Stimulatory effect of auxins on the growth and lipid productivity of Chlorella pyrenoidosa and Scenedesmus quadricauda

This study investigated the impact of various auxins on microalgal growth and cellular composition. Two freshwater algae, i.e., Chlorella pyrenoidosa and Scenedesmus quadricauda were used. Results were analyzed using principal component analysis (PCA) and canonical correspondence analysis (CCA). The stimulatory effect of auxins on lipid content and lipid production was found to be as follows: indole-3-propionic acid (IPA) > indole-3-acetic acid (IAA) > indole-3-butyric acid (IBA) > naphthalene acetic acid (NAA). This is the first report of an increased stimulatory effect of IPA on microalgae that differs from previous study. A concentration of 60 mg L− 1 IPA caused the maximum growth rate, which increased 3 fold compared to the control. Lipid productivity in the samples treated with auxins was generally higher than the controls, and reached 4 fold higher with the addition of IPA. Using PCA, this study provided evidence that IBA and NAA show similar stimulatory effects on cellular composition. The increase in biomass and lipid productivity demonstrates the potential application of plant hormones for improving microalgae growth in commercial-scale cultivation and thus reducing the cost of biofuel production.