Production of ethyl-butyrate in a self-sufficient reaction cascade (Acronym PEBcascade)

点击翻译按钮获取中文摘要

With this proposal, the applicants want to investigate a self-sufficient biotechnological reaction cascade to produce the fuel ethyl-butyrate. In general, ester production is a complex process involving multiple steps, such as the production of the precursors (an alcohol and a carboxylic acid), the chemical or enzymatic esterification, and the final product separation. In our approach, an artificial anaerobic mixed culture of Clostridia and yeast, or bacteria in combination with a surface displayed lipase will be used for the production of the ester in one reaction system. While the Clostridia are responsible for the production of butyrate, the yeast or bacteria produce ethanol. The lipase will be expressed at the cell-surface of the ethanol-producing strain. This approach is expected to achieve optimized productivities, as each organism is used to produce a component, and can thus be brought into an optimal process condition. In order to realize a novel production route of a biofuel process development in the project PEBcascade, biological research (microbiology, molecular biology) will be combined with biochemical engineering (process development, modelling). The project includes process development and modeling, a scale-up (to 50 liters), and an application of the fuel in a single-cylinder gasoline engine. In a first step, the biocatalyst, the butyrate production with clostridia, the ethanol production with yeast and bacteria, and the ester formation by different lipases, will be characterised separately in detail (WP1). The kinetic data will enable a selection of the "best" catalysts. The data will also be used for a first mathematical model to describe the demands for the establishment of a cascade reaction. WP2 focuses on the selection of an organic solvent for an in-situ product removal of the ethyl-butyrate. Of particular interest are the stability of the biocatalysts and the partitioning coefficients of the butyrate, ethanol, ethyl-butyrate and side-products. In order to fulfil the requirements of all biocatalysts, a media optimisation will be performed (WP3). In order to identify a suitable surface expression of the lipase, several strains and transporter systems will be compared in WP4. Lastly, identified strains shall be integrated in one reactor system. Here, the composition of the mixed culture and the performance of the self-sufficient reaction cascade will be investigated. The obtained data will be used for the refinement of the mathematical model (WP5). In WP+, the basic combustion properties of the ethyl butyrate will be investigated. This will be done in collaboration with the Institute of Vehicle Propulsion Systems (TUK). At the beginning of the project, it is planned to test commercial ethyl butyrate to determine the engine settings and, at the end of the project, to carry out comparative tests with the biotechnologically produced product.