Synergistic effects of enzymatic decomposition and mechanical stress in wood degradation

Wood mechanical properties deteriorate due to formation of cracks caused by mechanical loading and due to the loss of structural polymers as a result of enzymatic activity. How these processes contribute to wood degradation and whether the interaction between mechanics and enzymes accelerate wood degradation was studied. Lignocellulolytic enzymes and dynamic mechanical loading, either alone, in combination or successively were applied to native and hydrothermally modified Scots pine (Pinus sylvestris L.) veneers. Tensile testing was employed to evaluate the changes in mechanical properties of the specimens. Fibre saturation point and hydroxyl group accessibility before and after hydrothermal modification and subsequent enzymatic hydrolysis were assessed by differential scanning calorimetry and dynamic vapour sorption techniques. The study revealed that simultaneous mechanical and enzymatic treatments lead to a significant reduction in Scots pine tensile strength while successive application of the two treatments did not reduce wood tensile strength to the same extent. The finding points towards the importance of synergy between abiotic and biotic factors in wood deterioration. Further, hydrothermal modification, unlike enzymatic hydrolysis, significantly affected wood hygroscopicity, but did not influence how the wood reacted to the mechanical and enzymatic treatments.