Real-time response counterattack strategy of tolerant microalgae Chlorella vulgaris MBFJNU-1 in original swine wastewater and free ammonia

Global omics study of Tetraselmis chuii reveals time-related metabolic adaptations upon oxidative stress

Microalgae species encounter oxidative stress in their natural environments, prompting the development of species-specific adaptation mechanisms. Understanding these mechanisms can offer valuable insights for biotechnological applications in microalgal metabolic manipulation. In this study, we investigated the response of Tetraselmis chuii, an industrially important microalga, to H2O2-induced oxidative stress. Exposure to 0.5-mM H2O2 resulted in reduced cell viability, and higher concentrations led to a drastic decline. After 1 h of exposure to H2O2, photosynthetic capacity (Qy) was negatively impacted, and this reduction intensified after 6 h of continuous stress. Global multi-omics analysis revealed that T. chuii rapidly responded to H2O2-induced oxidative stress within the first hour, causing significant changes in both transcriptomic and metabolomic profiles. Among the cellular functions negatively affected were carbon and energy flow, with photosynthesis-related PSBQ having a 2.4-fold downregulation, pyruvate kinase decreased by 1.5-fold, and urea content reduced by threefold. Prolonged exposure to H2O2 incurred a high energy cost, leading to unsuccessful attempts to enhance carbon metabolism, as depicted, for example, by the upregulation of photosystems-related PETC and PETJ by more than twofold. These findings indicate that T. chuii quickly responds to oxidative stress, but extended exposure can have detrimental effects on its cellular functions. KEY POINTS: • 0.5-mM H2O2-induced oxidative stress strongly affects T. chuii • Distinct short- and long-term adaptation mechanisms are induced • Major metabolic adaptations occur within the first hour of exposure.

Synergistic treatment of digested wastewater with high ammonia nitrogen concentration using straw and microalgae

Microalgae as a promising approach for wastewater treatment, has challenges in directly treating digested piggery wastewater (DPW) with high ammonia nitrogen (NH4+-N) concentration. To improve the performance of microalgae in DPW treatment, straw was employed as a substrate to form a straw-microalgae biofilm. The results demonstrated that the straw-microalgae biofilm achieved the highest NH4+-N removal rate of 193.2 mg L-1 d-1, which was 28.8 % higher than that of culture system without straw. The final NH4+-N concentration in the effluent met the discharge standard of 5 mg L-1. Furthermore, the total organic carbon (TOC) released from straw facilitated bacterial proliferation and the secretion of extracellular polymeric substances (EPS). The EPS and TOC increased the suspension viscosity and surface tension, thereby enhancing the residence time of CO2 in the liquid phase and promoting CO2 fixation. This study presented a novel method for the biological treatment of high-ammonia-nitrogen DPW.

Bioenergy production from swine wastewater based on a combined process of anaerobic dynamic membrane reactor and microalgae cultivation: Feasibility and performance

Enhanced methane production and sustainable reduction of pollutants from anaerobic digestate are crucial for swine wastewater treatment. In this study, anaerobic dynamic membrane bioreactor (AnDMBR) was introduced to enhance methane production, then microalgae were cultivated on the digestate for nutrients recovery and lipid production. Results showed that pollutants can be effectively removed under various hydraulic retention time (HRT) conditions during long-term operation. Methanogenesis was enhanced with the reduction of HRT from 20 days to 10 days (0.23 L-CH4/g-CODremoved), but inhibited by shortening HRT to 5 days (0.09 L-CH4/g-CODremoved). Ammonia and phosphate in the digestate were effectively removed after microalgae cultivation. In addition, the highest microalgal biomass and lipid productivity (1.7 g/L and 17.5 mg/(L·d), respectively) were obtained using digestate ratio of 20 %, while microalgal growth was seriously restricted at high digestate content (>50 %). This work provides a prospective pathway for pollutants control and energy production from swine wastewater through integrating of AnDMBR technology with microalgae cultivation.