Abstract
This study explored various bioinspired processes to improve lignocellulosic materials, namely biomineralization, enzymatic grafting, and metal chelation. First, Sporosarcina pasteurii was utilized to biomineralize moso bamboo via microbially induced calcite precipitation (MICP). Extraction did not significantly affect the 3% post-leaching mass gain, indicating superficial microbial CaCO3 deposition, as confirmed by FTIR, XRD, SEM-EDS, and µCT analyses. Despite this, biomineralized bamboo showed improved fungal durability after soil block decay tests, exhibiting reduced mass loss against Gloeophyllum trabeum (G.t.: ~3%) and Trametes versicolor (T.v.: ~4%) compared to controls (G.t.: ~7% and T.v.: ~8%). Post-decay mechanical testing indicated enhanced compressive modulus (+500 MPa), compressive strength (+10 MPa), and elevated viscoelastic properties. Fire performance also improved, demonstrating shorter flaming durations (<150 s), higher residual mass (+4.5%), and slower degradation (~8%/min). Second, lignin nanoparticles (LNP) prepared through the hydroxymethylation of softwood Kraft lignin, followed by solvent shifting method, were enzymatically grafted onto loblolly pine using laccase. Reduction in particle size was observed and verified by particle size analysis and SEM. The LNP produced exhibited particle sizes within the nano-range (210 nm) compared to the micro-sized particles of KL (137 µm). The thermal properties and flame retardancy of control and treated pine after leaching were evaluated using thermogravimetric analysis (TGA) and thermal imaging via a modified UL 94 flammability test, respectively. The LNP-treated pine exhibited 9% higher residual mass, 2%/min lower thermal degradation rate, lower initial surface temperatures, and delayed ignition and heat transfer. The fungal durability of pine wood samples was tested against two brown-rot fungi, G.t. and R.p. (Rhodonia placenta), and two white-rot fungi, T.v. and I.l. (Irpex lacteus), by using soil-block tests. Lastly, loblolly pine was coated with calcium carbonate nanopowder chelated with citric acid (CA) and tartaric acid (TA). The combined acid treatment (CA-TA) achieved an 89% mass gain, while TA treatment exhibited higher leaching resistance (69% post-leaching mass gain). Under oxidative conditions, the coatings promoted char formation, yielding inorganic residues of 6.4% to 7.8%. Flame retardancy tests confirmed that the coatings delayed combustion. The TA treatment limited surface temperature to ~200 °C after 60 s, improving on the surface temperature of the control (>550 °C).