PRODUCTION OF BIOCHEMICALS AND BIOFUELS WITH NO CO2 PRODUCTION AND IMPROVED PRODUCT YIELDS

摘要

Traditional fermentation processes for the production of the majority of biochemicals and biofuels produce CO2 because of decarboxylation reactions, which limits the final mass yields of products. To overcome this limitation, we have developed a fermentation technology called MixoFerm? (also known as anaerobic, non-photosynthetic mixotrophy), which uses microorganisms capable of simultaneously consuming both organic (e.g., sugars) and inorganic (e.g., CO2, CO, or H2) substrates. With this technology, product mass yields for almost any biochemical or biofuel can be increased by at least 50%, and processes can be designed that result in no CO2 production. In order to achieve zero CO2 emissions for most products, exogenous reductant must be added to the system, since sugar lacks the necessary reducing energy to both fix CO2 and produce the product of interest. Here, we demonstrate concurrent consumption of both sugars and exogenously added reducing gases (CO and/or H2) to produce products of interest at enhanced mass yields and with no CO2 emissions. In addition, we have screened a library of acetogenic bacteria in order to find an optimal MixoFerm? host strain, one that consumes both a broad range of carbohydrates and gases. From this library, we identified strains with a broader carbohydrate consumption range than traditional acetogens like C. ljungdahlii or C. autoethanogenum, and characterized their ability to grow under a variety of MixoFerm? conditions to produce biochemicals at enhanced mass yields. With the ability to improve product yields for reduced products, especially for ethanol and other potential biofuels, MixoFerm? is a robust and flexible platform technology to improve process economics and product life-cycle analysis.