Growth, structure and oxygen penetration in particle supported autotrophic biofilms

Abstract

Particle supported autotrophic biofilms were cultivated in external-loop airlift reactors at two different pumice concentrations. Oxygen microelectrodes were used to investigate substrate transport and conversion. A special flow cell was designed for the measurement of oxygen concentration profiles in the particle supported biofilms under defined hydrodynamic conditions. The oxygen concentration profiles inside the biofilms were found to be steeper at high flow velocities in the bulk phase of the flow cell compared to those at low flow velocities. Furthermore, the oxygen flux increased and the thickness of the concentration boundary layer decreased with increasing flow velocity. This dependence was found to be more pronounced in less dense biofilms out of airlift reactors with lower pumice concentrations. In addition confocal laser scanning microscopy (CLSM) was used to visualize the biofilm structure. The volume fractions of bacteria and extracellular polymeric substances (lectin-specific EPS-glycoconjugates) were measured in living fully hydrated biofilms. Both the microelectrode and CLSM measurement showed the influence of shear stress on particle supported biofilms. A higher particle concentration led to dense biofilms with a homogeneous surface, lower thickness of the concentration boundary layer and steeper oxygen concentration profiles. The combination of both techniques allows a detailed and quantitative characterisation of particle associated biofilm structure and function.

Oxygen profiles and biomass distribution in biopellets of Aspergillus niger

“…4), but can be explained by the low mean biomass density of only 24.5 kg biomass per m 3 pellet volume. In particle fixed chemoautotrophic biofilms with a similar diameter, oxygen penetration was found to be 100 mm for biomass densities of 50 kg/m 3 (Boessmann et al, 2004). A considerable change in profiles can be observed after 65 h cultivation time.…”

“…In biofilm research, confocal laser scanning microscopy (CLSM) has been applied to quantify volumetric shares of bacteria and extracellular polymeric substances (Boessmann et al, 2003(Boessmann et al, , 2004Staudt et al, 2003Staudt et al, , 2004. Concerning fungal morphology, hyphal distributions of Rhizopus oligosporus were analyzed in solid-state cultivations and quantified by CLSM and image analysis (Nopharatana et al, 2003).…”

Treatment of Malting Wastewater in a Granular Sludge Sequencing Batch Reactor (SBR)

“…Nevertheless are particulate biofilms subject to diffusion limited mass transport processes, even under turbulent flow conditions [23]. Recent studies indicate on the other hand a distinctive pore structure (d P > 0.1 µm) pervading the granules to a peak depth of 500...900 µm [24].…”

Experimental and Computational Investigation of Biofilm Formation by Rhodopseudomonas palustris Growth under Two Metabolic Modes

“…Many studies have analyzed factors that influence the formation of heterotrophic biofilms, including the type and availability of nutrients [16,17,18,19], the flow velocities and hydrodynamic effects [20,21,22,23,24], the properties of the attachment surface, and the dependence of the microbial community structures on physiochemical parameters such as oxygen and light [25,26,27]. Several studies have examined factors that influence biofilms formed by mixed species of phototrophic bacteria [28,22,6,29].…”