Genetic modification of <i>Clostridium kluyveri</i> for heterologous <i>n</i> -butanol and <i>n</i> -hexanol production

Medium-chain carboxylates are required in various everyday products, including cosmetics, pharmaceuticals, and fragrances, and show a natural antimicrobial property. Furthermore, they represent food additives and serve as chemical building blocks for several other compounds. Traditionally, these carboxylates are produced from fossil resources, contributing to increased greenhouse gas emissions. Alternatively, they are derived from animal- or plant-based fat (e.g., coconut oil), which competes with agricultural land that is needed for food production. However, microbial chain elongation, which is a biotechnological approach relying on microbes, such as <i>Clostridium kluyveri</i>, is sustainable and a promising alternative to the conventional production of medium-chain carboxylates. Notably, it enables the use of industrial waste streams (e.g., off-gases and carbohydrate-rich industrial waste) as substrates, making the process more environmentally friendly. By applying our genetic system for <i>C. kluyveri</i>, a better understanding of microbial chain elongation can be achieved and potentially even enable an extension of its product portfolio.