A chemical approach to manipulate the algal growth, lipid content and high-value alpha-linolenic acid for biodiesel production

Abstract

Microalgal cultivation systems for energy production are not yet economically viable due to the low yield of lipids and biomass. In this study, we propose a chemical approach, using exogenous bioactive molecules for improving algal growth, lipid content and the production of high-value alpha-linolenic acid (ALA), using Chlorella protothecoides as a model. Based on our findings, among the cytokinin and auxin classes, Kinetin increased the biosynthesis of ALA by 26.5% at 1ppm concentration, and indole-3-butyric acid at 2ppm improved the biomass and lipid productivity up to 29.15±2.02gm−2day−1, and 6.69±0.56gm−2day−1, respectively. Methyl jasmonate as a stress-related phytohormone also showed a positive stimulatory effect on growth of C. protothecoides, and the biomass productivity was increased up to 25.26±1.48gm−2day−1 at the concentration of 5ppm (lipid content: 219.66±13.20mgg−1dw; lipid productivity: 5.61±0.25gm−2day−1; ALA: 0.81±0.16gm−2day−1). A difference in the composition of fatty acids, due to the type and concentrations of stress-related phytohormones was observed, and under the influence of stress-related phytohormones, the biosynthesis of saturated fatty acids increased, and polyunsaturated fatty acids decreased in C. protothecoides. Butylated hydroxyanisole, at a concentration of 0.05ppm, increased the ALA content by 60.5%. Our study shows that the proposed bioactive molecules could increase the biomass productivity of C. protothecoides at a lower cost compared to the use of acetate as a carbon source.