First aid for flood-damaged paper using saltwater: The inhibiting effect of saltwater on mold growth

摘要

With the aim of developing a new easy-to-use method for rescuing flood-damaged paper, the effect of saltwater on the inhibition of fungal growth on paper was investigated. This procedure could be used instead of, or assisted by freeze drying. Cellulose-digesting Trichoderma reesei, three types of fungi representative of fungi growing on paper (T. reesei, Aspergillus terreus, and Aureobasidium pullulans) and various naturally airborne fungi were cultured on cellulosic materials in liquid media containing artificial seawater with different salt concentrations. The addition of salts successfully inhibited the growth of T. reesei on microcrystalline cellulose at the concentration of 3.2% (m/m) or higher. The critical salt concentration, 3.2%, is within the general range of salt content in seawater. Other solutions of salts similar to sodium chloride also inhibited fungal growth. Although the observed growth-inhibiting effect was attributed to the high osmotic pressure of the salt solution, physiological effects depending on ion species used were also considered to be possible. The growth of all three types of fungi on copy paper was inhibited effectively when the salt concentration was increased. The growth of various fungi on pure cellulose, with enough oxygen supplied to pores, was completely inhibited (as assessed by visual examination) for 24 days at salt concentrations of 3.5% (m/m) or greater. The fact that the effect of saltwater on cellulosic materials was observed even under optimum medium conditions implies that fungi would be considerably inhibited on flood-damaged paper immersed in saltwater. This method is a promising first aid measure when circumstances do not allow for flood-damaged paper to be dried immediately.