Effect of linoleic acid and methyl jasmonate on astaxanthin content of Scenedesmus acutus and Chlorella sorokiniana under heterotrophic cultivation and salt shock conditions

Aquatic organisms, especially microalgae, are sources of highly bioactive metabolites which could be used in pharmaceutical, biofuels, food, agricultural, and cosmetics industries. In this research, the effect of linoleic acid (LA), as allelochemical and the precursor of two phytohormones, on astaxanthin production in Scenedesmus acutus and Chlorella sorokiniana was investigated under heterotrophic and salt stress conditions. In the absence of salt addition, addition of 32 mu M LA after 96 h post inoculation during C. sorokiniana cultivation enhanced cell astaxanthin concentration 1.6 times compared to the control (no addition of LA), while the addition of 160 mu M LA during the logarithmic phase of S. acutus enhanced astaxanthin production 10 times compared to the control. In C. sorokiniana under salt stress conditions, the incremental effect of LA on astaxanthin production is expanded, while salt addition did not have significant impact on astaxanthin production during S. acutus culture. In the presence of 20% salt, methyl jasmonate (MJ) treatment produced approximately threefold astaxanthin compared to LA in C. sorokiniana, while the astaxanthin formation for LA and MJ treatment in the presence of 20% salt were roughly equal during S. acutus culture. It can be therefore concluded that LA, as allelochemical and precursor of jasmonic and traumatic acid in oxylipin pathway, has an important role in the astaxanthin production in microalgae. Moreover, for the first time, the potential of LA as an enhancer of algal astaxanthin production was shown.