Acetic acid uptake rate controls H2 production in Chlamydomonas-bacteria co-cultures

Photobiological hydrogen production by green microalgae is considered as a promising alternative for renewable biofuel production. We have evaluated hydrogen production in the model microalga Chlamydomonas reinhardtii in co-cultures with different bacteria, including Pseudomonas spp., Escherichia coli and Rhizobium etli cultured in acetate-containing nutrient-replete media at three different light intensities (12, 50 and 100 PPFD). Co-culturing Pseudomonas spp. with Chlamydomonas can significantly improve algal hydrogen production, especially at moderate to high light intensities (50–100 PPFD). Enhancement of hydrogen production in co-cultures was clearly related to the lower capacity of these co-cultures to consume the acetic acid from the media. The longer the acetic acid remained in the media, the longer the cultures were able to sustain hypoxia and support hydrogen production. •Co-culturing Chlamydomonas with Pseudomonas in TAP medium improves H2 production.•Presence of acetate is the key to allow H2 production in Chlamydomonas co-cultures.•Reduced acetate uptake rate in co-cultures improves algal H2 production.