Anti-fungal properties of pyrolytic oils derived from softwood bark
D Mourant, Dian-Qing Yang, Xiao Lu, C Roy
Thermal decomposition of balsam fir and white spruce mixed bark residues at 450°C and under vacuum (< 20 kPa abs.) results in high yields of pyroligneous liquors rich in phenolic content. This vacuum pyrolysis process has been scaled-up to a pyrolysis plant with a feed capacity of 3.5 t/h of softwood bark, which is the largest plant of this type in the world. The pyrolytic aqueous condensates have been tested for their anti-fungal properties. One of the major objectives of this study was to identify which groups of chemical compounds were the most active to inhibit the growth of wood decay fungi. The fractionation of the pyrolytic aqueous phase in four distinct parts was accomplished by a liquid-liquid extraction method. The four fractions were named F1 (ether extractibles), F2 (ethyl acetate extractibles), F3 (neutral compounds) and F4 (phenolic compounds). Petri tests were conducted using two brown rot fungi (P. placenta and G. trabeum) and two white rot fungi (I. lacteus and T. versicolor). The composition of these fractions was analysed by GC/MS. Fraction F1, with concentrations of organic acids, phenols and derivatives (3.0% by weight), benzenediols (3.9% by weight), and a variety of other products (quinones, furans, etc.), was the most promising to inhibit the growth of decay fungi, while fraction F3 showed no inhibitive effect in the Petri dish agar test. C. versicolor was most sensitive to these fractions, while I. lacteus was the least. The addition of CuSO4 to the water soluble organics improved their ability against decay.