LAUSR

Marine microalgae constitute a natural source of compounds (e.g., alkanes, triacylglycerols) useful for biodiesel production—yet improvement of lipid productivity by microalgae is a sine qua non for the economic feasibility of such a microalga-based process. Toward this goal, five Tetraselmis strains, Tetraselmis suecica UW605, T. suecia AROSA, and three Tetraselmis sp. strains, coded as lipogenic (63LG and 75LG) or non-lipogenic (46NLG) on the basis of stationary-phase cell flotation features, were cultured semi-continuously and subjected to 10 and 30% renewal rates; the effects upon growth rate and lipidic profile were accordingly assessed. As expected, cell productivity by all strains was higher under a renewal rate of 30%. Chlorophyll, protein, and total lipid content per cell also increased with the highest renewal rate. Conversely, cell content of neutral lipids, measured with Nile red staining, decreased with increasing renewal rate. The non-lipogenic strain 46NLG revealed a much lower total lipid content, at the 10% renewal rate, than all other strains, but a higher neutral lipid content. This result supports the use of the flotation method for the selection of lipogenic strains. The diverse profiles of the various Tetraselmis strains and the effect of renewal rate on their neutral lipid content emphasize the importance of strain screening to promote a suitable microalgae selection for biodiesel production purposes.