Antifungal activity of different molecular weights of a biopolymer chitosan against wood decay fungi

IRG/WP 08-30456

A S O Mohareb, M E I Badawy

In recent years chitosan has been investigated as a natural polymer for wood preservation against fungal decay. From an environmental point of view, chitosan seems to possess a potential approaches as wood protecting agent. In this study, three different molecular weights of chitosan compounds (with approximately the same degree of deacetylation 83 ± 2 %) were evaluated as in vitro and in vivo assessments against two wood decay fungi (Coriolus versicolor and Poria placenta). Average molecular weights of chitosan samples were determined by measurements of intrinsic viscosity and were found to be 3.60×105 Dalton for low molecular weight (LMW), 6.11×105 Dalton for medium molecular weight (MMW) and 9.53×105 Dalton for high molecular weight (HMW). In vitro antifungal assay was carried out using of a mycelial radial growth inhibition technique. The results showed that the antifungal activity was increased with a decreasing of the molecular weight and a LMW chitosan was exhibited a high antifungal potency against Coriolus versicolor and Poria placenta with EC50 of 1876 and 1744 mg.L-1, respectively. In addition, the results revealed that Poria placenta was more sensitive to these compounds than Coriolus versicolor. Preliminary in vivo biological test was carried out on malt agar using a miniblock technique for beech and Scots pine sapwood with Coriolus versicolor and Poria placenta, respectively. After six weeks of exposure to fungal attack all chitosan protective systems tested proved their relative effectiveness when compared to the control specimens. Furthermore, chitosan LMW was the most effective compound among all treatments at the higher concentration against the tested fungi.


Keywords: chitosan, molecular weight, intrinsic viscosity, antifungal activity, wood preservation

Conference: 08-05-25/29, Istanbul, Turkey


Download document (201 kb)
free for the members of IRG. Available if purchased.

Purchase this document