Dark Fermentation Process by Thermotoga Neapolitana: Effect of Sugar Substrates

Significant efforts have been made in recent years to develop alternative energy vectors to reduce fossil fuel resource use, greenhouse gas emissions, and the release of harmful particulates. Among the alternative vectors, hydrogen (H2) is a promising option for achieving carbon neutrality because its combustion produces only water. Moreover, H2 is considered an excellent candidate for energy applications owing to its high heating value and high-octane number. H2 production can occur through dark fermentation, a biotechnological process that uses anaerobic bacteria to generate H2 and by-products (such as volatile fatty acids and CO2) from organic substrates. Specifically, the bacterium Thermotoga neapolitana efficiently converts carbohydrates into biogas, producing approximately four molecules of H2 and acetic acid per mole of consumed glucose. This study focuses on optimizing the dark fermentation process with T. neapolitana, analysing the effects of various substrates (monosaccharides and disaccharides) on bacterial growth and the production of H2 and acetic acid. The results indicated that T. neapolitana grew on all tested substrates, with fructose yielding the highest amount of H2 and mannose yielding the highest amount of acetic acid.