Morphology-driven downscaling of Streptomyces lividans to micro-cultivation

Actinobacteria are prolific producers of secondary metabolites and industrially relevant enzymes. Growth of these mycelial microorganisms in small culture volumes is challenging due to their complex morphology. Since morphology and production are typically linked, scaling down culture volumes requires better control over morphogenesis. In larger scale platforms, ranging from shake flasks to bioreactors, the hydrodynamics play an important role in shaping the morphology and determining product formation. Here, we report on the effects of agitation on the mycelial morphology of Streptomyces lividans grown in microtitre plates (MTP). Our work shows that at the proper agitation rates cultures can be scaled down to volumes as small as 100 l while maintaining the same morphology as seen in larger scale platforms. Using image analysis we compared the morphologies of the cultures; when agitated at 1400 rpm the mycelial morphology in microcultures approached that obtained in shake flasks, while product formation was also maintained. Our study shows that the morphology of actinobacteria in microcultures can be controlled in a similar manner as in larger scale cultures by carefully controlling the mixing rate. This could facilitate high-throughput screening and upscaling.