Showing papers on "Biofilm matrix published in 1997"

Substratum topography influences susceptibility of Salmonella enteritidis biofilms to trisodium phosphate.

Abstract: Established (48- and 72-h) Salmonella enteritidis biofilms grown in glass flow cells with or without artificial crevices (0.5-, 0.3-, and 0.15-mm widths) were subjected to a 10% trisodium phosphate (TSP) solution under different flow regimens (0.3, 0.6, 1.2, and 1.8 cm s-1). The abundance of biofilm remaining after TSP treatment, the biocidal efficacy of TSP, and the factors which contributed to bacterial survival were then evaluated by using confocal laser microscopy and a fluorescent viability probe. Biofilm age affected the amount of biofilm which remained following a 15-s exposure to TSP. After TSP treatment of 48-h biofilms, 29% of the original biofilm remained at the biofilm-liquid interface, whereas 75% of the biofilm remained at the base (the attachment surface). Following TSP treatment of 72-h biofilms, 27% of the biofilm material remained at the biofilm-liquid interface, 73% remained at the 5-micron depth, and 91% remained at the biofilm base. Results obtained using the BacLight viability probe indicated that TSP exposure killed all the cells in 48-h biofilms, whereas in the thicker 72-h biofilms, surviving bacteria (approximately 2% of the total) were found near the 5- and 0-micron depths. In the presence of artificially constructed crevices, an inverse relationship was shown to exist between bacterial survival (ranging from approximately 13 to 83% of total biofilm material) and crevice width. This relationship was further influenced by the velocity of TSP flow; high TSP flow velocities (1.8 cm s-1) resulted in the lowest number of surviving bacteria at the base of crevices (approximately 42% survival). Extended time courses demonstrated that after TSP stress was relieved, biofilms continued to grow within crevices but not in systems without crevices. It is suggested that advective TSP flux into crevices and through the biofilm matrix was enhanced under conditions of high flow. These results suggest that the inherent roughness of the substratum on which the biofilm was grown and the timing of TSP application are important factors controlling the efficacy of TSP treatment.

Einsatz von Enzymen zur Kontrolle der Biofilmbildung in Papiermaschinenkreisläufen

Abstract: Enzyme use for biofilming control in whitewater circuits has long been in the focus of discussions. This strategy is targeted to partly or completely replace organic microbicides that are currently being used. Since the selection of enzymes or enzyme systems is decisively dependent on the nature of the extracellular polymeric substances (EPS) in a biofilm, these substances had to be analysed in order to identify the principal components ofa biofilm matrix. Developing suitable analytics for the determination of EPS in biofilms was one of the crucial and most time consuming efforts in the context of enzyme use. By gaining in-depth knowledge of the EPS composition in biofilms occurring in PM circuits, researchers have enabled enzyme products to be provided for specific circuits. In addition, modern test methods allow biofilming phenomena to be studied in test rigs. These analytical methods and laboratory tests were used to create a number of enzyme formulations which have already been applied in the paper industry. Since April 1995, trials have been conducted on a paper machine for the production of woodfree writing and panting paper in a nepal process. These trials are aimed at reducing both the microbicide dosages and the specific treatment costs. Initially, a microbicide enzyme combination was added into the process. After two months, the microbicide dosage in whitewater 1 was reduced by 60% and after 4 months it was discontinued altogether In a second step, the enzyme dosages were optimized. Future project steps will be devoted to an optimization of the treatment costs. The experiences gained with enzymes for biofim control on a laboratory and mill scale have encouraged the authors to continue their work in this field. However, it seems doubtful whether enzymes are the sole answer to the complex problem of biofilming in PM whitewater circuits. A combined use of microbicides biodispersants and enzymes appears most promising when it comes to developing an environmentally compatible and low-cost method of treatment.

Determining The Biofilm Penetrating Ability Of Various Biocides Utilizing An Artificial Biofilm Matrix

Abstract: The efficacy of many commonly used biocides is often determined by laboratory evaluations against a variety of planktonic microorganisms. While these tests provide some information as to the performance of a biocide against a particular microorganism, they may not predict how well the biocide will perform under actual field conditions against the more problematic sissile form of the organisms. In order to address the issue of how well a biocide penetrates and kills the problematic microorganisms contained within a biofilm, an artificial biofilm system utilizing microorganisms embedded in alginate beads has been used to compare the efficacy of biocide treatments against both the planktonic and sessile form of the same organism. Pure cultures of Enterobacter aerogenes, as well as mixed field isolates, were used in the experiments. In addition, the alginate beads were prepared with actual system waters taken from a variety of industrial applications. In that way, all of the scale and corrosion inhibitors and other contaminants which are present in the actual system are also present in the model biofilm system. In all cases, the organisms contained within the artificial biofilm were significantly more difficult to kill than the corresponding planktonic microbes.