Optimization of Polyhydroxybutyrate (PHB) Microbial Culture by Azotobacter Beijerinckii DSMZ 1041

In the current work، azotobacter beijerinckii microorganism provided from Germany microbial bank is used. According to previous reports and the experiments conducted، it is inferred that the microorganism is able to accumulate poly (hydroxyl butyrate) granules in media containing high amounts of carbon sources and limited amounts of nitrogen sources. The effect of the different concentrations of carbon and nitrogen sources (glucose and ammonium chloride) on the cell dry weight (CDW)، the amount of glucose used by the microorganism، and the amount of the produced biopolymer is investigated. Ammonium chloride with concentrations of 0. 5 and 2 g. l-1 and glucose with concentrations of 30، 40، 50، and 60 g. l-1 were used as nitrogen and carbon sources respectively. The most of biopolymer was produced by glucose with a concentration of 60 g. l-1 and ammonium chloride with a concentration of 0. 5 g. l-1. The highest biomass efficiency (Yx/s) was obtained by glucose with a concentration of 30 g. l-1 and ammonium chloride with a concentration of 2 g. l-1 and the highest production efficiency (Yp/s) was gained using a concentration of 30 g. l-1 of glucose and a concentration of 0. 5 g. l-1 of ammonium chloride. The maximum productivity (Qp) was acquired in the media containing glucose with a concentration of 50 g. l-1 and ammonium chloride with a concentration of 1 g. l-1. The amount of biopolymer obtained through laboratory method was compared with response surface statistical method and the precision of the experiments conducted were examined. After extraction، Fourier-transform infrared (FT-IR) spectra and nuclear magnetic resonance (NMR) spectroscopy both verified the formation of biopolymer.