Production of Curdlan by some Bacteria Isolated from Egyptian Soils

Thirty two curdlan producing bacterial isolates were obtained from eight different Governorates in Arab Republic of Egypt. Four isolates namely K10, K17, K20 and K74 were selected as highly efficient of curdlan production. The effect of some nutritional and environmental factors on curdlan production by those selected isolates was investigated using shake flask as a batch culture. The optimum concentration of carbon and nitrogen sources was also studied. Incubation period and shaking rate at different levels were tested for the optimization of fermentation process to yield the highest curdlan amount. The bacterial isolate K10 was identified as Rhizobium radiobacter and gave the maximum yield of curdlan being 22g/L on the modified (YP) fermentation medium containing (g/L): 100 g sucrose, 9.5 g yeast extract (as a carbon and nitrogen sources, respectively), 0.5 g CaCo3, 1 g K2HPO4, 0.6 g MgSO4 with initial pH level 7 after 72 h of fermentation period at 30 oC on a rotary shaker at the shaking rate of 100 rpm with 50 mL of modified fermentation medium.