Antimicrobial Activity of Slow Pyrolysis Distillates from Pine Wood Biomass against Three Pathogens

The aim of this study was to evaluate the antimicrobial activity of wood distillates obtained from Scots pine (Pinus sylvestris) sawdust in order to explore new alternatives for the utilization of wood industry by-products. The distillates were produced by slow pyrolysis thermal conversion in three process phases with increasing temperatures, namely drying, torrefaction and pyrolysis, and three cooling units with different temperatures to condensate the distillates. This yielded nine different liquid fractions. The food-related pathogens, Salmonella, Listeria monocytogenes and Candida albicans, were evaluated for their susceptibility to the distillate fractions using an agar diffusion test. The antimicrobial activity was estimated by measuring the formed inhibition zones after the incubation period. In addition, the minimum inhibitory concentration (MIC) and microbicidic concentration were assayed for a selected fraction (T2) from the torrefaction phase with Bio-screen C. The results indicated that the distillates from the torrefaction and pyrolysis phases had antimicrobial activity against the tested microbes. The MIC value of the T2 fraction for all tested microbes was 0.83% (v/v). Furthermore, the T2 fraction was microbicidic for Salmonella and Listeria strains in 0.83% (v/v) solution and Candida strain in 1.67% (v/v) solution. In conclusion, Scots pine wood distillates obtained from slow pyrolysis have the potential to be developed as antimicrobial agents against pathogenic microbes. Next, research is needed to investigate the chemical composition of the distillates and to assess their safe use.