Modeling pH gradients in industrial-scale lactic acid bacteria fermentation using flow-informed compartment models

This study presents a numerical model of an industrial-scale lactic acid bacteria fermentation process that incorporates reactor hydrodynamics and chemical/biochemical reactions to resolve the impact of transport limitations on the industrial process. The model employs a three-dimensional CFD-based compartmentalization method that uses unsupervised clustering to build a simplified representation of the reactor volume while preserving essential mixing characteristics. This approach enabled fast simulations of the mixing dynamics over extended periods and facilitated the integration with reaction kinetics. The numerical model successfully simulated both batch and continuous processes, capturing the magnitude of gradients and quantifying their impact on process dynamics. During batch operation, pH gradients peaked during exponential growth but did not significantly affect biological growth, although more sensitive strains could be impacted. Continuous operation resulted in gradients in pH and substrate concentration, affecting the process dynamics and productivity. The compartment model's adaptability to different reactor designs and scales makes it a valuable tool for industrial applications. Here, the model can be used to develop effective scale-up strategies and ensure consistent product quality across the various production scales.