Lactoperoxidase System Research Articles

Study the effect of lactoperoxidase activation in combination with heat treatment or nisin on the microbiological quality of raw milk

The aim of the current study was to improve the microbiological quality of raw cow milk by activating the lactoperoxidase system using either nisin or heat treatment. A central composite experimental design with three factors was used to evaluate the effect of thiocyanate (SCN), hydrogen peroxide (H202) and nisin on the microbiological quality of raw milk. The experimental response was measured in terms of the logarithmic reduction in total microbial, total coliforms count, yeasts and molds. Our results indicate that the combination of both treatments was highly effective in destroying various microorganisms. In fact, the optimal values of each parameter (SCN, H202 and nisin) for a 6log, 5log and 4log reductions of the initial number of total aerobic mesophilic bacteria, coliforms, yeasts and molds were around 7 mg/L of SCN, 15 mg/L of H202 and 50 IU/mL of nisin, obtained after 72 h of incubation at 25 °C. Concerning the LPS activation at moderate temperature, our data suggest that this combination was very effective in destroying different microorganisms. Certainly, the total destruction of coliforms, yeasts and molds was noted after 96 h incubation at 25 °C after LPS activation for 4 h and 6 h followed by heat treatment (63 °C for 30 min). These results highlight a synergistic effect between the LPS activation and nisin or heat treatment in preserving microbiological quality of raw milk for 72 h or 96 h at 25 °C, respectively. Such treatments could be implemented by the dairy industry to enhance the quality of fresh milk and consequently of dairy products.

MicroRNA mediated suppression of airway lactoperoxidase by TGF-β1 and cigarette smoke promotes airway inflammation

Transforming Growth Factor Beta1 (TGF-β1) signaling is upregulated in Chronic Obstructive Pulmonary disease (COPD), smokers, and people living with HIV. Cigarette smoking and HIV are also independent risk factors for COPD. Chronic inflammation is a hallmark of COPD. However, the underlying mechanisms remain unknown. Previous research has suggested that TGF-β1 alters the airway epithelial microRNAome and transcriptome, potentially contributing to lung inflammation. The Lactoperoxidase (LPO) system is an integral component of innate immunity within the airway. LPO plays a crucial role in host defense by catalyzing the oxidation of thiocyanate to hypothiocyanite in the presence of hydrogen peroxide (H2O2), generating a potent antibacterial and antiviral agent. Additionally, the LPO system potentially aids in maintaining cellular redox balance by reducing the levels of H2O2, thus mitigating oxidative stress within the airway epithelium. LPO dysfunction can impair immune responses and exacerbate inflammatory processes in respiratory diseases.In this study, primary bronchial epithelial cells and bronchial cell lines were treated with TGF-β1 and exposed to cigarette smoke to characterize the effect of these factors on LPO and their downstream effects. RT-qPCR and Western Blot were applied to quantify mRNA and proteins’ expression. The levels of H2O2 were detected using the Amplex Red Assay. Magnetofection and transfection were applied to probe the effect of miR-449b-5p. Staining procedures using the MitoTracker Green and C12FDG dyes were used to establish mitochondria mass and senescence. The levels of pro-inflammatory cytokines were measured via Luminex assays.We found that TGF-β1 and cigarette smoke suppressed airway LPO expression, increasing H2O2 levels. This increase in H2O2 had downstream effects on mitochondrial homeostasis, epithelial cellular senescence, and the pro-inflammatory cytokine response. We demonstrate for the first time that airway LPO is regulated by TGF-β1-induced miRNA-mediated post-transcriptional silencing through miR-449b-5p in the lungs. Further, we identify and validate miR-449-5p as the candidate miRNA upregulated by TGF-β1, which is involved in LPO suppression. This paper demonstrates a new mechanism by which TGF-β1 can lead to altered redox status in the airway.

Improvement of Raw and Pasteurized Milk Quality through the Use of Lactoperoxidase Systems (LPSs) along the Dairy Value Chain, under Real Conditions in Ethiopia.

Lactoperoxidase systems (LPSs) can enhance the microbiological quality of raw milk when there is lack of cooling facilities. In this study, a total of 250 milk samples were collected from farmers, collectors, and factories. Experimental samples were both LPS-activated morning and overnight milk. The samples were tested with several chemical and microbiological tests, such as total bacterial count (TBC), total coliform count (TCC), and Escherichia coli count (EC). Results indicated that all LPS-activated milk samples had a higher quality than all the control samples. For instance, both the morning and overnight farm milk samples had mean TBCs of 5.79 log and 6.55 log cfu/mL, which is significantly (p < 0.05) lower than the control samples' mean TBC of 6.73 log and 7.31 log cfu/mL, respectively. When this was compared with the Ethiopian Standard, 51.4% of morning and 39.5% of overnight farm milk with LPS activation met the acceptable quality, while only 28% of morning and 15.7% of overnight control milk met the standard. Moreover, LPS activation has also significantly improved the shelf life of collectors' raw milk and pasteurized milk at the factories. Therefore, a better hygienic practice with LPS application can be practiced in conditions that lack cooling infrastructure and electricity.

High pressure processing plus technologies: Enhancing the inactivation of vegetative microorganisms.

High pressure processing (HPP) is a non-thermal technology that can ensure microbial safety without compromising food quality. However, the presence of pressure-resistant sub-populations, the revival of sub-lethally injured (SLI) cells, and the resuscitation of viable but non-culturable (VBNC) cells pose challenges for its further development. The combination of HPP with other methods such as moderate temperatures, low pH, and natural antimicrobials (e.g., bacteriocins, lactate, reuterin, endolysin, lactoferrin, lactoperoxidase system, chitosan, essential oils) or other non-thermal processes (e.g., CO2, UV-TiO2 photocatalysis, ultrasound, pulsed electric fields, ultrafiltration) offers feasible alternatives to enhance microbial inactivation, termed as "HPP plus" technologies. These combinations can effectively eliminate pressure-resistant sub-populations, reduce SLI or VBNC cell populations, and inhibit their revival or resuscitation. This review provides an updated overview of microbial inactivation by "HPP plus" technologies and elucidates possible inactivation mechanisms.

Activation of lactoperoxidase system and its potential for microbial inhibition and preservation of milk in the Great African Rift Valley climate

Activation of lactoperoxidase system and its potential for microbial inhibition and preservation of milk in the Great African Rift Valley climate

Modified Lactoperoxidase System as a Promising Anticaries Agent: In Vitro Studies on Streptococcus mutans Biofilms.

The lactoperoxidase (LPO) system shows promise in the prevention of dental caries, a common chronic disease. This system has antimicrobial properties and is part of the non-specific antimicrobial immune system. Understanding the efficacy of the LPO system in the fight against biofilms could provide information on alternative strategies for the prevention and treatment of caries. In this study, the enzymatic system was modified using four different (pseudo)halide substrates (thiocyanate, thiocyanate-iodide mixture, selenocyanate, and iodide). The study evaluated the metabolic effects of applying such modifications to Streptococcus mutans; in particular: (1) biofilm formation, (2) synthesis of insoluble polysaccharides, (3) lactate synthesis, (4) glucose and sucrose consumption, (5) intracellular NAD+ and NADH concentrations, and (6) transmembrane glucose transport efficiency (PTS activity). The results showed that the LPO-iodide system had the strongest inhibitory effect on biofilm growth and lactate synthesis (complete inhibition). This was associated with an increase in the NAD+/NADH ratio and an inhibition of glucose PTS activity. The LPO-selenocyanate system showed a moderate inhibitory effect on biofilm biomass growth and lactate synthesis. The other systems showed relatively small inhibition of lactate synthesis and glucose PTS but no effect on the growth of biofilm biomass. This study provides a basis for further research on the use of alternative substrates with the LPO system, particularly the LPO-iodide system, in the prevention and control of biofilm-related diseases.

Quality attributes of set yogurt made from lactoperoxidase system activated cow’s milk

The study aimed to assess the quality attributes of set yoghurt made from cow's milk preserved by lactoperoxidase system (LPs). Fresh cow's milk was collected from Datto milk collection center and samples were grouped to control and LPs activated. Set yoghurt was prepared immediately for the controlled samples, but in LPs activated milk, sample was kept for 9 h at 25 °C ± 2 before yoghurt was made. LP enzyme was activated within 2 h after milking by adding 1 mg/ml of sodium thiocyanate (SCN_) and hydrogen peroxide (H2O2). Totally, 36 L of cow's milk was used and the experiment was done in triplicates. Titratable acidity (TA) and pH were assessed every 30 min until coagulation formed. Yoghurt samples were stored for 21 days and different parameters were assessed including incubation duration, pH, TA, microbiological quality and sensory attributes. The results revealed that LPs partially suppressed the rate of acid production during incubation of cultured milk. Yoghurt made from LPs treated milk had significantly (P < 0.05) higher pH and lower TA values. Similarly, yoghurt made from LPs treated milk had lower total bacterial counts at 24-h, 72-h and 7-days of storages. Additionally, yoghurt from LPs activated milk had lower yeast and mold counts at 24-h and 7-days. Yoghurt made from LPs activated milk received better scores for the sensory attributes. In general, LPs activated milk can be used for making set yoghurt without a negative effect. Further studies are needed to illustrate the LPs activated milk fitness in making other cultured milk products.

High dietary iodine intake may contribute to the low death rate from COVID-19 infection in Japan with activation by the lactoperoxidase system.

We draw the attention of readers and governments to the death rate from coronavirus disease 2019 in Japan, continuing as a fraction of that experienced by many other developed nations. We think this is due to the activity of the powerful, protective lactoperoxidase system (LPO) which prevents serious airborne infections. The LPO system requires iodine, which is liberally provided by the typical Japanese diet but lacking in many others. One might consider the Japanese experience an incredibly large, open-label study exhibiting the preventative power of a high-iodine diet. We predict this favourable trend will continue for Japan because deadly variants of the severe, acute respiratory syndrome coronavirus 2 will be with us, forever.

Safety Assessment of the Modified Lactoperoxidase System-In Vitro Studies on Human Gingival Fibroblasts.

One strategy in caries prevention is to inhibit the formation of cariogenic biofilms. Attempts are being made to develop oral hygiene products enriched with various antimicrobial agents. One of them is lactoperoxidase-an enzyme that can oxidise (pseudo)halide ions to reactive products with antimicrobial activity. Currently, commercially available products utilise thiocyanate as a substrate; however, several alternatives that are oxidised to products with greater antimicrobial potential have been found. In this study, toxicity against human gingival fibroblasts of the lactoperoxidase system was evaluated using four different (pseudo)halide substrate systems-thiocyanate, iodide, selenocyanate, and a mixture of thiocyanate and iodide. For this purpose, cells were treated with the systems and then apoptosis, cell cycle, intracellular glutathione concentration, and mitochondrial superoxide production were assessed. The results showed that each system, after generating 250 µM of the product, inhibited cell divisions, increased apoptosis, and increased the percentage of dead cells. It was concluded that the mechanism of the observed phenomena was not related to increased superoxide production or the depletion of glutathione concentration. These findings emphasised the need for the further in vitro and in vivo toxicity investigation of the modified lactoperoxidase system to assess its safety and the possibility of use in oral hygiene products.

Al2O3@Ag composite structure as SERS substrate for sensitive detection of sodium thiocyanate.

Sodium thiocyanate (NaSCN) can be added to fresh milk to enhance the sterilization ability of the lactoperoxidase system (LP system) in milk, extending shelf life. However, excessive intake of NaSCN can be harmful to human health because it can prevent absorption of iodine leading to disease. Also NaSCN can be used as a marker to distinguish smokers from non-smokers. In this work, we successfully synthesized meatball-like Al2O3@Ag composite structures as surface-enhanced Raman scattering (SERS) substrates using a simple wet chemical method adapted to conventional laboratory conditions. The substrate exhibited strong SERS enhancement for NaSCN. Under the optimal experiment conditions, we obtained a detection limit of 0.28μg L-1 and a quantification limit of 1μg L-1, R2 = 0.992. Based on the analysis of the intensity of SERS characteristic peak, the substrate had good reproducibility and uniformity. In summary, the Al2O3@Ag composite structure achieved sensitive SERS detection of NaSCN. Combining the facile and low-cost methods, we believe that the SERS detection method developed in this work can be used as a potential candidate for biosensing applications in the future.

Excess iodine exposure acutely increases salivary iodide and antimicrobial hypoiodous acid concentrations in humans

The lactoperoxidase (LPO)-hydrogen peroxide-halides reaction (LPO system) converts iodide and thiocyanate (SCN−) into hypoiodous acid (HOI) and hypothiocyanite (OSCN−), respectively. Since this system has been implicated in defense of the airways and oropharynx from microbial invasion, in this proof-of-concept study we measured the concentrations of these analytes in human saliva from a convenience clinical sample of 40 qualifying subjects before and after acute iodine administration via the iodinated contrast medium used in coronary angiography to test the hypothesis that an iodide load increases salivary iodide and HOI concentrations. Saliva was collected and salivary iodide, SCN−, HOI and OSCN− were measured using standard methodology. The large iodine load delivered by the angiographic dye, several 100-fold in excess of the U.S. Recommended Daily Allowance for iodine (150 µg/day), significantly increased salivary iodide and HOI levels compared with baseline levels, whereas there was no significant change in salivary SCN− and OSCN− levels. Iodine load and changes of salivary iodide and HOI levels were positively correlated, suggesting that higher iodide in the circulation increases iodide output and salivary HOI production. This first of its kind study suggests that a sufficient but safe iodide supplementation less than the Tolerable Upper Limit for iodine set by the U.S. Institute of Medicine (1,100 µg/day) may augment the generation of antimicrobial HOI by the salivary LPO system in concentrations sufficient to at least in theory protect the host against susceptible airborne microbial pathogens, including enveloped viruses such as coronaviruses and influenza viruses.

Nanoformulation approach for improved antimicrobial activity of bovine lactoperoxidase.

Lactoperoxidase (LPO) is a glycosylated antimicrobial protein present in milk with a molecular mass of 78 kDa. LPO is included in many biological processes and is well-known to have biocidal actions, acting as an active antibiotic and antiviral agent. The wide spectrum biocidal activity of LPO is mediated via a definite inhibitory system named lactoperoxidase system which plays a potent role in the innate immune response. With the current advancement in nanotechnology, nanoformulations can be developed for stabilizing and potentiating the activity of LPO for several applications. In the research described in this Research Communication, fresh LPO purified from bovine mammary gland secretions was used for nanoparticle synthesis using a simple thermal process at different pH and temperatures. The round-shaped nanoparticles (average size 229 nm) were successfully synthesized at pH 7.0 and a temperature of 75°C. These nanoparticles were tested against four different bacterial species namely S. flexineri, P. aeruginosa, S. aureus, and E. coli. The prepared nanoparticles exhibited strong inhibition of the growth against all four bacterial species as stated by their MIC and ZOI values. These results may help in increasing the efficiency of lactoperoxidase system and will assist in identifying novel avenues to enhance the stability and antimicrobial function of LPO in drug discovery and industrial processes.

The Combined Effects of Bio-Components and Alginate Coating on Chemical and Sensory Quality of Chill-Stored Rainbow Trout Fillets

ABSTRACT The objective of the present study was to reduce lipid oxidation and preserve sensory quality of fish fillets maintained under refrigerator condition. The lactoperoxidase system (LPOS) or Zataria multiflora Boiss essential oil (ZEO) was added individually or in combination in biodegradable coatings. Fish fillets were analyzed for peroxide value (PV), free fatty acid value (FFA), fatty acid profile, thiobarbituric acid reactive substances (TBARS) value, and sensory evaluation. Suppressive effect of ZEO and LPOS was seen in the combined groups; so that PV value ranged from 0.32 (0 day) and 0.41 (4 day) meq/kg to 1.97 meq/kg on day 8. The lowest amount of TBARS (1.54 mg MDA/kg) and FFA (1.84% of oleic acid) was obtained in the samples treated with alginate coating containing LPOS and ZEO 1% at the end of storage. The use of ZEO and natural preservatives such as LPOS is presented as alternatives to chemical preservatives in seafood.

Atmospheric Reactive Oxygen Species and Some Aspects of the Antiviral Protection at the Respiratory Epithelium.

—The review summarizes literature data on molecular and biochemical mechanisms of nonspecific protection of respiratory epithelium. The special attention is paid to comprehensive analysis of up-to-date data on the activity of the lactoperoxidase system expressed on the surface of the respiratory epithelium which provides the generation of hypothiocyanate and hypoiodite in the presence of locally produced or inhaled hydrogen peroxide. Molecular mechanisms of production of active compounds with antiviral and antibacterial effects, expression profiles of enzymes, transporters and ion channels involved in the generation of hypothiocyanite and hypoiodite in the mucous membrane of the respiratory system in physiological and pathological conditions (inflammation) are discussed. A hypothesis about the effect of atmospheric air composition on the efficiency of hypothiocyanate and hypoiodite generation in the respiratory epithelium in the context of its antibacterial and antiviral protection is presented. The causes and consequences of insufficiency of the lactoperoxidase system caused by the action of atmospheric factors are discussed in the context of controlling the sensitivity of the epithelium to the action of bacterial agents and viruses. Good evidence exists that restoration of the lactoperoxidase system activity can be achieved by application of pharmacological agents aimed to compensate for the deficit of halides in tissues, and by the control of chemical composition of the inhaled air.

Activation of lactoperoxidase system in buffalo milk using dual enzyme (lactase &amp; glucose oxidase) and its effect on milk constituents

In the present investigation, lactoperoxidase (LP) system was activated in buffalo milk using 400 U of lactase with 350 U of glucose oxidase as the source of in situ hydrogen peroxide with 50 mg thiocyanate per litre of milk. On the basis of titratable acidity, clot on boiling, and alcohol test, milk remained acceptable up to 9–10 h. The hypothiocyanate ions level (57.629 ± 0.38mM) after 9th hour of LP activation maintained close to the level suggested in central composite rotatable design. The milk preserved using the standardised formulation to activate the LP system did not show any variation in physico‐chemical parameters of milk from the usual quality except for lactose content, which was measured using HPLC. Lactose content was reduced from initial 4.7% to 1.4%, 0.99% and 0.53% after 1, 2 and 4 h of activation at 37°C, respectively. Whey proteins remained unaffected as no changes were observed in their electrophoretic behaviour. Serine equivalents in both control and LP system–activated milk was 1.20 ± 0.001 mg/mL, indicating no proteolysis. Thiobarbituric acid values of LP‐activated milk at 0th hour and 9th hour were 0.81 ± 0.002 and 0.082 ± 0.003, respectively. No significant changes in free fatty acids were observed on account of LP‐system activation using the studied dual‐enzyme approach. LP‐activated milk remained heat stable up to 10 h at 37°C.

Antimicrobial Activity of Films and Coatings Containing Lactoperoxidase System: A Review.

The production of safe and healthy foodstuffs is considered as one of the most important challenges in the food industry, and achieving this important goal is impossible without using various processes and preservatives. However, recently, there has been a growing concern about the use of chemical preservatives and attention has been focused on minimal process and/or free of chemical preservatives in food products. Therefore, researchers and food manufacturers have been induced to utilize natural-based preservatives such as antimicrobial enzymes in their production. Lactoperoxidase, as an example of antimicrobial enzymes, is the second most abundant natural enzyme in the milk and due to its wide range of antibacterial activities, it could be potentially applied as a natural preservative in various food products. On the other hand, due to the diffusion of lactoperoxidase into the whole food matrix and its interaction and/or neutralization with food components, the direct use of lactoperoxidase in food can sometimes be restricted. In this regard, lactoperoxidase can be used as a part of packaging material, especially edible and coating, to keep its antimicrobial properties to extend food shelf-life and food safety maintenance. Therefore, this study aims to review various antimicrobial enzymes and introduce lactoperoxidase as a natural antimicrobial enzyme, its antimicrobial properties, and its functionality in combination with an edible film to extend the shelf-life of food products.

Comments on the Discussion Forum: Oromucosal immunomodulation as clinical spectrum mitigating factor in SARS-CoV-2 infection.

The mammalian lactoperoxidase system, consisting of lactoperoxidase and the H2O2‐producing enzyme duox, is our first line of defence against airborne microbes. This system catalyses the production of hypoiodite and hypoiodous acid in the presence of sufficient iodine. These products are highly efficient at destroying the H1N1 virus and the respiratory syncytial virus (RSV). Japan has not been affected as much as other nations during the COVID‐19 pandemic (death rate about 10% of the United States), and we think this is due to a diet high in iodine. With this in mind, we suggest four actions to prevent SARS‐CoV‐2 infections. First, health professionals should study the preventative effect of increasing iodine in the diets of the aged, institutionalized, diabetics andsmokers. Second, the recommended daily intake (RDI) for iodine should be significantly increased, to at least double, the current RDI. Governments should encourage the use and distribution of cheap iodized salts, kelp and seaweed. Third, more research should be done around the physiology and the protective effects of the lactoperoxidase system. Finally, the degradation products of the SARS‐CoV‐2 viral particle by hypoiodite and hypoiodous acid should be characterized; portions of the damaged particle are likely to elicit stronger immunity and better vaccines.

Lactose oxidase: An enzymatic approach to inhibit Listeria monocytogenes in milk

Listeria monocytogenes is a ubiquitous pathogen that can cause morbidity and mortality in immunocompromised individuals. Growth of L. monocytogenes is possible at refrigeration temperatures due to its psychrotrophic nature. The use of antimicrobials in dairy products is a potential way to control L. monocytogenes growth in processes with no thermal kill step, thereby enhancing the safety of such products. Microbial-based enzymes offer a clean-label approach for control of L. monocytogenes outgrowth. Lactose oxidase (LO) is a microbial-derived enzyme with antimicrobial properties. It oxidizes lactose into lactobionic acid and reduces oxygen, generating H2O2. This study investigated the effects of LO in UHT skim milk using different L. monocytogenes contamination scenarios. These LO treatments were then applied to raw milk with various modifications; higher levels of LO as well as supplementation with thiocyanate were added to activate the lactoperoxidase system, a natural antimicrobial system present in milk. In UHT skim milk, concentrations of 0.0060, 0.012, and 0.12 g/L LO each reduced L. monocytogenes counts to below the limit of detection between 14 and 21 d of refrigerated storage, dependent on the concentration of LO. In the 48-h trials in UHT skim milk, LO treatments were effective in a concentration-dependent fashion. The highest concentration of LO in the 21-d trials, 0.12 g/L, did not show great inhibition over 48 h, so concentrations were increased for these experiments. In the lower inoculum, after 48 h, a 12 g/L LO treatment reached levels of 1.7 log cfu/mL, a reduction of 1.3 log cfu/mL from the initial inoculum, whereas the control grew out to approximately 4 log cfu/mL, an increase of 1 log cfu/mL from the inoculum on d 0. When a higher challenge inoculum of 5 log cfu/mL was used, the 0.12 g/L and 1.2 g/L treatments reduced the levels by 0.2 to 0.3 log cfu/mL below the initial inoculum and the 12 g/L treatment by >1 log cfu/mL below the initial inoculum by hour 48 of storage at refrigeration temperatures. After the efficacy of LO was determined in UHT skim milk, LO treatments were applied to raw milk. Concentrations of LO were increased, and the addition of thiocyanate was investigated to supplement the effect of the lactoperoxidase system against L. monocytogenes. When raw milk was inoculated with 2 logcfu/mL, 1.2 g/L LO alone and combined with sodium thiocyanate reduced~0.8 logcfu/mL from the initial inoculum on d 7 of storage, whereas the control grew out to >1 logcfu/mLfrom the initial inoculum. Furthermore, in the higher inoculum, 1.2 g/L LO combined with sodium thiocyanate reduced L. monocytogenes counts from the initial inoculum by >1 log cfu/mL, whereas the control grew out 2 log cfu/mL from the initial inoculum. Results from this study suggest that LO is inhibitory against L. monocytogenes in UHT skim milk and in raw milk. Therefore, LO may be an effective treatment to prevent L. monocytogenes outgrowth, increase the safety of raw milk, and be used as an effective agent to prevent L. monocytogenes proliferation in fresh cheese and other dairy products. This enzymatic approach is a novel application to control the foodborne pathogen L. monocytogenes in dairy products.

Phenolic Compounds of Reynoutria sp. as Modulators of Oral Cavity Lactoperoxidase System.

Lactoperoxidase (LPO) together with its (pseudo)halogenation cycle substrates, H2O2 and thiocyanate ions oxidized to hypothiocyanite ions, form one of the main systems involved in antimicrobial defense within the oral cavity. In bacterial diseases such as dental caries, lactoperoxidase is oxidized to a form known as Compound II, which is characterized by its inability to oxidize SCN–, resulting in a decreased generation of antimicrobial products. Reynoutria sp. rizome extracts, due to their high polyphenol content, have been tested as a source of compounds able to regenerate the antimicrobial activity of lactoperoxidase through converting the Compound II to the native LPO state. In the presented study, acetone extracts of R. japonica, R. sachalinensis, and R. x bohemica, together with their five fractions and four selected polyphenols dominating in the studied in extracts, were tested toward lactoperoxidase reactivating potential. For this purpose, IC50, EC50, and activation percentage were determined by Ellman’s method. Furthermore, the rate constants for the conversion of Compound I–Compound II and Compound II–native-LPO in the presence of extracts, extracts fractions, and selected polyphenols were determined. Finally, the ability to enhance the antimicrobial properties of the lactoperoxidase system was tested against Streptococcus mutans. We proved that Reynoutria sp. rhizome is the source of lactoperoxidase peroxidation cycle substrates, which can act as activators and inhibitors of the antimicrobial properties of that system. The presented study shows that the reactivation of lactoperoxidase could become a potential therapeutic target in prevention and treatment support in some infectious oral diseases.

Artificial neural network and response surface methodology for modeling and optimization of activation of lactoperoxidase system

In the present study, the multi-component lactoperoxidase system (LPS) is used for improving milk safety and requires thiocyanate (SCN−) as a substrate for the generation of antimicrobial hypothiocyanite (OSCN−). The influence of four independent variables for activation of lactoperoxidase system on the improving the quality of raw goat milk were investigated and optimized using an artificial neural network and response surface methodology on the growth of total coliform count and bacterial count. The two models' predictive capabilities were compared in terms of root mean square error, mean absolute error, standard error of prediction, absolute average deviation, and coefficient of determination based on the validation data set. The results showed that properly trained artificial neural network model is more accurate in prediction than the RSM model. The optimum conditions were a temperature of 25 °C, storage time of 10 hr, NaSCN of 30 ppm and hydrogen peroxide of 18 ppm. For these conditions, an experimental total coliform count of 4.51 × 102cfu/mL and total bacteria count of 5.44× 104cfu/mLwas obtained, which was in reasonable agreement with the predicted content.The results indicate that the model is in substantial agreement with current research, and activating the LP System can extend the storage period of goat milkfor up to10hr when stored at 25 °C.The results revealed no significant differences in milk composition (protein content, fat content, lactose content, total solids, moisture content and ash content) were observed among activated and control goat milk samples.