The effects of UV laser radiation as sterilizer for cultural heritage

This work reports on a novel sterilization technique for bacteria which may be involved in deterioration of cellulose-based antiquities (paper, textile and wood). The bacterium we processed, a Nonomuraea sp. strain, was a mycelial microorganism belonging to the Actinomycetes group. This group includes many microorganisms that are able to attack cellulose and/or lignin. Escherichia coli was used as a reference microorganism. The UV source used as sterilizer was an excimer laser operating at 308 nm, 1 Hz. We demonstrated that, under different experimental conditions, the sterilization process was effective just after few seconds. For laser irradiation at 80 mJ/cm(2) per pulse, survival rate decreased of three orders of magnitude just after 75 s. The measurement of the absorption cross section for 308 nm photons on Nonomuraea sp. cells was also carried out.