A novel bacteriocin DY4-2 produced by Lactobacillus plantarum from cutlassfish and its application as bio-preservative for the control of Pseudomonas fluorescens in fresh turbot (Scophthalmus maximus) fillets

Probiotic performance of B. subtilis MS. 45 improves aquaculture of rainbow trout Oncorhynchus mykiss during acute hypoxia stress

The aim of this study was to produce mutant strains of Bacillus subtilis with high probiotic performance for use in the aquaculture of rainbow trout Oncorhynchus mykiss. The main strain of B. subtilis (MS) was irradiated with gamma rays (5.3 KGy). Subsequently, the B. subtilis mutant strain no. 45 (MS. 45) was selected for bacterial growth performance, resistance to acidic conditions, resistance to bile salts and antibacterial activity against Aeromonas hydrophila and Pseudomonas fluorescens. After 60 days, the rainbow trout (70.25 ± 3.89 g) fed with MS. 45 and MS were exposed to hypoxia stress (dissolved oxygen = 2 ppm). Subsequently, immune indices (lysozyme, bacterial activity and complement activity), hematological indices [hematocrit, hemoglobin, WBC, RBC, mean corpuscular volume (MCV)] and antioxidant factors (T-AOC, SOD and MDA)) were analyzed after and before hypoxia exposure. The expression of immunological genes (IFN-γ, TNF-α, IL-1β, IL-8) in the intestine and the expression of hypoxia-related genes (HIF-1α, HIF-2α, FIH1) in the liver were compared between the different groups under hypoxia and normoxia conditions. Growth, immunological and antioxidant indices improved in group MS. 45 compared to the other groups. Stress indices and associated immunologic and hypoxia expressions under hypoxia and normoxia conditions improved in MS. 45 compared to the other groups. This resulted in improved growth, immunity and stress responses in fish fed with the microbial supplement of MS. 45 (P < 0.05) under hypoxia and normoxia conditions, (P < 0.05), resulting in a significant improvement in trout aquaculture.

Antibacterial efficacy of phenyllactic acid against Pseudomonas lundensis and Brochothrix thermosphacta and its synergistic application on modified atmosphere/air-packaged fresh pork loins

Microbial contamination is a crucial problem that is difficult to solve for the meat industry. Therefore, this study explored the antibacterial efficacy of phenyllactic acid (PLA) against Pseudomonas lundensis (PL) and Brochothrix thermosphacta (BT) solely and in combination (PL + BT). It also provided insights into its synergistic preservation effect during inoculation in chilled (4 °C) fresh pork loins under air (AP) and modified atmosphere packaging (MAP). The minimum inhibitory concentration (MIC) of PLA was 10 mg/mL. Growth kinetics, scanning electron microscopy (SEM), zeta potential, and cell viability investigations showed that PLA treatment exhibited reduced bacterial growth, aided morphological alterations, and leakage in cell membrane integrity in vitro. Nonetheless, PLA and MAP (70 %N2/30 %CO2) showed an excellent synergistic antibacterial ability against spoilage indicators(total glucose, pH, TVB-N, and TBARS), bacterial counts than AP, without impairing organoleptic acceptability. These results demonstrate the broad antibacterial efficacy of PLA as a biopreservative for the meat industry.

Potential Impact of Combined Inhibition by Bacteriocins and Chemical Substances of Foodborne Pathogenic and Spoilage Bacteria: A Review

In recent years, food safety caused by foodborne pathogens and spoilage bacteria has become a major public health problem worldwide. Bacteriocins are a kind of antibacterial peptide synthesized by microbial ribosomes, and are widely used as food preservatives. However, when used individually bacteriocins may have limitations such as high cost of isolation and purification, narrow inhibitory spectrum, easy degradation by enzymes, and vulnerability to complex food environments. Numerous studies have demonstrated that co-treatment with bacteriocins and a variety of chemical substances can have synergistic antibacterial effects on spoilage microorganisms and foodborne pathogens, effectively prolonging the shelf life of food and ensuring food safety. Therefore, this paper systematically summarizes the synergistic bacteriostatic strategies of bacteriocins in combination with chemical substances such as essential oils, plant extracts, and organic acids. The impacts of bacteriocins when used individually and in combination with other chemical substances on different food substrates are clarified, and bacteriocin-chemical substance compositions that enhance antibacterial effectiveness and reduce the potential negative effects of chemical preservatives are highlighted and discussed. Combined treatments involving bacteriocins and different kinds of chemical substances are expected to be a promising new antibacterial method and to become widely used in both the food industry and biological medicine.

Complete Genome Sequencing and Bacteriocin Functional Characterization of Pediococcus ethanolidurans CP201 from Daqu

This study aims to sequence the whole genome of Pediococcus ethanolidurans CP201 isolated from Daqu and determine the anti-corrosion ability of bacteriocins on chicken breast. The whole genome sequence information of P. ethanolidurans CP201 was analyzed, and its gene structure and function were explored. It was found that gene1164 had annotations in the NR, Pfam, and Swiss-Prot databases, and was related to bacteriocins. The exogenous expression of the bacteriocin gene Pediocin PE-201 was analyzed based on the pET-21b vector and the host BL21, and the corresponding bacteriocin was successfully expressed under the induction of IPTG. After purification by NI-NTA column, enterokinase treatment, membrane dialysis concentration treatment, and SDS-PAGE electrophoresis, the molecular weight was about 6.5 kDa and the purity was above 90%. By applying different concentrations of bacteriocin to chicken breast with different levels of contamination, the control of pathogenic bacteria, the ordinary contamination level (OC) group, and the high contamination level (MC) group could be completely achieved with 25 mg/L bacteriocin. In conclusion, the bacteriocin produced by the newly isolated CP201 can be applied to the preservation of meat products to prevent the risk of food-borne diseases.

Evaluation of the antimicrobial mechanism of biogenic selenium nanoparticles against Pseudomonas fluorescens

Selenium nanoparticles (SeNPs) can be biosynthesized by most Lactic acid bacteria thereby converting toxic sodium into SeNPs. However, few studies have reported the antimicrobial activity of biogenic SeNPs against Pseudomonas fluorescens which are the main species of psychrotrophic bacteria in raw milk. This study reported the synthesis and characterization of SeNPs from Lactobacillus casei ZK-AS 1.1482, and the antimicrobial mechanism against P. fluorescens ATCC 13525. The synthesized SeNPs were amorphous with sizes ranging from 52 to 103 nm. Fourier transform infrared spectroscopy (FT-IR) spectra showed the presence of proteins, polysaccharides, and lipids on the surface of particles, which evidently stabilized the SeNPs structure and morphology. Energy-dispersive X-ray (EDX) analysis revealed that the nanoparticles contained selenium. In addition, the minimal inhibitory concentration (MIC) of SeNPs against P. fluorescens ATCC 13525 was 0.1 mg ml^-1 and the biofilm inhibition rate was 43.52 ± 0.26%. SeNPs decreased the number of living bacteria observed by confocal laser scanning microscopy (CLSM). Meanwhile, after SeNPs treatment, the intracellular adenosine triphosphate (ATP) concentration and antioxidant enzyme activity decreased, the content of reactive oxygen species (ROS) and the malondialdehyde (MDA) content increased, and lipid peroxidation intensified. Real-time fluorescence quantitative PCR (RT-qPCR) assay showed that the expression of flgA, luxR, lapD, MCP, cheA, c-di-GMP, phoB, and pstC gene were down-regulated after SeNPs treatment. The rfbC and DegT/DnrJ/EryC1/StrS gene were significantly up-regulated, indicating that SeNPs could destroy the integrity of cell membrane and thus play an antimicrobial role. Biogenic SeNPs are expected to be developed as an efficient and novel antimicrobial agent for application in the food industry.

Biotherapeutic microbial supplementation for ameliorating fish health: developing trends in probiotics, prebiotics, and synbiotics use in finfish aquaculture

Nutrition demands in aquaculture can be realized through quality aquafeeds as compounded diets that contribute to the growth and health of aquaculture species. Functional additives in feed, notably probiotics, prebiotics, and their admixture synbiotics, have been recently recognized for their biotherapeutic role as immunostimulants capable of conferring disease resistance, stress tolerance, and gastrointestinal health; counteracting the negative effects of anti-nutrients, pathogenic prevalence, and antimicrobials in finfish aquaculture. Formulated diets based on probiotics, prebiotics, and as a supplemental combination for synbiotics can significantly influence fish gut microbiomes, establishing the modalities of microbial dynamics to maximize host-associated benefits. These microbial functional-feed supplements are acclaimed to be biocompatible, biodegradable, and safe for dietary consumption as well as the environment. In fed fish aquaculture, prebiotic appended probiotic diet 'synbiotic' has propounded larger attention for its additional health and nutritional benefits. Synbiotic, prebiotic, and probiotic usage as functional feeds for finfish aquaculture thus provides promising prospects. Developing trends in their intended application are reviewed here forth.

Antibacterial Effect of Cell-Free Supernatant from Lactobacillus pentosus L-36 against Staphylococcus aureus from Bovine Mastitis

This study sought to analyze the main antibacterial active components of Lactobacillus pentosus (L. pentosus) L-36 cell-free culture supernatants (CFCS) in inhibiting the growth of Staphylococcus aureus (S. aureus), to explore its physicochemical properties and anti-bacterial mechanism. Firstly, the main antibacterial active substance in L-36 CFCS was peptides, which inferred by adjusting pH and enzyme treatment methods. Secondly, the physicochemical properties of the antibacterial active substances in L-36 CFCS were studied from heat, pH, and metal ions, respectively. It demonstrated good antibacterial activity when heated at 65 °C, 85 °C and 100 °C for 10 and 30 min, indicating that it had strong thermal stability. L-36 CFCS had antibacterial activity when the pH value was 2–6, and the antibacterial active substances became stable with the decrease in pH value. After 10 kinds of metal ions were treated, the antibacterial activity did not change significantly, indicating that it was insensitive to metal ions. Finally, scanning electron microscopy, transmission electron microscopy and fluorescence probe were used to reveal the antibacterial mechanism of S. aureus from the aspects of cell morphology and subcellular structure. The results demonstrated that L-36 CFCS could form 1.4–2.3 nm pores in the cell membrane of S. aureus, which increased the permeability of the bacterial cell membrane, resulting in the depolarization of cell membrane potential and leakage of nucleic acid protein and other cell contents. Meanwhile, a large number of ROS are produced and accumulated in the cells, causing damage to DNA, and with the increase in L-36 CFCS concentration, the effect is enhanced, and finally leads to the death of S. aureus. Our study suggests that the main antibacterial active substances of L-36 CFCS are peptides. L-36 CFCS are thermostable, active under acidic conditions, insensitive to metal ions, and exhibit antibacterial effects by damaging cell membranes, DNA and increasing ROS. Using lactic acid bacteria to inhibit S. aureus provides a theoretical basis for the discovery of new antibacterial substances, and will have great significance in the development of antibiotic substitutes, reducing bacterial resistance and ensuring animal food safety.

Antibacterial Mechanism of Dellaglioa algida against Pseudomonas fluorescens and Pseudomonas fragi

Pseudomonas fluorescens (P. fluorescens) and Pseudomonas fragi (P. fragi), two kinds of psychrotrophic Pseudomonas species with pathogenicity, are likely to contaminate foods and cause diseases even in fairly cold environments, an outcome which should be suppressed. This paper investigates the antibacterial mechanisms of Dellaglioa algida (D. algida), a new type of low-temperature-resistant Lactobacillus, on two such Pseudomonas. By the enzyme treatment approach, the antibacterial substance existing in the cell-free supernatant (CFS) of D. algida is preliminarily determined as organic acid or protein; then, its inhibition effects are assessed under various culture environments, including pH value, salinity, and culture time, where the best antibacterial performance is achieved at pH = 6.00, S = 0%, and culture time = 48 h. A series of experiments on biofilms indicate that D. algida is not only able to inhibit the generation or damage the integrality of the biofilm of the two mentioned Pseudomonas, but also can reduce the motility, including swarming and swimming, of P. fragi and restrain the swarming of P. fluorescens. The aformentioned developed antibacterial mechanisms show the possibility of using D. algida in applications as an inhibitor for psychrotrophic Pseudomonas in the food industry, by virtue of its strong suppression capability, especially in cold environments.

Isolation and identification of new source of bacteriocin-producing Lactobacillus plantarum C010 and growth kinetics of its batch fermentation

The control of food-borne pathogens and spoilage organisms in meat and related products is urgently needed. Bacteriocins produced by lactic acid bacteria (LAB) are promising natural food preservatives. In this study, six bacteriocin-producing bacteria were screened from soil and fresh cow dung. Pseudomonas koreensis PS1, a specific spoilage organism from spoiled chilled pork, was used as the indicator bacteria. From the analyses, the strain C010 was selected due to its high yield, broad spectrum, and subculture stability. Through morphological, biochemical, and 16S rDNA gene sequence analysis, this strain was identified as Lactobacillus plantarum. Crude bacteriocin extracted from the cell-free supernatant (CFS) of L. plantarum C010 was stable under high temperature, ultraviolet radiation, and protease attack (pepsin, trypsin, and proteinase K). The kinetics of bacterial growth and bacteriocin production by L. plantarum C010 were analyzed during batch fermentation. Bacteriocin was produced throughout the logarithmic growth phase, and the Leudeking-Piret model characterized the synthesis of bacteriocins. The present study indicates that this novel bacteriocin produced by bacteria is a promising option for reducing spoilage microorganisms and can be widely used as a bio-preservative in meat and other foods.

Photodynamic Effect of Riboflavin on Chitosan Coatings and the Application in Pork Preservation

Riboflavin (RF) was considered to be possessed of photoactivity to generate reactive oxygen species (ROS) under ultraviolet (UV) light, which is thought to be a favorable antibacterial candidate. Herein, RF was incorporated into chitosan (CS) coatings and treated under UV with different exposure times (2, 4, and 6 h) to improve the physicochemical and antibacterial properties. The results showed that the light transmittance and antibacterial performance of chitosan coatings gradually increased with the extension of the UV irradiation time. The antibacterial ability of chitosan coatings correlated with the generation of ROS: ∙OH and H₂O₂, which achieved 1549.08 and 95.48 μg/g, respectively, after 6 h irradiation. Furthermore, the chitosan coatings with UV irradiation also reduced the pH value, total volatile basic nitrogen (TVB-N), ΔE, and total viable counts (TVC) and improved sensory attributes of pork. In conclusion, the UV irradiated chitosan coatings could be used as an environmentally friendly antimicrobial packaging material to effectively delay the spoilage of pork, maintain its sensory quality and prolong its shelf life.

Effect of Gum Tragacanth-Sodium Alginate Active Coatings Incorporated With Epigallocatechin Gallate and Lysozyme on the Quality of Large Yellow Croaker at Superchilling Condition

This research was done to investigate the synergistic interactions of the gum tragacanth (GT)–sodium alginate (SA) active coatings, incorporated with epigallocatechin gallate and lysozyme, on the quality of large yellow croaker (Larimichthys crocea) during superchilling storage at −3°C. Results showed that the GT-SA active coatings, containing epigallocatechin gallate [EGCG (E), 0.32% w/v], and lysozyme [LYS (L), 0.32% w/v] have reduced the total viable count, psychrophilic bacteria, and Pseudomonas spp. by about 1.55 log CFU/g, 0.49 log CFU/g, and 1.64 log CFU/g compared to the control at day 35. The GT-SA active coatings containing EGCG and LYS were effective in lowering the formations of off-odor compounds such as total volatile basic nitrogen (TVB-N), malondialdehyde (MDA), and off-favor amino acid (histidine). The solid phase microextraction gas chromatography-mass spectrometer (SPME-GC/MS) was applied to characterize and to quantify the volatile compounds of large yellow croaker samples during superchilling storage, while the relative content of the fishy flavor compounds (including 1-octen-3-ol and acetoin) was significantly reduced in the active coatings treated samples. Furthermore, the GT-SA active coatings containing EGCG and LYS treatments was found to be more effective in retarding the migration of water based on magnetic resonance imaging (MRI) results and in maintaining the organoleptic quality of large yellow croaker in superchilling storage at −3°C according to the sensory evaluation results. The results showed that the GT-SA active coating containing EGCG and LYS was effective to be used as a fish preservative to improve the quality and to prolong the shelf life of large yellow croaker in a superchilling storage for at least 7 days.

Partial Purification of Bacteriocin from Lactobacillus pentosus Strain 124-2 Isolated from "Dadih"

&lt;b&gt;Background and Objective:&lt;/b&gt; Preservation using antimicrobials has been observed to inhibit the growth of pathogenic bacteria in food. Nowadays many people choose food preservatives that are safe for health and natural. Bacteriocins as food preservatives are safe because antimicrobials from the antimicrobial peptide group include GRAS (Generally Recognized As Safe). Bacteriocin-producing LAB can be found in various fermented foods, one of which is "Dadih". Bacteriocins are expected to inhibit the growth of pathogenic bacteria so that they can be developed as an alternative to food preservatives. &lt;b&gt;Materials and Methods:&lt;/b&gt; In this study, all experiments were performed with two replicates and the results were expressed as Mean±Standard Deviation (SD). &lt;b&gt;Results:&lt;/b&gt; Screening results showed that the DK8 isolate had the highest antimicrobial activity. The DK8 isolate was identified molecularly using 16s RNA sequencing, showing that the DK8 isolate had the highest similarity to &lt;i&gt;Lactobacillus pentosus&lt;/i&gt; strain 124-2. Bacteriocins from DK8 isolate and partially purified using ammonium sulfate precipitation at concentrations of 50, 60 and 70%. The addition of ammonium sulfate with a concentration of 50% showed the highest antimicrobial activity against &lt;i&gt;Salmonella&lt;/i&gt; sp. (12.63 mm) and &lt;i&gt;Escherichia coli&lt;/i&gt; (11.33 mm) while the highest antimicrobial activity against &lt;i&gt;Staphylococcus aureus&lt;/i&gt; was the addition of 60% ammonium sulfate (8.13 mm). &lt;b&gt;Conclusion:&lt;/b&gt; Lactic acid bacteria isolate was identified to have the highest similarity with &lt;i&gt;Lactobacillus pentosus&lt;/i&gt; strain 124-2 and precipitation using 50% ammonium sulfate showed the highest antimicrobial activity.

Bacteriocins: Properties and potential use as antimicrobials

A variety of bacteriocins originate from lactic acid bacteria, which have recently been modified by scientists. Many strains of lactic acid bacteria related to food groups could produce bacteriocins or antibacterial proteins highly effective against foodborne pathogens such as Staphylococcus aureus, Pseudomonas fluorescens, P. aeruginosa, Salmonella typhi, Shigella flexneri, Listeria monocytogenes, Escherichia coli O157:H7, and Clostridium botulinum. A wide range of bacteria belonging primarily to the genera Bifidobacterium and Lactobacillus have been characterized with different health‐promoting attributes. Extensive studies and in‐depth understanding of these antimicrobials mechanisms of action could enable scientists to determine their production in specific probiotic lactic acid bacteria, as they are potentially crucial for the final preservation of functional foods or for medicinal applications. In this review study, the structure, classification, mode of operation, safety, and antibacterial properties of bacteriocins as well as their effect on foodborne pathogens and antibiotic‐resistant bacteria were extensively studied.

Bacterial Diversity of Sun-Dried Spanish Mackerel in Dalian and Application of Lactobacillus plantarum X23 as a Biopreservative

ABSTRACT

Sun-dried Spanish mackerel is a common food in Dalian and made by adding salt and sun drying, which has special physical, chemical, and microbiological properties. In this study, the physicochemical properties and microbial composition of commercially available sun-dried Spanish mackerel in Dalian were assessed, and some Lactobacillus strains were screened as a biopreservative for sun-dried Spanish mackerel preparation. The results showed that the total volatile base nitrogen content in the traditional sun-dried Spanish mackerel samples from Dalian was within 30 mg/100 g, the histamine content was 7 to 17 mg/kg, and the dominant bacteria at the genus level were Lactobacillus, Psychrobacter, and Ralstonia. A strain with biopreservative potential was isolated from a sun-dried Spanish mackerel sample, identified as L. plantarum species by 16S rDNA sequencing, and assigned as L. plantarum X23. Fresh Spanish mackerel flesh was treated with 16% brine and L. plantarum X23 at a dose of 107 CFU/mL and then dried in the sun. The sun-dried Spanish mackerel flesh treated with 16% brine and L. plantarum X23 showed a decreased histamine and acid value, increased free amino acid content, and a higher sensory score compared with the sun-dried Spanish mackerel without L. plantarum X23 treatment (P < 0.05). In conclusion, the sun-dried Spanish mackerel purchased from the supermarkets in Dalian were safely edible, and L. plantarum X23 can significantly reduce the content of histamine and putrescine in self-made, low-salt, sun-dried Spanish mackerel and has potential as a biopreservative for sun-dried Spanish mackerel preparation.

HIGHLIGHTS

Shelf-Life Extension of Refrigerated Turbot (Scophthalmus maximus) by Using Weakly Acidic Electrolyzed Water and Active Coatings Containing Daphnetin Emulsions

This research was to investigate the effect of weakly acidic electrolytic water (WAEW) treatments combining with the locust bean gum (LBG) and sodium alginate (SA) active coatings, containing daphnetin emulsions on microbiological, physicochemical, and sensory changes of turbot (Scophthalmus maximus) during refrigerated storage at 4°C for 24 days. Results showed that WAEW, together with LBG-SA coatings containing daphnetin emulsions treatments, could significantly lower the total viable count (TVC), H₂S-producing bacteria, pseudomonas spp., and psychrotrophic bacteria counts, and inhibit the productions of off-flavor compounds, including the total volatile basic nitrogen (TVB-N), inosine (HxR), and hypoxanthine (Hx). Furthermore, the treatments also prevented textural deterioration, delayed water migration, and had higher organoleptic evaluation results. Therefore, WAEW, together with LBG-SA coatings, containing daphnetin emulsions treatments, had the potential to improve the quality of turbot during refrigerated storage.

Advances of peptides for antibacterial applications

In the past few decades, peptide antibacterial products with unique antibacterial mechanisms have attracted widespread interest. They can effectively reduce the probability of drug resistance of bacteria and are biocompatible, so they possess tremendous development prospects. This review provides recent research and analysis on the basic types of antimicrobial peptides (including poly (amino acid)s, short AMPs, and lipopeptides) and factors to optimize antimicrobial effects. It also summarizes the two most important modes of action of antimicrobial peptides and the latest developments in the application of AMPs, including antimicrobial agent, wound healing, preservative, antibacterial coating and others. Finally, we discuss the remaining challenges to improve the antibacterial peptides and propose prospects in the field.

Effect of locust bean gum-sodium alginate coatings incorporated with daphnetin emulsions on the quality of Scophthalmus maximus at refrigerated condition

In this study, the microbiological, physicochemical, and flavor changes of turbot (Scophthalmus maximus) coated with a composite active coating of locust bean gum (LBG) and sodium alginate (SA) supplemented with daphnetin emulsions (0.16, 0.32, 0.64 mg·mL^-1) were determined during 18 days of refrigerated storage (4 ± 1 °C). Results showed that LBG-SA coatings containing 0.32 mg·mL^-1 daphnetin emulsions could significantly lower the total viable count (TVC), psychrophiles, Pseudomonas spp. and H₂S-producing bacteria counts, and inhibit the productions of off-flavor compounds including the total volatile basic nitrogen (TVB-N), trimethylamine (TMA) and ATP-related compounds. 32 volatile compounds were identified by solid phase microextraction combined with gas chromatography-mass spectrometer method (SPME-GC/MS) during refrigerated storage and the treated turbot samples significantly lowered the relative content of fishy flavor compounds. Further, the LBG-SA coatings containing daphnetin could also delay the myofibril degradation of the turbot samples. These results indicated that the LBG-SA coatings with 0.32 mg·mL^-1 daphnetin were a potential alternative way to improve the quality of turbot during refrigerated storage.

Indigenous Bacteriocin of Lactic Acid Bacteria from "Dadih" a Fermented Buffalo Milk from West Sumatra, Indonesia as Chicken Meat Preservative

BACKGROUND AND OBJECTIVE

The bacteriocin isolated from fermented buffalo milk from West Sumatra-Indonesia, called Dadih, can be considered as a natural and safe antimicrobial compound for food products. The objective of this research was to evaluate the antimicrobial activity of bacteriocin from Dadih and its effectiveness as a preservative in chicken meat.

MATERIALS AND METHODS

This study used experimental method followed by statistical analysis using 3 experiments with duplication including experiment of meat samples (0 and 10% bacteriocin), storage temperatures (7 and 26°C) and storage duration (0, 1, 2, 3, 4, 5, 6 days and 0, 6, 12 hrs). Each experiment consists of a bacteriocin test, antimicrobial activity assay, physicochemical measurement and storability.

RESULTS

From 10 LAB isolates successfully obtained from Dadih, two isolates with D7 code and D10 code had the highest antimicrobial activity, reaching 11.75 mm and 12 mm, respectively. The meat treated by 10% of bacteriocin gave the lower total microbial (3rd and 5th day) and total E. coli (5th day) at 7 and 26°C. The pH and water activity (aw) values of chicken meat with 10% of bacteriocin showed lower values at 7 and 26°C. The application of bacteriocin to chicken meat was able to inhibit the microbial growth that was still below standard for 3 days at 7°C and 6 hrs at 26°C.

CONCLUSION

Based on research, lactic acid bacteria isolated from buffalo milk curd produced bacteriocin compound which has antimicrobial properties. This bacteriocin showed potential as a natural preservative for chicken meat by inhibiting the growth of pathogen microorganisms.

A review on preparation and chemical analysis of postbiotics from lactic acid bacteria

Postbiotics may be defined as soluble metabolites released by food-grade microorganisms during the growth and fermentation in complex microbiological culture, food or gut. It is rich in high and low molecular weight biologically active metabolites. There are still gaps concerning these substances, mainly how to use them for food applications. Although the most recent work on preparation and application of postbiotics from several probiotics are very encouraging, the suitability of postbiotics to combat microorganisms that deal with food safety should be tested mainly by analyzing the chemical composition and conducting antagonistic tests. Consequently, foods can effectively benefit from an identified postbiotic with a defined effect. This review approached the recent advances in relation to the preparation of postbiotics from lactic acid bacteria. The function of different instrumental analysis techniques and factors affecting the chemical composition of postbiotics were also comprehensively reviewed.

Purification, characterization, and mode of action of a novel bacteriocin BM173 from Lactobacillus crustorum MN047 and its effect on biofilm formation of Escherichia coli and Staphylococcus aureus

There is an increasing demand for dairy products, but the presence of food-spoilage bacteria seriously affects the development of the dairy industry. Bacteriocins are considered to be a potential antibacterial or antibiofilm agent that can be applied as a preservative. In this study, bacteriocin BM173 was successfully expressed in the Escherichia coli expression system and purified by a 2-step method. Furthermore, it exhibited a broad-spectrum antibacterial activity, high thermal stability (121°C, 20 min), and broad pH stability (pH 3-11). Moreover, the minimum inhibitory concentration values of BM173 against E. coli ATCC 25922 and Staphylococcus aureus ATCC 25923 were 14.8 μg/mL and 29.6 μg/mL, respectively. Growth and time-kill curves showed that BM173 exhibited antibacterial and bactericidal activity. The results of scanning electron microscopy and transmission electron microscopy demonstrated that BM173 increased membrane permeability, facilitated pore formation, and even promoted cell lysis. The disruption of cell membrane integrity was further verified by propidium iodide uptake and lactic dehydrogenase release. In addition, BM173 exhibited high efficiency in inhibiting biofilm formation. Therefore, BM173 has promising potential as a preservative used in the dairy industry.

Elucidating Antibacterial Activity and Mechanism of Daphnetin against Pseudomonas fluorescens and Shewanella putrefaciens

In this research, the antibacterial activity and mechanism of daphnetin against Pseudomonas fluorescens and Shewanella putrefaciens were evaluated. The minimum inhibitory concentration (MIC) of daphnetin on P. fluorescens and S. putrefaciens was 0.16 and 0.08 mg·mL−1, respectively. The growth curve test also showed that daphnetin had a good antibacterial effect. The results of intracellular component leakage and cell viability analysis illustrated that daphnetin destroyed the morphology of the cell membrane. According to scanning electron microscope and transmission electron microscope observations, the treated bacterial cells displayed obvious morphological and ultrastructural changes in the cell membrane of the two tested strains, whichconfirmed daphnetin’s damage to the integrity of the cell membrane. The findings indicated that daphnetin mainly exerted its antibacterial effect by destroying the membrane and suggested that it had good potential to be as a natural food preservative.

Antibacterial Activity and Mechanism of Lacidophilin From Lactobacillus pentosus Against Staphylococcus aureus and Escherichia coli

The main purpose of this study was to explore the antibacterial activity and mechanism of lacidophilin from Lactobacillus pentosus against Staphylococcus aureus and Escherichia coli. The effects of temperature, enzyme, metal ions, and pH on the antibacterial activity of L. pentosus were evaluated. The result showed that lacidophilin had good thermal stability and could be decomposed by trypsin completely. The antibacterial ability was affected by high concentration of metal ions, and the best antibacterial ability was acquired under acidic conditions. The antibacterial mechanism of lacidophilin was explored through studying cytomembrane injury, phosphorus metabolism, protein changes, and oxidative stress response of the indicator bacteria. It was shown that lacidophilin destroyed the cytomembrane of the bacteria and increased the cytomembrane permeability, which resulted in the leak of proteins, nucleic acids, and electrolytes. In addition, it further restrained phosphorus metabolism, caused changes of some protein contents, and increased cytomembrane lipid peroxidation and cell oxidative damage. All these might inhibit the growth of bacteria and even cause their death. This study identified a natural biological preservative with strong antibacterial activity against both Gram-positive and Gram-negative foodborne pathogens. The high antibacterial activity against the two types of bacteria reflected its potential in food preservation used as a natural food preservative.

Mining, heterologous expression, purification, antibactericidal mechanism, and application of bacteriocins: A review

Bacteriocins are generally considered as low-molecular-weight ribosomal peptides or proteins synthesized by G⁺ and G^- bacteria that inhibit or kill other related or unrelated microorganisms. However, low yield is an important factor restricting the application of bacteriocins. This paper reviews mining methods, heterologous expression in different systems, the purification technologies applied to bacteriocins, and identification methods, as well as the antibacterial mechanism and applications in three different food systems. Bioinformatics improves the efficiency of bacteriocins mining. Bacteriocins can be heterologously expressed in different expression systems (e.g., Escherichia coli, Lactobacillus, and yeast). Ammonium sulfate precipitation, dialysis membrane, pH-mediated cell adsorption/desorption, solvent extraction, macroporous resin column, and chromatography are always used as purification methods for bacteriocins. The bacteriocins are identified through electrophoresis and mass spectrum. Cell envelope (e.g., cell permeabilization and pore formation) and inhibition of gene expression are common antibacterial mechanisms of bacteriocins. Bacteriocins can be added to protect meat products (e.g., beef and sausages), dairy products (e.g., cheese, milk, and yogurt), and vegetables and fruits (e.g., salad, apple juice, and soybean sprouts). The future research directions are also prospected.

Isolation of Antibacterial, Nitrosylmyoglobin Forming Lactic Acid Bacteria and Their Potential Use in Meat Processing

The use of nitrite as a colorant and preservative in meat processing is associated with health risks. This study aimed to isolate nitrite-substituting lactic acid bacteria for use as natural biological colorants and preservatives. Among the 106 strains isolated from fermented foods, two strains with excellent ability to convert myoglobin and metmyoglobin (Met-Mb) to red nitrosylmyoglobin (Mb-NO) were selected. The superior ability to form Mb-NO was confirmed through UV-visible spectrophotometry, Fourier transform infrared spectrometry, electron spin resonance analysis, nitric oxide synthase activity assay, and Met-Mb reductase activity assay. The potent antibacterial activity was confirmed through biofilm and cytomembrane breakage of the indicator bacteria. Though performing 16S rDNA sequencing, they were identified as two different strains of Lactobacillus plantarum. Based on their favorable characteristics, their applications in the meat industry were further evaluated. This study identified a novel dual-function natural biological colorant and preservative to substitute nitrite in meat products. The application of the two strains would decrease the hazardous of nitrite to health.

Effect of the Combination of Vanillin and Chitosan Coating on the Microbial Diversity and Shelf-Life of Refrigerated Turbot (Scophthalmus maximus) Filets

The effect of the combination of vanillin and chitosan (VC) coating on the microbiota composition and shelf-life of turbot (Scophthalmus maximus) filets during a 15-day storage period at 4 ± 1°day was investigated in this study. The control and coated fish samples were analyzed periodically for sensory and chemical attributes [total volatile basic nitrogen (TVB-N), thiobarbituric acid reactive substances (TBARS), and pH] and the presence of dominant spoilage microbiota. The results suggested that the sensory and the chemical quality of turbot filets effectively improved after treatment with vanillin (final concentration 2 mg/ml) combined with 1% chitosan, and the shelf-life was prolonged for 6 to 7 days compared with the control group. Furthermore, high-throughput sequencing showed that Proteobacteria (52.2%) and Firmicutes (29.8%) were the dominant bacteria at the phylum level in fresh turbot filets, while Pseudomonadaceae (40.2%) and Lactobacillaceae (39.4%) were the dominant bacteria at the family level in deteriorated turbot filets. However, after VC treatment, the relative abundance of Pseudomonadaceae and Lactobacillaceae decreased significantly due to the growth inhibition of potential bacteria, specifically spoilage bacteria, along with the rich bacterial diversity at the end of storage. Therefore, our data indicated that VC treatment might be effective in decreasing bacteria-induced quality deterioration and in extending the shelf-life of refrigerated turbot filets.

An on-package colorimetric sensing label based on a sol-gel matrix for fish freshness monitoring

Fish freshness monitoring is important for consumers. This study aims to develop an colorimetric sensing label based on bromocresol green (BCG) and a sol-gel matrix layer coated onto filter paper to monitor fish freshness. Characterization results showed that the sol-gel layer was successfully coated, and the coating yield was 14.25%. The fish freshness could be detected clearly by the naked eye as the color of the sensing label changed. A Hue Saturation Value (HSV) model was used to correlate the response of the sensing label to the freshness of fish samples. Hue (H) values showed a linear response to the total volatile basic nitrogen (TVB-N) concentration in the range of 16.4-23.11 mg/100 g at room temperature, and in the range of 9.28-24.12 mg/100 g at a chilled temperature. The sensing label was applied to other types of fish, and showed an intense color change during the spoilage trial.

Beneficial bacteria for aquaculture: nutrition, bacteriostasis and immunoregulation

Despite being the fastest growing sector, the modern aquaculture industry faces serious challenges such as the lack of protein source in feed, the susceptibility to pathogens, and deterioration in quality during culture and storage. Bacterial biomass is considered as a proper protein source for feed, and the beneficial bacterial species protect aquatic animals from infection or reduce spoilage of products. In this review, we summarized the application of beneficial bacteria to aquatic products, focusing mainly on the nutritional, anti-pathogenic, anti-spoilage and immunoregulatory functions of these bacteria. We then discussed the relationship between beneficial bacteria, intestinal microbiota and host immunity, and the recent progress and drawbacks of the technology.

Effects of Bioactive Packaging Films Incorporated with Bifidocin A on Microbial Reduction and Quality Parameters of Chill-Stored Spanish Mackerel (Scomberomorus niphonius) Fillets

To evaluate the potential of bifidocin A for preservation of fresh Spanish mackerel fillets, the bioactive packaging films incorporated with bifidocin A (1 × minimal inhibition concentration (MIC), 2 × MIC and 4 × MIC) were developed, and their effects on the microbiological and physicochemical properties and sensory profile of mackerel fillets at refrigerated storage were investigated. Results showed that the incorporation of bifidocin A in cellulosic matrix films did not affect the thickness and elongation of the films, but reduced slightly the tension strength. The films incorporated with 2 × MIC and 4 × MIC bifidocin A presented a broad spectrum of activity against most tested bacteria, including some fish-borne specific spoilage bacteria such as Pseudomonas fluorescens, Shewanella putrefaciens, Brochothrix thermosphacta, and Micrococcus luteus, and maintained their 100% activity for 28 days during storage at 4°C. The bioactive packaging films incorporated with bifidocin A could generally suppress the growth of microflora, especially Pseudomonas and Enterobacteriaceae, as well as substantially inhibit the accumulation of total volatile basic nitrogen (TVB-N), thiobarbituric acid reactive substances (TBARS) and hypoxanthine, during chilled mackerel fillets storage. Overall, from a microbiological and physicochemical point of view, a much more effective treatment was achieved with 4 × MIC bifidocin A, extending the shelf life to 12 days and maintaining the relatively low TVB-N value (≤13.2 mg/100 g), TBARS value (≤0.45 mg MDA/kg), and K-value (≤32.8%), as well as a relatively high sensory score (≥7.1) during the whole storage. Hence, the bioactive packaging films incorporated with bifidocin A could be a promising hurdle technology and alternative to conventional processes used for improving the safety and quality of chilled mackerel fillets.

Preservation of Meat Products with Bacteriocins Produced by Lactic Acid Bacteria Isolated from Meat

Bacteriocins are ribosomal-synthesized antimicrobial peptides that inhibit the growing of pathogenic and/or deteriorating bacteria. The most studied bacteriocin-producing microorganisms are lactic acid bacteria (LAB), as they have great potential application in food biopreservation, since the majority have GRAS (Generally Recognized as Safe) status. The LAB-producing bacteriocins and/or bacteriocins produced by these bacteria have been widely studied, with the emphasis on those derived from milk and dairy products. On the other hand, isolates from meat and meat products are less studied. The objective of this review is to address the main characteristics, classification, and mechanism of action of bacteriocins and their use in food, to highlight studies on the isolation of LAB with bacteriocinogenic potential from meat and meat products and also to characterize, purify, and apply these bacteriocins in meat products. In summary, most of the microorganisms studied areLactococcus,Enterococcus,Pediococcus, andLactobacillus, which produce bacteriocins such as nisin, enterocin, pediocin, pentocin, and sakacin, many with the potential for use in food biopreservation.