Optimization of cryoprotectants to harvest high active cells of a Scenedesmus-lysing Enterobacter sp. during long-term preservation

Abstract

Algicidal bacteria have potential applications in control of algal blooms in water body, while retrieval of active algicidal bacteria with high activity is a limiting step for the long-term preservation. We explored methods for preservation and storage of algicidal bacteria by optimizing cryoprotectant compositions using the Plackett–Burman design (PB) and the response surface methodology (RSM) in this study. In the cryoprotectant formulation tests, higher cell survival rate of the algicidal bacterium Enterobacter sp. NP23 to Scenedesmus sp. indicated that sucrose, gelatin and glycerol as the potential cryoprotectants could significantly improve the cell survival during the long-term preservation and storage. Moreover, the optimal cryoprotectant composition from RSM analysis consisted of 48.5g/L of sucrose, 30.0g/L of gelatin and 28.4g/L of glycerol. This formulation maintained the cell survival rate to greater than 90% and the activity of Enterobacter sp. NP23 to Scenedesmus sp. did not show apparent decrease even after 18months of storage. Compared to other traditional cryoprotectant compositions, the optimized cryoprotectant composition is promising in maintaining the population of algicidal bacteria with high survival rates and alga-lysing activity in the preservation period tested in this study.