Exopolysaccharide production by cyanobacteria grown in closed photobioreactors and immobilized using white cotton towelling

Two exopolysaccharide (EPS) – producing cyanobacteria, Croococcus minutus and Nostoc insulare, were grown as batch cultures in closed cultivation systems (8-L flasks or 12-L and 250-L photobioreactorswith internal illumination) at light intensities ranging between 25 and 150µmol photon m^-2 s^-1. Another batch of each organism was immobilized on white cotton towelling and grown in 470-ml and17-L flat upright transparent chambers made of polycarbonate at light intensities of 0.5–1.5 µmol photon m^-2s^-1. Both cultivation systems were compared with regard to EPS productivity and technological feasibility. The EPS excreted by both cyanobacteria was separated into fractions which had different molecular weights (540–1600 kD) and analyzed for their sugar composition. Both organisms produced acidic EPS, which contained, respectively, 4.2 and 25.3% uronic acids.