“…In gas fermentation, chemolithoautotrophic organisms utilize gaseous substrates such as CO 2 , syngas (a mixture of H 2 and CO), biogas, and industrial off-gases to produce value-added chemicals or fuels (e.g., ethanol, isopropanol, butanol, and acetone) or polymers (e.g., poly-β-hydroxybutyrate, PHB). This is a more environmentally sustainable process as opposed to those based on fossil resources. − However, the slow growth and metabolism of autotrophs owing to the low mass transfer of gaseous feedstocks hinder the current methods of gas fermentation, thereby limiting its product yield and industrial scale-up. − To enhance gas fermentation, nonsustainable chemicals, such as perfluorocarbon nanoemulsions and n -hexadecane, have been added to the media to improve the solubility of gases and the gas–liquid mass transfer. − In addition, genetic tools have been employed to manipulate molecular mechanisms of microorganisms to increase the flux of target product production. − Nevertheless, this method is challenged by biosecurity, high costs, and genetic stability. , …”