Hydrogenophilic and Bioelectrochemical Production of Acetate with a Pure Culture of Acetobacterium Woodii

Abstract

In recent years there has been a growing interest in the potential use of autotrophic acetogenic bacteria to produce compounds of interest through CO₂ fixation, representing an alternative solution to currently used CO₂ storage technologies. This group of microorganisms are ubiquitous in nature and they are characterised by a Wood-Ljungdahl pathway that combines CO₂ fixation with adenosine triphosphate (ATP) synthesis by using H₂ as electron donor. In this work the autotrophic production of acetate by a pure colture of Acetobacterium woodii has been tested under hydrogenophilic or bioelectrochemical conditions. More in details, the hydrogenophilic tests were conducted at two different pH values (5.5 and 7.5) with an H₂ partial pressure of 0.52 atm, while bioelectrochemical tests were performed at an applied cathodic potential of -0.90 V vs. SHE (Standard Hydrogen Electrode). The bioelectrochemical tests were set up in H-type reactors (250 mL), in which graphite rods were used as electrodic material and an anion exchange membrane served to separate the anodic and cathodic chambers while allowing anions migration for electroneutrality maintenance. The hydrogenophilic tests resulted in different kinetics depending on the applied pH value. The bioelectrochemical tests, performed at a pH value of 7.5, reached an acetate production rate 2 times higher than in the hydrogenophilic experiments at pH 7.5, as well as an increase in the efficiency of using the reducing power, suggesting an improvement in hydrogen uptake. At pH 5.5, on the other hand, production is improved by increasing the partial pressure of H₂