Airlift Taylor Flow bioreactors as a novel platform to enhance H2-assisted CO2 bioconversion processes

Abstract

The microbial valorization of CO2 requires the development of novel bioreactor configurations capable of ensuring a cost-effective gas-liquid mass transfer. This study presents the design, characterization and performance evaluation of a novel Airlift Taylor Flow Reactor (ATFR), which integrates the gas-induced liquid recirculation of airlift systems, with the high gas-liquid mass transfer potential of Taylor flow in multicapillary systems. The liquid recirculation flow in the downcomer was quantified using a colour tracer method, and the volumetric oxygen mass transfer coefficient (kLa) was determined via the sulphite oxidation method, both with and without forced recirculation. The results showed that the implementation of forced mechanical recirculation via a centrifugal pump negatively impacted the total liquid recirculation and kLa. A maximum kLa of 891 ± 23 h 1 was achieved at a gas flow rate of 60 L min 1, representing a 75 % increase compared to the same condition with external forced liquid recirculation. The autotrophic growth of Cupriavidus necator showed a direct correlation with kLa, with a 171 % increase in maximum cell concentration and a 67 % increase in the specific growth rate when kLa increased from 183 to 364 h 1. These findings highlight the potential of the ATFR as a promising platform for gas-liquid mass transfer-limited processes, particularly in systems bioconverting poorly soluble gases such as H2, CH4, CO and O2.