Fig. 3.

Top: overview of the experimental setups used to characterize extracellular dextran production depending on the presence of sucrose in the pre-cultivation and maltose during dextran formation. Cells were cultivated in medium containing solely sucrose (suc), glucose + fructose + sucrose (glc + fru + suc), and glucose + fructose (glc + fru) for 18 h; harvested; and re-dissolved in 0.1 M citrate-phosphate buffer pH 4.5. This buffer was supplemented with either 0.1 M sucrose (suc) or 0.1 M sucrose + 0.1 M maltose (suc + mal). After 3 h of incubation, the cells were removed by centrifugation and sterile filtration. The cell-free supernatants were incubated for 24 h, followed by dextran isolation, and HPLC-RI and HPAEC-PAD measurements. Bottom: dextran yields for the described experiment. The bars indicate the produced dextran amounts in g/L, which were determined either gravimetrically (isolation) or via the calculated transglycosylation activity and the resulting dextran amounts after 24 h (calculation). Data are expressed with mean ± SD of three biological replicates