Development of a Jacketed Breathable Shake Flask With Process Monitoring, Control, and Bioreactor-Like Performance.

Shake flasks are widely used in early-stage bioprocess development but are limited by their inability to monitor and control key gas-transfer variables such as dissolved oxygen and carbon dioxide. In this study, we present a jacketed breathable flask system that enables real-time gas control in a standard shaking environment. Across multiple media formulations and fill volumes, this system consistently deferred oxygen limitation and enhanced culture performance, achieving > 150% higher biomass and 140% greater recombinant protein yield compared to conventional flasks. Time-resolved analysis of pH and extracellular metabolites revealed reduced accumulation of oxygen-sensitive byproducts, including acetate, pyruvate, and succinate, indicating a shift toward more efficient respiratory metabolism. The jacketed breathable flask also enabled continuous monitoring and regulation of critical process parameters, creating a bioreactor-like environment in a high-throughput, low-cost format. The biomass accumulation and specific growth rate observed in jacketed breathable flask are comparable to those reported for Escherichia coli cultures in stirred tank bioreactor application notes for Eppendorf BioBLU 3f. These findings establish breathable flasks as a scalable and accessible platform with bioreactor-like performance for upstream process optimization and accelerate biomanufacturing development at the lab scale.