title: The effect of pH and buffer concentration on anode biofilms of Thermincola ferriacetica.
abstract: We assessed the effects of pH and buffer concentration on current production and growth of biofilms of Thermincola ferriacetica - a thermophilic, Gram-positive, anode-respiring bacterium (ARB) - grown on anodes poised at a potential of -0.06V vs. SHE in microbial electrolysis cells (MECs) at 60°C. T. ferriacetica generated current in the pH range of 5.2 to 8.3 with acetate as the electron donor and 50mM bicarbonate buffer. Maximum current density was reduced by ~80% at pH5.2 and ~14% at 7.0 compared to pH8.3. Increasing bicarbonate buffer concentrations from 10mM to 100mM resulted in an increase in the current density by 40±6%, from 6.8±1.1 to 11.2±2.7Am(-2), supporting that more buffer alleviated pH depression within T. ferriacetica biofilms. Confocal laser scanning microscopy (CLSM) images indicated that higher bicarbonate buffer concentrations resulted in larger live biofilm thicknesses: from 68±20μm at 10mM bicarbonate to >150μm at 100mM, supporting that buffer availability was a strong influence on biofilm thickness. In comparison to mesophilic Geobacter sulfurreducens biofilms, the faster transport rates at higher temperature and the ability to grow at relatively lower pH allowed T. ferriacetica to produce higher current densities with lower buffer concentrations.
authors.affiliation: Swette Center for Environmental Biotechnology, The Biodesign Institute at Arizona State University, P.O. Box 875701, Tempe, AZ 85287-5701, United States. Electronic address: Bradley.lusk@asu.edu.
authors.forename: Bradley G
authors.initials: BG
authors.lastname: Lusk
authors.affiliation: Department of Civil Engineering, Kansas State University, 2123 Fiedler Hall, Manhattan, KS 66502, United States.
authors.forename: Prathap
authors.initials: P
authors.lastname: Parameswaran
authors.affiliation: Swette Center for Environmental Biotechnology, The Biodesign Institute at Arizona State University, P.O. Box 875701, Tempe, AZ 85287-5701, United States.
authors.forename: Sudeep C
authors.initials: SC
authors.lastname: Popat
authors.affiliation: Swette Center for Environmental Biotechnology, The Biodesign Institute at Arizona State University, P.O. Box 875701, Tempe, AZ 85287-5701, United States.
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Rittmann
authors.affiliation: Swette Center for Environmental Biotechnology, The Biodesign Institute at Arizona State University, P.O. Box 875701, Tempe, AZ 85287-5701, United States; School for Engineering of Matter, Transport and Energy, Arizona State University, 501 E Tyler Mall, Tempe, AZ 85287, United States.
authors.forename: Cesar I
authors.initials: CI
authors.lastname: Torres
mesh_terms: D000085:Acetates / Q000494:pharmacology; D001639:Bicarbonates / Q000494:pharmacology; D001674:Bioelectric Energy Sources / Q000382:microbiology*; D018441:Biofilms / Q000187:drug effects*; D002021:Buffers; D004553:Electric Conductivity; D004566:Electrodes; D006863:Hydrogen-Ion Concentration; D010459:Peptococcaceae / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology*; D011522:Protons; D012965:Sodium Chloride / Q000494:pharmacology
chemical_list: D000085:Acetates; D001639:Bicarbonates; D002021:Buffers; D011522:Protons; D012965:Sodium Chloride
keywords: Anode respiring bacteria; Biofilm; Microbial electrochemical cell; Thermophilic