Interactive effect of indole-3-acetic acid and diethyl aminoethyl hexanoate on the growth and fatty acid content of some microalgae for biodiesel production

Abstract

Enhancement of microalgal growth and fatty acid production is essential for development of a microalgae-based biodiesel production platform. Three different microalgal species (Scenedesmus obliquus GU732418, Ourococcus multisporus GU732424 and Chlorella vulgaris FR751187) were individually cultivated in media containing both indole-3-acetic acid (IAA) and diethyl aminoethyl hexanoate (DAH) at concentrations of 10−8−10−4 M. Combined phytohormones (10−8 to 10−5 M) increased the growth of all three species compared to growth in media without phytohormones. IAA and DAH supported the maximum growth of S. obliquusi (38.12 × 106 cells mL−1) at 10−8 M, O. multisporus (85.89 × 106 cells mL−1) at 10−6 M, and C. vulgaris (4.09 × 106 cells mL−1) at 10−5 M. Addition of 10−7 M IAA and DAH also assisted the removal of Zn2+ (97%), K+ (88%) and Mg2+ (99%) from the media by S. obliquus. The highest removal of Zn2+, K+, and Mg2+ by C. vulgaris was achieved at 10−5 M IAA and DAH. Under all experimental conditions (10−8−10−4 M IAA and DAH) the amounts of poly-unsaturated fatty acids were significantly increased. Palmitic acid, linoleic acid and γ-linolenic acid were the major fatty acids, accounting for 11.75–21.55%, 2.55–6.73%, and 52.93–75.89% of the total fatty acid content, respectively. The fatty acids that accumulated in O. multisporus and C. vulgaris were found to be suitable for production of high quality biodiesel with characteristics equivalent to crop seed oil-derived biodiesel.