Effect of hydraulic retention time on the modelling and optimization of joint 1,3 PDO and BuA production from 2G glycerol in a chemostat process

This study investigated the possibility to perform statistical optimization of an enriched mixed microbial consortium, MMC, fed in continuous with a highly inhibiting 2G glycerol, for the joint production of 1,3 propanediol (1,3 PDO) and butyric acid (BuA). Key variables taken into consideration were HRT, pH and feed concentration. The optimized process reached a glycerol consumption rate of 137 g/L/d and a maximum predicted production rate of 82.61 g/L/d and 21.13 g/L/d for 1,3 PDO and BuA, respectively. This corresponded to a 2.2 and 1.9-fold increase compared to the non-optimized process. The model was able to satisfactorily predict the joint maximum production of 1,3 PDO and BuA (22.6 and 8.1 g/L respectively) of the steady state also in non-sterile conditions, implying thus that MMC can be a robust and reliable biological production platform.