In this study, the effect of glycerol kinase overexpression in Synechocystis sp. PCC 6803 on lipid content was investigated. The glycerol kinase overexpressing Synechocystis cells (OE) had a higher lipid content than the wild type. The OE treated with phenol up to 1 mM showed a slight increase in the cell biomass whereas the total lipid production increased considerably (0.39 +/- 0.012 g/L) as compared to that of the wild type (0.26 +/- 0.01 g/L). The supplementation of 12 g/L glycerol to BG11 medium increased the lipid content of phenol treated OE from 22 to 35% with the increase of lipid production from 0.39 +/- 0.012 to 0.69 +/- 0.035 g/L. The RT-PCR analysis revealed that the expression of glpK was upregulated from 1.3 to 2.4 and from 1.89 to 3.64-fold after phenol treatment and glycerol supplementation respectively.