Abstract:Into DVS Gluconacetobacter xylinums cell suspension, 1% Glutamic acid, 5% trehalose, 10% skim milk, or a mixture of 0.575% glutamic acid ,0.075% trehalose and 6.4% skim milk was added as a cryoprotectant. Their effects of on the cytochemical properties of Direct-Vat-Starter (DVS) Gluconacetobacter xylinus (GBX) cells were determined and compared. Changes in the physiological activity of GBX cells was measured in terms of changes in DNA leakage, total antioxidant capacity, superoxide dismutase (SOD) activity, as well as cellulose synthase and ATP activity of the bacterial cells. The results showed that DNA leakage of the bacterial cells was reduced and total antioxidant capacity, SOD activity, cellulose synthase, and ATP synthase activities were increased by adding 1% glutamic acid, 5% trehalose, 10% skim milk or 0.575% glutamic acid + 0.075% trehalose + 6.4% skim milk as a cryoprotectant during freeze-drying process. The results indicated that the GBX cells were well protected by cryoprotectants, and the optimum protective effect was observed with the compound cryoprotectant 0.575% glutamic acid + 0.075% trehalose + 6.4% skim milk. The results from scanning electron microscopy (SEM) also verify that the various cryoprotectants could significantly reduce the damage to GBX cells during freeze-drying process, thus maintaining good physiological activity of GBX cells.
