Gu Zhiqiang, Liu Yuhuan, Zhu Liandong, Fan Boyou, Li Yuan, Liu Cuixia, Wang Yunpu, Cui Xian, Yu Zhigang, Ruan Roger, Zhang Qi
State Key Laboratory of Food Science and Resources, Engineering Research Center for Biomass Conversion, Ministry of Education, Nanchang University, Nanchang, Jiangxi 330047, PR China.
School of Resource and Environmental Sciences, Hubei Key Laboratory of Biomass-Resources Chemistry and Environmental Biotechnology, and Hubei International Scientific and Technological Cooperation Base of Sustainable Resource and Energy, Wuhan University, Wuhan 430079, China.
Water Res. 2025 Sep 1;283:123877. doi: 10.1016/j.watres.2025.123877. Epub 2025 May 20.
Microalgae-based biotreatment offers a sustainable and efficient solution for managing pig manure anaerobic digestion effluents (PMADE), a byproduct of intensive agricultural practices. Dissolved organic matter (DOM) in PMADE significantly influences microalgal physiological responses; however, the underlying mechanisms remain poorly understood. Here, we reveal a hormetic effect of DOM in PMADE on Chlorella sp. Moderate DOM concentrations (1000-1500 mg/L of COD) alleviated ammonium toxicity and promoted microalgal growth, whereas higher concentrations (>2000 mg/L of COD) exerted severe inhibitory effects. Through cascade extraction and targeted screening, we identified distinct impacts of five DOM fractions on Chlorella sp. Notably, low-molecular-weight acids and nitrogenous compounds, primarily dipeptides in the fractions, exhibited a promoting effect on growth by serving as carbon sources to enhance energy metabolism and protein synthesis. Among the fractions, antioxidant-active compounds further supported the growth by scavenging reactive oxygen species (ROS) and maintaining redox homeostasis. In contrast, fractions rich in alkanes and alkaloids, induced excessive ROS production under high concentrations, leading to impaired photosynthesis and severe DNA damage. Additionally, the substances such as humic acid and fulvic acid, as key components of PMADE, exhibited hormetic effects: at specific concentrations (humic acid<200 mg TOC/L; fulvic acid<100 mg TOC/L), they enhanced ROS scavenging, growth, photosynthesis and pigment accumulation, whereas exceeding these thresholds shifted their role from promotion to inhibition. Collectively, this study elucidates the dose-response relationship between DOM concentration and composition in relation to microalgal growth, identifies key DOM components influencing growth, and proposes targets for the selective removal of inhibitory DOM in PMADE.
基于微藻的生物处理为集约化农业实践的副产品猪粪厌氧消化废水（PMADE）的管理提供了一种可持续且高效的解决方案。PMADE中的溶解有机物（DOM）显著影响微藻的生理反应；然而，其潜在机制仍知之甚少。在此，我们揭示了PMADE中DOM对小球藻的 hormetic效应。适度的DOM浓度（化学需氧量为1000 - 1500mg/L）减轻了铵毒性并促进了微藻生长，而较高浓度（化学需氧量>2000mg/L）则产生了严重的抑制作用。通过分级萃取和靶向筛选，我们确定了五个DOM组分对小球藻的不同影响。值得注意的是，低分子量酸和含氮化合物（主要是组分中的二肽）通过作为碳源增强能量代谢和蛋白质合成，对生长表现出促进作用。在这些组分中，具有抗氧化活性的化合物通过清除活性氧（ROS）和维持氧化还原稳态进一步支持了生长。相反，富含烷烃和生物碱的组分在高浓度下诱导过量ROS产生，导致光合作用受损和严重的DNA损伤。此外，作为PMADE关键成分的腐殖酸和富里酸等物质表现出hormetic效应：在特定浓度下（腐殖酸<200mg TOC/L；富里酸<100mg TOC/L），它们增强了ROS清除、生长、光合作用和色素积累，而超过这些阈值则使其作用从促进转变为抑制。总的来说，本研究阐明了DOM浓度和组成与微藻生长之间的剂量反应关系，确定了影响生长的关键DOM成分，并提出了选择性去除PMADE中抑制性DOM的目标。
