Linalool as a green technological intervention: Enhancing bioprocess resilience and microbial functional redundancy in plant biomass fermentation against mold stress

Solid-state fermentation (SSF) of plant biomass is a cornerstone of sustainable bio-manufacturing, yet its industrial scalability is frequently compromised by mold-induced instability. Conventional synthetic preservatives often impose indiscriminate antimicrobial stress that disrupts functional microbiota. This study evaluates linalool, a plant-derived terpenoid, as an innovative modulator to enhance bioprocess resilience under varying mold pressures. Integrating 16S rRNA and ITS1 amplicon sequencing with untargeted UHPLC‑MS/MS metabolomics across four fermentation cycles, we revealed that linalool functions as a condition‑dependent microbial modulator rather than a broad‑spectrum inhibitor. At low to moderate mold stress, linalool enhanced community evenness (e.g., bacterial Shannon index 5.885 in slightly moldy cycle 1; 4.981 in moderately moldy cycle 3), whereas under intensified stress it drove single‑species dominance (e.g., Aspergillus at 95.6%). Linalool orchestrated a stage‑sensitive bacterial succession, shifting the community from Pantoea ‑dominated (49.7%) to Pseudomonas ‑enriched (44.1%) profile with increasing mold severity. In contrast, sodium dehydroacetate induced extreme oscillations, collapsing bacterial diversity or promoting atypical fungal colonizers such as Microascus (66.3%) and Wallemia (73.9%), accompanied by larger metabolic perturbations (log 2 (Fold Change) up to 8.9 versus 6.1). Metabolomic profiling showed that linalool upregulated flavonoid/anthocyanin biosynthesis pathways, while SDA enriched stress-related tryptophan and phenylalanine metabolism. By cycle 4, both treatments converged onto central carbon metabolism, but linalool-treated systems retained a more stable metabolic core. These results demonstrate that linalool exerts a milder, trajectory‑directed modulation that preserves functional redundancy and steers the microbiome toward a common metabolic homeostatic core, thereby offering a rational basis for designing green, stable, and resource-efficient fermentation processes in industrial biomass conversion.