Cogongrass (Imperata cylindrica) Leaf Extract Counteracts the Effects of Nitrogen Limitation and Induces Changes in Biomass, Lipid, and Fatty Acid Profile in Chlorella vulgaris UMT-M1 and Scenedesmus sp. KS-2

Abstract

This study assessed the feasibility of unhydrolyzed cogongrass as a medium fortificant for cultivation of Chlorella vulgaris UMT-M1 and Scenedesmus sp. KS-2. Nitrogen-limited media supplemented with 0.1–0.5% (w/v) cogongrass leaf extract induced changes in lipid content and produced effects that appear to counteract the effects of nitrogen depletion, restoring lipid and fatty acid content to levels similar to nitrogen-replete media while biomass was decreased. While nitrogen-limited media led to an increase in total lipid, oleic acid (C18:1) and monounsaturated fatty acid (MUFA) content and a decrease in palmitic acid (C16:0), polyunsaturated fatty acid (PUFA) and saturated fatty acid (SFA) content, the presence of cogongrass extract evidently cancelled this effect. As a sole ingredient, cogongrass reduced biomass, C16:0, PUFA and SFA, but increased total oil, C18:1 and MUFA to levels similar to N-limited media. Unexpectedly, a 45.8% increase in lipid productivity in Scenedesmus sp. under N-limitation was observed, despite a reduction in biomass. This study demonstrates that the extract from cogongrass and likely from other plant sources could potentially be used as a medium fortificant for microalga cultivation for lipid production. It could also be used as part of a cultivation strategy towards the production of desired fatty acid composition for biodiesel applications. In addition, this study could spark new research for alternative medium fortificants for microalga cultivation from various unutilized or waste plant biomass resources.