Physical characterization of exopolysaccharide produced by Lactobacillus plantarum KF5 isolated from Tibet Kefir

An exopolysaccharide producing strain KF5 was isolated from Tibet Kefir grains and identified as Lactobacillus plantarum with morphology, physiological, biochemical and 16S rDNA tests. KF5 exopolysaccharides (EPS) was revealed to have the carboxyl, hydroxyl, and amide groups by FT-IR spectroscopy. The GC analysis of KF5 EPS revealed that it was composed of mannose, glucose and galactose in an approximate ratio of 1:4.99:6.90 in nature. The micro-structure of KF5 EPS under different concentration was observed with atomic force microscopy. The SEM images of KF5 EPS showed smooth surfaces, exhibiting compact structure that showed plasticized films characteristics. Its melting point is 86.35 °C, which is lower than commercial gum. A degradation temperature (Td) of 279.59 °C was determined from the TG curve. It suggested a bit higher degradation temperature than locust gum, but lower than xanthan gum. Physical characteristics of KF5 EPS were different from other commercially available gums, which impart KF5 EPS potential applications in food industry.