Influence of Low-polyphosphates on Curdlan Production by Alcaligenes faecalis var. myxogene

Abstract:

A large amount of ATP is consumed to regenerate precursor UDPG for curdlan biosynthesis in Alcaligenes faecalis var. myxogens. In this study, low-polyphosphates with high-energy phosphate bond of Na4P2O7 (2P), Na5P3O10 (3P) and (NaPO3)6 (6P) were employed as high-energy phosphate bond and phosphate donor to substitute KH2PO4-K2HPO4 (1P) in medium for curdlan production by Alcaligenes faecalis var. myxogene. Results showed that curdlan production was enhanced 23% and 134% than that of control respectively, which reached 15.1 g/L and 30.0 g/L, when one-fold and two-fold high concentration of phosphate from 3P and 6P were added in the medium. Meanwhile, byproducts of acetic acid were decreased 87.5% and 77.7% respectively. Formic acid was also decreased 75.7% when two-fold 6P were added in the medium. However, when CaCO3 was removed in the medium, pH and biomass were decreased remarkably, therefore, little or no curdlan was produced when these low-polyphosphates were added in medium. When 3P and 6P were separately mixed with 1P at the amount of one-fold and two-fold high concentration of phosphate for fermentation, there was no change on curdlan production. Nevertheless, if 1P was used as buffer substance and without CaCO3 in the medium, curdlan production could be enhanced to 60.4% and 49.4% than that of the control when 6P was added at the amount of one-fold and two-fold high concentration, reached to 18.4 g/L and 16.9 g/L.

Key words:Low-polyphosphate, High energy phosphate bond, Curdlan, Residual phosphate, Organic acid