ISSN:0892-7014    

DOI:10.1080/08927019309386231

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

In continuous flow biofilm reactors (CFBR) stratification of the microbial community may develop in the direction of flow. Problems arise when substrate is transported into regions where the population size of the required species such as nitrifiers is underdeveloped. Results of experimental studies support this assumption. Equalisation of the species distribution appears to be necessary to maintain reasonable reactor performance under shock loading conditions. Uniform population size and species distribution was achieved in a sequencing batch biofilm reactor (SBBR), which provided positive results, and stratification of hetero‐trophs and nitrifiers was eliminated. Equalisation of the population size of heterotrophs was less effective because of the apparent acclimatisation potential of the bacteria.

ISSN:0892-7014    

DOI:10.1080/08927019309386232

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

This paper focuses on the determination of the specific growth rate (nb) of boundE. coliUB 1832 cells, a necessary parameter in describing biofilm formation.

ISSN:0892-7014    

DOI:10.1080/08927019309386233

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Cellular aggregation is a natural phenomenon shown by microorganisms which allows the cells to form biofilms. The study of immobilized microorganisms requires the development of microtechniques to evaluate their metabolism and stability. In aerobic conditions, the immobilization of recombinant microorganisms in carrageenan gel beads has been successfully explored to enhance plasmid stability when growth in the support was oxygen‐limited. A series of anaerobic continuous cultures of free and immobilizedEscherichia coliB (pTG201) andE. coliHB 101 (pKBF 367–11) have been developed, without selection pressure. In continuous culture of free cells, both exhibited segregational instability. The existence of strong competition between cells containing plasmid (P+ cells) and cells devoid of plasmids (P— cells) was favourable to the colonization of the bioreactor by the faster growing P— cells. Furthermore, pTG 201 was mainly dimeric while the plasmid copy number of pKBF 367–11 increased from 80 to 270, until plasmid loss. The immobilization ofE. coliB (pTG 201) andE. coliHB 101 (pKBF 367–11) within carrageenan beads resulted in high cellular density, maintenance of plasmids and stabilization of the plasmid copy number. The analysis of cell growth in the case of four different inoculum densities (103,9 × 104,5.5 × 106and 2 × 107cells.ml−1of gel bead) was followed with optical and scanning electron microscopy. Growth of bacteria was dependent on the distribution of nutrients within the carrageenan gel beads. The depth of nutrient penetration was a function of the consumption rate by the cells and the nutrient‐diffusivity in the gel. This system could be used for the study of recombinant bacterial behaviour in natural aggregates and biofilms which are characterized by cells growth rates limited by diffusion and by stability of process‐level microbial activities.

ISSN:0892-7014    

DOI:10.1080/08927019309386234

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

In order to classify the relative importance of the parameters governing the accumulation of biofilm in drinking water distribution systems, a study has been carried out, using an industrial pilot plant fed with finished waters, with three main objectives,viz. (i) determination of biofilm density on pipe surfaces (PVC or cement lined cast iron) as a function of the distance from the water treatment plant, (ii) evaluation of the growth rate of attached bacteria along the distribution system, and (iii) measurement of the behavior of the dissolved organic matter (DOC) in the water stream for system residence times of 40 to 240 h.

ISSN:0892-7014    

DOI:10.1080/08927019309386235

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Initial biofilm formation was studied during start‐up of anaerobic fixed‐bed reactors with polypropylene as substratum. Five reactors were operated in parallel at 35°C with synthetic wastewater containing acetate, propionate and butyrate as substrates varying the mode of system operation. System variations included (a) operation with recirculation, (b) continuous and discontinuous (fed‐batch) feeding, and (c) different organic loading rates (OLR). An enrichment culture from sludge of a municipal sewage treatment plant, grown in a stirred tank reactor at an OLR of 2g.l−1d−1for 72 d, was used as inoculum. Reactor performance and biofilm formation were followed over a period of 58 d. Highest biomass accumulation and maximal OLR of 23 kg CODm−3d−1were obtained in the reactor with the highest space loading. The polypropylene support acted not only as a substratum for biofilm growth but also as a filter retaining biomass in flocs. Scanning electron microscopy (SEM), phase contrast microscopy and epifluorescence microscopy documented various bacteria in the biofilm community and the floc population. Propionic acid and butyric acid oxidation were carried out byDesulfobulbussp., and bySyntrophomonassp. andSyntrophosporasp. respectively.Methanothrixsp. was the main acetotrophic methanogen in both floes and biofilm. Morphologically distinctMethanosarcinasp. were only retained in a network ofMethanothrixfilaments within flocs. Irregular coccoid methanogens of the generaMethanogeniumorMethanoculleuswere the main hydrogenotrophic methanogens with cells ofMethanospirillumsp.,Methanocorpusculumsp. andMethanobrevibactersp. occurring in lower numbers. Bacteria adhering during early phases of biofilm formation were detected as settlers responsible for primary colonisation and initiating development of a mature biofilm. Formation of microcolonies of trophic sub‐populations is demonstrated. Evidence forDesulfovibriosp. responsible for glycocalyx secretion was provided.

ISSN:0892-7014    

DOI:10.1080/08927019309386236

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

An existing dynamic biofilm multiple species computer simulation (Wanner & Gujer, 1986) is used to model both heterotrophic carbon‐oxidizing and autotrophic nitrogen‐oxidizing bacterial populations within an accumulating biofilm, a system characteristic of the biological nitrification treatment of domestic waste‐waters. Such simulation predicts spatial distributions of N‐number of microbial species metabolizing a possible M‐number of substrates in an expanding (or contracting) biofilm as a function of time. Here the effects of substrate mass transfer limitations and bacterial species distributions on the overall biofilm effectiveness factor, a heterogeneous reaction‐based concept commonly used to interpret the effects of mass transfer on immobilized biological processes, are assessed.

ISSN:0892-7014    

DOI:10.1080/08927019309386237

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A kinetic model for the selective release of specifically adhering cells by elution with a soluble free ligand is developed. The effect of hydrodynamic forces and competitive free ligand concentration on the release of specifically adhering cells are investigated using this model. Simplified cases of the general model under limiting conditions are considered as well as fractionation of cell mixtures by selective elution.

ISSN:0892-7014    

DOI:10.1080/08927019309386238

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

ISSN:0892-7014    

DOI:10.1080/08927019309386230

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor