Enhancing palm kernel cake nutritional quality through combined bacterial fermentation and enzymatic hydrolysis.

Background: Palm kernel cake (PKC), a non-conventional feed resource, contains a large amount of crude fibre (CF), mainly manna-polysaccharides, which are key limiting factors in regard to monogastric animal production. In this study, we have developed a synergistic bacteria-enzyme co-fermentation system to enhance the nutritional profile of PKC and evaluated its digestion dynamics using a physiologically relevant porcine in vitro gastrointestinal model.

Results: Sequential fermentation with Lactobacillus plantarum LY19 and Bacillus natto ND1 (48 h, 37 °C) degraded 3.0% crude fiber, yielding 9.30 g kg^-1 reducing sugars. Enzymatic treatment (β-mannanase 45 U g^-1 + cellulase 160 U g^-1 + acid protease 125 U g^-1) synergistically enhanced nutrient release: soluble protein increased 214% (0.72% to 2.26%), reducing sugars surged 13.8-fold (4.45 to 61.21 g kg^-1), with 55.3% fibre reduction (15.40% to 6.88%). In vitro digestion demonstrated an improvement in regard to dry matter (7.1% increase) and protein digestibility (17.0% increase), whereas colonic fermentation showed decreased concentrations of short-chain fatty acids and gases production during 48 h. 16S ribosomal RNA analysis revealed increased beneficial Lachnospiraceae NK4A136 alongside decreased pathogens (i.e. Escherichia-Shigella) and fibre-degrading taxa (i.e. Christensenellaceae R-7, UCG-005).

Conclusion: The integrated bacterial-enzymatic co-fermentation process significantly enhanced the nutritional profile of PKC through fibre reduction, protein solubilisation, and sugar release. This pretreatment improved in vitro small intestinal digestibility and modulated colonic fermentation patterns, as evidenced by favourable microbial community shifts. These findings demonstrate the potential of this bioprocessing strategy to expand PKC utilisation in swine nutrition. © 2025 Society of Chemical Industry.