Application of wood vinegars prepared from branches and tree tops of Cryptomeria japonica at different collection temperatures to evaluate their fungi resistance for moso [Phyllostachys heterocycla f. pubescens] bamboo material

In this study, wood vinegars were collected from the chimney outflow of earthen kiln at 6 different temperatures (80-159, 80-90, 91-100, 101-120, 121-140, and 141-159degC) during the charcoal preparation from the branches and tree tops of Cryptomeria japonica. These vinegars were used to evaluate the fungus resistance of airborne fungus particles, Aspergillus niger, Aspergillus flavus and Trichoderma viride after they as well as acetic acid and tap water (as the controls) were used to impregnate Moso bamboo specimens for 240 min using the vacuum method. The basic properties of the wood vinegars obtained were: pH values of 2.54 to 3.45, specific gravity ranging from 1.006 to 1.008, contents of organic acid ranged between 1.75 and 3.03%, soluble tar content from 0.186 to 0.629%, and the color difference (deltaE*) ranged from 8.37 to 14.36. The absorption by the bamboo specimens after having been processed with the various vinegars using the vacuum method ranged from 10.85 to 19.35 mg/cubic cm. The results of the macro-observation showed that after 70 days the growth rate of airborne fungus particle on the surface of bamboo specimens impregnated with vinegar at 80 to 159degC ranged between 10% and 15%, but it was close to 100% for either of the controls after only about 30 days. The FTIR analysis showed that the specimens treated with vinegar at 80 to 159degC did not contain the fungal chemical compounds, at 1654 /cm (C=O) and 1552 /cm (N-H), while the acetic acid and the tap water both showed the absorbance peaks. The C/N ratio of the airborne fungus particles of the specimen treated with vinegar at 80 to 159degC was 131.4%, but it was only about 90.5 to 102.8% for the controls. These results suggest that the compositions of the wood vinegars collected at different temperatures affect the fungus resistance of the bamboo material.