Overview

Our first module deals with the construction of an E. coli strain, which is able to accept electrons from electrodes which are used for the generation of ATP in the respiratory chain. We characterized it in our electrobiochemical reactor system testing different mediators, electrode materials and reactor set-ups. Our genetical achievements could be divided in two parts.
In the first part we investigated the effect of the C4 carboxylate transporter DcuB knockout on E. coli KRX. Furthermore we showed the integration of the outer membrane porine OprF (BBa_K1172507) into the bacterial genome by replacing the gene of E. coli C4 carboxylate antiporter DcuB. The functionality of the genome integrated outer membrane porine OprF in E.coli KRX ΔdcuB::oprF was investigated with a NPN-Uptake-Assay.
We demonstrated that the knockout of C4 carboxylate antiporter dcuB was successful. Our constructed E. coli KRX ΔdcuB::oprF strain shows no succinate export under anaerobic conditions. This demonstrates a successful knockout of the dcuB gene. Besides the phenotypical characetization (Biolog® analysis) showed that there is no significant respiratory activity of E.coli KRX ΔdcuB::oprF in the presence of fumarate. The electrobiochemical behavior of E. coli KRX with knocked out C4 carboxylate antiporter DcuB was tested in a H-cell reactor.
The second part deals with the investigation of fumarate reductase Frd (BBa_K1465102). Successful overexpression of the fumarate reductase Frd (BBa_1465102) could be proven via SDS-PAGE. The activity of the fumarate reductase could be shown via HPLC analysis of fumarate consumption and succinate production in E. coli overexpressing frd in an anaerobic cultivation (BBa_1465102). Furthermore we investigated the fumarate reductase activity in different E. coli strains by phenotypic MicroArray (PM) analysis with a Biolog® system.

We planned to design a reactor system that is suitable to investigate the electrochemical behaviour in bioprocesses. Such a reactor system needs to meet with several requirements for the investigation of electrochemically active microorganisms. The investigation of such microorganisms can not be carried out in common cultivation systems.
For the design of an electrobiochemical reactor system we had to tackle lots of challenges. We needed to consider which connections are necessary and had to make precise design drawings. In addition we needed to develop an appropriate measurement system.