Sunday, August 11, 2013
Pavilion (Sheraton San Diego)
Glycerol is a by-product of biodiesel production which is yielded at about 10% (w/w). In the present work an improvement of the dark fermentation of glycerol was proposed by surface immobilization of the microorganisms on supports. Four different supports were employed: magnetite (Fe2O3), activated carbon (AC), silica gel (SiO2) and alumina (γ-Al2O3). A newly isolated co: culture of Enterobacter spH1 and Citrobacter freundii H3 was immobilized on these supports. Effect of iron was studied by its impregnation over AC and SiO2.Modeling Gompertz equation was used to determine the maximum H2 production (Pmax,H2), H2 production rate (Rmax,H2) and H2 yield (YH2). The glycerol conversion and H2 production was dependent on the specific surface area (SBET) of the support and iron species. The order of the maximum H2 production was: Fe/AC (SBET= 736 m2/g)> AC (SBET= 1195 m2/g)> Fe/SiO2 (SBET= 440 m2/g)>SiO2 (SBET= 685 m2/g)>Fe2O3 (SBET= 205 m2/g)> γ-Al2O3 (SBET= 253 m2/g)> Free Culture (FC). The glycerol conversion in all cases was higher than that obtained from FC. The metabolites were mainly composed of 1,3-propanediol, ethanol, lactate, H2 and CO2. A progressive enhancement in the H2 production was clearly observed comparing the Fe2O3, Al2O3, SiO2 and AC supports. The H2 production on iron impregnated AC and SiO2 supports was enhanced comparing with the production achieved with the correspondent bare supports. These results indicate that support assisted carrier may enhance the productivity of H2 due to specific surface area attachment, biofilm formation of the microorganism and hydrogenase enzyme activation by iron species.