The Cause of Acetoin Production by myo-Inositol Deficient Saccharomyces carlsbergensis

Abstract

For elucidating the mechanism of acetoin accumulation by myo-inositol deficient Saccharomyces carlsbergensis the change of glucose concentration and pH during cultivation, stability of formed acetoin, the rate of acetoin synthesis and glucose uptake by resting cells were compared between normal and myo-inositol deficient yeast.
The consumption of glucose by the yeast was complete in 24 hours when myo-inositol was present in the medium, whereas 3/5 still remained in the same period of incubation and a half remained unconsumed when myo-inositol was absent. pH change of the medium during the cultivation was insignificant for influencing acetoin accumulation.
The cell suspensions decomposed no acetoin by 7.5-hour incubation and 30-40% by 10-hour incubation without notable difference between normal and myo-inositol deficient cells.
myo-Inositol deficient yeast cell suspensions produced about 6.7 times acetoin (200mμmoles/mg of dry cell weight/hr) of that by normal cell suspensions (30mμmoles/mg of dry cell weight/hr) with glucose as substrate. The external addition of myo-inositol to the reaction mixture did not decrease the acetoin production.
Glucose uptake by the deficient cells was slightly larger than that by nomal cells. Therefore, the problems such as the difference in glucose transport and the catabolism of the formed acetoin would be ruled out the from causes of the acetoin accumuation due to myo-inositol deficiency.