Calibration and testing for the cell counting approach
To establish the calibration relationship between biomass concentration and cell counting results, we first conducted cell counting experiments for each single culture (M. alcaliphilum 20ZR, S. sp.PCC7002, M. capsulatus and C. sorokiniana ). For each strain, cell counting was performed for 4 different biomass concentrations, with triplicates for each sample. To validate the effectiveness of the cell counting approach, we prepared static coculture samples by mixing given amounts of each individual microorganisms together. For each coculture pair, six coculture samples with different compositions were tested with triplicates.