Exopolysaccharides are partly growth associated products in Microcystis flos-aquae

We have investigated the kinetics of exopolysaccharide (EPS) synthesis in batch cultures of the cyanobacterium Microcystis flos-aquae. CO2 was titrated into the aeration gas to maintain constant pH and prevent CO2 limitation, and the incident light intensity was automatically optimised to prevent light limitation. Exponential and balanced growth was sustained for five to six cell generations until nitrate was depleted and cultures entered stationary phase. EPS was synthesised at a specific rate of 76 mg g−1 day−1 during the exponential growth phase and at a six times lower specific rate of 12 mg g−1 day−1 during stationary phase. EPS production was excellently described as a partly growth-associated product during both growth phases, although the carbohydrate monomer composition of EPS was modified during stationary phase. We therefore categorise EPS in M. flos-aquae as partly growth associated products.