Brassinosteroid improves lipid productivity and stress tolerance of Chlorella cells induced by high temperature

The application of exogenous brassinosteroids (BRs) against high-temperature stress in algae is poorly studied. The present work aims to assess the function of 2,4-epibrassinolide (EBL) on lipid production during the stress phase of Chlorella vulgaris cultivation induced by high temperature. The maximum growth rate was reached by the treatment with EBL at the optimum temperature of 25 A degrees C, while the highest lipid content was obtained by the treatment with EBL at 30 A degrees C, indicating that EBL significantly increases the lipid content of algae subjected to the stress induced by high temperature. Therefore, the maximum lipid productivity was obtained by cells in the media with EBL under optimum temperature (25 A degrees C). The application of Fourier transform infrared spectroscopy (FTIR) in this work demonstrated that this technique can effectively and rapidly determine the changes in lipid and carbohydrate. Principal component analysis (PCA) can provide a full view of multivariate shift of cell compositions (i.e., lipids, carbohydrates, and proteins), which is much faster than individual band comparison. Based on FTIR data and PCA analysis, we successfully demonstrated that overall composition changes in algal cell, including lipid, protein, and carbohydrate, in response to the assimilation of high temperature and plant hormones.