Statistical optimization of light intensity and CO₂ concentration for lipid production derived from attached...

Attached cultivation systems have been receiving extensive attention as a breakthrough in microalgae cultivation technology. However, there is a lack of studies that emphasize precise optimization of important parameters in attached cultivation of microalgae. In this study, the effects of two major environmental parameters in photoautotrophic cultivation, light intensity and CO₂ concentration, on the biomass and lipid surface productivity of Ettlia sp. YC001 were optimized by employing Response Surface Methodology (RSM) and validated experimentally. The optimum initial conditions for attached cultivation were use of seed from the late exponential phase (LE) and an inoculum surface density of 2.5 g/m². By optimization, maximum biomass surface productivity of 28.0 ± 1.5 g/m²/day was achieved at 730 μE/m²/s with 8% CO₂. The maximum lipid surface productivity was 4.2 ± 0.3 g/m²/day at 500 μE/m²/s with 7% CO₂. Change of the fatty acid composition with respect to changes in environment parameters led to improvement of biodiesel quality at higher light intensity and higher CO₂ concentration. Attached cultivation of Ettlia sp. YC001 has successfully produced biomass and lipids at a high production rate with relatively low light energy demand and high CO₂ utilization.