Safety Assessment and the Potential of a Postbiotic Powder Formulated from a Three-Strain Fermentation of <i>Lactobacillus salivarius</i> AP-32, <i>Lactobacillus paracasei</i> ET-66, and <i>Lactobacillus plantarum</i> LPL28

This study evaluated the safety, antimicrobial activity, and upper gastrointestinal gastroprotection of a postbiotic powder derived from <i>Lactobacillus salivarius</i> AP-32, <i>Lactobacillus paracasei</i> ET-66, and <i>Lactobacillus plantarum</i> LPL28. Safety assessments were performed in rodent models through acute and subchronic oral toxicity tests, genotoxicity assays, and biogenic amine analysis. No signs of toxicity were observed in either the acute (20 g/kg body weight, BW) or subchronic (3 g/kg BW) toxicity tests. Genotoxicity evaluations indicated no mutagenic activity in the Ames test (≤5000 µg/plate) and no chromosomal or micronuclear abnormalities in the spermatocyte or the peripheral blood assays (≤10 g/kg BW). Biogenic amines were undetectable in the postbiotic powder, further reinforcing its safety. The postbiotic powder showed significant direct antimicrobial activity. Additionally, it enhanced the inhibitory effects of probiotics against key upper gastrointestinal pathobionts including <i>Streptococcus mutans</i>, <i>Porphyromonas gingivalis</i>, <i>Fusobacterium nucleatum</i> subsp. <i>polymorphum</i>, and <i>Actinobacillus actinomycetemcomitans</i>, <i>Helicobacter pylori</i>. Moreover, the postbiotic powder demonstrated gastroprotective effects by promoting recovery in a hydrogen peroxide-induced gastric injury model. Based on these findings, the postbiotic powder is safe, non-toxic, and suitable for oral consumption at the tested doses, with promising antimicrobial and gastroprotective potential. Future research should explore its potential applications in health promotion and food safety.