Influent carbon to phosphorus ratio drives the selection of PHA-storing organisms in a single CSTR

• Published in: Water research X Vol. 16; p. 100150
• Main Authors: Brison, Antoine, Rossi, Pierre, Derlon, Nicolas
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.08.2022; Elsevier
• Subjects: Biomass PHA content; Cellular phosphorus requirements; Dual carbon and phosphorus limitation; Growth conditions; Long-term selection; Polyhydroxyalkanoates (PHAs); Growth conditions; Long-term selection; Biomass PHA content; Dual carbon and phosphorus limitation; Cellular phosphorus requirements; Polyhydroxyalkanoates (PHAs)
• ISSN: 2589-9147; 2589-9147
• DOI: 10.1016/j.wroa.2022.100150

•Selection of PHA-storers was studied in a single CSTR at high influent COD:P ratios.•Stable microbial community with >90% PHA-storers at optimal COD:P (800 gCOD gP−1).•Selective advantage for PHA-storers only when both C substrate and P limit growth.•Low cellular P requirements provide selective advantage at high influent COD:P ratios.•Pannonibacter sp. is a competitive PHA-storer at high influent COD:P ratios. Enriching a biomass with a high fraction of polyhydroxyalkanoate-storing organisms (PHA-storers) represents an essential step in the production of PHAs (bioplastics) from municipal wastewater using mixed microbial cultures. A major challenge is however to create selective growth conditions that are favourable to PHA-storers. Our study thus investigates to what extent the influent COD to phosphorus (COD:P) ratio can be used as a tool for the robust selection of PHA-storers in a single continuous-flow stirred-tank reactor (CSTR). Therefore, we operated five CSTRs in parallel, fed with synthetic wastewater (50% acetate - 50% propionate) with different COD:P ratios (200−1000 gCOD gP−1), and performed a detailed analysis of the microbial communities over long-term (30−70 solid retention times). Our study demonstrates that efficient and robust selection of PHA-storers can be achieved in a single CSTR at high influent COD:P ratios. The selective advantage for PHA-storers increases with the influent COD:P ratio, but only if growth conditions remain limited by both C-substrate and P. In contrast, selection performance deteriorates when COD:P ratios are too high and growth conditions are limited by P only. At an optimal COD:P ratio of 800 gCOD gP−1, a stable microbial community consisting of >90% PHA-storers and dominated by Pannonibacter sp. was selected in the long-term. Finally, our results suggest that high COD:P ratios provide a selective advantage to microorganisms with low cellular P requirements, explaining why different PHA-storers (i.e., Xanthobacter sp. vs. Pannonibacter sp.) were selected depending on the influent COD:P ratio (i.e., 200 vs. 800 gCOD gP−1). Overall, our results provide relevant insights for the development of a new approach for selecting PHA-storers, based on the use of a single CSTR and control of the influent COD:P ratio. [Display omitted] .