Enhanced Curdlan Production in Agrobacterium sp. ATCC 31749 by Addition of Low-polyphosphates

A large amount of adenosine triphosphate is required in curdlan biosynthesis by Agrobacterium sp. ATCC 31749 for uridine triphosphate regeneration. Three low-polyphosphates (Na4P2O7, Na5P3O10 and (NaPO3)6) with high energy phosphate bond were employed in the present work to substitute for KH2PO4-K2HPO4 in medium for curdlan production. The curdlan yield was enhanced by 23% and 134% when one fold phosphate molar concentration than control from Na5P3O10 and two-folds from (NaPO3)6 were added in the medium. The maximum curdlan yield of 30±1.02 g/L was obtained with addition of two-folds from (NaPO3)6 with CaCO3 in the medium. When CaCO3 was removed in the culture with the three low-polyphosphates, the pH and biomass production dropped remarkably, with little or no curdlan production. In the experiment with two-folds of (NaPO3)6 mixed with KH2PO4-K2HPO4 and CaCO3, curdlan production was not affected. However, if CaCO3 was not removed in medium, curdlan yield was improved by 49~60%. This indicated that the enhancement effect of (NaPO3)6 for curdlan production required the buffer substance such as CaCO3.