Cyanobacteria respond to salt stress with the accumulation of compatible solutes. For this purpose, the model organism Synechocystis sp. PCC 6803 synthesizes glucosylglycerol (GG) and sucrose to cope with increases of external salinity. Less is known about the degradation of these compounds when salinity decreases. Within this dissertation, the GG-degrading enzyme Glucosylglycerol hydrolase A (GghA) was identified and GghA as well as the sucrose-degrading invertase were biochemically characterized. The inactivation of invertase combined with other genetic manipulations illustrates the potential of biotechnological sucrose production with Synechocystis. Additionally, the recently identified sRNA IsaR1 was shown to affect GG synthesis.