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.