Investigating the Role of Plasma-Activated Water on the Growth of Freshwater Algae Chlorella Pyrenoidosa and Chlorella Sorokiniana

In the present study, we investigated the role of plasma-activated water (PAW) in inhibiting algae growth in the first set of experiments. In the second set of experiments, our aim was to understand the role of PAW as a nitrogen source for enhancing algae growth. We used two freshwater algae species, namely Chlorella Pyrenoidosa and Chlorella Sorokiniana, for this study. To prepare PAW, we utilized a pencil plasma jet with air as the plasma forming gas. The results clearly indicate that highly reactive PAW (characterized by low pH and high oxidizing potential) exhibits an algicidal effect. Treatment with PAW significantly reduced the growth of both algae species compared to the control group. Morphological analysis revealed damage to the algae cells, with ruptured cell structures observed after PAW treatment. In the second study, a less reactive PAW (characterized by high pH and low oxidizing potential) was employed as a nitrogen replacement in Bold's Basal Medium. The PAW-grown Chlorella Pyrenoidosa and Chlorella Sorokiniana showed higher growth compared to the control group. Additionally, higher concentrations of chlorophyll 'a' and 'b', sugar, and protein were observed in the PAW-grown algae compared to the control group. Furthermore, lower antioxidant enzymatic activities were observed in the PAW-grown algae compared to the control group. In conclusion, PAW with a high reactivity demonstrated algicidal efficacy, while PAW with a low reactivity can be used as a nitrogen source in aquaculture to enhance algae growth.