Brison Antoine, Rossi Pierre, Derlon Nicolas
ETH Zürich, Institute of Environmental Engineering, Zürich 8093, Switzerland.
Eawag, Swiss Federal Institute of Aquatic Science and Technology, Dübendorf 8600, Switzerland.
Water Res X. 2022 Jul 31;16:100150. doi: 10.1016/j.wroa.2022.100150. eCollection 2022 Aug 1.
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), 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, a stable microbial community consisting of >90% PHA-storers and dominated by 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., sp vs. sp. were selected depending on the influent COD:P ratio (i.e., 200 vs. 800 gCOD gP). 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.
富集含有高比例聚羟基脂肪酸酯储存菌（PHA储存菌）的生物质是利用混合微生物培养物从城市废水中生产PHA（生物塑料）的关键步骤。然而，一个主要挑战是创造有利于PHA储存菌的选择性生长条件。因此，我们的研究调查了进水化学需氧量与磷（COD:P）的比例在多大程度上可作为在单个连续流搅拌槽反应器（CSTR）中稳健选择PHA储存菌的工具。为此，我们并行运行了五个CSTR，用不同COD:P比例（200 - 1000 gCOD/gP）的合成废水（50%乙酸盐 - 50%丙酸盐）进料，并对长期（30 - 70个固体停留时间）的微生物群落进行了详细分析。我们的研究表明，在高进水COD:P比例下，可在单个CSTR中实现对PHA储存菌的高效稳健选择。PHA储存菌的选择优势随进水COD:P比例增加，但前提是生长条件同时受碳源和磷的限制。相反，当COD:P比例过高且生长条件仅受磷限制时，选择性能会下降。在最佳COD:P比例800 gCOD/gP时，长期选择出了一个稳定的微生物群落，其中PHA储存菌占比>90%，且以 菌属为主导。最后，我们的结果表明，高COD:P比例为细胞磷需求低的微生物提供了选择优势，这解释了为何根据进水COD:P比例（即200与800 gCOD/gP）选择了不同的PHA储存菌（即 菌属与 菌属）。总体而言，我们的结果为基于使用单个CSTR和控制进水COD:P比例来开发选择PHA储存菌的新方法提供了相关见解。
