UK.
J Appl Bacteriol. 1992 Jan;72(1):32-8. doi: 10.1111/j.1365-2672.1992.tb04878.x.
The conductance change due to growth of Saccharomyces cerevisiae Y112, Zygosaccharomyces bailii M and Rhodotorula rubra NCYC 63 in culture media containing glucose, tartrate pH buffer and ammonium ions as sole nitrogen source was compared with that in a medium containing L-asparagine as sole nitrogen source. Decreases in conductance were observed in glucose-ammonium cultures of all three yeasts while little change occurred in cultures with L-asparagine as sole nitrogen source. This supports the hypothesis that the metabolic activity primarily responsible for conductance change in yeast cultures is the uptake of charged ammonium ions as nitrogen source and the reaction of protons with pH buffer compounds. Rhodotorula rubra cultures with L-asparagine as sole carbon source caused large increases in conductance with growth. Chemical analyses of culture filtrates showed that this increase in conductance was due to use of L-asparagine as carbon source and the excretion of nitrogen surplus to biosynthetic needs as ammonium. In addition, the production of aspartate, acetate and bicarbonate contributed to the increase in conductance.
将酿酒酵母Y112、拜耳接合酵母M和深红酵母NCYC 63在含有葡萄糖、酒石酸盐pH缓冲液和铵离子作为唯一氮源的培养基中的生长所导致的电导变化，与在含有L-天冬酰胺作为唯一氮源的培养基中的电导变化进行了比较。在所有三种酵母的葡萄糖-铵培养物中均观察到电导降低，而以L-天冬酰胺作为唯一氮源的培养物中变化很小。这支持了以下假设：酵母培养物中主要负责电导变化的代谢活性是作为氮源摄取带电荷的铵离子以及质子与pH缓冲化合物的反应。以L-天冬酰胺作为唯一碳源的深红酵母培养物随着生长导致电导大幅增加。对培养滤液的化学分析表明，这种电导增加是由于使用L-天冬酰胺作为碳源以及将氮过剩以铵的形式排泄到生物合成需求之外。此外，天冬氨酸、乙酸盐和碳酸氢盐的产生导致了电导增加。
