Many biotechnologically relevant organisms cannot utilize cheap and abundant one carbon feedstocks, e.g. CO.sub.2, CO, formaldehyde, methanol, and methane, for growth and instead prefer complex feedstocks such as sugars. Disclosed herein is a system that enables organisms to consume one carbon molecules for growth and maintenance via a formyl-CoA elongation pathway. Utilization of one carbon feedstocks can replace the use of sugar as the primary means of cultivating organisms in biotechnological applications. This has the potential to be more cost effective and avoid the controversial use of food as feedstocks. Intermediates of the formyl-CoA elongation pathway may be also be converted to desired chemical products.

This disclosure provides a new conceptual framework in which orthogonal, new-to-nature carbon and energy conversion pathways facilitate the synthesis of fuels and chemicals from carboxylic acid intermediates (CAis) driven by genetically altered microorganisms. This allows the CAi platform to generate diverse products at ?100% carbon yield while retaining the established high product and energy efficiencies of fermentative metabolism. In another embodiment, a carboxylic acid platform for fuel and chemical production at high carbon and energy efficiency is also provided.