The use of chitosan in protecting wooden artifacts from damage by mold fungi

Background: Many buildings in Egypt e.g. museums, mosques and churches, do not possess controlled environments for minimizing the risks of damage of wooden artifacts due to the growth of fungi. Fungal damage usually appears as change in wood color, appearance of stains, and sometimes deformation of wooden surfaces. In this study we focused on the effect that some fungi exert on the properties of wooden artifacts and evaluated the effectiveness of different concentrations of chitosan on their protection against damage by mold fungi. Results: Samples were collected from different monuments and environments, and fungi growing on them were isolated and identified. The isolated Penicillium chrysogenum, Aspergillus flavus and /Aspergillus niger strains were used for the infestation of new pitch pine samples. The results revealed that the lightness of samples infected with any of the tested fungi decreased with increasing incubation times. XRD analysis showed that the crystallinity of incubated samples treated individually with the different concentrations of chitosan was lower than the crystallinity of infected samples. The crystallinity index measured by the first and the second method decreased after the first and second months but increased after the third and fourth months. This may due to the reducing of amorphous part by enzymes or acids produced by fungi in wooden samples. Conclusions: The growth of fungi on the treated wood samples decreased with increasing the concentration of chitosan. Hence, it was demonstrated that chitosan prevented fungal growth, and its use could be recommended for the protection of archeological wooden artifacts.

Isolation and characterisation of antibiotic producing microorganisms in composted Nigerian soil.

Compost samples obtained from different locations within the premises of the university of Lagos were analysed to determine the presence and types of antibiotic-producing bacteria, fungi and actinomycetes using nutrient agar, potato Dextrose agar and starch casein nitrate agar respectively as culture media. A variety of bacteria were isolated and these included Staphylococcus aureus, B. subtilis, B. pumilis, B. lactesporus, B. megaterium, B. pulvifaciens, B. licheniformis, Streptococus spp., Corynebacterium spp. and E. coli. The fungal isolates encountered were Aspergillus niger, A. flarus, T. viridae, P. chrysogenum, P. pinofylum and Absida spp., while the following actinomycetes were identified: Norcadia spp., Micromonospora spp., Streptomyces scabies, S. reticuli and S. hygroscopicus. When these organisms were screened for antibiosis, the following species were found to be antibiotic producers: B. licheniformis, B. subtilis, Penicillium chrysogenum, Streptomyces reticuli, S. hygroscopicus and Micromonospora spp. The fungus Penicillium chrysogenum had the highest rate of antibiotic production with an inhibitory zone width of 17mm while Trichoderma viridae produced toxins lytic to other fungal hyphae.