The proposed research will characterize gas-liquid mass transfer in mycelial fermentations and optimize reactor performance utilizing a model mycelial fermentation. A new chemical technique for the measurement of mass transfer coefficient will be utilized to characterize the gas-liquid mass transfer. An unsteady-state chemical technique utilizing an instantaneous reaction between ozone and indigo dye has been developed and is well- suited for modelling mycelial fermentations because of low ionic strengths and ease of data collection and analysis. The biological phase will be modeled with cellulose fibers, which in suspension behave similarly to mycelular growths. This model system will be used to characterize the gas- liquid mass transfer as a function of stirrer speed, gassing rate and solids concentration in a variety of agitated reactors. The replacement of turbine agitators with hydrofoil impellers has significant industrial interest, primarily due to energy savings and lower shear exposure for the mycelial broth. The reaction of glucose to gluconic acid by Aspergillus niger will be carried out in the most promising reactor configurations to determine if the improvements in gas-liquid mass transfer translate into improvements in the mycelular reactor performance.
