Chitosan and chitosan oligomers are receiving increasing attention due to their
antimicrobial properties. In the present study, they were assayed as a preventive treatment against
white-rot decay of Populus wood (very important in economic and environmental terms), caused
by Trametes versicolor fungus. Their capacity to incorporate different chemical species into the
polymer structure with a view to improving their anti-fungal activity was also assessed by mixing
oligo-chitosan with propolis and silver nanoparticles. The minimum inhibitory concentration of
medium-molecular weight chitosan (MMWC), chitosan oligomers (CO), propolis (P), nanosilver
(nAg), and their binary and ternary composites against T. versicolor was determined in vitro. Although
all products exhibited anti-fungal properties, composites showed an enhanced effect as compared
to the individual products: 100% mycelial growth inhibition was attained for concentrations of 2.0
and 0.2 mg mL1 for the CO-P binary mixture, respectively; and 2 g mL1 for nAg in the ternary
mixture. Subsequently, MMWC, CO, CO-P and CO-P-nAg composites were tested on poplar wood
blocks as surface protectors. Wood decay caused by the fungus was monitored by microscopy and
vibrational spectroscopy, evidencing the limitations of the CO-based coatings in comparison with
MMWC, which has a higher viscosity and better adhesion properties. The usage of MMWC holds
promise for poplar wood protection, with potential industrial applications.
