Photosystem I fluorescence as a physiological indicator of hydrogen production in Chlamydomonas reinhardtii

Abstract

This study investigated the interrelations between hydrogen synthesis and Photosystem I electron transport rate in Chlamydomonas reinhardtii. The fluorescence of both photosystems (PS I and PS II) was monitored using a Dual Pulse Amplitude Modulated (PAM) Fluorometer. Hydrogen synthesis was induced by eliminating sulphur from the growth media (TAP-S). Multiple physiological parameters [rETR, Y (I), Y (II), NPQ, α, F_v/F_m and YI:YII] were recorded using the Dual PAM and correlated to hydrogen produced. There was a 66% increase in Photosystem I rETR_max during hydrogen production. A significant direct correlation existed between PS 1 rETR_max and hydrogen evolution values over the ten-day period (r = 0.895, p < 0.01) indicating that PS I can be considered as a driver of H₂ production. Significant correlations between rETR_max of PS I and H₂ evolution suggest a novel physiological indicator to monitor H₂ production during the three critical phases identified in this study.

Keywords: Biohydrogen; Chlamydomonas reinhardtii; Photosystem I and II; Pulse Amplitude Modulated (PAM) Fluorometry; Renewable energy.