Vacuum lyophilization preservation and rejuvenation performance of anammox bacteria

The storage of anaerobic ammonia oxidizing bacteria (anammox) plays an important role in the application of anammox. Glycerol, sodium alginate and DMSO were used as the cryoprotectant, and vacuum lyophilization was used to prepare the anammox bacteria powder. Simultaneously, the control experiment was set up with the same protectant and preservation time. Bacteria powders were preserved using vacuum lyophilization and preserved at 4 °C for 60 days. During the 54 days of rejuvenation, the reactors that were inoculated with bacteria powder preserved by different methods showed significant difference. The results show that the anammox bacteria powder with 3 wt% DMSO as the cryoprotectant and without the substrate solution presented the best rejuvenation effect. The average specific anammox activity was 115.84 mg-N·(g VSS·d)^-1 with an activity recovery rate of 89%, and its stoichiometric ratio (Rs and Rp) was 1.33 and 0.21, which were very close to the theoretical values. The vacuum lyophilization method for the long-term preservation of anammox bacteria was effective.