Improvement in the Photobiological Hydrogen Production of Aggregated Chlorella by Dimethyl Sulfoxide.

Photobiological hydrogen production plays a vital role in generating clean renewable energy owing to its low energy consumption and environmental friendliness. Although materials-induced Chlorella aggregates have been developed to achieve sustained photobiological hydrogen production under normal aerobic conditions, the yield is relatively low and equals only 0.42 % of the light-to-H2 energy-conversion efficiency. Herein, we report that only 0.5 vol % dimethyl sulfoxide in an aqueous environment significantly enhances the H2 yield produced by aggregated Chlorella, reaching 0.69 % of the light-to-H2 energy-conversion efficiency. This improvement can be attributed to an increase in the cellular respiration rate by dimethyl sulfoxide, which results in a decrease in the oxygen content inside the aggregates and, ultimately, to the activation of more hydrogenases. More generally, this strategy consists of a functional enhancement in organism-material hybrids by using small molecules.