Isolation and identification of an exopolysaccharide-producing lactic acid Bacterium strain from Chinese Paocai and biosorption of Pb(II) by its exopolysaccharide

Lactic acid bacteria isolated from various traditional Chinese fermented foods were screened for the production of exopolysaccharides (EPS). The strain 70810 from Chinese Paocai, which was identified as Lactobacillus plantarum (HQ259238) by morphological, physiological, biochemical, and 16S rDNA tests, was selected due to its highest EPS production capability (0.859 g/L) for further study. Biosorption of Pb(II) from aqueous solutions by 70810 EPS was studied with parameters of initial pH, contact time, initial Pb(II) concentration, adsorbent dosage, and temperature, respectively. Maximum adsorption of Pb(II) was observed at pH 5, 30 °C, and 6 h, respectively. The adsorption capacity was also found to be dependent upon initial Pb(II) concentration and adsorbent dosage. Surface adsorption of the metal at surface of 70810 EPS was confirmed through scanning electron microscopy. Fourier transform infrared spectroscopy spectra analysis indicated that some functional groups (for example, -OH, COO-, C = O, and -NH) of 70810 EPS were involved in Pb(II) biosorption process. PRACTICAL APPLICATION: Lactobacillus plantarum 70810 can be used as a starter culture for the production of some fermented foods (for example, yoghurt or fermented soybean milk) and the production of EPS that can meet consumer's demand for products with low levels of additives. The EPS may be used as a potential biosorbent for the removal of heavy metal from environment and these fermented foods maybe have the potential effect to excrete lead from human body.