Lipidomics analysis of microalgal lipid production and heavy metal adsorption under glycine betaine-mediated alleviation of low-temperature stress.

Heavy metal pollution in the cold region is serious, affecting human health and aquatic ecology. This study investigated the ability of microalgae to remove heavy metals (HMs) and produce lipid at low temperature. The removal efficiency of different HMs (Cd, Cu, Cr and Pb), cell growth and lipid synthesis of microalgae were analyzed at 15 °C. Moreover, addition of glycine betaine (GB) further enhanced the productivity of microalgae in treating HMs and lipid production, and simultaneously increased the antioxidant capacity of microalgae against environmental stresses. The results showed that the highest lipid productivity of 100.98 mg L d and the removal efficiency of 85.8 % were obtained under GB coupled with Cr. The highest glutathione content of 670.34 nmol g fresh alga was achieved under GB coupled with Pb. In addition, lipidomics showed that GB was able to up-regulate the triglyceride and diglyceride content, influenced fatty acid composition to regulate the microalgal metabolism, and mediated lipid accumulation under 15 °C mainly through the regulation of glycerol ester metabolism. This study provided a new perspective on microalgal lipid production and the removal of HMs in cold regions and provided evidence for the use of phytohormones to improve the algal environmental resistance.