Real time monitoring of hydrogenotrophic methanogenesis under deep saline aquifers conditions

To investigate the microbial response to deep underground gas injection, specifically CO ₂ and H ₂ , a new optically transparent high-pressure reactor was developed to monitor autotrophic microbial growth via in situ and ex situ characterization techniques. The main advantages rely on avoiding any decompression phases during the entire process, thanks to direct optical access. Here, we monitored the growth of the model methanogenic strain Methanothermococcus thermolithotrophicus by applying different H ₂ /CO ₂ partial pressures at a total pressure of 100 bar, which is representative of the deep underground storage environment. Additionally, we measured the methane production of the strain at the end of the incubation, which resulted in an increase in methane production with increasing CO ₂ and H ₂ partial pressures until a certain point. These reactors can be used to investigate deep microbial strains under pressure conditions close to their natural environments, eliminating decompression biases.