Rapid Lipid Content Screening in Neochloris Oleoabundans by Carbon-Based Dielectrophoresis ^†

The use of microalgae as a biomass source for biofuel production has drawn the attention of many scientists due to several associated environmental advantages over conventional terrestrial crops, including microalgae growing using wastewaters and a higher CO₂ fixation rate, contributing to the reduction of atmospheric concentration. Consequently, a reliable cytoplasmic lipid screening process in microalgae is a valuable asset for harvesting optimization in mass production processes. In this study, the heterogeneous cytoplasmic lipid content of Neochloris oleoabundans was dielectrophoretically assorted in a microfluidic device using castellated carbon microelectrodes. The experiments carried out over a wide frequency window (100 kHz to 30 MHz) at a fixed amplitude of 7 VPP showed a significant contrast between the dielectrophoretic behavior of high lipid content and low lipid content cells at the low frequency range (100–800 kHz). A weak response for the mid and high frequency ranges (1–30 MHz) was also identified for high and low lipid content samples, allowing one to establish an electrokinetic footprint of the studied strain. These results suggest that the development of a reliable screening process for harvesting optimization is possible through a fast and straightforward mechanism, such as dielectrophoresis, which is a low-cost and easy-to-machine material that employs glassy carbon. The experimental setup in this study involved in vitro culturing of nitrogen-replete (N+) and nitrogen-deplete (N-) cell suspensions to promote low and high lipid production in cells, respectively. Cell populations were monitored using spectrophotometry, and the resulting lipid development among cells was quantified by Nile red fluorescence.