Hydrogen photoproduction in green algae Chlamydomonas reinhardtii sustainable over 2 weeks with the original cell culture without supply of fresh cells nor exchange of the whole culture medium

Abstract

Unicellular green algae Chlamydomonas reinhardtii are known to make hydrogen photoproduction under the anaerobic condition with water molecules as the hydrogen source. Since the hydrogen photoproduction occurs for a cell to circumvent crisis of its survival, it is only temporary. It is a challenge to realize persistent hydrogen production because the cells must withstand stressful conditions to survive with alternation of generations in the cell culture. In this paper, we have found a simple and cost-effective method to sustain the hydrogen production over 14 days in the original culture, without supply of fresh cells nor exchange of the culture medium. This is achieved for the cells under hydrogen production in a sulfur-deprived culture solution on the {anaerobic, intense light} condition in a desiccator, by periodically providing a short period of the recovery time (2 h) with a small amount of TAP(+S) supplied outside of the desiccator. As this operation is repeated, the response time of transition into hydrogen production (preparation time) is shortened and the rate of hydrogen production (build up time) is increased. The optimum states of these properties favorable to the hydrogen production are attained in a few days and stably sustained for more than 10 days. Since generations are alternated during this consecutive hydrogen production experiment, it is suggested that the improved hydrogen production properties are inherited to next generations without genetic mutation. The properties are reset only when the cells are placed on the {sulfur-sufficient, aerobic, moderate light} conditions for a long time (more than 1 day at least).

Molecular Hydrogen, a Neglected Key Driver of Soil Biogeochemical Processes

“…(a) Photoproduction. Photoproduction of H 2 in aquatic sediments is performed by unicellular algae such as Chlorella fusca (phylum Chlorophyta), Tetradesmus obliquus (formerly Scenedesmus obliquus; phylum Chlorophyta) (72), and Chlamydomonas reinhardtii (73), as well as Cyanobacteria. In soils, several purple nonsulfur bacteria perform photoproduction, including Rhodobacter capsulatus (phylum Proteobacteria) (74) and Rhodopseudomonas rutila (phylum Proteobacteria) (75).…”

Biohydrogen from Microalgae: Production and Applications

“…Regarding media components, the aforementioned S deprivation gives the expected effects only if preceded by a photosynthetic growth phase, providing all of the necessary elements for growth. More recently, alongside this strategy, which envisages separate growth and a deprivation step with several operational issues, a different modality that involves minimal quantities of S to simulate a condition of starvation has also been tested [25,26]. Moreover, particular attention should be paid to the carbon source used: it has been observed that an increase in starch reserves during the phase preceding S deprivation can be crucial in supporting production.…”

Analysis of Unique Motility of the Unicellular Green Alga Chlamydomonas reinhardtii at Low Temperatures down to −8 °C

“…In the academic field, C. reinhardtii plays a significant role as a model organism for studying phototaxis, photosynthesis, and the genetics and physiology of flagellar motility. Research has also been reported on clean energy production, such as hydrogen production [ 26 , 27 , 28 , 29 ], and in statistical studies related to the spatial distribution of cells [ 30 ]. Particularly in temperature-related research, it has been utilized as a model plant system for examining many aspects of the heat stress response [ 31 , 32 ], and more recently, it has been used in studies of cold-induced responses [ 24 ].…”