The production of a cold-induced extracellular biopolymer by Pseudomonas fluorescens BM07 under various growth conditions and its role in heavy metals absorption

The psychrotrophic bacterium Pseudomonas fluorescens BM07 was induced to excrete an extracellular biopolymer when cells were grown aerobically at 10 °C and its secretion was inhibited at 30 °C. The biopolymer was easily torn apart from the cells by using a shear force under centrifugation (8700 × g, 30 min) and collected as a well-separated mucoid layer in centrifuge tube. The production of the biopolymer was affected by factors such as the types of carbon and nitrogen sources, temperature, and pH. The best production of 2.5 g/l was obtained when the cells were grown on M1 medium containing 70 mM sucrose and 0.2% (w/v) Casamino Acids. In Kings B enriched medium a maximum biopolymer production of up to 3.4 g/l and growth rate of 2.1 g/l, were achieved using 1:1 ratio of C/N. Addition of NaCl and ethanol to the medium led to a decrease in biopolymer production and growth rate of BM07 strain. FT-IR spectroscopy demonstrated the presence of carboxyl, amine, hydroxyl and methoxyl functional groups in the biopolymer. BM07 biopolymer showed high ion binding capacity with particular preference to uptake cadmium and mercury (～45 and 70%, respectively). The percentage removal of cobalt, zinc, nickel and copper cations were between 20 and 30%. Overall ion uptake by BM07 biopolymer showed a definite preference for larger over smaller cations (Hg > Cd > Ni > Zn > Cu > Co).