Optimization of succinoglycan hydrocolloid production by Agrobacterium radiobacter grown in sugar beet molasses and investigation of its physicochemical characteristics

This study examines and compares the structural and rheological properties of the produced succinoglycan exopolysaccharide (EPS) as functions of substrate, time, total soluble solid and agitation rate of fermentation. Fourier transform infrared (FTIR) spectroscopy, proton nuclear magnetic resonance (1H NMR) spectroscopy, thin-layer chromatography (TLC), differential scanning calorimetry (DSC), thermo gravimetric analysis (TGA), controlled stress rheometer and U-tube viscometry were employed. It was revealed that the biogum composed of glucose and galactose units, carrying pyruvate, succinate and acetate groups in the presence of succinoglycan. The EPS produced from sucrose (EPS-S) showed a lower degree of succinylation and acetylation compare to the EPS produced from molasses (EPS-M). The melting temperature (Tm) of samples was clearly different and Tm for EPS-M was significantly higher than EPS-S. The activation energy (Ea) of EPS-S (258 kJ/mol) was also higher than EPS-M (121 kJ/mol). According to the TGA thermograms, EPS-M was more thermally stable than the EPS-S. Moreover, the quantity of EPS-M was 2 times higher than that of EPS-S. The biogums behaved non-Newtonian, shear-thinning, and the viscosity of EPS-M was higher than EPS-S at all tested conditions.