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Autotrophic hydrogen photoproduction by operation of carbon-concentrating mechanism in Chlamydomonas reinhardtii under sulfur deprivation condition

Hong, Min Eui, Shin, Ye Sol, Kim, Byung Woo, Sim, Sang Jun
Journal of biotechnology 2016 v.221 pp. 55-61
Chlamydomonas reinhardtii, algae culture, anaerobic conditions, carbon dioxide, cost effectiveness, energy efficiency, hydrogen, hydrogen production, interphase, light intensity, microalgae, oxygen, oxygen production, photosynthesis, starch, sulfur
Under autotrophic conditions, starch plays an important role in establishing anoxic conditions during PSII-dependent hydrogen (H2) photoproduction in microalgae. This is because starch is the sole organic substrate during respiratory consumption of internal oxygen (O2) from PSII-dependent direct pathway. Herein, we propose a novel approach to further facilitate the internal starch synthesis of Chlamydomonas reinhardtii through the operation of carbon-concentrating mechanism (CCM) along with a two-stage process based on sulfur (S) deprivation, thereby resulting in enhanced anaerobic capacity during PSII-dependent H2 photoproduction. When CCM-induced cells were exposed to high levels of carbon dioxide (CO2) (5%, v/v) with S deprivation, internal levels of starch were significantly elevated by retaining a functional CCM with the boosted photosynthetic activity during 24h of O2 evolution phase (I) of S deprivation. Consequently, during H2 production phase of S deprivation at irradiance of 50μEm−2s−1, the concentrations of starch and H2 in CCM-induced cells were remarkably enhanced by 65.0% and 218.9% compared to that of CCM-uninduced cells, respectively. The treatment of low-CO2-driven CCM induction prior to S deprivation is a cost-effective and energy-efficient strategy that significantly improves the solar-driven H2 production by microalgae; this is particularly realizable in an industrial scale.