Cyclic β-(1, 2)-glucan production by Rhizobium meliloti MTCC 3402

• Response surface methodology was used for process optimization of cyclic β-(1, 2)-glucan.
• Glucan yield was enhanced upto 5.13 g/L, which is the first report for glucan production by CCD.
• Umbelliferone was encapsulated by glucan and characterized.
• Dye binding was tested with aniline blue and congo red.

Cyclic β-(1, 2)-glucan is a water soluble biopolymer linked by β-(1, 2)-glucose residues. Its production by Rhizobium meliloti is enhanced by adopting a two step response surface methodology. Initial screening design indicates that the amount of mannitol, glutamic acid and sodium chloride are significant than the medium pH and temperature. Central composite design shows that sodium chloride contributes significantly to the yield and its interaction with glutamic acid is strong. A non linear regression model is developed from the experimental data and using the conditions predicted by the model it is possible to experimentally achieve a glucan yield of 5.13 g/L. Glucan encapsulates umbelliferone (a hydrophobic drug) efficiently, and appears as strands with particle size of 2 nm. It binds to aniline blue and congo red dyes which are used in tissue imaging and increases the maximum absorbance values. This indicates that its biocompatibility nature could be exploited in medical applications.