Bacteriocin-producing Lactic Acid Bacteria Research Articles

Physicochemical and sensory characterization of functional synbiotic Labneh fortified with the bacteriocin-producing Lactiplantibacillus plantarum strain GA7 and nano-encapsulated Tirmania pinoyi extract

BackgroundFunctional foods and dairy products are gaining global attention due to their nutritional value and health-promoting characteristics. Lactic acid bacteria (LAB) are one of the promising components included in these products, thanks to their probiotic properties and ability to produce bioactive compounds such as bacteriocins. On the other hand, ectomycorrhizal wild mushrooms (truffles) are known for their ethnomycological importance. Hence, we aimed to develop a functional dairy product using a bacteriocin-producing LAB isolate that has probiotic potentials together with the bioactive extract of a truffle mushroom.ResultsScreening for bacteriocin-producing LAB led to the selection of four safe isolates that also showed promising probiotic potentials. Isolate No. 7 was selected due to its wider antimicrobial spectrum and was identified as Lactiplantibacillus plantarum strain GA7. Out of resulting bands from Tricine SDS-PAGE analysis, a band (its molecular mass was approximately 7 kDa) exhibited antimicrobial activity. Amino acid sequencing of this active band detected 62 amino acid residues with 100% identity to plantaricin ASM1 bacteriocin. Simultaneously, an ethyl acetate extract was prepared from a truffle sample identified as Tirmania pinoyi. Safety of this truffle was confirmed and its extract exerted promising antioxidant and hypocholesterolemic activity. Prepared functional dairy products (Labneh) fortified with L. plantarum GA7 and nano-encapsulated T. pinoyi extract exhibited superior physicochemical, sensory and antioxidant properties compared to control. Moreover, an increase in probiotic count was observed in presence of T. pinoyi extract. Furthermore, prepared Labneh using the bacteriocin-producing L. plantarum GA7 and nano-encapsulated T. pinoyi extract remained unspoiled for over 60 days, compared to control, which spoiled after 21 days.ConclusionBesides improving Labneh physicochemical, sensory and antioxidant properties, the presence of the bacteriocin-producing L. plantarum GA7 has contributed in significantly extending its shelf life, while T.pinoyi extract showed prebiotic influence on probiotic count. As far as we know this is the first study describing production of a functional synbiotic dairy product fortified with bacteriocin-producing probiotic LAB and bioactive T. pinoyi truffle extract.

Antimicrobial activities and bacteriocins of lactic acid bacteria isolated from Nigeria indigenous fermented cowmilk “nunu”

Nunu is a nutritious fermented yoghurt-like milk beverage that can serve as a source of lactic acid bacteria (LAB) with antimicrobial and bacteriocin potentials. Nunu samples were screened for LAB with antimicrobial activity against test organisms. Three LAB, namely Lactobacillus parafarraginis OCLP1, L. fermentum CSL58 and L. buchneri MZE12 out of a total of 14 isolates produced antimicrobial activity against Bacillus anthracis CHF-2011-32b, B. cereus DHM5-1, Providencia vermicola KSVDL-09-71600, P. rettgeri SIRT3, P. stuartti SILT11 and other test organisms. Antimicrobial factors were assayed in LAB cell-free extracts (CFE), neutralized CFE, and ammonium sulphate precipitants of the CFE, and Lactobacillus parafarraginis OCLP1 demonstrated highest activity with zone of inhibition = 20.33±3.51 mm­, 13.33±1.09 mm and 25.33±2.52 mm respectively. The CFE of the LAB especially L. parafarraginis OCLP1 demonstrated wide activity spectra by inhibiting both the gram-positive and gram-negative bacteria tested. Result of plasmid curing of the LAB indicate that the bacteriocins of L. parafarraginis OCLP1 was plasmid-encoded while the others have their gene clusters on the chromosome. This study concluded that bacteriocin-producing LAB can be found in “nunu” and recommend the use of the isolated LAB as starter in fermented food production after ensuring their safety through toxicological studies.

Technological and safety properties of bacteriocin-producing <i>Enterococcus</i> strains isolated from traditional Turkish cheeses

The aim of this study was to identify bacteriocin-producing lactic acid bacteria (LAB) isolated from traditional Turkish cheeses, evaluate their antibacterial properties and technological characteristics, and determine the safety properties of isolates. The isolated strains were identified as Enterococcus faecium DP8.3, DP9.3, and Enterococcus mundtii DP35.1, which are genetically different from each other. The bacteriocins produced by these isolates exhibited stability under high temperatures and maintained their antibacterial activity across a broad pH spectrum. The bacterial strains were fast acid producers, lacked proteolytic or lipolytic activity, were susceptible to antibiotics, and did not show antibiotic resistance or virulence genes. In addition, all the Enterococcus strains decarboxylated tyrosine and showed tdc gene expression. According to the technological properties and safety assessment of the strains, it is believed that they can be used as protective adjunct cultures in the food industry.

Antagonistic activities against selected pathogens of a bacteriocin-producing lactic acid bacteria isolated from Balao-balao, a fermented rice-shrimp mixture

Lactic acid bacteria from a fermented rice-shrimp mixture traditionally known in the Philippines as Balao-balao were isolated in the present study. Screening of lactic acidproducing strains revealed that ten isolates showed promising inhibitory activities against test microorganisms namely Staphylococcus aureus BIOTECH 1634, Escherichia coli BIOTECH 1582, Bacillus subtilis BIOTECH 1679 and Vibrio harveyi SEAFDEC 010. Of interest was isolate PL12, a bacteriocin-producing strain which showed the highest inhibitory activity against the pathogens tested. Isolate PL12 was identified as Pediococcus pentosaceus (GenBank accession number MF353992) with 100% similarity by 16S rDNA sequence analyses. Excluding the effects of organic acids and hydrogen peroxide, the cell-free supernatant (CFS) of PL12 isolate exhibited strong antagonistic activities against test pathogens in an agar well diffusion assay. These results confirmed the isolate’s proteinaceous nature and are indicative of typical characteristics of bacteriocins. To further concentrate the proteins present in the CFS, ammonium sulfate precipitation followed by column purification (Sep-Pak C18 cartridge column) was performed. Positive antagonism of PL12 bacteriocin was observed in both Gram-positive and Gram-negative bacteria tested. The highest inhibitory activity was found against E. coli in every purification step. These results suggested that bacteriocin-producing PL12 isolate can be a promising preservative in the food industry and as probiotics in aquaculture since it possesses antagonistic activities against V. harveyi.

Bacteriocins from lactic acid bacteria: strategies for the bioprotection of dairy foods

Lactic acid bacteria (LAB), essential in fermenting milk, produce an array of antimicrobial compounds, notably bacteriocins, which contribute to the extended shelf life of dairy goods. Bacteriocins, ribosomally synthesized peptides, display broad or narrow-spectrum antimicrobial activity, thus holding promise in food preservation. The classification of LAB bacteriocins is intricate, reflecting evolving genomic insights and biosynthesis mechanisms. Strategies for integrating bacteriocins into dairy products include purified forms, bacteriocin-producing LAB, and bacteriocin-containing fermentates, each with distinct advantages and considerations. Optimization of fermentation conditions, encompassing time, temperature, pH, and culture medium, is essential for maximizing bacteriocin production. This optimization facilitates enhanced quality and safety of fermented dairy items, aligning with the growing consumer preference for natural, minimally processed foods. Furthermore, the incorporation of bacteriocins into a hurdle approach alongside thermal and non-thermal treatments holds promise for augmenting food bioprotection while reducing reliance on chemical preservatives. This comprehensive overview underscores the potential of LAB bacteriocins as a natural, effective alternative to conventional food preservatives, offering insights into their application and optimization in dairy product preservation.

Sucuk, Turkish-Style Fermented Sausage: Evaluation of the Effect of Bioprotective Starter Cultures on Its Microbiological, Physicochemical, and Chemical Properties

Bio-protection is one of the most popular natural protection methods to control food safety and shelf life. Lactic acid bacteria, especially Lactobacilli strains, are used in the food industry for this purpose due to their probiotic properties and, accordingly, bioprotective properties. We aimed to investigate the role of the bacteriocin-producing lactic acid bacteria Lactobacillus sakei and Pediococcus acidilactici in inducing microbiological, physicochemical, and chemical changes in the Turkish-style fermented sausage sucuk. The effects of protective cultures were compared with those of commercial starter cultures consisting of Pediococcus pentosaceus + Staphylococcus carnosus; a non-cultured group was used as a control. L. sakei inoculation and, to a lower extent, P. acidilactici inoculation resulted in the rapid domination of lactic acid bacteria (LAB) in the environment, whereas commercially used starter cultures and the non-cultured group showed lower counts of LAB. Moreover, L. sakei and P. acidilactici succeeded in inhibiting pathogens including S. aureus, E. coli, and Enterobacteriaceae. The number of enterococci decreased notably in the L. sakei-inoculated sucuk samples; however, an increase was determined in the samples inoculated with P. acidilactici. On the other side, the effect of commercial starter cultures was not sufficient for the inhibition of food-borne pathogens in the sucuk samples. Consequently, the inoculation of protective cultures, particularly of L. sakei, can provide a considerable contribution to improving microbial quality and food safety, retarding lipid oxidation, and increasing proteolytic activities in sucuk without important changes in its sensory properties.

Effects of bacteriocin-producing Lactiplantibacillus plantarum on bacterial community and fermentation profile of whole-plant corn silage and its in vitro ruminal fermentation, microbiota, and CH4 emissions

BackgroundSilage is widely used to formulate dairy cattle rations, and the utilization of antibiotics and methane emissions are 2 major problems for a sustainable and environmentally beneficial ruminant production systems. Bacteriocin has received considerable attention because of its potential as an alternative to antibiotics in animal husbandry. However, the impact of bacteriocin-producing lactic acid bacteria on the microbiological conversion process of whole-plant corn silage and rumen fermentation remains limited. The purpose of this study was to assess the effect of 2 class IIa bacteriocin-producing strains Lactiplantibacillus plantarum ATCC14917 and CICC24194 on bacterial community composition and ensiling profiles of whole-plant corn silage and its in vitro rumen fermentation, microbiota, and CH4 emissions.ResultsBoth bacteriocin-producing strains increased the lactic acid concentration in silage fermented for 7 d, whereas the lowest lactic acid was observed in the ATCC14917 inoculated silage fermented for 90 d (P < 0.05). The highest DM content was observed in the CICC24194 treatment (P < 0.05), and the silages treated with both strains had the lowest DM loss (P < 0.05). Bacteriocin-producing strains promoted the growth of Levilactobacillus brevis on d 60 of ensiling. In addition, treatment with bacteriocin-producing strains increased the in vitro DM digestibility (P < 0.05) and decreased the CH4 production (P < 0.05). The results of random forest and clustering analyses at the genus level showed that ATCC14917 increased the relative abundance of the influential variable Bacillus compared to that in the control group, whereas CICC24194 decreased the relative abundance of the influential variable Ruminococcaceae UCG-005. The CICC24194 treatment had the lowest total bacterial, fungal, protozoan, and methanogen populations (P < 0.05).ConclusionsBoth class IIa bacteriocin-producing L. plantarum strains improved the fermentation quality of whole-plant corn silage by regulating the bacterial community composition during ensiling, with CICC24194 being the most effective. Both bacteriocin-producing strains mitigated CH4 production and improved digestibility by modulating the interactions among rumen bacteria, protozoa, methanogens, and the composition of fibrolytic bacteria.

Isolation and identification of bacteriocin-producing lactic acid bacteria from Daqu and mining of bacteriocin gene

Isolation and identification of bacteriocin-producing lactic acid bacteria from Daqu and mining of bacteriocin gene

Improving the Functionality of Yogurt after Fortification with a Synbiotic Combination of a Potential Probiotic and Bacteriocin-Producing Bacteria and Hydnora abyssinica Phytosomes

Functional dairy products are attracting consumers’ attention, as they simultaneously have nutritional and health benefits. Hence, we aimed in this study to fortify a dairy product (yogurt) with phytosomes of extract from Hydnora abyssinica (a holoparasitic plant that has ethnobotanical value) and a potential bacteriocin-producing probiotic lactic acid bacterium (LAB). Goat cheese was screened for LAB with promising antimicrobial activity, and the safety and probiotic potential of the selected isolate were studied. As a result, strain GA5 was selected due to its wide antimicrobial activity that was suggested to be caused by bacteriocin production. Moreover, this strain showed promising stress tolerance, in vitro antioxidant activity (95 ± 2.8%), and hydrophobic potential (87.18 ± 3.43%). Strain GA5 was molecularly identified as Lactiplantibacillus plantarum GA5. On the other hand, a hydromethanolic extract was prepared from H. abyssinica flowers, and its prebiotic potential and polyphenol content were evaluated. This extract was also encapsulated in phytosomes. Then, the physical and morphological characteristics of prepared phytosomes were studied. Yogurt fortified with these ingredients (L. plantarum GA5 together with free H. abyssinica extract or its extract encapsulated in phytosomes) showed higher antioxidant content, viscosity, texture profile, and sensory properties than the control. Furthermore, the yogurt remained unspoiled for over 21 days, indicating that the added ingredients prolonged its shelf life. As far as we know, this is the first study describing the fortification of yogurt with H. abyssinica phytosomes and a potential bacteriocin-producing probiotic LAB.

BACTERIOCIN PRODUCED BY LACTIC ACID BACTERIA: A PROBIOTIC

Chemical preservatives, usually used during the long period, to protect the food materials by controlling undesirable bacteria and harmful spoiler, have been proved as toxic to human health. Conscious consumers have serious awareness to purchase safe foods without chemical additives. In the recent years, bio-preservation is gained increasing attention to harmonize consumer demands along with standard food quality. Various attempts are growing on the use of micro-organisms or their antimicrobial metabolites for the protection of food products. The bacteriocins produced by lactic acid bacteria (LAB) have a relatively broad antimicrobial spectrum against variety of food-borne pathogenic and spoilage bacteria. Bacteriocin-producing lactic acid bacteria or bacteriocins can be used in foods as bio-preservatives. The review is focused on bacteriocin produced by lactic acid bacteria.

Complete genome sequence of Ligilactobacillus agilis LDTM47, bacteriocin-producing lactic acid bacteria isolated from broiler gastrointestinal tract

Complete genome sequence of Ligilactobacillus agilis LDTM47, bacteriocin-producing lactic acid bacteria isolated from broiler gastrointestinal tract

Bacteriocin producing lactic acid bacteria from camel milk and its fermented products: A review

Bacteriocin producing lactic acid bacteria from camel milk and its fermented products: A review

Essential Oils and Their Combination with Lactic Acid Bacteria and Bacteriocins to Improve the Safety and Shelf Life of Foods: A Review.

The use of plant extracts (e.g., essential oils and their active compounds) represents an interesting alternative to chemical additives and preservatives applied to delay the alteration and oxidation of foods during their storage. Essential oils (EO) are nowadays considered valuable sources of food preservatives as they provide a healthier alternative to synthetic chemicals while serving the same purpose without affecting food quality parameters. The natural antimicrobial molecules found in medicinal plants represent a possible solution against drug-resistant bacteria, which represent a global health problem, especially for foodborne infections. Several solutions related to their application on food have been described, such as incorporation in active packaging or edible film and direct encapsulation. However, the use of bioactive concentrations of plant derivatives may negatively impact the sensorial characteristics of the final product, and to solve this problem, their application has been proposed in combination with other hurdles, including biocontrol agents. Biocontrol agents are microbial cultures capable of producing natural antimicrobials, including bacteriocins, organic acids, volatile organic compounds, and hydrolytic enzymes. The major effect of bacteriocins or bacteriocin-producing LAB (lactic acid bacteria) on food is obtained when their use is combined with other preservation methods. The combined use of EOs and biocontrol agents in fruit and vegetables, meat, and dairy products is becoming more and more important due to growing concerns about potentially dangerous and toxic synthetic additives. The combination of these two hurdles can improve the safety and shelf life (inactivation of spoilage or pathogenic microorganisms) of the final products while maintaining or stabilizing their sensory and nutritional quality. This review critically describes and collects the most updated works regarding the application of EOs in different food sectors and their combination with biocontrol agents and bacteriocins.

Dual Role of Probiotic Lactic Acid Bacteria Cultures for Fermentation and Control Pathogenic Bacteria in Fruit-Enriched Fermented Milk.

The food industry has been developing new products with health benefits, extended shelf life, and without chemical preservation. Bacteriocin-producing lactic acid bacteria (LAB) strains have been evaluated for food fermentation to prevent contamination and increase shelf life. In this study, potentially probiotic LAB strains, Lactiplantibacillus (Lb.) plantarum ST8Sh, Lacticaseibacillus (Lb.) casei SJRP38, and commercial starter Streptococcus (St.) thermophilus ST080, were evaluated for their production of antimicrobial compounds, lactic acid and enzyme production, carbohydrate assimilation, and susceptibility to antibiotics. The characterization of antimicrobial compounds, the proteolytic activity, and its inhibitory property against Listeria (List.) monocytogenes and Staphylococcus (Staph.) spp. was evaluated in buriti and passion fruit-supplemented fermented milk formulations (FMF) produced with LAB strains. Lb. plantarum ST8Sh was found to inhibit List. monocytogenes through bacteriocin production and produced both L(+) and D(-) lactic acid isomers, while Lb. casei SJRP38 mainly produced L(+) lactic acid. The carbohydrate assimilation profiles were compatible with those usually found in LAB. The potentially probiotic strains were susceptible to streptomycin and tobramycin, while Lb. plantarum ST8Sh was also susceptible to ciprofloxacin. All FMF produced high amounts of L(+) lactic acid and the viability of total lactobacilli remained higher than 8.5 log CFU/mL during monitored storage period. Staph. aureus ATCC 43300 in fermented milk with passion fruit pulp (FMFP) and fermented milk with buritipulp (FMB), and Staph. epidermidis KACC 13234 in all formulations were completely inhibited after 14days of storage. The combination of Lb. plantarum ST8Sh and Lb. casei SJRP38 and fruit pulps can provide increased safety and shelf-life for fermented products, and natural food preservation meets the trends of the food market.

Identification of lactic acid bacteria with anti-listeria activity. Characterization and application of a bacteriocinogenic strain in the control of Listeria monocytogenes in cheese.

The purpose of the research paper was firstly to identify bacteriocin-producing lactic acid bacteria characterizing strains with anti-listeria activity and, secondly, to characterize bacteriocin evaluating its in vitro efficiency as a natural preservative and, thirdly, to evaluate the anti-listeria effect of the bacteriocinogenic strain of Lactiplantibacillus plantarum in cheeses and produce an edible film with anti-listerial effect. Of 355 lactic acid bacteria strains tested, two were able to produce bacteriocin against Listeria monocytogenes and were identified as Lactiplantibacillus plantarum and Lactiplantibacillus pentosus. A bactericidal effect of strain QS494 (Lactiplantibacillus plantarum) was observed in the first 8 h, with a reduction of 1.7 log, using cell-free supernatant with Listeria monocytogenes, where viable cells were counted on listeria selective agar. Both strains showed good technological characteristics and were without production of virulence factors. Changes in the pH of the cell-free supernatant obtained from Lactiplantibacillus plantarum did not affect its antimicrobial activity, which remained stable after heat treatments for up to 15 min at 121°C. Inhibitory activity was also observed after 12 weeks of storage at -20°C. In the evaluation of the anti-listeria effect in cheeses, a 3 log reduction in the Listeria monocytogenes count was observed in 120 h in cheeses produced with bacteriocinogenic lactic acid bacteria, while in cheeses produced with non-bacteriocinogenic culture, we observed a 2 log increase in the count. Edible films produced with the addition of precipitate from the cell free supernatant showed an antimicrobial effect against Listeria monocytogenes. Thus, the two strains studied have technological and biosafety potential.

Bacteriocin production and technological properties of Enterococcus mundtii and Enterococcus faecium strains isolated from sheep and goat colostrum.

Enterococci are lactic acid bacteria (LAB) that play a role in the aroma formation, maturation, and sensory development of fermented foods such as meat and dairy products. They also contribute to the improvement of the extended shelf life of fermented foods by producing bacteriocin. The aim of this study was to isolate bacteriocin-producing LAB from sheep and goat colostrum, to characterize the bacteriocin-producing strains, and determine the technological properties of the strains. A total of 13 bacteriocin-producing LAB was isolated and identified as 11 Enterococcus mundtii and two Enterococcus faecium. The strains were found to be genetically different from each other by phylogenetic analysis of 16S rRNA gene sequences and random amplified polymorphic-DNA (RAPD-PCR). It has been determined that bacteriocins show activity in a wide pH range and are resistant to heat, lose their activity with proteolytic enzymes and α-amylase, but are resistant to detergents. While the presence of the munKS gene was detected in all of the strains, it was determined that E. faecium HC121.4, HC161.1, E. mundtii HC147.1, HC166.5, and HC166.8 strains contained multiple enterocin genes. Trisin-SDS-PAGE analysis revealed two active protein bands of approximately 5.1 and 5.5kDa in E. faecium HC121.4 and one active protein band with a weight of approximately 4.96kDa in other strains. E. mundtii strains and E. faecium HC161.1 were identified as mundticin KS producers, and E. faecium HC121.4 was defined as an enterocin A and B producer. Except for E. mundtii HC166.8, acid production of strains was found to be slow at 6h and moderate at 24h. None of them showed extracellular proteolytic and lipolytic activities. It was found that the strains had esterase, esterase lipase, leucine arylamidase, acid phosphatase, and naphthol-AS-Bl-phosphohydrolase activities, while protease activities were low and peptidase activities were high. In conclusion, bacteriocin producer 13 Enterococcus strains isolated from sheep and goat colostrum were found to have the potential to be included in starter culture combinations.

Isolation, Characterization, and Effect on Biofilm Formation of Bacteriocin Produced by Lactococcus lactis F01 Isolated from Cyprinus carpio and Application for Biopreservation of Fish Sausage.

The aim of this work was the screening of bacteriocin-producing LABs isolated from fish, the selection of promising/prominent strain(s), the characterization of the bacteriocin produced, and the evaluation of its potential to be used as biopreservative(s). Amplification and sequencing of the 16S rRNA gene of the bacteriocin-producing strain was performed. Then a partial purification of the produced bacteriocin, using a combination of ammonium sulfate and chloroform-methanol precipitation, was done. Its molecular weight was determined by SDS-PAGE. In addition, the action spectrum, the hemolysis test, and its ability to inhibit biofilm formation were analyzed. A total of 88 isolates of lactic acid bacteria (LAB) including one bacteriocin producer, which was identified as Lactococcus lactis F01, were collected. The bacteriocin was partially purified with an estimated yield of 40%. Regarding the SDS-PAGE profile, the secreted bacteriocin has molecular weight of about 3.5 kDa and was identified as class I bacteriocin. The antimicrobial test showed that the bacteriocin inhibits pathogenic and/or spoilage bacteria, 10 Gram-positive and 16 Gram-negative bacterial species. Moreover, it can inhibit biofilm formation from 1.3% (Escherichia coli) to 63.92% (Pseudomonas aeruginosa ATCC15692) depending on the strain. The hemolytic activity of novel bacteriocin was observed at the concentration of 10 μg/ml of bacteriocin crude extract, which was 0.7 ± 0.0029%. In addition, it exhibited good thermal and pH stability with retained antibacterial activity of 85.25% after treatment at 121°C for 20 min, as well as at a pH range between 2.0 and 10.0. Moreover, this bacteriocin showed the ability to inhibit the growth of bacterial culture load in fish sausage stored at 8°C for 28 days. Considering the results obtained, bacteriocin could be potentially exploited as an alternative to chemical preservatives or as a substitute for antibiotics.

Inhibition of Listeria monocytogenes in Fresh Cheese Using a Bacteriocin-Producing Lactococcus lactis CAU2013 Strain.

In recent years, biocontrol of foodborne pathogens has become a concern in the food industry, owing to safety issues. Listeria monocytogenes is one of the foodborne pathogens that causes listeriosis. The major concern in the control of L. monocytogenes is its viability as it can survive in a wide range of environments. The purpose of this study was to isolate lactic acid bacteria with antimicrobial activity, evaluate their applicability as a cheese starter, and evaluate their inhibitory effects on L. monocytogenes. Lactococcus lactis strain with antibacterial activity was isolated from raw milk. The isolated strain was a low acidifier, making it a suitable candidate as an adjunct starter culture. The commercial starter culture TCC-3 was used as a primary starter in this study. Fresh cheese was produced using TCC-3 and L. lactis CAU2013 at a laboratory scale. Growth of L. monocytogenes (5 Log CFU/g) in the cheese inoculated with it was monitored during the storage at 4°C and 10°C for 5 days. The count of L. monocytogenes was 1 Log unit lower in the cheese produced using the lactic acid bacteria strain compared to that in the cheese produced using the commercial starter. The use of bacteriocin-producing lactic acid bacteria as a starter culture efficiently inhibited the growth of L. monocytogenes. Therefore, L. lactis can be used as a protective adjunct starter culture for cheese production and can improve the safety of the product leading to an increase in its shelf-life.

Efficacy of Bacteriocin Producing Lactic Acid Bacteria Isolated from Ugba and Okpiye Against some Selected Bacterial Food Spoilage Agents

Numerous food products owe their production and characteristics to the fermentative activities of microorganisms. Bacteriocins are antimicrobial proteins produced by bacteria that kill or inhibit the growth of other related species. Lactic acid producing bacteria were isolated from Ugba and Okpiye using standard methods. The test organisms used were Staphylococcus aureus, Pseudomonas aeruginosa (VRFPA04) and Escherichia coli (ST2747) Fifty (50) samples of Ugba and Okpiye were collected and evaluated for the presence of bacteriocin lactic acid producers using a selective medium; De Mann Rogosa Sharpe (MRS) agar. A total of 288 isolates was isolated from the two traditional food condiments; 148 from ugba and 140 from Okpiye. It was observed that the total lactic acid bacterial count in Ugba ranges from 5.80 x 104 to 1.7 x 107 cfu/ml on MRS medium; while that of Okpiye ranges from 5.0 x 104 to 2.0 x 107 cfu/ml on MRS medium. Lactic acid bacterial count was higher in Ugba than in Okpiyeconsidering the mode of storage in the market. The highest inhibitory activity was demonstrated against E. coli in Ugba sample while the least activity was demonstrated against P. aeuroginosa, also a significant high level of inhibition was shown against S. aureus while P. aeuroginosa and E. coli had little or no inhibitory activities recorded for Okpiye samples. The bacteriocin producers isolated from Ugba and Okpiye (U5, U6, OK1, OK2, OK3 and OK4) were identified as Lactobacillus sp and Lactococcus sp based on their morphological and biochemical characteristics. The antibacterial activity of the bacteriocins produced by the lactic acid bacteria has potential for use in biopreservation of condiments against food spoilage agents.

Biosynthesis and Production of Class II Bacteriocins of Food-Associated Lactic Acid Bacteria

Bacteriocins are ribosomally synthesized peptides made by bacteria that inhibit the growth of similar or closely related bacterial strains. Class II bacteriocins are a class of bacteriocins that are heat-resistant and do not undergo extensive posttranslational modification. In lactic acid bacteria (LAB), class II bacteriocins are widely distributed, and some of them have been successfully applied as food preservatives or antibiotic alternatives. Class II bacteriocins can be further divided into four subcategories. In the same subcategory, variations were observed in terms of amino acid identity, peptide length, pI, etc. The production of class II bacteriocin is controlled by a dedicated gene cluster located in the plasmid or chromosome. Besides the pre-bacteriocin encoding gene, the gene cluster generally includes various combinations of immunity, transportation, and regulatory genes. Among class II bacteriocin-producing LAB, some strains/species showed low yield. A multitude of fermentation factors including medium composition, temperature, and pH have a strong influence on bacteriocin production which is usually strain-specific. Consequently, scientists are motivated to develop high-yielding strains through the genetic engineering approach. Thus, this review aims to present and discuss the distribution, sequence characteristics, as well as biosynthesis of class II bacteriocins of LAB. Moreover, the integration of modern biotechnology and genetics with conventional fermentation technology to improve bacteriocin production will also be discussed in this review.