# Proteolytic lactic acid bacteria for food safety and One Health: Degradation of cow’s milk allergens and prospects for hypoallergenic dairy development

## TL;DR

Scientists found bacteria that can break down milk allergens, offering a natural way to make hypoallergenic dairy products for better food safety and health.

## Contribution

Identification of proteolytic lactic acid bacteria capable of degrading cow’s milk allergens with probiotic and safety potential for hypoallergenic dairy development.

## Key findings

- Seven LAB isolates effectively degraded β-lactoglobulin and β-casein, major milk allergens.
- L. rhamnosus S46 completely degraded β-LG and showed high survival in simulated gastrointestinal conditions.
- Most isolates lacked virulence genes and hemolytic activity, indicating safety for probiotic use.

## Abstract

Cow’s milk allergy (CMA) is one of the most common food allergies, particularly in infants and young children, caused mainly by β-lactoglobulin (β-LG) and caseins. Conventional methods to reduce milk allergenicity, including heat and pressure treatments, often compromise nutritional quality or lack industrial feasibility. Safe, natural approaches to allergen reduction are essential for both food safety and One Health perspectives, as CMA contributes to nutritional deficiencies and impacts global health. This study aimed to isolate and characterize proteolytic lactic acid bacteria (LAB) from Chinese dairy products and fermented foods, evaluate their ability to degrade major cow’s milk allergens, and assess their probiotic and safety profiles for application in hypoallergenic dairy products.

Seventy-six LAB isolates were obtained from dairy and fermented foods and screened for proteolytic activity using skim milk agar and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The most active isolates were identified by phenotypic characterization and 16S ribosomal RNA sequencing. Probiotic potential was evaluated through in vitro gastrointestinal tolerance, bile salt hydrolase (BSH) activity, antimicrobial activity, and antibiotic susceptibility. Safety was assessed through hemolytic activity and screening for virulence-associated genes.

Seventy isolates exhibited proteolytic activity, of which 7 (S30, S44, S46, S52, S63, S67, and S76) showed strong hydrolysis of β-LG and β-casein. These were identified as Streptococcus thermophilus, Lactobacillus fermentum, Lactobacillus plantarum, Lactobacillus casei, Lactobacillus rhamnosus, and Lactobacillus paracasei. Notably, L. rhamnosus S46 achieved complete degradation of β-LG while maintaining high survival (>83%) under simulated gastrointestinal conditions, with BSH activity and broad antimicrobial effects. Most isolates lacked virulence genes and hemolytic activity, except L. paracasei S67.

Proteolytic LAB strains, particularly L. rhamnosus S46 and L. plantarum S52, exhibited strong allergen-degrading activity, probiotic potential, and safety profiles, supporting their application in hypoallergenic dairy production. From a food safety and One Health perspective, these strains represent natural, functional alternatives for reducing milk allergenicity, improving consumer health, and supporting sustainable dairy innovation. However, in vivo validation and pilot-scale trials in real dairy systems are necessary to confirm industrial feasibility and consumer acceptance.