Dynamic metabolic profiling of the marine microalga Chlamydomonas sp. JSC4 and enhancing its oil production by optimizing light intensity

Abstract

BackgroundMarine microalgae are among the most promising lipid sources for biodiesel production because they can be grown on nonarable land without the use of potable water. Marine microalgae also harvest solar energy efficiently with a high growth rate, converting CO2 into lipids stored in the cells. Both light intensity and nitrogen availability strongly affect the growth, lipid accumulation, and fatty acid composition of oleaginous microalgae. However, very few studies have systematically examined how to optimize lipid productivity by adjusting irradiance intensity, and the metabolic dynamics that may lead to improved lipid accumulation in microalgae have not been elucidated. Little is known about the mechanism of lipid synthesis regulation in microalgae. Moreover, few studies have assessed the potential of using marine microalgae as oil producers.ResultsIn this work, a newly isolated marine microalga, Chlamydomonas sp. JSC4, was selected as a potential lipid producer, and the effect of photobioreactor operations on cell growth and lipid production was investigated. The combined effects of light intensity and nitrogen depletion stresses on growth and lipid accumulation were further explored in an effort to markedly improve lipid production and quality. The optimal lipid productivity and content attained were 312 mg L−1 d−1 and 43.1% per unit dry cell weight, respectively. This lipid productivity is the highest ever reported for marine microalgae. Metabolic intermediates were profiled over time to observe transient changes during lipid accumulation triggered by combined stresses. Finally, metabolite turnover was also assessed using an in vivo13C-labeling technique to directly measure the flow of carbon during lipid biosynthesis under stress associated with light intensity and nitrogen deficiency.ConclusionsThis work demonstrates the synergistic integration of cultivation and dynamic metabolic profiling technologies to develop a simple and effective strategy for enhancing oil production in a marine microalga. The knowledge obtained from this study could be useful in assessing the feasibility of marine microalgae biodiesel production and for understanding the links between dynamic metabolic profiles and lipid biosynthesis during the course of microalgal cultivation.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-015-0226-y) contains supplementary material, which is available to authorized users.

Rapid in vivo lipid/carbohydrate quantification of single microalgal cell by Raman spectral imaging to reveal salinity-induced starch-to-lipid shift

“…Image reconstruction from the carbohydrate and lipid marker bands in microalgal cells showed aggregated structures that correspond well to the reported starch granule and lipid droplet structures in Chlamydomonas sp. [17] (Fig. 3).…”

“…, using a colorimetric method with an anthrone reagent) [16] and fatty-acid transesterification coupled with GC/MS quantification [17]. …”

Analysis of triacylglycerol accumulation under nitrogen deprivation in the red alga Cyanidioschyzon merolae

“…Both oil bodies and starch granules were significantly smaller than those found in other microalgae such as Chlamydomonas (Iwai et al, 2014;Ho et al, 2015;Siaut et al, 2011;Toyoshima & Sato, 2015). The starch granules were about 100-300 nm in diameter and present in the periphery of the cytoplasm extending ahead of the nucleus.…”

Biodiesel production from wet microalgae feedstock using sequential wet extraction/transesterification and direct transesterification processes

“…JSC4, which was provided by the Center for Bioscience and Biotechnology, National Cheng Kung University, Tainan, Taiwan and was shown to possess high lipid content (Ho et al, 2015;Nakanishi et al, 2014). The culture conditions were based on the optimal conditions reported by Nakanishi et al (2014).…”