Kim Yujin, Flinkstrom Zachary, Candry Pieter, Winkler Mari-Karoliina H, Myung Jaewook
Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Republic of Korea.
Department of Civil and Environmental Engineering, University of Washington, Seattle, WA, United States.
Front Bioeng Biotechnol. 2023 Jul 31;11:1210392. doi: 10.3389/fbioe.2023.1210392. eCollection 2023.
Aquatic environments account for half of global CH emissions, with freshwater wetlands being the most significant contributors. These CH fluxes can be partially offset by aerobic CH oxidation driven by methanotrophs. Additionally, some methanotrophs can convert CH into polyhydroxyalkanoate (PHA), an energy storage molecule as well as a promising bioplastic polymer. In this study, we investigate how PHA-accumulating methanotrophic communities enriched from wetlands were shaped by varying resource availability (i.e., C and N concentrations) at a fixed C/N ratio. Cell yields, PHA accumulation, and community composition were evaluated in high (20% CH and 10 mM NH ) and low resource (0.2% CH and 0.1 mM NH ) conditions simulating engineered and environmental settings, respectively. High resource availability decreased C-based cell yields, while N-based cell yields remained stable, suggesting nutrient exchange patterns differed between methanotrophic communities at different resource concentrations. PHA accumulation was only observed in high resource enrichments, producing approximately 12.6% ± 2.4% (m/m) PHA, while PHA in low resource enrichments remained below detection. High resource enrichments were dominated by methanotrophs, while low resource enrichments remained significantly more diverse and contained only a minor population of methanotrophs. This study demonstrates that resource concentration shapes PHA-accumulating methanotrophic communities. Together, this provides useful information to leverage such communities in engineering settings as well as to begin understanding their role in the environment.
水生环境占全球甲烷排放的一半，其中淡水湿地是最主要的排放源。这些甲烷通量可以被甲烷氧化菌驱动的好氧甲烷氧化部分抵消。此外，一些甲烷氧化菌可以将甲烷转化为聚羟基脂肪酸酯（PHA），这是一种能量储存分子，也是一种很有前景的生物塑料聚合物。在本研究中，我们调查了从湿地富集的积累PHA的甲烷营养群落如何在固定碳氮比下受到不同资源可用性（即碳和氮浓度）的影响。分别在模拟工程和环境条件的高资源（20%甲烷和10 mM氨）和低资源（0.2%甲烷和0.1 mM氨）条件下评估细胞产量、PHA积累和群落组成。高资源可用性降低了基于碳的细胞产量，而基于氮的细胞产量保持稳定，这表明不同资源浓度下甲烷营养群落之间的养分交换模式不同。仅在高资源富集培养中观察到PHA积累，产生约12.6%±2.4%（m/m）的PHA，而低资源富集培养中的PHA含量仍低于检测限。高资源富集培养以甲烷氧化菌为主，而低资源富集培养的多样性明显更高，仅含有少量甲烷氧化菌。这项研究表明，资源浓度塑造了积累PHA的甲烷营养群落。总之，这为在工程环境中利用此类群落以及开始了解它们在环境中的作用提供了有用信息。
