Photobiological hydrogen production from Synechocystis sp. PCC 6803 encapsulated in silica sol–gel

Hydrogen production was measured from viable wild-type and M55 mutant cells of Synechocystis sp. PCC 6803 encapsulated in silica sol–gel derived from tetraethoxysilane, tetramethoxysilane, and a mixture of tetraethoxysilane with methyltriethoxysilane. Glycerol and polyethylene glycol were used as additives in concentrations up to 14 wt.% to increase porosity and pore connectivity and to reduce stress on the encapsulated cells. Mixtures were evaluated for hydrogen production in a high-throughput screening assay, and samples were imaged with environmental scanning electron microscopy. Compositions showing improved H 2 production were selected for further study via quantitative analysis of H 2 production in GC vial assays. H 2 production activity was monitored for up to 5 days and H 2 production from encapsulated cells was observed at levels comparable to or exceeding cells suspended in liquid media.