Screening and Whole-Genome Analysis of Probiotic Lactic Acid Bacteria with Potential Antioxidants from Yak Milk and Dairy Products in the Qinghai-Tibet Plateau.

Abstract

This study aimed to isolate lactic acid bacteria (LAB) with strong antioxidant activity and potential probiotic properties from yak milk and dairy products in the Qinghai-Tibet Plateau. Initial screening of the isolates was performed using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging assay and a hydrogen peroxide tolerance test. Subsequently, the antioxidant capacity of the isolates was assessed through five distinct assays: 2,2'-azino-bis (3-ethylbenzthiazoline)-6-sulfonic acid (ABTS) radical scavenging ability, superoxide anion radical scavenging ability, hydroxyl radical scavenging ability, a DPPH scavenging assay, and a reducing activity assay. The strains with the stronger antioxidant potential were then further evaluated for their probiotic properties. Whole-genome sequencing was conducted on Lactobacillus plantarum QL01. Among 1205 isolates, 9 strains exhibited potential antioxidant capabilities. Following probiotic property evaluation, QL01 was identified as a safe candidate due to its strong growth, strong adhesion ability, and resilience to acidic, bile, and simulated gastrointestinal conditions. Genome analysis revealed that most of QL01's genes were involved in carbohydrate metabolism. Further examination of antibiotic resistance and virulence factors confirmed its safety, meanwhile genes linked to adhesion and stress responses underscored its probiotic potential. In conclusion, QL01, a strong antioxidant strain, was successfully isolated, and its probiotic potential was confirmed through comprehensive in vitro and genomic analyses.