Data-driven optimization and DFT-elucidated bleaching of kombucha fermentation-derived bacterial cellulose for thermal insulation.

The brown bacterial cellulose (BC) pellicle from kombucha fermentation cannot be used as a colorless substrate unless chromophores are removed without degrading the cellulose scaffold, a trade-off that existing decoloration methods have not resolved. Here we report a hydrogen peroxide bleaching strategy that selectively removes these chromophores while preserving the cellulose Iβ scaffold. A Box-Behnken design with random forest regression (training R2 = 0.847) identified temperature (56.8%) as the dominant parameter and showed that higher treatment temperature consistently reduced residual DPPH scavenging, with no interior optimum within the tested ranges. Density functional theory on ten LC-MS identified chromophores showed that H2O2 susceptibility is governed by LUMO energy, with flavonoid glycosides (LUMO ≤ -1.8 eV) as the most vulnerable class. Fukui analysis localized attack to oxygen sites, and FTIR confirmed loss of ester CO (-83%) and aromatic CC (-23%). The selected treatment (3 wt% H2O2, 80 °C, 2 h) yielded a white pellicle with 94% native crystallinity (CrI = 88.4%), raising decomposition temperature by 90 °C and achieving thermal conductivity of 0.038 ± 0.003 W m-1 K-1 (42% below control, within 15% of polyurethane foam). Peroxide self-decomposition eliminates the need for a separate quenching step. These results establish H2O2-bleached BC as a renewable thermal insulator and demonstrate a mechanistically grounded methodological framework that may be adaptable to other pigmented polysaccharide materials pending substrate-specific evaluation.