Enhancing Cyanobacterium aponinum carbon uptake and metabolic flux under gas dispersion and aeration using pulp mill wastewater

Abstract

Aeration and gas dispersion critically influence the growth and carbon conversion efficiency of cyanobacterial systems, yet the direct impact on cellular metabolism remains underexplored. This knowledge gap limits the development of scalable cultivation systems optimized for carbon capture and bioproduct formation. In this study, the halophilic Cyanobacterium aponinum PCC10605 was cultured in atomizer-assisted condition at varying flow rates to evaluate the effect on biomass yield, metabolite accumulation, and CO₂ uptake dynamics. Maximum biomass productivity of 5.79 g/L was achieved at 1.5 vvm gas flowrate with atomization at day 7; where glycogen, lipid, and protein concentrations reached 3.20, 1.07, and 1.10 g/L, respectively. A comprehensive kinetic modeling incorporating reaction rate constant (kr), diffusion rate constant (k_D), biomass accumulation and metabolic transformation constant (M) to explore the dominating factors in CO₂ fixation, biomass and metabolic components simultaneously. Dimensionless analysis further revealed that biomass formation was predominantly under diffusion control, with 60 % attributed to CO₂ transfer from gas to liquid phase. Finally, algae successfully increased biomass and protein amounts in a medium mixed with pulp mill wastewater under gas dispersion. These results clearly deciphered that dispersion overcomes the gas to liquid interfacial barrier, thereby offer design principles for advanced carbon capture and metabolic output through microalgal biotechnology.