Potential CO2 fixation and optimal Dunaliella tertiolecta cultivation: Influence of fertilizer, wavelength of light-emitting diodes, salinity and carbon supply strategy

Abstract

NPK-fertilizer based optimum culture medium was formulated for Dunaliella tertiolecta cultivation using 100% CO2 and different wavelength light emitting diodes (LEDs) involving green, white, red, pink and blue. The influence of decision variables like fertilizer, salinity, carbon supply strategy and LEDs with different wavelength was investigated to maximize algae-biomass, lipid and CO2 sequestration. NaCl was used to vary salinity of the culture medium, whereas carbon supply strategy was adopted for algae-biomass growth by varying NaOH dozing. Five levels and four variables response surface method (RSM) was used to fix the optimum values of the decision variables and the efficacy of RSM-oriented results were compared with the binary coded genetic algorithm (GA). Algae-biomass growth, lipid production and CO2 sequestration were enhanced significantly using optimally formulated fertilizer medium over standard artificial seawater based f/2 medium. Carbon supply strategy was found to be the most important variable for optimal algal cultivation, whereas (NPK-NaOH, NaCl-NaOH), (NaCl-LED, NPK-LED, NPK-NaOH) and (NaOH-LED, NPK-LED) were the most influencing interactions to maximize biomass growth, lipid productivity and CO2 sequestration, respectively. Following cultivation parameters, i.e., fertilizer (gL−1), NaCl (gL-1), LED, and NaOH (gL-1) were obtained to maximize algae-biomass (1.9696gL-1), lipid (0.7068gL-1) and CO2 sequestration (0.2434gL-1 d-1): (0.43, 32.99, red-72%/pink-28%, 1.09), (0.47, 59.24, red-86%/pink-14%, 1.29) and (0.46, 41.99, red-81%/pink-19%, 1.26), respectively, using simple GA. Three multi-objective optimization.