The role of plasma-activated water on the growth of freshwater algae Chlorella Pyrenoidosa and Chlorella Sorokiniana

TL;DR

This study explores how plasma-activated water affects freshwater algae, showing it can inhibit growth through oxidative damage or promote growth when used as a nitrogen source, with potential applications in aquaculture.

Contribution

It demonstrates the dual role of plasma-activated water in both inhibiting and enhancing algae growth, depending on its reactivity, which is a novel insight for aquaculture applications.

Findings

Oxidizing PAW inhibits algae growth and damages cell structure.

Less reactive PAW promotes algae growth and increases chlorophyll, sugars, and proteins.

PAW can serve as a nitrogen source in algae cultivation.

Abstract

In the present work we have conducted two studies. In the first study, we investigated the role of plasma-activated water (PAW) in algae growth inhibition and in the second study, efforts are made to understand the role of PAW as a nitrogen source for algae growth enhancement. Two freshwater algae species are selected for the present study named Chlorella Pyrenoidosa and Chlorella Sorokiniana. The PAW is prepared using a pencil plasma jet and air as a plasma forming gas. The plasma is characterized electrically and identification of generated species in plasma is carried out using optical emission spectroscopy. The study clearly indicated that more oxidizing PAW exhibits algicidal effect. The PAW treatment with both the algae species substantially decreased their growth compared to control. Moreover, the morphology of algae cells showed damage and cells structure get ruptured after PAW treatment. In the second study, a less reactive PAW (low oxidizing potential) used as a nitrogen replacement in Bolds Basal Medium. The PAW-grown Chlorella Pyrenoidosa and Chlorella Sorokiniana showed higher growth compared to control. Also, a higher concentration of chlorophyll a and b, sugar, and protein observed compared to control. Further, we observed lower antioxidant enzymatic activities in PAW-grown algae compared to control. In conclusion, the PAW has algicidal efficacy as well as can be used as nitrogen source in aquaculture to enhance algae growth.