Preservation efficiency of new cryoprotectant used for Acidithiobacillus ferrooxidans in liquid nitrogen

The efficiency of a new cryoprotectant, GP, for the preservation of Acidithiobacillus ferrooxidans (A. ferrooxidans) strain DC in liquid nitrogen was investigated. The optimal concentration of this new cryoprotectant for the maximal viable cell recovery and the highest ferrous ion oxidation activity was determined. The results show that 30% (volume fraction) GP is optimal for the cryopreservation with 84.4% of cells surviving, completely oxidizing ferrous ions within 120 h, and growing to a final density of 5.8×107 cell/mL after 6 d in the culture. Furthermore, the optimal residual GP concentration for viable cell recovery after culture of thawed cells in 9K medium for 6 d is 0.6% (volume fraction). At this concentration, strain DC completely oxidizes ferrous ions within 108 h and grows to a final cell density of 6.8×107 mL−1. Thus, GP is a simple, effective cryoprotectant for the preservation of A. ferrooxidans strain DC in liquid nitrogen.