Growth kinetics of Rhizopus formosa MUCL 28422 on raw cassava flour in solid state fermentation

Solid state fermentations were carried out using a strain of Rhizopus formo sa MUCL 28422 for its ability to grow on raw cassava. Optimal substrate com position, as estimated by surface response design experiments, was 10% each of cassava bagasse and soybean flour and 80% cassava flour. Optimal fermen tation conditions were: temperature 32 degrees C, initial pH and moisture o f the substrate 6.5 and 64%, respectively, and inoculum size 10(6)-spores g (-1) dry matter. These conditions were employed for studying the kinetics o f the biotransformation of cassava flour using Oxygen Uptake Rate (OUR) and Carbon dioxide Evolution Rate (CER) during the process. The respiratory qu otient was similar to 1, corresponding to an aerobic process in the first 2 4-26 h. Sporulation started after 26 h of fermentation when the respiratory quotient showed a trend to increase up to similar to 6, Biomass estimation , based on oxygen consumption (Y-x/o) gave a value of 0.531 g biomass g(-1) O-2 consumed and the maintenance coefficient (m) was of the order of 0.068 g O-2 consumed g(-1) biomass h(-1). The corresponding value for the specif ic growth rate (mu) was 0.16 h(-1). (C) 1999 Society of Chemical Industry.