Valorization of Bamboo Carbonization Byproduct for Sustainable Antifungal Protection of Natural Bamboo

Current antifungal methods for bamboo rely on toxic chemicals or destructive pretreatments. Bamboo vinegar, a byproduct of forestry processing residue, offers antifungal potential for bamboo protection, yet systematic comparisons between extracts from different raw material forms are lacking. To address this, a bamboo vinegar extract (BVE) system with high permeability and leaching resistance was developed for nondestructive, long-term mold protection of natural bamboo. BVE exhibited significantly stronger inhibition against three molds (inhibition zones: 2.21–2.48 cm) than bamboo vinegar powder extract (BVPE) (1.45–2.05 cm). 4-Methylcatechol (2.31% in BVE, absent in BVPE) was identified as the key bioactive constituent accounting for this potency difference. BVE penetrated 2 cm-thick natural bamboo within 3 s─over 10-fold faster than water─without delignification or destructive pretreatment, preserving 100.8% tensile strength and 116.6% flexural strength. BVE alone retained full antifungal efficacy after simulated rainfall (28 days, grade 0, >99% efficacy). Glutaraldehyde cross-linking further reduced mass loss and minimized color changes. Mechanistically, both extracts induced oxidative stress, causing membrane damage, content leakage, morphological collapse, and mitochondrial dysfunction. This work offers a nondestructive, highly permeable strategy for bamboo protection, transforming the bamboo carbonization byproducts into a functional material that safeguards bamboo itself.