A large amount of adenosine triphosphate with high energy phosphate bonds is required for uridine triphosphate regeneration during curdlan biosynthesis by Agrobacterium sp. ATCC 31749. To supply high energy for curdlan synthesis, three low-polyphosphates ($Na_4P_2O_7$, $Na_5P_3O_{10}$, and $(NaPO_3)_6$) with higher energy phosphate bonds were employed to substitute for $KH_2PO_4-K_2HPO_4$ in fermentation medium. Two genes encoding the polyphosphate metabolizing enzymes, polyphosphate kinase and exopolyphosphatase, were amplified and showed 95% homology to those in Agrobacterium sp. C58 by sequence analysis. The curdlan yields were enhanced by 23 and 134% when phosphate concentrations 0.024 mol/L of $Na_5P_3O_{10}$ and 0.048 mol/L of $(NaPO_3)_6$ respectively, were added in the medium. The maximum curdlan yield of $30{pm}1.02$ g/L was obtained with the addition of 0.048 mol/L of $(NaPO_3)_6$ with 5 g/L $CaCO_3$ in the medium. When $CaCO_3$ was removed from the culture and the three low-polyphosphates were added, the pH and biomass yield dropped remarkably and little or no curdlan was produced. The culture containing 0.048 mol/L of $(NaPO_3)_6$ was mixed with $KH_2PO_4-K_2HPO_4$ and $CaCO_3$ in the medium, but showed no effect on curdlan production. However, curdlan yield was improved by 49 ~ 60% when $CaCO_3$ was removed from the medium and $KH_2PO_4-K_2HPO_4$ acted as a buffer. It appears that the positive effect of $(NaPO_3)_6$ on curdlan production required the buffering capacity of $CaCO_3$ and the absence of $KH_2PO_4-K_2HPO_4$ competing as a phosphate supplier.