Pellet-specific behavior in filamentous cultivations cannot be resolved in pilot-scale bioreactors because measurements are population-averaged and pellet populations exhibit stochastic heterogeneity. This work therefore aimed to establish a micro-scale cultivation platform for pellet-resolved investigations of filamentous microorganisms. For this purpose, a previously developed micro bubble column reactor (MBCR) was adapted for multi-day cultivation of the filamentous actinomycete Actinomadura namibiensis, the sole natural producer of the antiviral lantibiotic labyrinthopeptin A1. Reactor operation was characterized at gas flow rates of 4.7, 10.7, and 18.0 mL/min by determining volumetric mass transfer coefficients and performing online image analysis of bubble and pellet size distributions. A gas flow rate of 10.7.0 mL/min provided the best compromise between oxygen supply, hydrodynamic stability, and reproducible pellet morphology. During cultivation, dissolved oxygen decreased by only 2-3 %, indicating sufficient oxygen availability in the MBCR. The platform enabled determination of substrate consumption and product formation metrics normalized to both projected pellet area and inoculated pellet number throughout cultivation. Overall, the presented extension of the MBCR platform broadens its application to pellet-forming actinomycetes and demonstrates the potential of pellet-resolved characterization during filamentous cultivations, providing a basis for future mechanistic investigations of pellet-scale bioprocess behavior.
Z. J. Kozanecka, E. Lädke, L. Pastwa, P. Gronotte, M. Neumann-Schaal, J. Liu, M. Böl, R. Krull
A new application of a micro bubble column system for analyzing filamentous cultures at pellet level
Biochemical Engineering Journal, 235, 110316, (2026) [Link]