title: Dynamics of biofilm formation during anaerobic digestion of organic waste.
abstract: Biofilm-based reactors are effectively used for wastewater treatment but are not common in biogas production. This study investigated biofilm dynamics on biofilm carriers incubated in batch biogas reactors at high and low organic loading rates for sludge from meat industry dissolved air flotation units. Biofilm formation and dynamics were studied using various microscopic techniques. Resulting micrographs were analysed for total cell numbers, thickness of biofilms, biofilm-covered surface area, and the area covered by extracellular polymeric substances (EPS). Cell numbers within biofilms (10(11) cells ml(-1)) were up to one order of magnitude higher compared to the numbers of cells in the fluid reactor content. Further, biofilm formation and structure mainly correlated with the numbers of microorganisms present in the fluid reactor content and the organic loading. At high organic loading (45 kg VS m(-3)), the thickness of the continuous biofilm layer ranged from 5 to 160 μm with an average of 51 μm and a median of 26 μm. Conversely, at lower organic loading (15 kg VS m(-3)), only microcolonies were detectable. Those microcolonies increased in their frequency of occurrence during ongoing fermentation. Independently from the organic loading rate, biofilms were embedded completely in EPS within seven days. The maturation and maintenance of biofilms changed during the batch fermentation due to decreasing substrate availability. Concomitant, detachment of microorganisms within biofilms was observed simultaneously with the decrease of biogas formation. This study demonstrates that biofilms of high cell densities can enhance digestion of organic waste and have positive effects on biogas production.
authors.affiliation: Ulm University, Institute of Systematic Botany and Ecology, Albert-Einstein-Allee 11, 89081 Ulm, Germany; Ulm University, Institute of Microbiology and Biotechnology, Albert-Einstein-Allee 11, 89081 Ulm, Germany. Electronic address: susanne.langer@uni-ulm.de.
authors.forename: Susanne
authors.initials: S
authors.lastname: Langer
authors.affiliation: Ulm University, Institute of Systematic Botany and Ecology, Albert-Einstein-Allee 11, 89081 Ulm, Germany. Electronic address: daniel.schropp@uni-ulm.de.
authors.forename: Daniel
authors.initials: D
authors.lastname: Schropp
authors.affiliation: Ulm University, Institute of Microbiology and Biotechnology, Albert-Einstein-Allee 11, 89081 Ulm, Germany. Electronic address: frank.bengelsdorf@uni-ulm.de.
authors.forename: Frank R
authors.initials: FR
authors.lastname: Bengelsdorf
authors.affiliation: RMIT University, Institute of Civil, Environmental and Chemical Engineering, Melbourne, Vic 3001, Australia. Electronic address: maazuza.othman@rmit.edu.au.
authors.forename: Maazuza
authors.initials: M
authors.lastname: Othman
authors.affiliation: Ulm University, Institute of Systematic Botany and Ecology, Albert-Einstein-Allee 11, 89081 Ulm, Germany. Electronic address: marian.kazda@uni-ulm.de.
authors.forename: Marian
authors.initials: M
authors.lastname: Kazda
mesh_terms: D000693:Anaerobiosis; D001105:Archaea / Q000378:metabolism* / Q000648:ultrastructure; D001419:Bacteria / Q000378:metabolism* / Q000648:ultrastructure; D058491:Bacterial Load; D061249:Batch Cell Culture Techniques; D018441:Biofilms / Q000254:growth & development*; D056804:Biofuels; D019149:Bioreactors; D005285:Fermentation; D008461:Meat Products; D008697:Methane / Q000096:biosynthesis*; D059013:Microbial Consortia / Q000502:physiology*; D011312:Pressure; D013696:Temperature; D014866:Waste Products
chemical_list: D056804:Biofuels; D014866:Waste Products; D008697:Methane
keywords: Anaerobic biofilm; Anaerobic digestion; Biofilm formation; Biogas