Metagenomic Insights into Microbial Community Succession and its Functional Changes during Natural Fermentation of...

Food waste is a global concern, necessitating sustainable management strategies. While fermentation offers a promising approach to valorizing food waste, studies about microbial dynamics and functionality assessment of semi-controlled naturally fermented food waste are still seldom. This study employed whole-genome metagenomic sequencing to investigate the microbial succession and functional pathways during natural fermentation of food waste over 15 days. Physicochemical analysis revealed that pH decreased from 5.20 to 4.32 on day 3 and then neutralized. Protein, lipids, and carbohydrate were in the range of 4.03-4.90%, 9.99-17.78%, and 85.44-77.84%, respectively. Taxonomic profiling revealed clear community restructuring from an initially diverse consortium dominated by Enterobacter, Klebsiella, Pseudomonas, and Acinetobacter (collectively > 45% relative abundance at day 0) to a highly specialized lactic acid bacteria (LAB) community (> 80% by day 15). Lactobacillus helveticus and Limosilactobacillus panis emerged as the late-stage co-dominant species, together accounting for 60-75% of the total reads. Functional annotation based on the PFAM, eggNOG, GO, and EC databases revealed a progressive reduction in gene family richness and metabolic breadth, with early samples being enriched in carbohydrate-active enzymes, membrane transporters, and amino acid metabolism pathways. By contrast, late-stage communities were dominated by LAB-associated fermentative functions, including lactate and acetate production, stress-response modules, and transport systems supporting acid tolerance, driven mainly by Lactobacillus, Weissella, Streptococcus, Gluconobacter, Aeromonas, Saccharomyces, Klebsiella, and Cronobacter. These findings provide insights into the microbial dynamics and functional adaptations during natural fermentation of food waste, contributing to the development of optimized waste valorization strategies.