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Inhibitors of biofilm damage on mineral materials


The project focussed on the development of a strategy to inhibit and eliminate biofilms on building surfaces and to introduce these techniques into conservation society and companies. This was achieved by demonbstrating the results in a minimum of 10 Conferences and 20 publications among which an end user brochure edited and produced by Historic Scotland. The polyphasic treatment approach will lead to new horizons in restoration and conservation of monuments and may fuse the knowledge and skill also with the producer lione of intelligent or self cleaning building materials.
The prototype of a portable photodynamic treatment for rock biofilms in situ was developed at the laboratory of environmental biotechnology. In further experimentation the group focussed experimentally on rose of Bengal, Nuclear fast red and methylen blue as accelerators of cell penetration and destruction. Initially it was considered that a portable light excitation device would be necessary to activate the photodynamic treatments. However, early screening studies demonstrated that the PDTs were sufficiently activated under natural light. In terms of the field studies the treated surfaces were all going to be exposed to natural light. It was decided that there would not be any need for the portable device.
The objective was to evaluate different apoptosis signals, pigment inhibitors, exopolysaccharide inhibitors, permeabilizers and photodynamic treatments for their "in vitro" effectiveness against bacteria, fungi and algae commonly found in deteriorated stone materials. Model organisms were selected from those commonly found on deteriorated stone and plaster substrates. Selected photodynamic treatments were screened for effectiveness against algae/cyanobacteria both in vitro and on stone and painted plaster substrates. The concept of a polyphasic approach to inhibiting detrimental growth of biodeteriorative and or unaesthetic biofilms seems extremely valid after the first two years of experimental approach. The literature reviews have shown clearly a necessity to analyse for and to inhibit biofilm growth on monument mineral materials. The selection of a few non-toxic or low toxic compounds for cambatting detrimental biofilms was in urgent need. The combination of biocides with permeabilizers and photodynamic treatments turned out as a very promising tool, which now is in the field testing phase. Special compounds, combined with photodynamic activation treatments seem to be a very attractive alternative to costly and environmentally hazardous treatments effected until now in many monuments worldwide.
The polyphasic treatment was tested in laboratory and in four field sites. Scotland had established two sites, Germany one full site in Oldenburg and two small testing sites at a quarry and the BIOGEMA offices. In Spain a field site was established on the roof of INASMET Technologies. The field sites were analyzed in respect of climatic exposure and growth of natural biofilm. After biofilm development occurred, the films were treated and the success was tested using techniques developed within the project consortium. Also the field site results indicate strongly, that polyphasic treatments using permeabilizers, pigment inhibitors, polysaccharide inhibitors, and photosensitizers considerably reduces the amount of dangerous biocides necessary for efficient treatment of biofilm infections on mineral surfaces.
The BIODAM team has successfully approached surface damage by microbial biofilms. The biofilm builder resist to treatment by being embedded in protective slime and pigment layers. Biocide treatment is less and less favoured by conservators and restorers. Official agencies and offices turn increasingly away from industrial microbicidal products offered on the market. BIODAM aimed at minimizing the numbers and amounts (concentrations) of biocidal substances. This was achieved by successfully testing a polyphasic treatment using cell permeabilizers, photosensitizers activated by sunlight, polysaccharide (slime) inhibitors, pigment inhibitors and low amounts of traditional biocides simultaneously. This new combined technique is very important for the further development of strategies to avoid excessive use of insecticides, herbicides and biocides on ICOMOS sites and other UNESCO protected areas and buildings. Presently field experiments are ongoing beyond the durance of the BIODAM project with the ultimate goal to demonstrate that a combined photoactivation and cell penetration treatment will drastically reduce the amount of potentially poisonous and dangerous substances frequently in use to ban biological damage to objects of art also on a long-term scale. Historic Scotland and BIOGEMA helped by ICBM, CvO-University of Oldenburg will propagate and further develop the technique. Information can be received by these partners.