title: Dynamic metabolic profiling of the marine microalga Chlamydomonas sp. JSC4 and enhancing its oil production by optimizing light intensity.
abstract: BACKGROUND
  Marine 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.
  
  
  RESULTS
  In 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 vivo (13)C-labeling technique to directly measure the flow of carbon during lipid biosynthesis under stress associated with light intensity and nitrogen deficiency.
  
  
  CONCLUSIONS
  This 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.
authors: Organization of Advanced Science and Technology, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe, 657-8501 Japan.
authors: Shih-Hsin
authors: SH
authors: Ho
authors: Organization of Advanced Science and Technology, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe, 657-8501 Japan.
authors: Akihito
authors: A
authors: Nakanishi
authors: Organization of Advanced Science and Technology, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe, 657-8501 Japan.
authors: Xiaoting
authors: X
authors: Ye
authors: Department of Chemical Engineering, National Cheng Kung University, Tainan, 701 Taiwan ; Research Center for Energy Technology and Strategy, National Cheng Kung University, Tainan, 701 Taiwan ; Center for Bioscience and Biotechnology, National Cheng Kung University, Tainan, 701 Taiwan.
authors: Jo-Shu
authors: JS
authors: Chang
authors: Center for Bioscience and Biotechnology, National Cheng Kung University, Tainan, 701 Taiwan.
authors: Chun-Yen
authors: CY
authors: Chen
authors: Organization of Advanced Science and Technology, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe, 657-8501 Japan.
authors: Tomohisa
authors: T
authors: Hasunuma
authors: Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe, 657-8501 Japan ; Biomass Engineering Program, RIKEN, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045 Japan.
authors: Akihiko
authors: A
authors: Kondo
keywords: Biodiesel; Carbon flux; Chlamydomonas sp; Light intensity; Lipids; Metabolite profiling; Microalgae; Nitrogen depletion