Slightly Acidic Electrolyzed Water Significantly Restrains the Accumulation of the Microalgae Pseudokirchneriella subcapitata in Hydroponic Systems.

AIMS: This study explored the effects of slightly acidic electrolyzed water (SAEW) on algae to exploit technologies that effectively suppress algal growth in hydroponic systems and improve crop yield.

METHODS AND RESULTS: The effects of SAEW on algal growth and the response mechanisms of algae to SAEW were investigated. Moreover, we studied whether the application of SAEW adversely affected tomato seedling growth. The results showed that SAEW significantly inhibited algal growth and destroyed the integrity of the algal cells. In addition, the intracellular oxidation-reduction system of algae was greatly influenced by SAEW. The H2O2, O2-, malondialdehyde (MDA), and reactive oxygen species (ROS) fluorescence signals were significantly induced by SAEW, and superoxide dismutase (SOD), peroxidase (POD), and glutathione reductase (GR) activities were greatly enhanced by a low SAEW concentration but significantly inhibited by SAEW with a high available chlorine concentration, which may contribute to heavy oxidative stress on algal growth and cell structure break down, eventually causing the death of algae and cell number decrease. We also found that regardless of the concentration of SAEW (from 10 to 40 mg·L-1), there was no significant change in the germination index, length, or fresh weight of the hydroponic tomato seedlings.

CONCLUSIONS: Our findings demonstrate that SAEW can be used in hydroponic systems to restrain algae with no negative impact on tomato plants.