Production of Curdlan by Agrobacterium sp. DH-2 Using Sugarcane Molasses-Based Medium

Curdlan is an extracellular polysaccharide produced by microorganisms with various applications in the food and biomedical fields. In order to reduce the cost of producing curdlan, the production of curdlan by Agrobacterium sp. DH-2 using sugarcane molasses as a carbon source was investigated. Pretreatment of sugarcane molasses reduced the metal content and resulted in an increase in curdlan production compared to untreated molasses. The composition of the medium based on pretreated molasses was optimized for curdlan production. The addition of (NH4)2HPO4 was found to be effective in increasing curdlan production, while the addition of corn steep liquor, CaCO3, KH2PO4, and MgSO4 did not have a significant effect. An orthogonal design was used to optimize the amount of (NH4)2HPO4 added and the sugar concentration of pretreated molasses. Maximum curdlan production of 13.0 g/L was obtained in the optimized medium, which contained a sugar concentration of 60 g/L of pretreated molasses and 1.0 g/L of (NH4)2HPO4. The curdlan produced in the molasses-based medium had an average molecular weight of 0.49 × 106 Da. FT-IR spectra and TGA thermal analysis showed that there were no significant differences between the curdlan produced and commercial curdlan. These results suggested that pretreated sugarcane molasses supplemented with (NH4)2HPO4 as a nitrogen resource could be used for economical production of curdlan.