Synthetic microbial community to enhance the fermentation and feed valorization of pineapple waste

Global livestock industry is confronted with severe feed-supply pressure, and valorizing agro-industrial by-products has become a promising way to alleviate feed resource shortages. Large quantities of pineapple waste are produced annually during pineapple processing, but antinutritional factors greatly limit its direct application in pig diets. Pineapple waste (PW) is a promising agro-industrial by-product for feed production; however, its high levels of antinutritional factors and structural carbohydrates limit its utilization in monogastric animals. This study aimed to develop a synthetic microbial community (SysComs) for upgrading PW into a functional feed ingredient. Four functional strains were separately screened according to their dominant single degrading or metabolite-synthesizing traits, and further combined into a synthetic community owing to their complementary metabolic capacities, including tannin-degrading Lactiplantibacillus plantarum, xylan-degrading Pediococcus pentosaceus, phytase-producing Lactobacillus fermentum, and butyrate-producing Clostridium butyricum. Fermentation with SysComs markedly improved the nutritional and functional properties of PW. Compared with raw PW, fermented pineapple waste (FPW) showed substantial reductions in tannin and phytate contents, with removal rates reaching 80.65 and 89.62%, respectively. Total dietary fiber and insoluble dietary fiber were significantly decreased, whereas soluble dietary fiber increased from 5.60 to 8.18%. Meanwhile, butyrate concentration increased from 1.65 to 6.63%, accompanied by a decrease in pH from 6.10 to 4.87. Microbial community analysis showed that SysComs fermentation shifted PW from a contaminant-rich microbial community toward a lactic acid bacteria-dominated structure, with enrichment of Lactobacillus, Levilactobacillus, Enterococcus, Bacillus, and Weissella. Untargeted metabolomics further revealed that fermentation extensively remodeled the metabolite profile of PW, with 258 metabolites upregulated and 437 downregulated. Pathways related to flavonoid biosynthesis, flavone and flavonol biosynthesis, and secondary metabolite biosynthesis were significantly enriched. Luteolin, taxifolin, phlorizin, and gallocatechin were markedly increased. In pig experiment, dietary FPW supplementation significantly increased average daily gain by 13.10% and improved gross energy digestibility from 85.36 to 87.46% compared with the control group (p < 0.05). Moreover, FPW reshaped the colonic microbiota by increasing microbial richness and enriching beneficial fiber-degrading and short-chain fatty acid-associated taxa, including Christensenellaceae R-7 group, Lachnospiraceae NK4A136 group, and Monoglobus. These findings demonstrate that SysComs fermentation effectively reduced antinutritional factors, enhanced nutrient accessibility, enriched functional metabolites, and improved growth performance and gut microbial ecology in pigs. Targeted microbial fermentation is an effective strategy for converting pineapple waste into a high-value functional feed ingredient.