Improved hydrogen production in immobilized Chlamydomonas reinhardtii cells with inhibited inter-photosystem electron transfer
Fatemeh Khosravitabar, Fikret Mamedov
Abstract
The production of molecular hydrogen (H 2 ) by microalgae holds great promise, and immobilization techniques offer potential for further advancement in this field. The current study focuses on investigating the positive impact of immobilization on maintaining the stability and activity of photosystem II (PSII) over incubation time, with the aim of enhancing H 2 production potential in green microalgae Chlamydomonas reinhardtii . For this purpose, immobilized cells within alginate beads were treated with small concentrations of 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB) inhibitor to induce the partial inhibition of inter-photosystem electron transport, recently reported as a novel approach for sustaining microalgal H 2 production. A comparative analysis of fluorescence decay kinetic changes and EPR spectroscopy of the cell beads revealed the superior capacity of immobilization for sustaining PSII stability and activity in batch culture over time. Treatment of the cell beads with 3.5 μM DBMIB led to sustained H 2 production yielding over 200 μmol H 2 /mg Chl within 3 weeks, with an average H 2 production rate of approximately 10 μmol/mg Chl per day, both of which were roughly twice as high as those observed in free cells treated with DBMIB. Our findings underscore the significance of integrating immobilization with a proven and effective method for H 2 production, thereby enhancing its sustainability and productivity. • Clamydomonas cells immobilized in alginate beads remained viable during long-term incubation. • Immobilization enhanced the stability of the PSII electron transport for at least 30 days. • DBMIB treatment doubled the H 2 production in the immobilized cells.