Growth characteristics, biohydrogen production and photochemical activity of photosystems in green microalgae Parachlorella kessleri exposed to nitrogen deprivation

The biohydrogen (H-2) generation in green microalgae is associated with electron transfer during photosynthesis. In this study, the ability of Parachlorella kessleri RA-002 isolated in Armenia to generate biohydrogen (H-2) in TAP and Tamiya media with and without nitrogen deprivation have been determined. Nitrogen deprivation led to a suppression of the growth rate and a decrease in the content of photosynthetic pigments in algae, as well as to increase of H-2 yield. The highest H-2 yield was found during the growth of algae in TAP and Tamiya media under nitrogen-deprived conditions, which was 4-5 times more compared to control cells grown without nitrogen deprivation. Diuron inhibited this process, indicating that H-2 generation was due to PS II activities. The analysis of the effect of nitrogen-deprived conditions on the activity of photosystem I and II has been carried out. Nitrogen deprivation suppressed of photosynthetic activity of PS II (up to 20% compared to control) that facilitated the formation of anaerobic conditions increasing the total yield of H-2. (C) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

The study investigated the biohydrogen generation in green microalgae under nitrogen-deprivation conditions, finding that Parachlorella kessleri RA-002 showed significantly increased H-2 yield in TAP and Tamiya media. Nitrogen deprivation led to higher H-2 production possibly due to enhanced PS II activity. Additionally, the study revealed that nitrogen deprivation suppressed photosynthetic activity of PS II while facilitating the anaerobic conditions necessary for increased H-2 yield.