Microbial species on a polychrome sculpture from a ruined church: Evaluation of the microbicide PBK against further biodeterioration

The main goal of this research was to isolate and identify microorganisms g rowing on a polychrome wooden sculpture found buried in the basement of a d amaged church in Gora, near Petrinja, Croatia. After isolation, the microor ganisms were identified by their morphological characteristics and by means of biochemical tests. The following were identified among the moulds isola ted: Alternaria tenuis 1211, Sordaria timicola 1051, Paecilomyces variotii 1001 and Penicilliium chrysogenum 615. The dominant bacteria isolated were Bacillus sp. And streptomyces sp. In order to prevent further attack due to the development of microorganisms before and after the restoration, the po lychrome sculpture was treated with an antimicrobial material. In this case , the preservative selected was methyl-isothiazolone PBK. To find the optim um concentration for preservation, solutions with concentrations between 30 and 210mgl(-1) of microbicide were prepared and tested separately on each isolated microorganism. It was found that solutions with a concentration of the microbicide methl-isothiazolone PBK between 30 and 60mgl(-1) inhibited the growth of almost all the isolated bacteria and moulds, except the moul d Soradria fimicola 150l, which was only inhibited by solutions containing 180 mgl(-1). For the protection of these wooden sculptures from further bio deterioration it was suggested that a solution containing 180mgl(-1) of met hyl-isothiazolone PBK be applied.