A step-forward in the characterization of microalgal consortia: Microbiological and kinetic aspects

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, q(max), and half-saturation constant, K-s). 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 q(max) and K-s values were in the range of -0.027 - 0.038 gCO(2) gVSS(-1) h(-1) and 4.0-18.2 gCO(2) m(-3), respectively, for irradiances from 45 to 140 mu mol m(-2) s(-1). While increases in irradiance did not impact significantly the q(max) values, a 3.1-fold increase in irradiance mediated a 4.5-fold decrease in K-s. This suggested that the activation of the photosynthetic system driven by irradiance increases can be quantified by changes in K-s.