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

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 degrees 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.