Development of a High-Cell-Density Production Process for a Biotherapeutic Yeast, Saccharomyces cerevisiae var. boulardii, for Use as a Human Probiotic

Saccharomyces cerevisiae var. boulardii is a probiotic yeast widely recognized for its ability to enhance gut health and modulate a host’s microbiome. However, there are limited data on its large-scale cultivation in stirred tank bioreactors and subsequent downstream processing into a functional probiotic product. Different recipe formulations were evaluated and the recipe with the highest biomass yield and lowest process time was selected. Once the optimised batch was validated in the replicate batches, the statistical analysis indicated a high level of reproducibility, with low variability across key performance indicators such as biomass concentration (unit), CFU production (CFU.mL−1), and substrate utilization efficiency (g.g−1). The mean growth age in the bioreactor was 25.33 ± 1.16 h, with a CV of 4.56%, indicating minimal deviation between batches. Similarly, the final viable concentration exhibited a mean of 1.46 × 108 CFU.mL−1 with a CV of 11.68%, remaining within an acceptable range for biological processes, while the final biomass concentration had the lowest variability (CV of 3.94%) and a 95% CI of 12.134–13.266 g.L−1, highlighting the accuracy and consistency of the process. Productivity indicators, including cell productivity (growth time—biomass) and YPP (biomass), maintained low CV values (3.933% and 3.389%, respectively), reinforcing process efficiency and stability. The overlapping 95% confidence intervals across batches further confirmed that no statistically significant deviations existed, ensuring minimal batch-to-batch variability, and validating the scalability and robustness of the fermentation process. These findings provide strong evidence for the feasibility of large-scale probiotic yeast production that meets industrial production standards. The final freeze-dried product retained an 81% viability post-exposure to simulated gastrointestinal conditions, meeting WHO probiotic viability standards. These findings establish a scalable, optimized process for probiotic yeast production, with potential applications in biopharmaceutical manufacturing and functional food development, as confirmed by the techno-economic evaluations performed using SuperPro Designer®.