Reactor Designs and Configurations for Biological and Bioelectrochemical C1 Gas Conversion: A Review

Abstract

Microbial C1 gas conversion technologies have developed into a potentially promising technology for converting waste gases (CO2, CO) into chemicals, fuels, and other materials. However, the mass transfer constraint of these poorly soluble substrates to microorganisms is an important challenge to maximize the efficiencies of the processes. These technologies have attracted significant scientific interest in recent years, and many reactor designs have been explored. Syngas fermentation and hydrogenotrophic methanation use molecular hydrogen as an electron donor. Furthermore, the sequestration of CO2 and the generation of valuable chemicals through the application of a biocathode in bioelectrochemical cells have been evaluated for their great potential to contribute to sustainability. Through a process termed microbial chain elongation, the product portfolio from C1 gas conversion may be expanded further by carefully driving microorganisms to perform acetogenesis, solventogenesis, and reverse β-oxidation. The purpose of this review is to provide an overview of the various kinds of bioreactors that are employed in these microbial C1 conversion processes.

Syngas Fermentation to Acetate and Ethanol with Adaptative Electroactive Carboxydotrophs in Single Chambered Microbial Electrochemical System

“…In order to infer the reductive capabilities of abiotic operation, amperometry was performed with an applied potential of −0.5 V. Reductive catalytic current (RCC) generations were recorded with an average of −0.03 mA. Generated reductive currents illustrate the syngas reduction tendencies [ 14 , 21 , 22 ]. Consistent charge transfer from the cathode surface to the outer membrane electroactive components of the microbe depicts the substrate reduction capability of the carboxydotrophic biocatalyst [ 14 , 22 ].…”

“…Generated reductive currents illustrate the syngas reduction tendencies [ 14 , 21 , 22 ]. Consistent charge transfer from the cathode surface to the outer membrane electroactive components of the microbe depicts the substrate reduction capability of the carboxydotrophic biocatalyst [ 14 , 22 ]. Continuous syngas sparging into the medium with optimal flow rate enabled the electrogenic activity of the biocatalyst towards product formation by consuming the externally discharged charge.…”

“…In order to infer the reductive capabilities of abiotic operation, amperometry was performed with an applied potential of −0.5 V. Reductive catalytic current (RCC) generations were recorded with an average of −0.03 mA. Generated reductive currents illustrate the syngas reduction tendencies [14,21,22]. Consistent charge transfer…”

“…Microbial mediated process of carbon sequestration, which is considered a potential strategy, can also play a crucial role in this regard [ 11 , 12 ]. Syngas fermentation through the Wood–Ljungdahl pathway (WLP) owned microbes contributes to the synthesis of short-chain carboxylic acids [ 9 , 13 ] and can sustain the toxic effects of CO [ 14 ]. However, desired product synthesis from the crude syngas fermentation is still challenging [ 15 , 16 , 17 ].…”

“…Microbial electrochemical systems (MESs) mediated syngas conversion facilitates electrochemically assisted fermentation for the synthesis of metabolic products from gaseous feedstock [ 19 , 20 ]. Integration of inert conductive material (electrode) and electric poised conditions can augment additional gas conversion rates in the gas electro fermentation [ 14 , 20 ].…”