Abstract

Induction of copper ion (Cu 2+ ) stress is a method used to increase lipid accumulation in microalgae, but it decreases cell growth. In this work, the impacts of gamma-aminobutyric acid (GABA) coupled with Cu 2+ stress on the biomass and oil yield in Monoraphidium sp. QLY-1 were investigated. Results suggested that the combined treatment of GABA and Cu 2+ resulted in a higher lipid content (55.13%) than Cu 2+ treatment (48.43%). Furthermore, GABA addition upregulated the levels of lipid-relevant genes, cellular GABA, ethylene (ETH), and antioxidant enzyme activities and alleviated oxidative damage caused by Cu 2+ stress. The autophagy-relevant gene atg8 was also upregulated by GABA treatment. Further exploration indicated that cell autophagy induced the lipid content up to 58.09% with GABA and Cu 2+ stress treatment. This investigation demonstrates that the coupling strategy can stimulate lipid production and shed light on the underlying mechanisms in lipid biosynthesis, cell autophagy, and stress response of microalgae.