The impact of oxygen transfer and rheological characteristics on bacterial protease production in pilot-scale bioreactors

Abstract

Biotechnology research prioritizes microbial fermentation and its scale-up for industrial enzyme production. Though protease production studies using shake flasks are widespread, there are still few insights into scale-up that take mass transfer and hydrodynamics into consideration. This study reports the successful scale-up of extracellular alkaline protease production by Bacillus sp. S2 MTCC 13117 from shake flasks to a 300 L fermenter. pH, dissolved oxygen (DO) and glucose consumption were the important fermentation parameters that were tracked at different scales. The volumetric oxygen transfer coefficient (kLa), oxygen uptake rate (OUR), oxygen transfer rate (OTR) were some of the essential oxygen dynamics that were evaluated. Reproducibility was established by the process's universal yield coefficients on different scales. Due to higher oxygen transfer, bioreactors made it possible to achieve quicker peak production, 36 hours in 19 L and 24 hours in 300 L than shake flasks whose peak was at 44 hours. Higher protease production was achieved by optimized broth rheology, gas hold-up, impeller speed and aeration, which promised excellent applications in the biomedical field such as scaffold processing, tissue decellularization and debridement of wounds. The future application of bacterial proteases in tissue engineering and regenerative medicine is supported by this scalable method.