Lactoperoxidase is a naturally occurring heme peroxidase enzyme predominantly found in bovine milk. It plays an important role in the natural antimicrobial defense system [1,2]. With a molecular weight of 78,000 Da, this single-chain glycoprotein catalyzes the oxidation of thiocyanate ions (SCN) in the presence of hydrogen peroxide (H2O2), generating hypothiocyanite (OSCN⁻), which serves as the primary antimicrobialagent [2,3].

The lactoperoxidase system (LPS) consists of three essential components: lactoperoxidase enzyme, thiocyanate substrate, and hydrogen peroxide [4,5]. When these components interact, the enzyme catalyzes the formation of hypothiocyanite, which exhibits potent antimicrobial activity against bacteria, viruses, and fungi [1,3]. This natural system occurs in various biological fluids including milk, saliva, and tears [2,6].

The generated hypothiocyanite has a controlled half-life of approximately 400 minutes, ensuring effective antimicrobial activity without persistent residues [7]. This time-limited activity makes the system ideal for food preservation and therapeutic applications where temporary antimicrobial protection is desired [3,5].

Lactoperoxidase demonstrates exceptional heat stability, maintaining activity at temperatures up to 78°C [2,5]. The enzyme retains full activity during standard milk pasteurization processes (63°C for 30 minutes), making it suitable for various thermal processing applications [5]. This thermal stability, combined with pH stability across a wide range approximately 5.5–8.0)), enables versatile industrial applications [2,8].

The lactoperoxidase system represents a natural biopreservative approach that extends milk shelf life by 7-74 hours depending on storage temperature [5,8]. At ambient temperatures (30°C), the system provides 7-8 hours of preservation, while refrigerated conditions (15°C) extend shelf life by up to 74 hours [8]. This preservation effect occurs without altering the nutritional quality or sensory properties of dairy products [4,5].

Industrial applications include fresh cheese production, frozen dairy desserts, and fermented milk products [7]. The system is particularly valuable in regions without reliable refrigeration infrastructure, enabling safe milk collection and transport over extended periods [8,9]. FAO/WHO guidelines specifically recommend lactoperoxidase system activation for milk preservation in developing countries [8,10].

Research demonstrates the lactoperoxidase system's broad-spectrum antimicrobial activity against major foodborne pathogens, including Escherichia coli, Salmonella typhimurium, Listeria monocytogenes and Staphylococcus aureus [3,11]. In one study, the system achieved a bacterial reduction of 1.68 ± 0.1 log CFU/mL against E. coli in reduced-lactose whey under optimal conditions [3].

The antimicrobial mechanism involves oxidation of essential sulfhydryl groups in bacterial enzymes, disrupting cellular metabolism and causing bacterial death [1,2]. This mechanism proves effective against both gram-positive and gram-negative bacteria while maintaining selectivity that preserves beneficial microorganisms [1,5].

In addition to the thiocyanate-based system, lactoperoxidase can also catalyze the oxidation of iodide (I⁻) to hypoiodite (OI⁻), which exhibits strong antimicrobial properties. The LPO–iodide–hydrogen peroxide combination has demonstrated inhibitory effects against Actinobacillus actinomycetemcomitans similar to those achieved with conventional antibiotics such as ampicillin [2,20].

Lactoperoxidase naturally occurs in human saliva at concentrations of 2-7 μg/mL in healthy individuals, playing a crucial role in oral antimicrobial defense [6,12]. Clinical applications of lactoperoxidase-enriched products demonstrate significant benefits for dental health, with studies showing up to 95% reduction in cariogenic bacteria such as Streptococcus mutans and Lactobacillus species [6,13].

Research using lactoperoxidase-containing lozenges demonstrates significant improvements in oral health parameters [13]. Clinical trials show substantial reductions in plaque formation and gingival inflammation following lactoperoxidase treatment [6,14]. The enzyme's specificity targets pathogenic organisms while preserving beneficial oral microbiota essential for oral health [13].

Studies indicate lactoperoxidase's effectiveness against periodontal pathogens including Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans [6,14]. The system reduces plaque accumulation and gingival bleeding while supporting overall periodontal health maintenance [6,13]. Clinical parameters including plaque index scores show significant improvements following lactoperoxidase treatment protocols [14].

The lactoperoxidase system has achieved widespread regulatory approval for food preservation applications [7,15]. The FDA has granted GRAS (Generally Recognized as Safe) status for lactoperoxidase use in food products [7]. Additional approvals from international bodies including Oral Health and Dental Care Industrial and Therapeutic Applications WHO, FAO, and Food Standards Australia New Zealand confirmed the system's safety and efficacy [4,8,16].

Manufacturing applications extend beyond dairy products to include meat preservation, seafood processing, and bakery products [17]. The system's natural origin and safety profile make it an attractive alternative to synthetic preservatives [7,17]. Industrial use protocols have been established for optimal system activation and maintenance [8,16].

Lactoperoxidase finds applications in cosmetic and personal care products due to its antimicrobial properties and safety profile [7]. The enzyme is incorporated into oral care products including toothpastes, mouthwashes, and dental gels [6,13]. Personal care applications include hand sanitizers, skin care products, and antimicrobial lotions [7].

Research demonstrates that lactoperoxidase-containing cosmetic formulations provide effective antimicrobial protection while maintaining skin compatibility [11]. The enzyme's natural origin and biocompatibility make it suitable for sensitive skin applications [7]. Safety studies confirm no adverse reactions or sensitization from topical lactoperoxidase use [9]. Recent studies have further shown that lactoperoxidase-containing cosmetic gels in combination with laser therapy can improve the condition of comedogenic skin by reducing sebum production, decreasing porphyrin levels, and controlling Cutibacterium acnes populations [21]. These findings highlight lactoperoxidase's potential as a safe and effective active ingredient in skincare products aimed at maintaining microbial balance and supporting skin health.

Beyond bacterial activity, lactoperoxidase demonstrates significant antiviral properties against multiple viral pathogens [18]. Research shows effectiveness against influenza viruses, herpes simplex virus type 1 (HSV-1), and hepatitis C virus [18]. The antiviral mechanism involves oxidative damage to viral envelope proteins and nucleic acids [3,18]. Clinical studies demonstrate that lactoperoxidase-containing formulations reduce viral load and infection duration in respiratory tract infections [22]. The enzyme's broad-spectrum antiviral activity makes it valuable for preventing and treating various viral infections [3,18].

The lactoperoxidase system exhibits antifungal properties against various pathogenic fungi and yeasts [3,11]. Research demonstrates effectiveness against Candida albicans and other opportunistic fungal pathogens [11]. The system's ability to target multiple pathogen types simultaneously provides comprehensive antimicrobial protection [1,3].

Extensive toxicological studies confirm lactoperoxidase's safety for human consumption and topical application [7,9]. WHO evaluation and Codex Alimentarius guidelines provide international validation of the system's safety [8,10]. Studies demonstrate no mutagenic, carcinogenic, or toxic effects from lactoperoxidase consumption at recommended levels [9,15].

Clinical trials involving extended use periods show no adverse reactions or laboratory abnormalities [7,19]. The enzyme's natural occurrence in human biological fluids provides additional safety assurance [6,12]. Regulatory bodies worldwide have established acceptable daily intake levels based on comprehensive safety data [8,15].

Lactoperoxidase has achieved the most comprehensive regulatory approval among natural antimicrobial systems [4,7,8]. FDA GRAS status enables use in food products throughout the United States [7,15]. LPO is also accepted in dietary supplements (1–2 mg/serving) and cosmetics, including toothpaste, creams, and skin antiseptics. European food safety authorities have approved lactoperoxidase for various food applications as a novel food ingredient [23]. Additional approvals exist in Canada, Australia, New Zealand, and numerous other countries [16].

The system meets international standards established by FAO/WHO Codex Alimentarius for food additives [8,10]. These approvals are based on extensive safety and efficacy data accumulated over decades of research and commercial use [7,9]. Ongoing monitoring confirms continued safety and effectiveness across all approved applications [15,16].

Lactoperoxidase purification employs ion exchange chromatography to achieve 98-99% purity levels as recommended by international dairy federation standards [16]. Quality assurance protocols include testing for enzymatic activity, protein content, and microbiological safety [7,15]. Manufacturing facilities maintain strict compliance with good manufacturing practices (GMP) and hazard analysis critical control points (HACCP) systems [8,16].

Temperature-controlled storage and handling procedures ensure enzyme stability and activity retention throughout the supply chain[5][8]. Regular quality testing confirms consistent enzymatic activity and antimicrobial effectiveness across production batches [16]. Traceability systems enable complete product tracking from raw materials to final applications [7,15].