Effect of Ethephon as an Ethylene-Releasing Compound on the Metabolic Profile of Chlorella vulgaris

In this study, Chlorella vulgaris (C. vulgaris) was treated with ethephon at low (50 mu M) and high (200 mu M) concentrations in medium and harvested at 0, 7, and 14 days, respectively. The presence of ethephon led to significant metabolic changes in C. vulgaris, with significantly higher levels of alpha-tocopherol, gamma-aminobutyric acid (GABA), asparagine, and proline, but lower levels of glycine, citrate, and galactose relative to control. Ethephon induced increases in saturated fatty acids but decreases in unsaturated fatty acids. The levels of highly saturated sulfoquinovosyldiacylglycerol species and palmitic acid bound phospholipids were increased on day 7 of ethephon treatment. Among the metabolites, the productivities of alpha-tocopherol (0.70 mu g/L/day) and GABA (1.90 mu g/L/day) were highest for 50 and 200 mu M ethephon on day 7, respectively. We propose that ethephon treatment involves various metabolic processes in C. vulgaris and can be an efficient way to enrich the contents of alpha-tocopherol and GABA.