Analysis of the local gas hold-up, under constant retrofitted power input in a multiphasic mycelial fermentation model

Abstract

Multiphase fermentations are still poorly understood since much of the available information focused on global rather than local data and the most used parameter to control the dispersion of gas in the stirred tank is the agitation rate. However, the energy dissipated in the stirred tank is influenced by the properties of the broths, such as viscosity. Therefore, the objective of this work was to use a retrofitted power input strategy in order to maintain constant the total power input per unit volume (Pg/V), studying the local gas hold-up (φ) and interfacial area (a) values in three regions in a pilot-scale stirred tank at different values of Trichoderma harzianum mycelial biomass concentration, airflow rate and constant Pg/V. We found that the constant Pg/V regime was an effective strategy that allows to discern the effects of different parameters in the local values of gas hold-up and interfacial area. Under constant retrofitted total gassed power input, the biomass concentration showed no influence on the local values of interfacial area and gas hold-up. Depending on the position of the probe, φ and a varied up to 60.6% and 63.8%, respectively. The highest Pg/V and airflow rate conditions determined the highest values in φ and a, but not in the same proportion in the three zones tested.