A novel bulk-gas-to-atomized-liquid reactor for enhanced mass transfer efficiency and its application to syngas fermentation

Abstract

Syngas fermentation for fuels and chemicals is limited by the low rate of gas-to-liquid mass transfer. In this work, a unique bulk-gas-to-atomized-liquid (BGAL) contactor was developed to enhance mass transfer. In the BGAL system, liquid is atomized into discrete droplets, which significantly increases the interface between the liquid and bulk gas. Using oxygen as a model gas, the BGAL contactor achieved an oxygen transfer rate (OTR) of 569 mg·L -1 ·min -1 and a mass transfer coefficient (KLa) of 2.28 sec -1 , which are values as much as 100-fold greater than achieved in other kinds of reactors. The BGAL contactor was then combined with a packed bed to implement syngas fermentation, with packing material supporting a biofilm upon which gas saturated liquid is dispersed. This combination avoids dispersing these gas-saturated droplets into the bulk liquid, which would significantly dilute the dissolved gas concentration. Although this combination reduced overall KLa to 0.45-1.0 sec -1 , it is still nearly 20 times higher than achieved in a stirred tank reactor. The BGAL contactor/packed bed bioreactor was also more energy efficient in transferring gas to the liquid phase, requiring 8.63-26.32 J mg -1 O2 dissolved, which is as much as four-fold reduction in energy requirement compared to a stirred tank reactor. Fermentation of syngas to ethanol was evaluated in the BGAL contactor/packed bed bioreactor using Clostridium carboxidivorans P7.Ethanol productivity reached 746 mg·L -1 ·hr -1 with an ethanol/acetic acid molar ratio of 7.6. The ethanol productivity was two-fold high than the highest level previously reported. The exceptional capability of BGAL contactor to enhance mass transfer in these experiments suggests its utility in syngas fermentation as well as other gas-liquid contacting processes.

Engineering Acetogenic Bacteria for Efficient One-Carbon Utilization

“…Because C1 gases, unlike other substrates such as glucose or glycerol, are gaseous substrates, the gas-to-liquid mass transfer rate is critically affected by the physical properties of gas solubility. Many studies have attempted to increase the fixing efficiency of C1 gases through various gas fermentation techniques, such as increasing the partial pressure of the gas ( Phillips et al, 1993 ; Bredwell and Worden, 1998 ; Hurst and Lewis, 2010 ; Orgill et al, 2013 ; Sathish et al, 2019 ; Bae et al, 2022 ). However, this approach also has physical limitations, and thus, genetic attempts should be made to overcome the low productivity, yield, and cell density of acetogens by developing a platform acetogen strain with increased C1 gas fixation efficiency and expanding it to a commercial scale.…”

Impacts of Syngas Composition on Anaerobic Fermentation

“…Clostridium carboxidivorans [33,34], Clostridium aceticum [35], Acetobacterium woodii [36], Blautia producta, Clostridium autoethanogenum [37], Clostridium difficille, Clostridium ljungdahlii, Clostridium magnum, Eubacterium limosum, Moorella Thermoacetica, Clostridium scatologenes, Clostridium coskatii [38] and Butyribacterium methylotrophicum are examples of acetogenic carboxydotrophic microorganisms [39][40][41].…”

Gas Biological Conversions: The Potential of Syngas and Carbon Dioxide as Production Platforms

“…Nevertheless, it is known that high gas mass transfer is only attained in STR at the expense of high power input for agitation, which may compromise the economic sustainability of the process. Other reactor configurations used in gas fermentation not relying on mechanical mixing for increasing kLa are bubble columns, gas-lift reactors, STR coupled to hollow fiber membrane modules (HFMBR), trickle bed reactors (TBR) and a few other special reactor designs such as U-loop bioreactor, Bulk-Gasto-Atomized-Liquid (BGAL) reactor and Multi-Orifice Baffled Bioreactor (MOBB) [21][22][23][24][25][26].…”