LAUSR

Abstract The characterization of a non-axenic microalgal culture was performed, including microbiological (massive sequencing of 18S and 16S rRNA) and kinetic aspects (maximum specific CO2 uptake rate, qmax, and half-saturation constant, KS). An innovative setup for the retrieval of kinetic parameters without CO2 limiting conditions was developed. The microbiological characterization showed that Acutodesmus deserticola was by far the predominant microalgae with a relative abundance of over 99.9%, while the following abundance order was observed for bacterial phyla: Proteobacteria> Bacteroidetes> Firmicutes > Chlorobi > Ignavibacteriae > Chloroflexi. The qmax and KS values were in the range of 0.027 – 0.038 gCO2 gVSS−1 h−1 and 4.0–18.2 gCO2 m-3, respectively, for irradiances from 45 to 140 μmol m−2 s−1. While increases in irradiance did not impact significantly the qmax values, a 3.1-fold increase in irradiance mediated a 4.5-fold decrease in KS. This suggested that the activation of the photosynthetic system driven by irradiance increases can be quantified by changes in KS.