Speaker
Description
Humic substances play critical roles in environmental remediation and soil fertility, yet natural humification requires decades to centuries. Here, we report a synergistic approach combining microbial fermentation with manganese dioxide (MnO₂) catalysis to produce mature humic-like substances (HLS) within 15 days. This work represents the first systematic demonstration of yeast-mineral synergy for accelerated humification of hydroquinone. We screened multiple microbial systems (Lactobacillus acidophilus, Saccharomyces cerevisiae, vitamin C-supplemented yeast, and rennet enzymes) and employed multi-technique characterization (UV-Vis, FTIR, XRD, SEM, XPS, solid-state ¹³C NMR, and DFT calculations) to elucidate HLS formation mechanisms. Results reveal a dual-pathway mechanism governing HLS formation: MnO₂ catalyzes rapid aromatic network condensation (30–45% of carbon) via surface-templated radical coupling, while microbial metabolism simultaneously generates and preserves aliphatic domains (50–60% of carbon). This parallel-pathway mechanism produces dual-domain architectures integrating aromatic stability (UV-Vis absorption up to 450 nm, E₄/E₆ ratios of 3–4, and organized π-π stacking with 4.0 Å spacing) with aliphatic flexibility. The optimal S. cerevisiae + MnO₂ system yields a carbon distribution of 55% aliphatic and 35% aromatic carbon, closely matching natural humic acids, along with hierarchical porous morphologies (10–100 nm pore networks) and favorable electronic properties (HOMO-LUMO gap of 1.40 eV; binding energy of −111.13 kcal/mol). Vitamin C supplementation enables additional compositional control, maintaining approximately 60% aliphatic content through antioxidant protection while promoting organized layered structures capable of exfoliation. Control experiments without MnO₂ confirmed the essential role of the catalyst in accelerating both oxidative condensation and structural organization. This bio-mineral synergistic platform enables molecular-level control over aromatic-aliphatic architectures unachievable via single-component systems, providing a mechanistic foundation for rational design of advanced materials for heavy metal remediation, organic pollutant degradation, and soil carbon sequestration.
