Metabolome and Metagenome Integration Unveiled Synthesis Pathways of Novel Antioxidant Peptides in Fermented Lignocellulosic Biomass of Palm Kernel Meal

Approximately one-third of the entire world’s food resources are deemed to be wasted. Palm kernel meal (PKM), a product that is extensively generated by the palm oil industry, exhibits a unique nutrient-rich composition. However, its recycling is seldom prioritized due to numerous factors. To evaluate the impact of enzymatic pretreatment and Lactobacillus plantarum and Lactobacillus reuteri fermentation upon the antioxidant activity of PKM, we implemented integrated metagenomics and metabolomics approaches. The substantially enhanced (p < 0.05) property of free radicals scavenging, as well as total flavonoids and polyphenols, demonstrated that the biotreated PKM exhibited superior antioxidant capacity. Non-targeted metabolomics disclosed that the Lactobacillus fermentation resulted in substantial (p < 0.05) biosynthesis of 25 unique antioxidant biopeptides, along with the increased (p < 0.05) enrichment ratio of the isoflavonoids and secondary metabolites biosynthesis pathways. The 16sRNA sequencing and correlation analysis revealed that Limosilactobacillus reuteri, Pediococcus acidilactici, Lacticaseibacillus paracasei, Pediococcus pentosaceus, Lactiplantibacillus plantarum, Limosilactobacillus fermentum, and polysaccharide lyases had significantly dominated (p < 0.05) proportions in PMEL, and these bacterial species were strongly (p < 0.05) positively interrelated with antioxidants peptides. Fermented PKM improves nutritional value by enhancing beneficial probiotics, enzymes, and antioxidants and minimizing anti-nutritional factors, rendering it an invaluable feed ingredient and gut health promoter for animals, multifunctional food elements, or as an ingredient in sustainable plant-based diets for human utilization, and functioning as a culture substrate in the food sector.