초록
<P>1,3-Propanediol (1,3-PDO) can be produced biologically through glycerol fermentation. While such a process typically involves a pure culture system, particularly for crude glycerol, there would be operational advantages if a mixed population could be used. However, in the latter case the yield is typically low. Here, we use electrical current as the driving force for a mixed population fermenting glycerol in the cathode of a microbial bioelectrochemical system (BES). The carbon and electron flows were monitored by a titration and off-gas analysis (TOGA) sensor, and the syntrophic interactions in the BES were also investigated. Results show that on a carbon yield basis, current enhanced 1,3-PDO production from 24.8% (without current) to 50.1% (with a polarized biocathode at −0.9 V versus standard hydrogen electrode, SHE). Flux analysis indicated that the reductive current can be integrated into glycerol metabolism to enhance 1,3-PDO yield and that glycerol metabolism was redirected from propionate fermentation to 1,3-PDO production. A polarization of −0.6 V (vs SHE) resulted in more fermentative hydrogen production (from 2.7% to 8.0% on electron basis). 1,3-PDO production was also enhanced with hydrogen supply (37.7% on carbon basis), by suppressing hydrogen fermentation. Moreover, interspecies hydrogen transfer encouraged hydrogenotrophic methanogenesis, which was also accelerated by the cathodic polarization.</P><P><B>Graphic Abstract</B><BR><IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/esthag/2013/esthag.2013.47.issue-19/es402132r/production/images/medium/es-2013-02132r_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/es402132r'>ACS Electronic Supporting Info</A></P>