Activity Of Lactic Acid Bacteria Research Articles

Single-step conversion of rice straw to lactic acid by thermotolerant cellulolytic lactic acid bacteria

Lactic acid (LA) is an important intermediate product used for numerous industrial applications in food, cosmetic and bioplastic production. To reduce the cost of lactic acid production, lignocellulosic substrates have been extensively investigated as a source of sugars for fermentation. This study aimed to produce lactic acid by thermotolerant cellulolytic lactic acid bacteria (LAB) through a simplified process using rice straw (RS) as the substrate without the addition of any external hydrolytic enzymes. All 20 LAB strains were isolated from RS-buried soil, and the carbon utilization, growth, and cellulase activity of select LAB were evaluated. RS was pretreated with 1.5% (v/v) H3PO4 at 121 °C for 15 min to obtain a hydrolysate containing 1.54 g/L glucose and 0.94 g/L xylose, and toxic chemicals (furfural and hydroxymethylfurfural) were not detected. Among the LAB isolates, the homofermentative Enterococcus spp. SLC45-3 produced 83.9% L-LA with 2% glucose as the sole carbon source. The highest total LA of 2.20±0.03 g/L was obtained after the cultivation of SCL45-3 in RS hydrolysate at 45 °C and 150 rpm and was close to the LA content of 2.06±0.05 g/L obtained with the RS hydrolysate supplemented with untreated RS. The addition of untreated RS enhanced CMCase activity, and during incubation, constant LA production was detected from 36 to 96 h. Thus, SLC45-3 is a potential LAB candidate for L-LA production through the direct bioconversion of RS under moderate temperature without cellulase supplement.

Metabolic characteristics of lactic acid bacteria and interaction with yeast isolated from light-flavor Baijiu fermentation

During spontaneous fermentation of light-flavor Baijiu, the microbial diversity decreased gradually. Lactic acid bacteria (LAB) and yeast predominated at the end of fermentation and showed a strong positive correlation with esters in Baijiu. Exploring the metabolic characteristics of LAB and interactions with yeast are important for revealing the mechanism of Baijiu fermentation. The carbon source utilization heatmap showed that Lactobacillus acetotolerans, Lactobacillus brevis, and Lactobacillus hilgardii could utilize various organic acids. Lactobacillus plantarum could utilize a variety of amino acids. The utilization efficiency of different substrates was supposed to be an important factor for different LAB species dynamics during fermentation. The effects of pH, temperature and ethanol on the esterase activity of LAB were further analyzed. The results showed that pH was the most significant factor on esterase activity, and all the strains showed the highest activity at pH 7.0. Principal component analysis indicated that co-culture of LAB and Saccharomyces cerevisiae could promote the formation of esters, and the co-culture of Lactobacillus acetotolerans or Leuconostoc mesenteroides with Pichia anomala could promote the production of esters and alcohols. LAB showed a weak inhibitory effect on the growth of yeast, whereas the growth of LAB was significantly inhibited by yeast in the co-culture system. The results of this work will broaden our knowledge regarding the esterase activity, carbon source utilization efficiency of LAB and interactions with predominant yeast, which will provide a theoretical basis for the dynamics of different LAB species and their effects on the flavor of Baijiu.

A new probiotic Lactobacillus plantarum strain isolated from traditional dairy together with nanochitosan particles shows the synergistic effect on aflatoxin B1 detoxification.

The present study aimed to evaluate the effects of new Lactobacillus plantarum strain isolated from dairy products as well as chitosan nanoparticles on reducing aflatoxin B1 (AFB1) toxicity In vitro. After collection and preparation of yogurt, cheese, milk, and whey products, lactic acid bacteria (LABs) were isolated and identified using biochemical and molecular methods. pH, bile, and salt tolerance tests were used to measure probiotic activity. Then, the antimicrobial activity of LABs against gastrointestinal pathogens was studied. The strain isolated from cheese (C1) was selected as the appropriate strain and antibiotic susceptibility test was performed for this strain. Then, the effect of C1 isolate and chitosan nanoparticles on reducing aflatoxin B1 (AFB1) in the medium was studied by measuring AFB1 using the enzyme-linked immunosorbent assay (ELISA) and high-performance liquid chromatography (HPLC). The results of biochemical evaluations indicated the separation of different strains of L. plantarum. Antimicrobial activity test showed extensive antimicrobial activity of C1 isolate. The results showed that this strain has good probiotic activities. This strain was shown to be resistant to erythromycin, fusidic acid, gentamicin, kanamycin, nalidixic acid, neomycin, ofloxacin, and vancomycin antibiotics. C1 strain together with chitosan nanoparticles was able to reduce AFB1 in the medium and, when both were used simultaneously, a synergistic effect was seen in reducing AFB1 from the medium. Based on the findings, it can be concluded that the new C1 L. plantarum strains together with chitosan nanoparticles had synergistic effects on reducing AFB1 toxin in food products.

Characterization and Antibacterial Activity of Lactic Acid Bacteria Isolated from Traditionally Fermented Foods against Some Selected Food Pathogens

This study identified the antimicrobial compounds found in lactic acid bacteria isolated from several traditional fermented foods, such as ogi, ugba, and yoghurt, as well as their antimicrobial effectiveness against a few chosen food pathogens. Fifteen (15) food samples including five each for yoghurt, ogi, and ugba were tested for the presence of lactic acid bacteria. Nine organisms were isolated from the food samples and were phenotypically and genotypically characterized. It was discovered that two of the isolates were Lactococcus spp, five Lactobacillus spp, one Bacillus spp, and one Streptococcus spp. The genotypic characterization revealed that the lactic acid bacteria isolates Lactococcus lactis subsp. lactis 0711XYBLS, Lactobacillus fermentum CS19, Lactococcus lactis and Lactobacillus fermentum were closely related at 99% evolutionary distance. For the sole purpose of this research, Lactococcus lactis subsp. lactis 0711XYBLS and Lactobacillus fermentum CS19 were utilized to determine their antimicrobial potentials against selected food pathogens. Antimicrobial metabolites, diacetyl, hydrogen peroxide and lactic acid were produced by the isolated lactic acid bacteria at varying concentrations. The selected lactic acid bacteria isolates were tested against food pathogens and their clear zones of inhibitions were noted. Lactococcus lactis subsp lactis 0711XYBLS isolated from ogi showed the highest antibacterial activity against Gram positive and Gram negative food pathogens ranging from 18.67 ± 1.15 to 12.67 ± 0.57 and 16.33 ± 0.56 to 8.00 ± 6.08 respectively whereas Lactobacillus fermentum CS19 showed antibacterial activity for Gram positive food pathogens at 16.00 ± 1.00 to 8.67 ± 1.15 and 15.33 ± 1.15 to 8.67 ± 0.57 in Gram negative food pathogens. Between the pathogens, a significant difference was recorded at a significant level of p<0.05. Nevertheless, both organisms demonstrated strong antibacterial activity against the chosen food pathogens and have the potential to be used as new antimicrobial agents. This potential can be used extensively in the food industry as biopresevatives rather than chemical preservation, which may be harmful to consumer’s health.

Capabilities of bio-binding, antioxidant and intestinal environmental repair jointly determine the ability of lactic acid bacteria to mitigate perfluorooctane sulfonate toxicity.

Perfluorooctane sulfonate (PFOS) is a novel environmental contaminant that can be enriched in humans through the food chain, causing liver diseases, neurotoxicity and metabolic disorders. Lactic acid bacteria (LAB) are safe food-grade microorganisms that exhibit high antioxidant activity and bio-binding capacity towards toxins. Here, strains of LAB with different PFOS binding capacities and antioxidant activities were selected and analyzed for their ability in mitigating the toxic effects of PFOS. The results showed that the PFOS binding capacity and antioxidant activity of LAB largely influenced their ability in alleviating the toxic effects of PFOS. Notably, the individual LAB strains with low PFOS binding capacities and antioxidant activities also attenuated the toxic effects of PFOS, which was shown to up-regulate the contents of short-chain fatty acids (SCFAs) in the cecum and of tight junction proteins in the intestines of mice. Therefore, the mitigation pathway of PFOS-induced toxic damage by LAB is not limited to bio-binding and antioxidant. Repairing the gut environment damaged by PFOS is also essential for LAB to alleviate the toxic damage due to PFOS and may be partly independent of the bio-binding and antioxidant. Therefore, LAB as an alternative pathway for alleviating PFOS toxicity is suggested.

Characterization of functional effects of different LAB isolated from sourdoughs in Turkey

In this study, the technological properties of five different lactic acid bacteria (LAB) isolated from sourdough collected from three cities of Turkey (Gümüşhane, Manisa, Ankara) and Cyprus were investigated. For this purpose, antimicrobial, antifungal, phytase, and proteolytic activities of these bacteria and their effect on pH were examined. The pH of the prepared solutions decreased to 3.8 and 4.4 from 6.3 by LAB addition following 24 h incubation. Lactiplantibacillus plantarum O6F-25 strain showed the best inhibitory effect against four gram-positive and four gram-negative bacteria. In terms of proteolytic activity, Lactiplantibacillus plantarum 45MK-32 was the most effective strain. The antifungal effects of LAB were tested against Aspergillus flavus, Aspergillus niger, and Penicillium carneum. Levilactobacillus brevis KCO-48 was the most effective LAB strain. Phytase activities (710.40 – 840.37 U.mL-1) of LAB studied except Limosilactobacillus fermentum (29GT-19), which has the lowest phytase activity, were not significantly different (P < 0.05). This study revealed that sourdough LABs have the potential to be used as biopreservative and produce functional food products.

Bioprotective potential of lactic acid bacteria and their metabolites against enterotoxigenic Escherichia coli.

Escherichia coli is one of the main pathogens that impacts swine production. Given the need for methods for its control, the in vitro effect of lactic acid bacteria (LAB) and their metabolites against E. coli F4 was evaluated through cell culture and microbiological analysis. The strains Limosilactobacillus fermentum 5.2, Lactiplantibacillus plantarum 6.2, and L. plantarum 7.1 were selected. To evaluate the action of their metabolites, lyophilized cell-free supernatants (CFS) were used. The effect of CFS was evaluated in HT-29 intestinal lineage cells; in inhibiting the growth of the pathogen in agar; and in inhibiting the formation of biofilms. The bioprotective activity of LAB was evaluated via their potential for autoaggregation and coaggregation with E. coli. The CFS did not show cytotoxicity at lower concentrations, except for L. fermentum 5.2 CFS, which is responsible for cell proliferation at doses lower than 10 mg ml-1. The CFS were also not able to inhibit the growth of E. coli F4 in agar; however, the CFS of L. plantarum 7.1 resulted in a significant decrease in biofilm formation at a dose of 40 mg ml-1. Regarding LAB, their direct use showed great potential for autoaggregation and coaggregation in vitro, thus suggesting possible effectiveness in animal organisms, preventing E. coli fixation and proliferation. New in vitro tests are needed to evaluate lower doses of CFS to control biofilms and confirm the bioprotective potential of LAB, and in vivo tests to assess the effect of LAB and their metabolites interacting with animal physiology.

Antimicrobial Activity of Lactic Acid Bacteria (Lab) Isolated from Yoghurt and Fish against Pathogenic Bacteria Isolated from Fish in Ethiopia

Pathogenic bacteria are causative agent of infectious diseases in fish. Antimicrobials are widely applied in fish products for prevention of fish-borne diseases. The global concern of antimicrobial resistance of bacteria raises attentiveness of the different ways of using antimicrobial peptides (AMPs). The aim of the present study was to detect the antimicrobial activity of the AMPs from Lactic acid bacteria (LAB) against the growth of pathogenic bacteria isolated from fish in Ethiopia. Cell Free Supernatants (CFSs) from 4 strains of LAB consisting of lactobacillus paracasei sub.paracasei, lactobacillus casei LC2W, Pediococcus acidilactici and lactobacillus plantarum were tested against pathogenic bacteria of Aeromonas hydrophila, Aeromonas veronii, Edwardsiella tarda, Escherichia coli, Proteus mirabilis, Pseudomonas fluorescens and Shigella flexneri via using agar well diffusion assay. All tested CFSs revealed antimicrobial activity against the tested fish pathogenic isolates at different extents. CFSs of lactobacillus plantarum, Lb. casei LC2W and lactobacillus paracasei sub.paracasei showed strong antibacterial activity against Edwardsiella tarda (19 mm), Aeromonas hydrophila (18 mm) and Pseudomonas fluorescens (18 mm) respectively, with the well diffusion assay. The study shows the antimicrobial activity of the 4 strains of LAB CFSs against the bacterial fish pathogens and indicates the application opportunities as fish product bio preservative.

Screening for probiotic attributes of lactic acid bacteria isolated from human milk and evaluation of their anti-diabetic potentials

ABSTRACT Lactic acid bacteria (LAB) have gained much attention recently due to their probiotic attributes with anti-ACE and anti-glycation potentials targeting management of diabetes. This study was designed to isolate LAB from human milk and to evaluate their potential for inhibitory activities on ACE and AGEs formation using in vitro assay models. Among 12 LAB isolates, many strains exhibited strong probiotic attributes including tolerance to low pH, high salt, gastric, and intestinal juices with higher cell adhesion. Further, cell-free extracts of LAB tested for in vitro anti-ACE and anti-AGEs activities evidenced Lacticaseibacillus casei MKU1, Lacticaseibacillus paracasei MKU2, Lactiplantibacillus pentosus MKU3, L. paracasei MKU7, L. delbrueckii GERU3 and Lactobacillus delbrueckii MKU10 as strong ACE and AGEs inhibitors. Subsequently, Principal Component Analysis showed a positive correlation with anti-ACE (p ≤ .01) and anti-glycation (p ≤ .05) activity of LAB. Overall, this study suggests that six Lactobacillus isolates of human milk with superior probiotic attributes looks promising as potential probiotic strains.

Characterization, Acidifying, and Antibacterial Activity of Lactic Acid Bacteria Against Spoilage Strains Present in Chicken Meat

Nowadays, through their beneficial roles, lactic acid bacteria have been used as natural additives for the formulation of several products especially in the food industry; as they reduce the pathogen load and improve the quality of fermented food. This work focuses on the technological study of five homolactic strains isolated from three fermented barley preparations belonging to three species: Lactobacillus plantarum, Pediococcus spp, and Lactococcus lactis ssp. The experiment focused on testing their acidifying activity and their antibacterial action against a range of spoilage strains isolated from chicken meat. The identification was carried out based on the study of the cultural, morphological characters and biochemical tests which revealed the presence of five strains namely: Escherichia Coli, Salmonella sp, Staphylococcus aureus, Proteus vulgaris, and Klebsiella pneumonia. The results obtained showed that the strains (SC1, SC4, and SC5) have acidifying activities, in parallel with a significant antibacterial effect compared to the other strains (SC2, SC3) whose respective values were 1.63±0.07%, 0.99±0.23% and 1.29±0.65% for SC1, SC4 and SC5. Moreover, the cell-free culture supernatant (CFCS) inhibition zones range from 19.5 ± 0.70 mm to 10.25 ± 0.35 mm.

Role of Lactic Acid Bacteria in Food Preservation and Safety.

Fermentation of various food stuffs by lactic acid bacteria is one of the oldest forms of food biopreservation. Bacterial antagonism has been recognized for over a century, but in recent years, this phenomenon has received more scientific attention, particularly in the use of various strains of lactic acid bacteria (LAB). Certain strains of LAB demonstrated antimicrobial activity against foodborne pathogens, including bacteria, yeast and filamentous fungi. Furthermore, in recent years, many authors proved that lactic acid bacteria have the ability to neutralize mycotoxin produced by the last group. Antimicrobial activity of lactic acid bacteria is mainly based on the production of metabolites such as lactic acid, organic acids, hydroperoxide and bacteriocins. In addition, some research suggests other mechanisms of antimicrobial activity of LAB against pathogens as well as their toxic metabolites. These properties are very important because of the future possibility to exchange chemical and physical methods of preservation with a biological method based on the lactic acid bacteria and their metabolites. Biopreservation is defined as the extension of shelf life and the increase in food safety by use of controlled microorganisms or their metabolites. This biological method may determine the alternative for the usage of chemical preservatives. In this study, the possibilities of the use of lactic acid bacteria against foodborne pathogens is provided. Our aim is to yield knowledge about lactic acid fermentation and the activity of lactic acid bacteria against pathogenic microorganisms. In addition, we would like to introduce actual information about health aspects associated with the consumption of fermented products, including probiotics.

Screening for the Probiotic Activities of Lactic Acid Bacteria Isolated from the Gastrointestinal Tract of Traditional Poultry in Côte d'Ivoire

In the view to overcome the problem of antibiotic multi-resistance of pathogens encountered in poultry farming, the most appropriate strategy was suggested to be the use of probiotic lactic acid bacteria (LAB) strains. Thus, this study aimed to evaluate the probiotic properties of LAB isolated from gastrointestinal tract of Ivorian traditional chickens for potential application as probiotic in broiler production. So, after a preliminary screening for pH 2.0 tolerance, the probiotic characters like tolerance to bile salt, hydrophobicity, auto and co-aggregation properties, antimicrobial activity and antibiotic susceptibility were evaluated. The results showed that amongst the 90 LAB investigated, a total of 15 isolates were able to grow after 90 min exposed to pH 2.0. The resistance of these 15 isolates to 0.3% bile salt was more than 50%. A test of their adhesion ability to host epithelial cells using cell surface hydrophobicity produced a range of 50.25% to 92.57%. The isolates had weak auto-aggregation ability and high coaggregation with the pathogens Salmonella enteritidis and Escherichia coli. They had wide spectrum inhibitory activity against challenging zoonotic and foodborne pathogens. Furthermore, all the five selected strains showed resistance to Colistin while 60-80% resistance was demonstrated against Oxacillin, Gentamicin and Kanamycin. Based on above characteristics, the LAB strains Pediococcus acidilactici JK148 and Lactobacillus pentosus JK151 which showed excellent probiotic potentials were selected as chicken probiotic candidates.

Antagonistic Activity of Lactic Acid Bacteria and Rosa rugosa Thunb. Pseudo-Fruit Extracts against Staphylococcus spp. Strains

Staphylococcus bacteria are ubiquitous microorganisms. They occur in practically all environments. They also show the ability to colonize the skin and mucous membranes of humans and animals. The current trend is to look for new natural factors (e.g., plant extracts rich in polyphenols) limiting the growth of undesirable bacteria in food and cosmetics or use as an adjunct in antibiotic therapy. The aim of this study was to evaluate the effect of extracts from Rosa rugosa Thunb. on the antagonistic properties of selected lactic acid bacteria strains in relation to Staphylococcus spp. isolates. The biological material consisted of seven strains of lactic acid bacteria (LAB) and seven strains of bacteria of the Staphylococcus genus. The anti-staphylococcal properties of the Rosa rugosa Thunb. pomace extracts (the tested extracts were characterized by a high content of polyphenols, namely 8–34 g/100 g DM/dm) were tested using the well method. The conducted research showed that the pomace extracts of the pseudo-fruit (Rosa rugosa Thunb.) had the ability to inhibit the growth of Staphylococcus spp. bacteria. The minimum concentration of polyphenols inhibiting the growth of staphylococci was in the range of 0.156–0.625 mg/mL. The conducted research showed that combined lactic acid bacteria and extracts from the pomace from the pseudo-fruit Rosa rugosa Thunb. (LR systems) may be factors limiting the growth of Staphylococcus spp. bacteria. As a result of the research, two-component antagonist systems consisting of LAB cultures and extracts from Rosa rugosa Thunb. pomace were developed, which effectively limited the growth of the test strains of Staphylococcus spp. In 41% of all tested cases, the zone of inhibition of growth of bacteria of the genus Staphylococcus spp. after the use of two-component antagonist systems was higher than that as a result of the control culture (without the addition of extracts).

Lacto-fermented polypeptides integrated with edible coatings for mango (Mangifera indica L.) bio-preservation

Mango (Mangifera indica L.) is one of the most important tropical fruits due to its pleasant taste and high nutrient content including vitamins, minerals, and phytochemicals. Post-harvest fungal diseases, mainly anthracnose, stem-end rot, and aspergillus rot are among the major problems in mango provision throughout all the supply chain stages. Fungal diseases create large economic losses and present a health risk for consumers due to the production of mycotoxins (aflatoxin and patulin). In the last two decades, chemical methods for fungal control have been prevalent because of their low cost and simple practicing features. However, recent consumer trends and regulations have limited the use of chemicals in fruits at the post-harvest stage. Bio-preservation is a promising alternative technique applied to control the post-harvest fungi with high safety for the consumer and environment. Antifungal polypeptides are made by different living beings including bacteria, fungi, protozoa, plants, invertebrates, and vertebrates. Polypeptides including small peptides produced by lactic acid bacteria (LAB) have a higher potential to employ as food bio-preservatives due to their promising antifungal ability with generally recognized as safe (GRAS) status. Lacto-fermented polypeptides inhibit a broad range of fungal growth, and thus enhance the quality and extend the shelf life through reducing biotic stress, respiration, and ethylene biosynthesis of post-harvested fruits. Recently, polypeptides, mainly bioactive peptides, and bacteriocins received great attention for their potential bio-preservation activity against pathogenic fungi in fruits. Moreover, the development of edible coating enhanced the stability of the bioactive polypeptides and expanded their applications for fruit preservation. This article reviews the fungi associated with main mango diseases, major causal organisms, antifungal activity of LABs’ polypeptides on mango, and their antifungal performances to control the postharvest mango spoilage. Besides, this review highlights the potential applications of Lacto-fermented polypeptides-enriched edible coating to control the pathogenic fungi of mango.

Green strategies to control redox potential in the fermented food industry

Lactic acid bacteria (LAB) are important microorganisms in the food industry as functional starters for the manufacture of fermented food products and as probiotics. Redox potential (Eh) is a parameter of the physicochemical environment of foods that influences key oxidation-reduction reactions involved in process performances and product quality. Eh can be modified by different methods, using redox molecules, catalytic activity of enzymes or LAB themselves, technological treatments like electroreduction or heating, and finally gases. Nowadays new applications for food manufacture must undertake green process innovation. This paper presents the strategies for Eh modification in a sustainable manner for production of LAB biomass (starters, probiotics) and fermented food products (fermented milks, cheeses and others). While the use of chemical or enzymes may be subject to controversy, the use of gases offers new opportunities, in combination with LAB. Protection against food-borne microorganisms, an increasing growth and viability of LAB, and a positive impact on food flavour are expected.

Antagonistic Activity of Lactic Acid Bacteria Against Pathogenic Vibrios and Their Potential Use as Probiotics in Shrimp (Penaeus vannamei) Culture

Probiotic use in aquaculture settings can be an approach for disease control and dietary supplementation. We assessed the antagonistic effect of culture supernatants of lactic acid bacteria on the growth of known shrimp pathogens,Vibrio(Listonella)anguillarum,Vibrio alginolyticus, andV. harveyi, using a quantitative microplate bioassay. Supernatants fromLactobacillus curvatussubsp.curvatus, L. plantarum, andPediococcus acidolacticisignificantly inhibited the growth of these vibrios. The active component(s) were heat stable (> 100°C) and resistant to freeze-thawing. Most of this inhibitory activity was brought about by the production of an acid pH; however, there was evidence for other factors playing a role. In the search for novel probiotic bacteria, an organism was isolated from the gastrointestinal tract of healthy whiteleg shrimp (Penaeus vannamei)—identified tentatively asCarnobacterium maltaromaticum. This isolate, however, had less potent vibriocidal activity than the lactic acid bacteria and reduced shrimp survival at a dose of 1 × 107bacteria/shrimp. During a 28-day feeding trial, juvenileP. vannameifed withL. plantarumsupplemented diets showed no gross changes in growth parameters compared with the control. We suggest that lactic acid bacteria could be incorporated into biofloc formulations to purge the growth of pathogenic vibrios in pond settings, rather than being fed directly to shrimp.

Enhanced antimicrobial activity against Alicyclobacillus acidoterrestris in apple juice by genome shuffling of Lactobacillus acidophilusNX2‐6

AbstractFood safety and quality are seriously compromised by the growth of spoilage bacteria in food. Various lactic acid bacteria (LAB) may inhibit the growth of spoilage bacteria in food and animal feed. In our study, the antibacterial activity of Lactobacillus acidophilus NX2‐6 was improved by genome shuffling. The starting populations were obtained via 60Coγ‐ray, diethyl sulfate mutagenesis, and UV mutagenesis of protoplasts. The optimal conditions for protoplast formation and regeneration were found to be 30 mg/ml of lysozyme at 37°C for 40 min. The protoplasts were inactivated by UV irradiation for 110 s or by heating at 58°C for 30 min. After two rounds of genome shuffling, the inhibitory activity of strain F50 was improved by 5.6‐fold compared to the original strain. The shuffled strain has broad‐spectrum antibacterial activity and is a promising candidate for bio‐preservative. The antibacterial substances produced by L. acidophilus NX2‐6 can be applied to the preservation of apple juice. The results showed that the growth of Alicyclobacillus acidoterrestris in apple juice was significantly inhibited by the addition of 0.1% culture supernatant with acidocin NX2‐6 at 28°C and 0.2% culture supernatant with acidocin NX2‐6 at 45°C for 30 days. The sugar−acid ratio, pH value, clarity, and fruit flavor of apple juice were well maintained during storage. This study showed that genome shuffling was an effective strategy to improve the bacterial inhibitory activity of LAB and that the shuffled LAB and their metabolites are expected to be used as bio‐based food protectors for food safety.

Lactic Acid Bacteria as Biopreservation Against Spoilage Molds in Dairy Products - A Review.

Mold spoilage of dairy products such as yogurt is a concern in dairy industry. Not only does it lead to substantial food waste, economic losses, and even brand image damage, but it may also cause public health concern due to the potential production of mycotoxin. Good hygiene practices are necessary to prevent contamination, but contamination may nevertheless occur at the production site and, not least, at the site of the consumer. In recent years, there has been a growing interest from consumers for “clean label” food products, which are natural, less-processed, and free of added, chemical preservatives, and a wish for shelf lives of considerable length in order to minimize food waste. This has sparked an interest in using lactic acid bacteria (LAB) or their metabolites as biopreservatives as a way to limit the growth of spoilage organisms in dairy products. A range of compounds produced by LAB with potential antifungal activity have been described as contributing factors to the inhibitory effect of LAB. More recently, growth inhibition effects caused by specific competitive exclusion have been elucidated. It has also become clear that the sensitivity toward both individual antifungal compounds and competition mechanisms differ among molds. In this review, the main spoilage molds encountered in dairy products are introduced, and an overview of the antifungal activity of LAB against different spoilage molds is presented including the main antifungal compounds derived from LAB cultures and the sensitivity of the spoilage molds observed toward these compounds. The recent findings of the role of competitive exclusion with emphasis on manganese depletion and the possible implications of this for biopreservation are described. Finally, some of the knowledge gaps, future challenges, and trends in the application of LAB biopreservation in dairy products are discussed.

Nematicidal Activity of Lactic Acid Bacteria against Root-Knot Nematodes

Root-knot nematodes are economically important obligate parasites of plant root that parasitize more than 3000 species of plant. Lactic Acid Bacteria (LAB) are well known as strong producers for wide range of organic acids that have been suggested recently to possess a remarkable lethal effect on root-knot nematodes. In the present ‘study’ 37 LAB strains were isolated from soil and agricultural wastes by using MRS medium and screened for their nematicidal activity under lab conditions. Four bacterial isolates, recorded lethal effect on second stage juveniles by more than 94%, were selected and identified by molecular method. Further, the nematicidal activity at two concentrations (i.e 50 and 10%) of the most promising ten LAB cultures was screened. The nematicidal activity of LAB was positively correlated to the concentration of their suspension cultures.2S4 (Pediococcus pentosaceus MW558270), 2S5 (Pediococcus pentosaceus MW558883), 3S1 (Pediococcus pentosaceusMW558885) and 1A3 (Pediococcus pentosaceus MW558152) isolates showed significant mortality effect by 88.42, 87.37, 81.05 and 85.96%at the low concentration (10%), respectively. In order to confirm the relationship between organic acid production by LAB and their nematicidal activity, an artificial succinic acid, lactic acid, malic acid, acetic acid, and their mixtures were tested at concentration of 1% for their ability to inhibit juvenilesvitality. The mixture of acids induced the maximum mortality effect by 100% followed by lactic acid which recorded 99.66% mortality effect. The microscopic studies and the malformation pattern of the juveniles indicating that the nematicidal activity of LAB may be derived mainly from their natural organic acids mainly lactic acid.

Antifungal activity of lactic acid bacteria and their application in food biopreservation.

Lactic acid bacteria (LAB) are ubiquitous bacteria associated with spontaneous lactic fermentation of vegetables, dairy and meat products. They are generally recognized as safe (GRAS), and they are involved in transformation of probiotic lacto-fermented foods, highly desired for their nutraceutical properties. The antifungal activity is one of the exciting properties of LAB, because of its possible application in food bio-preservation, as alternative to chemical preservatives. Many recent research works have been developed on antifungal activity of LAB, and they demonstrate their capacity to produce various antifungal compounds, (i.e. organic acids, PLA, proteinaceous compounds, peptides, cyclic dipeptides, fatty acids, and other compounds), of different properties (hydrophilic, hydrophobic and amphiphilic). The effectiveness of LAB in controlling spoilage and pathogenic fungi, demonstrated in different agricultural and food products, can be due to the synergistic effect between their antifungal compounds of different properties; where the amphiphilic-compounds allow the contact between the target microbial cell (hydrophilic compartment) and antifungal hydrophobic-compounds. Further studies on the interaction between compounds of these three properties are to de be developed, in order to highlight more their mechanism of action, and make LAB more profitable in improving shelf life and nutraceutical properties of foods.