Impairment of the Glycolytic System and Actin in Baker's Yeast during Frozen Storage

Abstract

After frozen storage for 7 d, the viability and CO₂ productivity of a conventional baker's yeast strain D greatly decreased. The viability of a freeze-tolerant strain, DFT, used for the frozen dough method slightly decreased after the same storage period, while the CO₂ productivity greatly decreased. The CO₂ productivity and DNase I inhibitory activity of actin of the cell-free extracts prepared immediately after thawing from 7-d frozen-stored cells markedly decreased in both strains. In DFT; however, the productivity and the inhibitory activity of the cell-free extract increased when the extract was prepared after incubation of the frozen-thawed cells at 30°C. The increase in the inhibitory activity first occurred and then the increase in the CO₂ productivity. Gel filtration patterns of actin and glycolytic enzymes were compared between cell-free extracts of both strains. Peaks of actin and activity peaks of hexokinase and pyruvate kinase decreased in the strain D after frozen storage, but only slightly in the strain DFT. After frozen storage, phosphofructokinase activity peak Shifted to a lower molecular weight in strain D.