Increased hydrogen production in co-culture of Chlamydomonas reinhardtii and Bradyrhizobium japonicum

► Decreasing the oxygen content in the cultures of Chlamydomonas reinhardtii is essential for its hydrogen productivity. ► Co-cultivation of Bradyrhizobium japonicum and C. reinhardtii promoted oxygen consumption and improved hydrogen yield. ► B. japonicum promoted H2 yield and growth of the transgenic alga, lba, by 14 times and 26% respectively.