Steady state model for evaluation of external and internal mass transfer effects in an immobilized biofilm

Cyclic voltammetry of biofilms of wild type and mutant Geobacter sulfurreducens on fuel cell anodes indicates possible roles of OmcB, OmcZ, type IV pili, and protons in extracellular electron transfer

“…Charge compensation is more hindered in the absence of acetate since protons are generated inside the biofilm by step 1. The minimum diffusion coefficient determined above is low compared to that of protons in water (9.3 Â 10 À5 cm 2 s À1 ) 64 or even in a (hypothetical) dense biofilm (9.3 Â 10 À6 cm 2 s À1 ) 65,66 and is consistent with proton diffusion being limited in turn by buffer diffusion at the biofilm/media interface. It is recognized that the above treatment is qualitative and not rigorous because microorganisms are not individual enzymes, nor were the voltammograms fitted to simulations of steps 1-4 to yield values for various reaction parameters including the degree of possible heterogeneity among the microbes and mediators in the biofilm (work in progress), it does provide however, a useful model for studying the mechanism of extracellular ET in the Geobacter sulfurreducens biofilms.…”

“…Our results indicate that WT G. sulfurreducens forms a conductive network of bound ET mediators that most likely utilizes OmcZ to transfer electrons through the biofilm and OmcB to transfer electrons across the electrode/biofilm interface; that pili are important in both reactions, that OmcS and T are of secondary importance to the former, and that OmcE is not involved in extracellular ET during anode reduction in spite of being necessary for Fe(III) oxide reduction. In the case of Heller's electrode immobilized redox enzymes, 52,65 co-immobilized organometallic complex's that are covalently attached within a porous polymer matrix by flexible linkers transfer electrons from the enzymes (analogous to step 2), among themselves (analogous to step 3), and with the electrode surface (analogous to step 4) through a series of thermally activated collisions. In the case of G. sulfurreducens, homogenous ET may be occurring between individual OmcZ proteins along a cell's outer membrane and by cell-to-cell contact toward the electrode surface where OmcB on the innermost microbes to the anode surface mediate the heterogeneous electron transfer reaction.…”

External Mass Transfer Model for Hydrogen Peroxide Decomposition by Terminox Ultra Catalase in a Packed-Bed Reactor

“…In many cases this assumption is often but not always valid. So, in the case of significant EDR the combined effect of EDR and IDR is described (Mudliar et al, 2008). The analysis of a combined effect of EDR and IDR can also be indicated in the case of hydrogen peroxide decomposition (HPD) by catalase (Traher and Kittrell, 1974;Greenfield et al, 1975).…”

A new approach for development of kinetics of wastewater treatment in aerobic biofilm reactor

“…The biomass per unit surface area, i.e., (X f L f ) is constant indicating the steady state condition of biofilm. Various research studies have been reported on modeling of biofilm reactor (Williamson and McCarty 1976;Rittmann and McCarty 1980;Suidan and Wang 1985;Strand 1986;Kim and Suidan 1989;Golla and Thomas 1990;Heath et al 1990;Saez and Rittman 1991;Lee 1997;Rauch et al 1999;Tsuno et al 2002;Pritchett and Dockery 2001;Perez et al 2005;Shaoying et al 2005;Hsien and Lin 2005;Mudliar et al 2008;Jiang et al 2009;Qi and Morgenroth 2005;Rao et al 2010;Liao et al 2012;Eldyasti et al 2012;Gullicks et al 2011), but no simplified method was developed for determining the kinetic coefficients. Indeed, the kinetic coefficients are needful for solving the biofilm model and hence for the process design of the biofilm reactor.…”