Elucidating the role of jasmonic acid in oil accumulation, fatty acid composition and gene expression in Chlorella vulgaris (Trebouxiophyceae) during early stationary growth phase

Manipulation of microalgae cultivation is an important approach as the growth conditions will determine the quality and compositions of lipids produced by the cells. This study attempts at maximizing the production of lipids in Chlorella vulgaris (Trebouxiophyceae) through introduction of the plant hormone jasmonic acid (JA). Exogenous application of JA at early stationary growth phase promoted microalgal growth with increment of up to 51% of cell density relative to the control. JA also transiently increased the total oil production of microalgal cells by 54%. Interestingly, this increment also induced significantly higher production of saturated (SFA) and monounsaturated (MUFA) without compensating the production of polyunsaturated fatty acid (PUFA). Further analysis of fatty acid compositions showed that JA stimulated the production of C16:0 (palmitic acid), C18:0 (stearic acid) and C18:1 (oleic acid) at early stationary growth phase whilst C18:3 n-3 (α-linolenic acid) at later stationary growth phase. This transient modification of fatty acid compositions was correlated with the fatty acid biosynthetic gene expression as quantified by real-time PCR. Taken together, our results indicated that JA significantly increased microalgal lipid accumulation and could be utilized in cultivation to facilitate commercial mass production of microalgae lipids.