Semiquantitative Detection of Hydrogen-Associated or Hydrogen-Free Electron Transfer within Methanogenic Biofilm of Microbial Electrosynthesis

Abstract

Hydrogen-entangled electron transfer is verified as an important extracellular pathway of sharing reducing equivalents to regulate biofilm activities within the diversely anaerobic environment, especially in microbial electrosynthesis system. However, the lack of useful methods for in-situ hydrogen detection in cathodic biofilm, the role of hydrogen involved in electron transfer is still debatable. Herein, the cathodic biofilm was constructed in the CH4-produced microbial electrosynthesis reactors, in which the hydrogen evolution dynamic was analyzed to confirm the presence of hydrogen-associated electron transfer nearby the cathode within the micrometre scale. The fluorescent in-situ hybridization images indicated that a colocalized community of archaea and bacteria developed within the thick of biofilm 58.10 μm at cathode suggesting the hydrogen gradient detected by microsensor was consumed by the collaboration of bacteria and archaea. Coupling microsensor and cyclic voltammetry test further provided the semi-quantitative results of hydrogen-associated contribution to methane generation ( around 21.20% ± 1.57% having a potential of -0.5 V to 0.69 V). This finding provides deep insight into the mechanism of electron transfer in biofilm on conductive materials. IMPORTANCE: Electron transfer from the electrode to biofilm is of great interest to the fields of microbial electrochemical technology, bioremediation and methanogenesis. It has promising application potential to boost more value-added products or pollutant degradation. Importantly, the microbial ability to obtain electrons from electrode and utilizing it brings a new insight into the direct interspecies electron transfer during methanogenesis. Previous studies had verified the direct pathway of electron transfer from the electrode to the pure-culture bacterium, but it was rarely reported how the methanogenic biofilm of mixed cultures shares electrons by hydrogen-associated or hydrogen-free pathway. In the current study, a combination method of microsensor and cyclic voltammetry successfully semi-quantified the role of hydrogen in the electron transfer from the electrode to methanogenic biofilm.

Linkage of community composition and function over short response time in anaerobic digestion systems with food fermentation wastewater

“…The preacclimation enabled the cultures to maintain the PD values which would be beneficial for a community adapting to the environment. However, the washout and enrichment in the CSTRs indicated that a specifically functional unit would be enhanced with decreasing PD, which commonly occurred in our previous studies ( Cai et al., 2016 , Cai et al., 2019 , Cai et al., 2020 ).…”

Intermittent electro field regulated mutualistic interspecies electron transfer away from the electrodes for bioenergy recovery from wastewater

“…In such systems, microbial consortia colonized the electrode to metabolize multifarious substrates via extracellular electron transfer had achieved versatile implications in biosynthesis for value-added products, and simultaneous pollutants degradation. The functional core of mutualistic interspecies electron transfer is considered to develop on and around the electrode (Cai et al, 2020). It has been proved that the electricity-stimulated system can regulate the establishment of microbial community structures and electron transfer pathways, which dramatically improve methane recovery efficiency and overall systems' stability.…”

Optimized Electrical Stimulation Period Facilitated Microbial Electromethane Generation with CO2 Conversion

“…It is known that microbial activity at this thickness level affects the electron transfer and H 2 diffusion in the biofilm. 45 Therefore, IV-1 h shortened the electron transfer distance by enriching electroactive microorganisms close to the cathode, thus constructing an effective electron transfer pathway.…”