Formulation and Cost-Effective Drying of Probiotic Yeast

Saccharomyces boulardii yeast is considered as a probiotic according to the World Health Organization (WHO). Like any other probiotic, Saccharomyces boulardii is available as a freeze-dried formulation. Although freeze drying is the most preferred method of preserving the microorganisms, the process is very expensive. The cost of capsules containing freeze-dried probiotic yeast is certainly out of reach of the underprivileged population of the world. Hence, the present work focuses on developing a new formulation and cost-effective drying process for probiotic yeast. Freeze drying was compared with fluidized bed drying (FBD) and heat pump-assisted fluidized bed drying (HP-FBD) techniques for drying of Saccharomyces boulardii formulation. The process involves addition of lactose and microcrystalline cellulose to the biomass obtained by centrifugation and then making the dough. This blend is then extruded and spheronized to form granules. Heat pump fluidized bed drying of the formulation resulted in higher activity retention compared to atmospheric fluid bed drying. This encouraged further experimentation using HP-FBD to study the effect of various operating variables such as air temperature, air humidity, and velocity on the drying kinetics and the deactivation kinetics. It was observed that the temperature and humidity play a major role in the deactivation and drying, whereas the change in air velocity has comparatively less effect on both parameters. The effective diffusivity and the deactivation rate constants were correlated to the temperature using an Arrhenius-type equation.