Carbon dioxide sequestration by Chlorella pyrenoidosa toward biomass and lipid production: an integrated multi-optimized management

The aim of this investigation was to evaluate the efficiency of unicellular microalga Chlorella pyrenoidosa cultivated in dairy industry wastewater for CO2 sequestration and its influence on biomass and lipid production. For this purpose, three process parameters-CO2 (2-10%), wavelength (420-680 nm), and temperature (20-50 degrees C)-were optimized using the central composite design (CCD) with response surface methodology (RSM). A total of twenty sets of experimental runs obtained by CCD were studied to optimize the process parameters for maximum biomass (mg L-1), CO2 fixation (mg L day(-1)), and lipid yield (%). The highest biomass yield of 1.43 g L-1 and maximum CO2 fixation of 14.55 (mg L day(-1)) were obtained with 5% CO2, a temperature of 35 degrees C, and a wavelength of 520 nm. On the other hand, a maximum lipid yield of 34.21% was obtained with 5% CO2, a temperature of 35 degrees C, and a wavelength of 420 nm. The most influential binary interaction among the selected variables for biomass production and CO2 sequestration was found to be LED + Temp > CO2 + Temp > CO2 + LED. Meanwhile, the behavior of lipid content was highly influenced by the interaction of CO2 + Temp > CO2 + LED > LED + Temp. The highest degree of positive correlation was observed between biomass yield and CO2. Fourier transform infrared spectroscopy (FTIR) reveals a strong signal at 1400-1700 cm(-1), confirming the existence of a carbonyl group (-COOR-).