title: Evaluation of novel starch-deficient mutants ofChlorella sorokinianafor hyper-accumulation of lipids.
abstract: When green algae are exposed to physiological stresses such as nutrient deprivation, growth is arrested and the cells channel fixed carbon instead into storage compounds, accumulating first starch granules and then lipid bodies containing triacylglycerides. In recent years there has been significant interest in the commercial exploitation of algal lipids as a sustainable source of biodiesel. Since starch and lipid biosynthesis involves the same C3 precursor pool, it has been proposed that mutations blocking starch accumulation should result in increased lipid yields, and indeed several studies have supported this. The fast-growing, thermotolerant algaChlorella sorokinianarepresents an attractive strain for industrial cultivation. We have therefore generated and characterized starch-deficient mutants ofC. sorokinianaand determined whether lipid levels are increased in these strains under stress conditions. One mutant (ST68) is shown to lack isoamylase, whilst two others (ST3 and ST12) are defective in starch phosphorylase. However, we find no significant change in the accumulation or profile of fatty acids in these mutants compared to the wild-type, suggesting that a failure to accumulate starch per se is not sufficient for the hyper-accumulation of lipid, and that more subtle regulatory steps underlie the partitioning of carbon to the two storage products.
authors: Institute of Structural and Molecular Biology, University College London, London WC1E 6BT, UK.
authors: Sofie
authors: S
authors: Vonlanthen
authors: Unité de Glycobiologie Structurale et Fonctionnelle, UMR 8576, CNRS, Université des Sciences et Technologies de Lille, F-59655 Villeneuve d'Ascq, France.
authors: David
authors: D
authors: Dauvillée
authors: Institute of Structural and Molecular Biology, University College London, London WC1E 6BT, UK.
authors: Saul
authors: S
authors: Purton
keywords: Biofuel; Chlorella; Isoamylase; Microalgae; Starch; Triacylglycerides