Microbial synergy between and enables anaerobic CO conversion to polyhydroxyalkanoates.

The high cost of traditional substrates has hindered the large-scale adoption of polyhydroxyalkanoates (PHAs) as sustainable alternatives to petrochemical plastics. One-carbon (C1) substrates like carbon monoxide (CO) offer a low-cost, sustainable feedstock, but efficient biocatalytic systems for their conversion to PHAs have been lacking. Here, we report the first successful anaerobic production of PHAs from CO using a synthetic co-culture of and . In this system, catalyzes the water-gas shift reaction, converting CO into H and CO. subsequently transforms these products into acetate, serving as an organic carbon source for PHA accumulation by . Neither organism, in monoculture, was able to grow on CO alone, underscoring the importance of the microbial synergy. While continuous cultivation in chemostats proved unstable, fed-batch cultivation achieved a PHA production rate of 58 ± 11 mg L day with a final PHA content of 38 ± 5% (dry weight). This study introduces a pioneering anaerobic route for PHA synthesis from CO, representing a significant advance toward sustainable PHA production from C1 substrates.