Quorum sensing molecule C8-HSL enhances Chlorella growth and lipid accumulation via ROS mediated metabolic reprogramming.

Quorum sensing molecules play important roles in microbial metabolic regulation; however, their involvement in microalgal carbon allocation remains poorly understood. In this study, the effects of N-octanoyl-l-homoserine lactone (C8-HSL) on Chlorella sp. growth and lipid accumulation were systematically investigated, with particular focus on the involvement of reactive oxygen species (ROS). C8-HSL significantly promoted cell proliferation, resulting in a 30.9% increase in cell density at the late cultivation stage relative to the untreated control. It also enhanced lipid synthesis while maintaining or enhancing microalgal growth, with neutral lipid content and lipid productivity at the end of cultivation increasing by 33.1% and 25.1%, respectively. C8-HSL-treated cultures showed increased intracellular ROS levels and activated antioxidant defense responses. Transcriptomic analysis at the late cultivation stage revealed coordinated upregulation of genes related to photosynthesis, central carbon metabolism, acetyl-CoA generation, and fatty acid biosynthesis, suggesting a transcriptional state consistent with altered carbon allocation toward storage and lipid synthesis. Antioxidant supplementation attenuated C8-HSL-induced lipid accumulation, supporting ROS involvement. Overall, C8-HSL contributed to the coordinated enhancement of microalgal growth and lipid accumulation, partially through ROS-associated metabolic regulation, potentially providing a useful strategy for improving microalgal biomass and lipid production under non-stress conditions.