Production of H sub(2) by sulphur-deprived cells of the unicellularcyanobacteria Gloeocapsa alpicola and Synechocystis sp. PCC 6803during dark incubation with methane or at various extracellular pH

摘要

Aims:To examine sulphur (S) deprivation in combination with the presence of methane (CH sub(4)) and changes in extracellular pH as a method to enhance in situ hydrogen (H sub(2)) generation during fermentation in the unicellular non-diazotrophic cyanobacteria Gloeocapsa alpicola and Synechocystis PCC 6803. Methods and Results:The level of H sub(2) production, measured using a gas chromatography, was determined in S-deprived cells of G. alpicola and Synechocystis PCC 6803 during fermentation. Starvation on S enhanced the rate of H sub(2) production by more than fourfold in both strains. S-deprived cyanobacteria were able to maintain maximum rate of H sub(2) production during at least 8 h of fermentation representing the entire dark period of a day. Increased H sub(2) production was observed during dark anoxic incubation with a gas phase of 100% CH sub(4) (up to four times) at lower pH of the medium (5.0-5.5). Conclusions:S-deprivation in combination with CH sub(4), added or maybe produced by another micro-organisms, and changes in the pH of the media can be used to further increase the specific capacity of unicellular non-N sub(2)-fixing cyanobacteria to produce H sub(2) during fermentation with the overall aim of applying it for outdoor photobiological H sub(2) production. Significance and Impact of the Study:S-deprivation with respect to H sub(2) production is well studied in the green algae Chlamydomonas reinhardtii while its application for H sub(2) production in cyanobacteria is novel. Similarly, the stimulation of H sub(2) generation in the presence of CH sub(4) opens up new possibilities to increase the H sub(2) production. Natural gas enriched with H sub(2) seems to be a perspective fuel and may be an intermediate step on the pathway to the exploitation of pure biohydrogen.