Anti-mold activity and reaction mechanism of bamboo modified with laccase-mediated thymol

Abstract

Exogenous mold infection of bamboo-based material results in the reduction of bamboo durability. Thymol, a remarkably safe and green fungicide, can be successfully applied on bamboo to resist mold attacks. The leachability of volatile thymol in bamboo led to a decrease in bamboo anti-mold activity due to the lack of chemical bond attachment. In this study, a novel laccase-mediated system was used to improve bamboo anti-mold activity by enhancing the fixation of thymol. The results showed that this modification considerably restricted the rate of mold infection. The volatility of thymol in modified bamboo decreased from 0.10 % to 0.05 %, which extended the activity persistence of mold resistance. Meanwhile, the surface hydrophobicity of the modified bamboo increased from 45.3 ° to 118.6 °. Among the three major components of bamboo investigated, only lignin experienced a grafting reaction with thymol catalyzed by laccase. The ether bond was identified as the major linkage between lignin and thymol in laccase-mediated thymol-modified bamboo via multiple characterization methods. This work not only demonstrates a feasible avenue for bamboo preservation, but also elucidates the inter- and intra-chemical bonds in bamboo after laccase-mediated thymol modification.