α-Glucosidase Inhibitory and Antibacterial Activity of Fermented Mackerel By-Product Muscle and Skin Hydrolysates: In Vitro and In Silico Peptidomics Analysis

Abstract

Mackerel (Scomberomorus commerson) processing by-products represent an abundant yet underutilized protein source that can be valorized into bioactive peptides through microbial fermentation. This study investigated the α-glucosidase inhibitory and antibacterial activities of hydrolysates produced from fermented mackerel muscle, skin, and mixed by-products using Pediococcus pentosaceus IL13, with ultrafiltration applied to enrich low-molecular-weight peptides (<3 kDa). All hydrolysates exhibited concentration-dependent α-glucosidase inhibitory activity, with the mixed hydrolysate showing the lowest IC₅₀ value (34.692 mg/mL). The <3 kDa fractions consistently displayed the strongest antibacterial activity against both Gram-positive and Gram-negative bacteria, particularly Listeria monocytogenes, indicating enrichment of potent low-molecular-weight antibacterial peptides. LC-HRMS-based peptidomic analysis identified 211 peptides, from which 35 representative sequences were selected based on relative abundance for in silico evaluation. Several peptides were predicted to be novel, non-toxic, and non-allergenic. Among them, the collagen-derived peptide SPAMPVPGPMGPMGPR exhibited the highest predicted antidiabetic potential, whereas AVFPSIVGRPR was identified as the most promising antibacterial peptide based on consensus predictions from multiple antimicrobial peptide prediction platforms. These findings demonstrate that fermentation coupled with ultrafiltration effectively generates multifunctional bioactive peptides from mackerel by-products, supporting their sustainable utilization as promising ingredients for functional foods and nutraceutical applications.