Stain Fungi and Discoloration Control on Rubberwood (Hevea brasiliensis Muell. Arg.) by Vacuum-Pressure Treatment with Catechin from Gambir (Uncaria gambir Roxb.)

Abstract

Recently, the morphological and molecular features of five stain fungi infecting rubberwood (Hevea brasiliensis), namely Paecilomyces maximus, Paecilomyces formosus, Penicillium crustosum, Paecilomyces lecythidis and Aspergillus chevalieri, have been studied. Prior to this study, the authors revealed that catechin from gambir (Uncaria gambir) could inhibit the growth of the white-rot fungus Schizophyllum commune, and it was important to determine the bioactivity of the aforementioned agent against A. chevalieri. The efficacy of the biocidal agent was examined using a laboratory wooden block test. Rubberwood blocks, 8 mm in thickness, 20 mm in width, and 30 mm in length, were impregnated with catechin solution at concentrations of 6%, 9%, 12%, and 15% (w/v) using the vacuum-pressure method, and their bioactivity was monitored over three weeks through visual and scanning electron microscope assessment of fungal growth as well as the discoloration intensity of the wood samples. The results showed that catechin treatment increased the resistance of wood samples to A. chevalieri. Overall, the higher the catechin concentration, the lower the fungal growth. The lowest fungal growth was observed in the wood samples treated with 12% and 15% catechin (score of 0), demonstrating no discoloration. In contrast, the fungal growth score of the untreated wood samples reached 4, indicating severe discoloration. Catechins appear to be adequate biofungicides against stain fungi in rubberwood.

Environmental Suitability for Conservation and the Risk Period for Fungal Damage of Wooden Cultural Heritages in Korea

“…Among them, temperature (T) and relative humidity (RH) are highly related to meteorological conditions, greatly affecting the germination and growth of various airborne fungi inside and outside WCHs. In particular, in the Korean Peninsula with four distinct seasons, when high internal T and RH conditions are created in summer, and simultaneously the air quality inside the space is stagnant, the germination and growth of rot fungi and imperfect fungi, which gain nutrition from organic cultural heritages, cause biological damage to the materials of the heritage structures (Ham et al, 2021;Hong et al, 2018Hong et al, , 2019Lee et al, 2022;Nandika et al, 2023;Priadi et al, 2021Priadi et al, , 2023Yun et al, 2021). For example, in the 1990s, Seosagan-Jang, one of the storage places for Tripitaka in Haeinsa Temple, had poor ventilation, causing high RH during the rainy season every year and continuous mildew growth on the surface of several printing wood blocks stored inside (Park, 2011).…”