Dr. Thaddeus Ezeji, associate professor Department of Animal Sciences, has been awarded a grant from the United States Department of Agriculture (USDA). The USDA grant award has been approved with a total budget of $467,122.00 for 3 years. The project, "Development of a separation system for efficient fermentation of mixed substrates and in situ recovery of hydrophobic bulk chemical," is set to begin on August 01, 2019. There are three other Ohio State Co-Project Directors involved: Dr. Ajay Shah (Food, Agriculture and Biological Engineering), Dr. Victor Ujor (Ohio State University Agricultural Training Institute/Ohio State-ATI), and Dr. Wilson Ho (Chemical and Biomolecular Engineering). The Non-Technical Summary of the project is below.
Often, biosynthesis reactions that produce valuable fuels and chemicals do not generate compounds at levels that are economically feasible for large scale production because most fermentation processes are product limiting due to feedback inhibition and product toxicity to the fermentation microorganisms; thus, culminating in low concentrations in the bioreactor. A case in point is butanol, a four-carbon alcohol. Even though butanol can be produced renewably via acetone butanol ethanol (ABE) fermentation and has excellent fuel attributes, such as high energy content, low vapor pressure, good blending with gasoline, compatibility with oil infrastructure and automobiles without engine modification, butanol is not used as a biofuel because of its high production cost. However, fossil-derived butanol is currently used in numerous applications in the production of solvents, plasticizers, butylamines, amino resins, butyl acetates, and lacquers.
Despite numerous merits, ABE fermentation suffers from a number of limitations (e.g. low titer, productivity, and poor production economics) due to butanol toxicity to microbial cells and high substrate cost. To address these, we have developed real time in situ recovery methods, namely gas stripping and vacuum-assisted gas stripping. However, these technologies are fraught with high level of water removal from the bioreactor requiring the need to replenish water, and at the same time excessive energy requirement for butanol separation from a highly diluted recovered butanol stream. Although these previous efforts have led to improvements in ABE fermentation, there is need to further resolve inter-twined issues related to substrate compatibility, butanol toxicity to microorganisms and excessive water removal from the bioreactor. To resolve these issues, we propose a novel lignocellulose compatible separation technology comprised of a water-butanol separation unit with water repelling properties that: (1) removes fuels and bioproducts in real-time from the bioreactor/fermenter during fermentation to prevent product toxicity to the fermentation microorganisms and allow fermentation to go on unimpeded, and (2) eliminates or minimizes water escaping the bioreactor with butanol.
The overall goal of the proposed project, therefore, is to develop a novel fermentation technology with real-time product recovery that incorporates five key attributes namely: (I) compatibility with cheap fibrous, colloidal, and impure substrates; (II) support of the growth of fermentation microorganisms; (III) simplicity of operation; (IV) reduction of water losses from the bioreactor/fermenter and generation of high concentration of butanol; and (V) technically feasible and cost effective system. It is our expectation that accomplishing these attributes will result in a robust commercializable technology for fermentative production of hydrophobic bulk chemicals such as butanol.