Influence of nitrogen-limitation regime on the production by Chlorella vulgaris of lipids for biodiesel feedstocks

Abstract

Microalgae have the potential to provide large amounts of lipid-containing biomass that could be used as a renewable oil feedstock for biofuel use. Many fast-growing algae, such as Chlorella vulgaris, when grown under nutrient-sufficient conditions, have a lipid profile that is unsuitable for biodiesel use, since the triacylglyceride content is too low. However, growth under nitrogen limitation has been shown to increase triacylglycerides. Here we investigate the most effective nitrogen-limitation regime and find that rather than transferring cells to a medium without nitrogen, the maximal triacylglyceride productivity (46 mg/l/day) is achieved by allowing the cells to deplete the nitrogen naturally. Detailed analysis of the fatty acid composition of the lipids indicated that there was a high proportion of α-linolenic acid (C18:3) under all conditions, so that it would have to be blended with other feedstocks in order to adhere to international standards for biodiesel.

Acknowledgements

The authors are grateful to the following for the support and advice they provided: Nic Davies (Department of Chemistry, University of Cambridge, UK), Prof. Sue Harrison and Melinda Griffiths (Department of Chemical Engineering, University of Cape Town, SA), Geraldine Heath (Department of Plant Sciences, University of Cambridge, UK), Dr. Beatrix Schlarb-Ridley and Dr. Derek Bendall (Department of Biochemistry, University of Cambridge, UK).

Ethical conduct of research

The authors state that they have obtained appropriate institutional review board approval or have followed the principles outlined in the Declaration of Helsinki for all human or animal experimental investigations. In addition, for investigations involving human subjects, informed consent has been obtained from the participants involved.

Financial & competing interests disclosure

Financial support from the EPSRC is gratefully acknowledged. The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

No writing assistance was utilized in the production of this manuscript.