FIG 4.

Long-term H₂ (A, C, and E) and O₂ (B, D, and F) photoproduction yields from Calothrix 336/3 (A and B), Anabaena PCC 7120 (C and D), and the ΔhupL mutant of Anabaena PCC 7120 (E and F) entrapped in alginate films. In contrast to the experiment shown in Fig. 1, the cumulative yields are presented. The gas phase in the headspace of the vials was renewed periodically with Ar supplemented with 6% CO₂ (Ar + CO₂), air (air), or air supplemented with 6% CO₂ (air + CO₂). In the case of Calothrix 336/3, the kinetic curves from the films treated with air plus CO₂ with lower Chl a content per area unit are also presented. The insets represent the typical H₂ (inset E) and O₂ (inset F) photoproduction curves during a single cycle of air treatment.