Prebiotic potential and modulation of the fecal microbiota by konjac oligo-glucomannan prepared using Pediococcus acidilactici mannanase.

In this study, konjac oligo-glucomannan (KOGM) was prepared from konjac glucomannan (KGM) by enzymatic hydrolysis using β-mannanase derived from Pediococcus acidilactici HDM2. The prepared KOGM had an average molecular weight of 13.4 kDa under optimized conditions (50 °C, pH 6.0, 80 U mL-1 and 180 min). The KOGM exhibited selective prebiotic potential by promoting probiotic growth, particularly Lacticaseibacillus paracasei HD1.7 and Lactiplantibacillus plantarum CICC 6076. In contrast, it inhibited the growth of potentially harmful bacteria, including Klebsiella pneumoniae and Enterobacter spp. Its prebiotic potential was further evaluated using an in vitro fecal fermentation model with six treatment groups: blank control, commercial mannan oligosaccharides (MOS), KGM, KOGM, KGM combined with HDM2 (KGM2), and KOGM combined with HDM2 (KOGM2). After 24 h of fermentation, the KOGM2 group exhibited the lowest pH (3.89 ± 0.03, P < 0.05) and increased production of short-chain fatty acids (SCFAs), particularly acetate (2062.72 μg mL-1), propionate (1356.81 μg mL-1), and valerate (16.89 μg mL-1). Notably, the KGM2 group produced the highest acetate level, while KGM yielded the greatest butyrate content (206.7 ± 15.0 μg mL-1). α and β diversity analyses revealed that KGM and KOGM treatments enhanced microbial diversity and accelerated community stabilization. Furthermore, KOGM enriched beneficial phyla such as Bacteroidetes and Actinobacteria, stimulated the growth of beneficial genera including Bifidobacterium, Prevotella, and Limosilactobacillus, and reduced potential pathogens including Escherichia-Shigella and Proteobacteria. These findings highlight the prebiotic potential of enzymatically prepared KOGM, which effectively modulates gut microbiota composition and promotes beneficial metabolic activity.