Category Archives: Lactobacillus

Research – Bioprotective Lactic Acid Bacteria and Lactic Acid as a Sustainable Strategy to Combat Escherichia coli O157:H7 in Meat

Posted on January 9, 2023 by | Leave a comment

MDPI

Abstract

Human infection by Enterohemorrhagic Escherichia coli (EHEC) constitutes a serious threat to public health and a major concern for the meat industry. Presently, consumers require safer/healthier foods with minimal chemical additives, highlighting the need for sustainable solutions to limit and prevent risks. This work evaluated the ability of two antagonistic lactic acid bacteria (LAB) strains, Lactiplantibacillus plantarum CRL681 and Enterococcus mundtii CRL35, and their combination in order to inhibit EHEC in beef (ground and vacuum sealed meat discs) at 8 °C during 72 h. The effect of lower lactic acid (LA) concentrations was evaluated. Meat color was studied along with how LAB strains interfere with the adhesion of Escherichia coli to meat. The results indicated a bacteriostatic effect on EHEC cells when mixed LAB strains were inoculated. However, a bactericidal action due to a synergism between 0.6% LA and LAB occurred, producing undetectable pathogenic cells at 72 h. Color parameters (a*, b* and L*) did not vary in bioprotected meat discs, but they were significantly modified in ground meat after 24 h. In addition, LAB strains hindered EHEC adhesion to meat. The use of both LAB strains plus 0.6% LA, represents a novel, effective and ecofriendly strategy to inactivate EHEC in meat.

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Posted in EHEC, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, LAB, Lactobacillus, Lactobacillus plantarum, microbial contamination, Microbial growth, Microbiological Risk Assessment, Microbiology, Microbiology Investigations, Microbiology Risk, STEC, STEC E.coli

Research – Recent Trends and Applications of Nanoencapsulated Bacteriocins against Microbes in Food Quality and Safety

Posted on December 28, 2022 by | Leave a comment

MDPI

Abstract

Bacteriocins are ribosomal-synthesized peptides or proteins produced by bacterial strains and can inhibit pathogenic bacteria. Numerous factors influence the potential activity of bacteriocins in food matrices. For example, food additives usage, chemical composition, physical conditions of food, and sensitivity of proteolytic enzymes can constrain the application of bacteriocins as beneficial food preservatives. However, novel bacteriocin nanoencapsulation has appeared as an encouraging solution. In this review, we highlight the bacteriocins produced by Gram-negative bacteria and Gram-positive bacteria including lactic acid bacteria that have shown positive results as potential food preservatives. In addition, this review encompasses the major focus on bacteriocins encapsulation with nanotechnology to enhance the antimicrobial action of bacteriocins. Several strategies can be employed to encapsulate bacteriocins; however, the nanotechnological approach is one of the most effective strategies for avoiding limitations. Nanoparticles such as liposomes, chitosan, protein, and polysaccharides have been discussed to show their importance in the nanoencapsulation method. The nanoparticles are combined with bacteriocins to develop the nano-encapsulated bacteriocins from Gram-negative and Gram-positive bacteria including LAB. In food systems, nanoencapsulation enhances the stability and antimicrobial functionality of active peptides. This nanotechnological application provides a formulation of a broad range of antimicrobial peptides at the industry-scale level. Nano-formulated bacteriocins have been discussed along with examples to show a broader antimicrobial spectrum, increase bacteriocins’ applicability, extend antimicrobial spectrum and enhance stability.

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Posted in Antimicrobials, Bacteriocin, Decontamination Microbial, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, Food Pathogen, Gram Negative Bacteria, Gram Positive, LAB, lactic acid bacteria, Lactobacillus, microbial contamination, Microbial growth, Microbiological Risk Assessment, Microbiology, Microbiology Investigations, Microbiology Risk, Pathogen, pathogenic

Research – Tofu Whey Wastewater as a Beneficial Supplement to Poultry Farming: Improving Production Performance and Protecting against Salmonella Infection

Posted on December 24, 2022 by | Leave a comment

MDPI

Tofu whey wastewater (TWW) is a by-product of the tofu production process, and contains high amounts of organic products and Lactobacillus ap. However, no studies have been reported on whether naturally fermented TWW can be used as a beneficial additive for poultry production. This study analyzed the main nutritional components and microbial flora of naturally fermented TWW from rural tofu processing plants and their effect on chick production performance, role in modulating the biochemical and immune parameters, and protection against Salmonella enteritidis (S. enteritidis) infection. It was observed that the average pH of TWW was 4.08; therefore, the total viable count was 3.00 × 109 CFU/mL and the abundance of Lactobacillus was 92.50%. Moreover, TWW supplementation increased the total weight gain and feed intake, reduced the feed/gain ratio, increased the length and relative weight of the gut, and reduced the colonization and excretion of S. enteritidis in chickens. Additionally, TWW decreased oxidative damage and pro-inflammatory cytokine secretion caused by S. enteritidis infection. In addition, TWW supplementation ensured the structure of the intestine remained relatively intact in S. enteritidis-infected chicken. Furthermore, TWW markedly promoted the intestinal barrier integrity and up-regulated the relative abundance of Lactobacillus, counteracting the changes in gut microbiota caused by S. enteritidis infection in chicken. In conclusion, our data demonstrated that TWW could be used as a beneficial addition to poultry production, providing a research basis for the further development of TWW as a health care application in in food-producing animal.

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Posted in Decontamination Microbial, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, Lactobacillus, microbial contamination, Microbial growth, Microbiological Risk Assessment, Microbiology, Microbiology Investigations, Microbiology Risk, Salmonella

Research – Microbial Properties of Raw Milk throughout the Year and Their Relationships to Quality Parameters

Posted on October 4, 2022 by | Leave a comment

MDPI

Raw milk microbiota is complex and influenced by many factors that facilitate the introduction of undesirable microorganisms. Milk microbiota is closely related to the safety and quality of dairy products, and it is therefore critical to characterize the variation in the microbial composition of raw milk. In this cross-sectional study, the variation in raw milk microbiota throughout the year (n = 142) from three farms in China was analyzed using 16S rRNA amplicon sequencing, including α and β diversity, microbial composition, and the relationship between microbiota and milk quality parameters. This aimed to characterize the contamination risk of raw milk throughout the year and the changes in quality parameters caused by contamination. Collection month had a significant effect on microbial composition; microbial diversity was higher in raw milk collected in May and June, while milk collected in October and December had the lowest microbial diversity. Microbiota composition differed significantly between milk collected in January–June, July–August, and September–December (p < 0.05). Bacterial communities represented in raw milk at the phylum level mainly included Proteobacteria, Firmicutes and Bacteroidota; Pseudomonas, Acinetobacter, Streptococcus and Lactobacillus were the most common genera. Redundancy analysis (RDA) found strong correlations between microbial distribution and titratable acidity (TA), fat, and protein. Many genera were significantly correlated with TA, for example Acinetobacter (R = 0.426), Enhydrobacter (R = 0.309), Chryseobacterium (R = 0.352), Lactobacillus (R = −0.326), norank_o__DTU014 (R = −0.697), norank_f__SC-I-84 (R = −0.678), and Subgroup_10 (R = −0.721). Additionally, norank_f__ Muribaculaceae was moderately negatively correlated with fat (R = −0.476) and protein (R = −0.513). These findings provide new information on the ecology of raw milk microbiota at the farm level and contribute to the understanding of the variation in raw milk microbiota in China. View Full-Text

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Posted in Decontamination Microbial, Faecal Streptpcocci, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, Group B Streptococcus, Lactobacillus, microbial contamination, Microbiological Risk Assessment, Microbiology, Microbiology Investigations, Microbiology Risk, Pseudomonas, Raw Milk

Research – Evaluation of the safety and efficacy of lactic acid to reduce microbiological surface contamination on carcases from kangaroos, wild pigs, goats and sheep

Posted on May 14, 2022 by | Leave a comment

EFSA

Studies evaluating the safety and efficacy of lactic acid to reduce microbiological surface contamination from carcases of wild game (i.e. kangaroos and wild pigs) and small stock (i.e. goats and sheep) before chilling at the slaughterhouse were assessed. Wild pig and kangaroo hide‐on carcases may have been chilled before they arrive at the slaughterhouse and are treated after removal of the hides. Lactic acid solutions (2–5%) are applied to the carcases at temperatures of up to 55°C by spraying or misting. The treatment lasts 6–7 s per carcass side. The Panel concluded that: [1] the treatment is of no safety concern, provided that the lactic acid complies with the European Union specifications for food additives; [2] based on the available evidence, it was not possible to conclude on the efficacy of spraying or misting lactic acid on kangaroo, wild pig, goats and sheep carcases; [3] treatment of the above‐mentioned carcases with lactic acid may induce reduced susceptibility to the same substance, but this can be minimised; there is currently no evidence that prior exposure of food‐borne pathogens to lactic acid leads to the occurrence of resistance levels that compromise antimicrobial therapy; and [4] the release of lactic acid is not of concern for the environment, assuming that wastewaters released by the slaughterhouses are treated on‐site, if necessary, to counter the potentially low pH caused by lactic acid, in compliance with local rules.

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Posted in cross contamination, Decontamination Microbial, food contamination, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, LAB, lactic acid bacteria, Lactobacillus, Lactobacillus casei, Lactobacillus plantarum, Lactobacillus rhamnosus, Lactobacillus sakei, Lactobacillus saki, Lactococcus, microbial contamination, Microbiological Risk Assessment, Microbiology, Microbiology Investigations, Research

Research – Role of Lactic Acid Bacteria in Food Preservation and Safety

Posted on April 30, 2022 by | Leave a comment

MDPI

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.

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Posted in Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, LAB, lactic acid bacteria, Lactobacillus, Lactobacillus casei, Lactobacillus plantarum, Lactobacillus rhamnosus, Lactobacillus sakei, Lactobacillus saki, microbial contamination, Microbiological Risk Assessment, Microbiology, Microbiology Investigations, Research

Research – Microbial Diversity and Safety in Fermented Beverages

Posted on March 6, 2022 by | Leave a comment

MDPI

For thousands of years, humans have exploited the natural process of fermentation of various foods to preserve them, and to enjoy the changes in the sensory characteristics that could be produced. Recently, the world of fermented beverages has gone through a rapid transformation linked to deep changes in consumer preferences, consumption habits, climate, new regulations and entry of emerging countries, accompanied by safety concerns and an important reduction in economic resources available to people. As with all food handling and preparation, we need to be sure the fermented food produced is safe. Fermentation is a complex biological process where microbial diversity takes place and the environment created inside of the fermented food provides the conditions to reduce the risk of pathogenic bacteria growth, thus providing safe food. In addition, food manufacturers fermenting food carefully control their processing and must comply with the National Food Standards Codes. Although these products have a generally good food safety record, sometimes inadequate manufacturing practices or the presence of acidophilic pathogens could compromise food safety. In fact, fermented beverages may adversely become contaminated with pathogens or microbial toxins and thereby transform into vehicles that can transmit diseases to the consumers. Moreover, many microorganisms can deteriorate the physical-chemical and sensory properties as well as the flavor of the final products. In this editorial, we present an overview of a review and six original research papers published in the Special Issue “Fermentation Process and Microbial Safety of Beverages” of the Beverages journal.

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Posted in Aspergillus, Bacillus, escherichia coli, Food Micro Blog, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, Lactobacillus, microbial contamination, Microbiological Risk Assessment, Microbiology, Microbiology Investigations, Research, Saccharomyces cerevisiae, Saccharomyces cerevisiae, Yeasts

Research – Enhanced antimicrobial activity against Alicyclobacillus acidoterrestris in apple juice by genome shuffling of Lactobacillus acidophilus NX2-6

Posted on February 26, 2022 by | Leave a comment

Wiley Online

Food 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.

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Posted in Decontamination Microbial, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, LAB, lactic acid bacteria, Lactobacillus, microbial contamination, Microbiological Risk Assessment, Microbiology, Microbiology Investigations, Research, UV Microbiology

Research – Antagonistic Effects of Conjugated Linoleic Acids of Lactobacillus casei Against Foodborne Enterohemorrhagic Escherichia coli 

Posted on February 13, 2022 by | Leave a comment

Journal of Food Protection

Probiotics in fermented foods or commercially available supplements benefit the host by providing metabolites/peptides. The production of these metabolites varies with available substrates/prebiotic present in the system and their concentration. In this study, 0.5% peanut flour (PF) was used to stimulate the growth and production of metabolites of wild-type Lactobacillus casei (LC wt ) and compare with an engineered L. casei (LC CLA ) capable of converting a higher amount of conjugated linoleic acid (CLA). The total extracellular metabolites present in the cell-free cultural supernatant (CFCS) of LC wt (without peanut), LC wt+PF (with peanut), and LC CLA were collected after 24 h and 48 h of incubation, and their antagonistic activities against enterohemorrhagic Escherichia coli (EHEC EDL933) growth and pathogenesis were evaluated. All the collected metabolites exhibited varying efficiency in restraining EDL933 growth while supplementing low concentration of CLA to the 48-h CFCS from LC wt showed augmented antagonism toward EDL933. A downregulation of key virulence genes was observed from metabolites collected at 48-h time point. These observations indicate that the presence of metabolites in CFCSs including CLA, produced by Lactobacillus , which was further identified by gas chromatography-mass spectrometry; plays a critical role. This study demonstrates the potential applicability of Lactobacillus -originated CLA in the prevention of EDL933 mediated illnesses.

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Posted in Decontamination Microbial, E.coli, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Testing, Lactobacillus, Lactobacillus casei, Lactococcus, microbial contamination, Microbiological Risk Assessment, Microbiology, Microbiology Investigations, Probiotic

Research – Probiotic Lactobacilli Do Not Protect Chickens against Salmonella Enteritidis Infection by Competitive Exclusion in the Intestinal Tract but in Feed, Outside the Chicken Host

Posted on January 22, 2022 by | Leave a comment

MDPI

Lactobacilli are commonly used as probiotics in poultry to improve production parameters and to increase chicken resistance to enteric infections. However, lactobacilli do not efficiently colonise the chicken intestinal tract, and also, their anti-infection effect in vivo is sometimes questionable. In this study, we therefore evaluated the potential of a mixture of four Lactobacillus species (L. salivarius, L. reuteri, L. ingluviei and L. alvi) for the protection of chickens against Salmonella Enteritidis infection. Whenever the chickens were inoculated by lactobacilli and S. Enteritidis separately, there was no protective effect of lactobacilli. This means that when lactobacilli and S. Enteritidis are exposed to each other as late as in the crop of chickens, lactobacilli did not influence chicken resistance to S. Enteritidis at all. The only positive effect was recorded when the mixture of lactobacilli and S. Enteritidis was used for the inoculation of feed and the feed was anaerobically fermented for 1 to 5 days. In this case, chickens fed such a diet remained S. Enteritidis negative. In vitro experiments showed that the protective effect was caused by acidification of feed down to pH 4.6 due to lactobacilli fermentation and was associated with S. Enteritidis inactivation. The probiotic effect of lactobacilli was thus expressed in the feed, outside the chicken host. View Full-Text

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Posted in Animal Feed, Animal Feed Salmonella, Animal Feed Testing, Food Micro Blog, Food Microbiology Blog, Food Microbiology Research, Lactobacillus, microbial contamination, Microbiological Risk Assessment, Microbiology, Microbiology Investigations, Research, Salmonella