Removal of paper microbial contamination by means of dielectric barrier discharge

Paper due to the influence of wide range of agents undergoes different degradation processes that result in alarming conditions of most of the historical documents. One of the problems that have to be solved is the paper biodeterioration by microbiological agents. Generally the paper material sterilization can be achieved by chemical and/or physical means, such as heat, chemical solutions, gases and radiation. Most conventional sterilization techniques are associated with some level of additional damage to the material or medium supporting the microorganisms. It is therefore desirable to focus the research activities on the new techniques that are both efficient in microorganism removal and gentle to the medium supporting the microorganisms. This contribution presents results of the the microbial contamination removal from the paper using the plasma generated at atmospheric pressure. Aspergillus niger, the fungi commonly found in libraries and archives has been chosen as a bio-indicator enabling to evaluate the effect of plasma assisted microbial inactivation. Dielectric barrier discharge (DBD) operated at atmospheric pressure was used for the paper sterilization because of its easy applicability for archive prints. This technique has also advantage in cost of process as the expensive vacuum pumping equipment is not necessary and high reactant concentrations make sterilization process very fast. Certain amount of fungi was spread on Whatman paper no. 1 and it was cultivated on agar plates. Afterwards the dried paper samples were treated in DBD performed in pure nitrogen, argon or helium. The treatment time and the plasma power density were varied in order to see the effect of the plasma treatment on the fungi removal. After the treatment, the microbial abatement was evaluated by the standard plate count method. This proved a positive effect of the DBD plasma treatment on fungi removal. Moreover the influence of the plasma treatment on the paper properties was invest- - igated.