Polyhydroxyalkanoates production by a mixed photosynthetic consortium of bacteria and algae

► A photosynthetic system for mixed culture PHA production without aeration is proposed. ► A mixed photosynthetic consortium of bacteria and algae successfully produced PHA. ► Carbohydrates were produced and used as an additional energy source for carbon uptake. ► Oxygen produced by algae enables bacterial homeostasis during PHA consumption. ► Thus far, total PHA accumulation of 20% has been achieved. For the first time, a mixed photosynthetic culture (MPC) consisting of a consortium of bacteria and algae was investigated for its capacity to accumulate polyhydroxyalkanoates (PHA). The culture was subjected to a feast and famine regime in an illuminated environment without supplying oxygen or any other electron acceptor. The MPC accumulated PHA during the feast phase and consumed it in the famine phase, where the PHA consumption was made possible due to oxygen production by algae. The internal cycling of carbohydrates was also observed, which was likely linked to bacterial glycogen being used as an additional source of energy for acetate uptake during the feast phase, and restored in the famine phase via PHA degradation. The MPC reached a PHA content of 20%, with a PHA storage yield per acetate similar to aerobic systems, opening up the possibility of a new sunlight-driven PHA production process without the need for aeration.