The phytohormone abscisic acid increases triacylglycerol content in the green microalga Chlorella saccharophila (Chlorophyta)

Abstract

Microalgae are currently a very promising source of biomass and triacylglycerol (TAG) for biofuels. In a previous study, we identified Chlorella saccharophila as a suitable source of oil for biodiesel production because it showed high biomass and lipid content with an appropriate fatty acid methyl esters profile. To improve the TAG accumulation in C. saccharophila, in this study we evaluated the effect of abscisic acid (ABA) addition on cell concentration, lipid content and TAG production in this microalga. First, we evaluated the effects of four ABA concentrations (1, 4, 10, and 20 µM) added at the beginning of a single-stage cultivation strategy, and found that all concentrations tested significantly increased cell concentration and TAG content in C. saccharophila. We then evaluated the addition of 1 µM ABA during the second stage of a two-stage cultivation strategy and compared it with a nitrogen deficiency treatment (ND) and a combination of ND and ABA (ND + ABA). Although ABA alone significantly increased lipid and TAG contents compared with the control, ND showed significantly higher TAG content, and ND + ABA showed the highest TAG content. When comparing the results of both strategies, we found a superior response in terms of TAG accumulation with the addition of 1 µM ABA at the beginning of a single-stage cultivation system. This strategy is a simple and effective way to improve the TAG content in C. saccharophila and probably other microalgae as a feedstock for biodiesel production.

Is Genetic Engineering a Route to Enhance Microalgae-Mediated Bioremediation of Heavy Metal-Containing Effluents?

“…In Scenedesmus quadricauda , ABA improved cell growth by 2.1-fold, and induced the accumulation of saturated fatty acids by 12% under nitrogen starvation [ 254 ]. Similar results were reported for Chlorella saccharophila , E. gracilis , and C. saccharophila , following ABA treatment under HM stress [ 255 , 256 ].…”

Phytohormones and Effects on Growth and Metabolites of Microalgae: A Review

“…In a microalgae S. quadricauda, culture supplemented with 2 µM, ABA increased biomass production 2.1-fold in nitrogen-limited conditions after 48 h of cultivation, so this may be a potential strategy for efficient microalgal cultivation for biofuel production [67]. Meanwhile, lipid accumulation of microalgae with only ABA supplemented has also been revealed [32,33]. It was shown that 1.0 mg/L ABA imposed an augmentation of lipid productivity of C. vulgaris ZF strain and FACHB-31 by 123% and 44%, respectively [32].…”

Influence of Light Intensity and Photoperiod on the Photoautotrophic Growth and Lipid Content of the Microalgae Verrucodesmus verrucosus in a Photobioreactor

“…As demonstrated in this research paper, where the best photoperiod for obtaining lipids was 12:12 (Table 1), these results are similar to those obtained in other research papers where they evaluated Chlorella vulgaris, and higher biomass production and lipid content were achieved under 12 h: 12 h light:dark cycles relative to a 24 h: 0 h continuous illumination condition [28]. In Nannochloropsis sp., lipid content and growth rate were highest under an 18 h:6 h light/dark cycle compared with 24 h:0 h and 12 h:12 h cycles [12,22]. In Nannochloropsis gaditana, biomass concentration was highest under a 12 h:12 h light/dark cycle, while lipid content was highest under a 16 h:8 h cycle, relative to 24 h:0 h and 8 h:16 h cycles [9].…”

“…Cellular concentration was determined using a Neubauer hemacytometer (Hausser Scientific, Horsham, PA, USA) and a Primo Star microscope (Carl Zeiss, Oberkochen, Germany). The cells were harvested by centrifugation and dried at 70 • C. Growth rate parameters of each treatment were calculated on the basis of cell count during exponential phase of growth [22]. Following growth parameters were calculated from the observed data [23].…”