Modeling the influence of the microbial loading level of fluidized bed granules on physical–mechanical and microbiological tablet properties

In order to be able to administer efficient probiotic formulations, it is necessary to process the respective microorganisms gently into suitable dosage forms such as tablets maintaining their viability. In previous studies, the process chain consisting of fluidized bed granulation for life-sustaining drying of Saccharomyces cerevisiae as well as subsequent processing into tablets was investigated. Granules based on dicalcium phosphate (DCP), lactose (LAC) and microcrystalline cellulose (MCC) as carrier materials were produced and tableted, and physical–mechanical as well as microbiological tablet properties were evaluated. This revealed a carrier material-specific influence of granulation on both physical–mechanical and microbiological tablet characteristics. But the extent, to which this depends on the added cell mass, has not yet been investigated. This is addressed in the present study by examining the influence of the loading of the carriers with different amounts of yeast cells and the measurement of the resulting mechanical properties of the tablets and the survival of the microorganisms. Thereby, material-specific effects of loading on compressibility, compactibility and tabletability, but also on the survival of the yeast cells were found and related to the specific deformation mechanisms. Existing models for describing the physical–mechanical relationships are used, adapted and combined, which enables excellent correlations. In addition, empirical models are developed to describe the survival of the microorganisms during tableting the differently loaded granules.