Cell diameter doesn't affect lipid productivity of Chlorococcum littorale

Abstract

We hypothesized that cells with different diameter have different division rates, which could affect lipid productivity (lipid content × biomass productivity). In the present work we assessed the influence of cell diameter, as a sorting parameter, on both biomass and lipid productivity of Chlorococcum littorale. Prior to sorting, cells were grown in a batch-wise nitrogen run-out including a long nitrogen depleted phase (N −) to stop cell division, thus only having vegetative cells (Pre-sorting). Cell sorting was done at the end of this N − phase using FACS (fluorescence assisted cell sorting) based on forward scatter as a proxy for diameter (size ranges (μm): 5–6 (small), 8–9 (medium), 11–14 (large) and 5–14 (control)). The sorting was done in 2 pools: multiple-cell (100 cells) and single-cell. After sorting, cells were recovered under low-light for 2 weeks, and used to start the Post-sorting experiment (analogous to Pre-sorting). The populations derived from different sorted pools, single-cell and multiple-cell, showed similar size distributions after re-growth. No difference was observed in biomass and lipid productivities among Post-sorting cells and when compared to Pre-sorting cells under nitrogen depletion. We concluded that cellular size had no effect on both biomass and lipid productivity of C. littorale.