Metagenomic insights into postbiotic-mediated modulation of strawberry surface microbiome and metabolic activity

The increasing demand for sustainable alternatives to chemical disinfectants in postharvest fruit handling has incentivized exploration into microbiome-based interventions. We evaluated the impact of lactic acid bacteria (LAB)-derived postbiotic formulations (FF1, FF2, FF3) and a commercial disinfectant (CD) on the microbial community structure of the strawberry fruit surface.

Taxonomic and functional changes in the microbial communities were evaluated using shotgun metagenomic sequencing, enabling comprehensive profiling of microbial composition and functional potential through gene family abundance, EggNOG functional categories, KEGG pathways, and MetaCyc metabolic reconstruction. The tested formulations consisted of a precipitated peptide-protein extract (PP) from Weissella cibaria UTNGt21O (FF2), used as the antimicrobial agent, and an exopolysaccharide (EPS) from W. confusa UTNCys2-2 (FF3), serving as a biopolymer carrier, applied in combination (FF1: PPGt21O + EPSCys2-2) or individually.

Our integrated analysis revealed that the highly suppressive formulation, FF1, outperformed the CD by fundamentally restructuring the microbial landscape. Taxonomically, FF1 notably reduced the abundance of key opportunistic spoilage or hazardous organisms. Rather than acting as an indiscriminate biocide, FF1 functioned as a targeted ecological disruptor. Functional profiling (eggNOG, KEGG, and MetaCyc) suggested potential shifts in functional capacity, including a reduced relative abundance of genes associated with translation machinery, cellular membrane expansion (stearate biosynthesis), and host lipid degradation (fatty acid β-oxidation). In parallel, the FF1-treated microbiome showed a higher relative abundance of genes linked to stress-response functions, including heat shock proteins and cell wall-related processes such as peptidoglycan maturation. In contrast, less restrictive formulations (FF2 and FF3) permitted the proliferation of opportunists such as Pseudomonas spp. and Xanthomonas fragariae, accompanied by active energy-consuming and tissue-degrading metabolic signatures.

These findings suggest possible underlying mechanisms of LAB-derived postbiotics, demonstrating that FF1 forces the surface microbiome into a metabolically restricted, non-degradative survival state, potentially contributing to the preservation of postharvest strawberry quality.