The average molecular weight of native dextran produced by L. mesenteroides NRRL B512F had been investigated and the values for average molecular weight were determined in the range of 9 x 106 to 500 x 106 Da [39-42]. Evidence of the presence of long branches had also been adduced from the studies on the molecular weight and viscosity during the biosynthesis of dextran [40]. The relationships between the molecular weight and the intrinsic viscosity [η] had been investigated over a wide range of molecular weight [43-45]. Hibbert et al. [46] have also detected differences in physical and chemical properties of dextran produced by L. mesenteroides.