Rheological properties of a novel high viscosity polysaccharide, A49-pol, produced by Bacillus polymyxa

Abstract

An exopolysaccharide, designated as A49-Pol, was produced from Bacillus polymyxa KCTC 8648P in nitrogen sufficient conditions. The viscosity of the culture broth increased up to 2x 104 cP in 38 hours of culture and then decreased to 1.5 x 104 cP at 48 hours. The 1.0% (w/v) solution of purified A49-Pol represented pseudoplasticity with a viscosity of 2.7 x 104 cP which was two times higher than xanthan at the same concentration. The viscosity of the A49-Pol solution was also greatly affected by its concentration in comparison with the xanthan solution. The viscosity of 1.0% A49-Pol solution was 930-fold higher than its 0.2% solution, whereas the corresponding viscosities of xanthan solution experienced only 17-fold difference. The viscosity was observed to be maximum at pH 7.0 in both A49-Pol and xanthan solutions, and gradually decreased as the pHs of the polysaccharide solutions went to acidic or alkaline regions. The viscosity of A49-Pol solution was very sensitive to temperature compared to xanthan and decreased with increasing temperature. The viscosity of 0.6% solution of A49-Pol was 8,100 cP at 10°C and 55 cP at 50°C. The viscosity was also affected by the presence of surfactants such as Span 20 and Triton X-100; with 0.5% Triton X- 100 (v/v), the viscosity of A49-Pol solution increased by 50%.