Enhancing pectin degradation and improving nutritional accessibility in potato pulp through co-fermentation: From molecular structure to nutrient release.

To upgrade potato pulp (PP), a starch extraction byproduct with high water-holding capacity, this study established a synergistic solid-state fermentation (SSF) system using Bacillus subtilis BSM1 and Aspergillus niger H1. Under optimized conditions (60% moisture, 34 °C, 96 h), pectin degradation reached 29.26 ± 0.41%. SEM and FTIR analyses confirmed structural disruption of PP, enhancing substrate accessibility. Metabolomics revealed significant enrichment of hexuronic acids and bioactive peptides. Fermentation increased the content of small peptides in potato pulp from 0.42 ± 0.01 g/kg to 0.61 ± 0.03 g/kg and the total sugar content from 3.27 ± 0.35% to 12.96 ± 1.14%. The fermentation process increased the total amount of easily absorbable nutrients and improved the digestibility of the potato pulp. In vivo trials using a piglet model showed that replacing 10% dietary corn with fermented PP significantly increased jejunal amylase and β-galactosidase activities, while improving the duodenal villus-to-crypt ratio. At the same time, we used weaned piglets as a digestive model to investigate the digestibility of fermented potato pulp. The results showed that the mixed microbial community broke down the complex cellulose-pectin structure of the potato pulp, thereby improving the bioavailability of its nutrients. These findings indicate that this bioprocessing strategy can convert low-value potato pulp into high-value functional food ingredients, with utilization potential comparable to that of corn.