Optimization of the growth parameters of Aspergillus foetidus

The batch production of gluconic acid in the presence of glucose, sucrose a nd molasses was investigated using free mycelia of Aspergillus foetidus NRR L 337 in shake flasks. Eight growth parameters were chosen as independent v ariables. The temperature, pH, substrate type and initial concentrations, i noculum percentage and shake rate directly affected the specific microorgan ism growth and gluconic acid production rates. The optimum temperature and initial pH values were found to be 33 degrees C and five to six, respective ly. The maximum specific growth and gluconic acid production rates were est ablished as 57 g/dm(3) of glucose, 75 g/dm(3) of sucrose and 150 g/dm(3) of molasses. The optimum values of the shake rate, inoculum percentage and in itial ammonium nitrate concentration were determined as 100 1/min, 0.5% and 1.5 g/dm(3), respectively. The maximum gluconic acid concentrations corres ponding to these initial substrate concentrations were observed to be 8.3 g /dm(3) 17.4 g/dm(3) and 37.0 g/dm(3), respectively. The optimum specific mi crobial growth and gluconic acid production rates were found as 0.0145 1/h and 0.0375 g/g x h, respectively, for the fermentation conditions of S-Go= 57 g/dm(3), T = 28 degrees C, initial pH = 6.5, N = 84 1/min, A = 0.5 g/dm( 3) and I= 0.5%.