João Alegre Queiroz:
Betreuer: Cornelia Bähr
Fed-batch technique for shaken flask system with retarded feeding of nutrient
Fed-batch technique is broadly applied in industrial bioprocesses. Nonetheless,screenings for microbial production strains are performed in batch mode. Since physiological conditions are completely different between these two operation modes, results might lead to a wrong strain selection. A state-of-the-art approach to fed-batch release in shaken flasks is based on diffusion. Applied technology relies on a concentrated nutrient solution immersed and separated from the medium by a regenerated cellulose membrane. The driving force for release is the concentration gradient. Consequently, nutrient accumulates at the beginning of the culture, when the concentration gradient is maximal and consumption rate is minimal. This study investigates the possibility of applying an additional diffusion barrier for delaying the release. Two types of materials acting as barrier were tested: cigarette filter and felt. Refractometer experiments showed that glucose release started immediately after immersion of the diffusion tip in the medium when no additional barrier was used. Lower release rates were achieved as glucose solution concentration in the reservoir decreased, both with and without additional barrier. The system was also evaluated with a culture of Corynebacterium glutamicum DM1730. On-line monitoring was carried out through measurements of the oxygen transfer rate (OTR) with a respiratory activity monitoring system (RAMOS). A constant feeding of glucose to the system was achieved and accumulation of glucose was lower using an additional diffusion barrier.
Fed-batch, Shaken flasks, Respiractory Activity Monitoring System, Diffusion barrier, Corynebacterium glutamicum DM 1730, regenerated cellulose