A microscale approach for simple and rapid monitoring of cell growth and lipid accumulation in Neochloris oleoabundans

Due to the increasing environmental problems caused by the use of fossil fuels, microalgae have been spotlighted as renewable resources to produce biomass and biofuels. Therefore, the investigation of the optimum culture conditions of microalgae in a short time is one of the important factors for improving growth and lipid productivity. Herein, we developed a PDMS-based high-throughput screening system to rapidly and easily determine the optimum conditions for high-density culture and lipid accumulation of Neochloris oleoabundans. Using the microreactor, we were able to find the optimal culture conditions of N. oleoabundans within 5 days by rapid and parallel monitoring growth and lipid induction under diverse conditions of light intensity, pH, CO₂ and nitrate concentration. We found that the maximum growth rate (μ _max = 2.13 day^-1) achieved in the microreactor was 1.58-fold higher than that in a flask (μ _max = 1.34 day^-1) at the light intensity of 40 μmol photons m^-2 s^-1, 5 % CO₂ (v/v), pH 7.5 and 7 mM nitrate. In addition, we observed that the accumulation of lipid in the microreactor was 1.5-fold faster than in a flask under optimum culture condition. These results show that the microscale approach has the great potential for improving growth and lipid productivity by high-throughput screening of diverse optimum conditions.