This work is a first attempt to investigate polysaccharide content of Prasinococcus sp. in comparison with the model strain of Porphyridium cruentum, as a potential polysaccharide producer, under two different light intensities with two different sodium glyoxylate monohydrate concentrations in F/2 medium. The microalgae strains were cultured in 1000 mL glass bottles containing 900 mL of F/2 medium at the air flow rate of 1 vvm under the temperature of 22 +/- 2 degrees C at two different light intensities (10 mu E m(-2)s(-1) and 50 mu E m(-2)s(-1)) with two different concentrations of sodium glyoxylate monohydrate (control, 0.25, and 1.25 mM C2HNaO3 center dot H2O) for 14 days. The maximum specific growth rates of 0.236 day(-1) and 0.298 day(-1), which corresponded to the doubling times of 2.945 day and 2.325 day, were obtained in F/2 control medium and in the low level glyoxylate treatment (0.25 mM) under 50 mu E m(-2)s(-1) for Prasinococcus sp. and P. cruenturn, respectively. It is also important to underline that higher light intensity had a direct influence, whereas no effect was observed for glyoxylate treatments on the growth of Prasinococcus cells. Additionally, both high light intensity and mild level of glyoxylate stimulated faster growth for P. cruentum. On the other hand, total monosaccharide amount of exopolysaccharide fraction of P. cruentum increased with increasing the glyoxylate level, while the mild level of glyoxylate treatment (0.25 in mM C2HNaO3 center dot H2O) stimulated the monosaccharide production of Prasinococcus cells.