UTILIZATION OF EXPERIMENTAL-DESIGNS FOR OPTIMIZATION OF RHIZOPUS-ARRHIZUS CULTURE

Biomass production by the fungus Rhizopus arrhizus and sucrose consumption were optimized in batch fermentation using experimental designs. Optimal culture conditions were: sucrose, 130 g litre-1; yeast extract, 15 g litre-1; NH4NO3, 3.7 g litre-1; C/N ratio, 20/1; temperature, 30-degrees-C; inoculum size, 1500-5000 spores litre-1; 5 to 10-day cultures. Regulation of pH was found to be unnecessary. After 10-day culture, the yield of biomass was 18.6 g litre-1, sucrose was entirely consumed and the total organic carbon decreased by 79%. The use of experimental designs allowed the authors to determine the optimal values for five parameters (sucrose and yeast extract concentrations, temperature, inoculum size and the C/N ratio), and to test the effects of seven different mineral ions (PO4(2-), Mg2+, Ca2+, Mn2+, Fe2+, Zn2+ and K+) with only 36 experiments, which saved time as compared with the classical method.