Isolation of wild microalgae from natural water bodies for high hydrogen producing strains

摘要

Water samples from various marine, freshwater and terrestrial environments in China have been collected and screened in our laboratory for wild clones of microalgae since 2008. Hundreds of microalgal clones were purified through plate streaking, of which 52 strains have been screened for their ability to produce H_2 under anaerobic conditions. Twenty eight strains including 13 freshwater green algae, 12 marine green algae and 3 cyanobacteria were found to evolve H_2 under sulfur or nitrogen deprivation. Parietochloris incisa, Chlorella protothecoides, Chlorella capsulata, Nannochloropsis sp., Tetraselmis helgolandica, Pyramimonas sp., Chlorella autotrophica, Dunaliella apiculata, Tetraselmis striata and Tetraselmis tetrathele were first reported as new H_2 producing species. Among those H_2 producing strains, freshwater C. protothecoides showed the highest H_2 producing capacity (2.93 H_2 ml/l/ h) and accumulated up to 123.6 ml H_2 per liter culture under sulfur deprivation. Marine C. autotrophica and T. striata were two notable green marine species that produced H_2 pho-totrophically, with 3.73 ml/1 and 20.11 ml/1 of H_2 yield respectively. Our results also demonstrated that both the likelihood of a strain producing H_2, and the average H_2 output, in freshwater strains were much higher than that in marine strains. In addition, the time for inducing H_2 production in freshwater strains was short compared to the marine ones. All three Arthrospira strains tested were able to generate H_2 under sulfur (S-) deprivation though the cultures would quickly lose their vitality in S-deprived medium. Interestingly, Arthrospira produced H_2 under nitrogen deprivation, and the H_2 yield was even higher than under S-depletion. However, neither tested chrysophyte nor diatom produced any H_2 under anaerobiosis caused by S-deprivation.