TECHNOLOGY FOCUS - BIOLOGY - Preferred Components: The bacteria is oxygen-consuming bacteria; obligatory aerobic bacteria; and Pseudomonas fluorescens. The co-culture comprises 103-108 (preferably 104-107, especially 105-106) algae cells per ml. The algae comprise green algae; unicellular, photosynthetic algae; algae having a Fe-hydrogenase enzyme; and Platmonas subcordiformis, Rhodobacter sphaeroide and Chlamydomonas reinhardtii.    TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Method: The method (M2) further involves depleting at least some of the bacteria in the culturing medium to generate a bacteria-reduced culturing medium following step (b') and prior to, or during step (c'), where depleting is effected by the oxygen consumption of the algal culture that is equal to or greater than photosynthetic oxygen production of the algal culture, as measured under high intensity illumination. The methods (M1) and (M2) further involves affecting any of the steps prior to culturing the algae under anaerobic conditions under illuminated conditions, where illumination during the step of culturing the algae under anaerobic conditions is of greater intensity than during any of the steps prior to the culturing the algae under anaerobic conditions. In the methods (M1) and (M2), the bacteria-reduced culturing medium is essentially devoid of the bacteria; the propagation medium is essentially devoid of the bacteria; the culturing medium is essentially devoid of sulfur; the culturing the algae under anaerobic conditions is effected under illuminated conditions; all of steps are effected under illuminated conditions; the bacteria are comprised in a bacterial containment in fluid association with an algae containment, where the algae containment is separated from the bacterial containment by a fluid- and gas-permeable and bacterial impermeable barrier; the bacterial containment is located within the algae containment and separated from it by the fluid- and gas-permeable and bacterial impermeable barrier; the bacterial containment is a dialysis bag; the bacterial containment is remote from the algae containment and in fluid association with it via fluid connecting unit and separated from it by a fluid- and gas-permeable and bacterial impermeable barrier; bacterial containment further comprises a carbon source; a volume of the algae in the co-culture is 5-50 times greater than a volume of the bacteria; a volume of the algae in steps (b) and (b') is 20 times greater than a volume of the bacteria; the culturing in (b) and (c), and (b') and (c') is 4-60 (preferably 10-40, especially 30) hours; and the hydrogen gas generation is detectable after culturing the algae for 30 hours. EXAMPLE - No suitable example given.