Optimization of polyphosphate production by Bacillus megaterium strain G11

Polyphosphates، also called volutin granules، are linear polymers from orthophosphates linked by energy-rich phosphoanhydride bands that have been seen in bacteria، yeasts، fungi، plants and animals. These polymers are completely safe and nontoxic، and have numerous applications in food and drug industries. Due to the great importance and wide range of the utilization of these polymers in various industries، several factors such as various carbon sources، carbon source concentration and phosphorus concentration were studied and optimized. In order to increase polyphosphate production in Bacillus megaterium strain G11. The optimization process was carried out with determination of the amount of polyphosphate accumulated in cell and phosphorus removed from the medium. One-way ANOVA and Tukey tests were used in order to determine whether there was a significant difference between data obtained in this research. Growth of B. megaterium in the presence of sucrose (OD=3. 026) was better than glucose (OD=2. 616) whereas polyphosphate production and phosphorus removal from medium were higher in the presence of glucose (0. 033 g g-1 dry cell weight and 1. 61 g l-1، respectively). On the other hand، polyphosphate production and phosphorus removal from medium coordinately were decreased with increasing glucose concentration. Furthermore، in studying the effects of phosphorus، we faced two phases of rising and falling. Actually، the increase of phosphorus concentration (0. 25-1 g l-1) in medium caused an increase in polyphosphate production and phosphorus removal from medium whereas both of them were decreased with a more increase in amount of phosphorus (1-4 g l-1). One-way ANOVA and Tukey tests showed that there was a significant difference (P<0. 01) between data obtained at each optimization step and the best glucose and di potassium phosphate concentrations for polyphosphate production were 5 and 0. 5 g l-1 respectively. Discussion and According to data obtained in this study، the best carbon source for cell growth and proliferation was not the best source for polyphosphate production and phosphorus removal from medium. Since there was no statically significant difference between 1، 2، and 0. 5 g l-1 concentrations for polyphosphate production، therefore، for industrialization and economization in the level of phosphorus consumption، 0. 5 g l-1 was the best phosphorus concentration.