Photobioreactor strategies for improving the CO _2 fixation efficiency of indigenous Scenedesmus obliquus CNW-N: Statistical optimization of CO _2 feeding, illumination, and operation mode

摘要

Statistical experimental design and bioreactor strategies were applied to enhance CO _2 fixation ability of microalga Scenedesmus obliquus CNW-N. Four operating parameters strongly influencing microalgal CO _2 fixation efficiency (namely, CO _2 concentration, CO _2 flow rate, magnesium concentration, and light intensity) were optimized with response surface methodology. The optimal range of parameters achieving the best overall performance of specific growth rate and CO _2 fixation rate was determined with overlay counter plot techniques. Optimal ranges of CO _2 concentration, CO _2 flow rate, magnesium concentration and light intensity were 2.0-2.5%, 0.3-0.5vvm, 1.7-2.7mM and 180-250μmolm ~(-2)s ~(-1), respectively, achieving a specific growth rate of >1.22d ~(-1) and CO _2 fixation rate of >800mgL ~(-1)d ~(-1). Semi-batch operations further enhanced the biomass productivity, photosynthesis efficiency, and CO _2 fixation rate to 1030mgL ~(-1)d ~(-1), 10.5%, and 1782mgL ~(-1)d ~(-1), respectively. This performance is better than the results reported by most related studies.