Hydrogen production by immobilized Synechocystis sp. PCC 6803

• Synechocystis PCC 6803 immobilisation in calcium alginate.
• Bio-hydrogen production by immobilised Synechocystis PCC 6803 cells.
• H2 production rate with immobilised cells is higher than with suspension cultures.

The ability of the immobilized Synechocystis sp. PCC 6803 cells to produce hydrogen via an indirect light driven process was investigated. Cells were successfully immobilized in a calcium alginate gel matrix. Beads were prepared by using 3% (w/v) alginate and 2% (w/v) calcium chloride, and were stable showing minimal cell leakage. Beads had a mean diameter of 5.06 ± 0.18 mm, a volume of 67.8 ± 2.4 μL and a mean cell dry weight of 46.3 ± 0.8 μg. Immobilized cells retained their viability, as shown by measurement of the Fv/Fm ratio, for at least 30 days. The maximum rate of hydrogen production reached 5.73 ± 0.69 mL H2 mg cells−1 (e.g., 40.6 ± 4.9 μmol H2 mg chl−1 h−1).