Fungal and enzymatic pretreatments of bamboo lignocellulose towards high-strength biocomposites: Biological macromolecule/enzyme interaction and bonding enhancement.

An energy-intensive and chemical-consuming pretreatment of bamboo is often required to develop its high-performance composites. This study is to evaluate a fungal and enzymatic pretreatment as a sustainable surface modification approach towards high-strength bamboo biocomposites based on D. sinicus. Extracellular enzyme activity analysis suggested that the lignin oxidative enzyme and pectinase secreted by the white-rot fungus T. versicolor achieved higher reaction than the hydrolytic enzymes throughout the pretreatment. Chemical structure analysis revealed that lignin and hemicellulose were partially depolymerised and/or removed during the pretreatment, leading to a relatively higher cellulose content in D. sinicus. The analysis of physical property and microstructure suggested that the surface wettability and porosity of pretreated D. sinicus were significantly improved, facilitating the spreading and penetration of adhesive resins, which subsequently contributed to the superior interfacial bonding of the biocomposites. The tensile strength of the biocomposites increased from 195.8 MPa to 245.8 MPa and the bonding strength increased from 4.9 MPa to 6.3 MPa after the pretreatment, which were 1.26 times and 1.28 times those of the untreated biocomposite respectively. The results proved that the fungal and enzymatic pretreatment is a promising, eco-friendly and efficient surface modification approach for the preparation of high-strength lignocellulosic biocomposites.