Microorganisms In Foods Research Articles

Towards Impact of Modified Atmosphere Packaging (MAP) on Shelf-Life of Polymer-Film-Packed Food Products: Challenges and Sustainable Developments

In this article, we report in detail the use of protective gases to extend the shelf-life of polymer-film-packed foodstuff and reduce the most typical bacteria and microorganisms that negatively affect the quality and lifetime of a given packaging. This article provides significant information about the most important advantages of using protective gases and examples of gases or gas mixtures which can be used for almost every kind of foodstuff depending on the application. We also discuss how protective gases change the level of microorganisms in food using gases and how the shelf-life of food can be enhanced using correct gases or gas mixtures. The article also provides imperative information on the selection of correct protective gases for specific applications, especially for food production, to preserve against the most typical threats which can appear during the packaging or production process. Packaging innovations can reduce the environmental impact of food and polymer packaging waste by prolonging products’ shelf-lives and by reducing waste along the production and distribution chain and at the household level.

Application of Lab-on-Chip for Detection of Microbial Nucleic Acid in Food and Environment.

Various diseases caused by food-borne or environmental pathogenic microorganisms have been a persistent threat to public health and global economies. It is necessary to regularly detect microorganisms in food and environment to prevent infection of pathogenic microorganisms. However, most traditional detection methods are expensive, time-consuming, and unfeasible in practice in the absence of sophisticated instruments and trained operators. Point-of-care testing (POCT) can be used to detect microorganisms rapidly on site and greatly improve the efficiency of microbial detection. Lab-on-chip (LOC) is an emerging POCT technology with great potential by integrating most of the experimental steps carried out in the laboratory into a single monolithic device. This review will primarily focus on principles and techniques of LOC for detection of microbial nucleic acid in food and environment, including sample preparation, nucleic acid amplification and sample detection.

Effects of antibiotics on the development and intestinal bacterial diversity of black soldier fly larvae

The effects of four antibiotics (metronidazole (M) levofloxacin (L), sodium ampicillin (A), and streptomycin sulphate (S)) and their pair-wise combinations at three doses on the development and intestinal bacterial diversity of the black soldier fly (BSF;Hermetia illucens) larvae were studied. At a low dose M and L were able to inhibit larval growth. At a high dose, all antibiotics were shown to inhibit larval growth. However, the pair-wise combinational use of the antibiotics did not effectively enhance the inhibitory effect. The gut bacterial diversity of the normal control (NC) was significantly higher than the antibiotic-treated groups with 737 operational taxonomic units (OTUs) from the larval guts of NC, compared to 305 and 227 from ML and AS. The number of anaerobic bacteria in ML was significantly lower than in NC and AS, with the relative abundance of OTUs from larval guts of ML being only about 0.01, compared to 0.4 for NC and 0.15 for AS. These results indicated that antibiotics at the experimental concentration did not affect the palatability of food for insects, but they would affect the diversity of food and intestinal microorganisms of BSF larvae, and the inhibitory effect of antibiotics on growth and development of BSF larvae displayed in this study was a complex effect.

Genomic and Phenotypic Evaluation of Potential Probiotic Pediococcus Strains with Hypocholesterolemic Effect Isolated from Traditional Fermented Food.

The use of probiotic microorganisms in food with the aim to confer health benefits to the host is one of the most critical roles of functional foods. Many pediococci bacteria frequently related to the meat environment, have technological properties, and are therefore commercially used as starter in the production of fermented meat products, such as different types of sausages. In this study, different lactic acid bacteria were isolated, identified to the species level, and then evaluated for their safety and functionality as possible probiotics. Different properties, such as resistance to simulated human gastrointestinal conditions, antimicrobial activity, and cholesterol-lowering effects, have been studied. Finally, the complete genome of one strain, namely P. acidilactici IRZ12B, which showed interesting features as a promising probiotic candidate, was sequenced and further studied. The results revealed that IRZ12B possesses interesting probiotic properties, particularly cholesterol-lowering capability and antimicrobial activity. In silico analysis evidenced the absence of plasmids, transmissible antibiotic resistance genes, and virulence factors. We also detected a bacteriocin encoding gene and a cholesterol assimilation-related protein. The phenotypical and genomic outcomes described in this study make P. acidilactici IRZ12B a very interesting cholesterol-lowering potential probiotic strain to be considered for the development of novel non-dairy-based functional foods.

Recent Advances in the Application of the Antimicrobial Peptide Nisin in the Inactivation of Spore-Forming Bacteria in Foods.

Conventional thermal and chemical treatments used in food preservation have come under scrutiny by consumers who demand minimally processed foods free from chemical agents but microbiologically safe. As a result, antimicrobial peptides (AMPs) such as bacteriocins and nisin that are ribosomally synthesised by bacteria, more prominently by the lactic acid bacteria (LAB) have appeared as a potent alternative due to their multiple biological activities. They represent a powerful strategy to prevent the development of spore-forming microorganisms in foods. Unlike thermal methods, they are natural without an adverse impact on food organoleptic and nutritional attributes. AMPs such as nisin and bacteriocins are generally effective in eliminating the vegetative forms of spore-forming bacteria compared to the more resilient spore forms. However, in combination with other non-thermal treatments, such as high pressure, supercritical carbon dioxide, electric pulses, a synergistic effect with AMPs such as nisin exists and has been proven to be effective in the inactivation of microbial spores through the disruption of the spore structure and prevention of spore outgrowth. The control of microbial spores in foods is essential in maintaining food safety and extension of shelf-life. Thus, exploration of the mechanisms of action of AMPs such as nisin is critical for their design and effective application in the food industry. This review harmonises information on the mechanisms of bacteria inactivation from published literature and the utilisation of AMPs in the control of microbial spores in food. It highlights future perspectives in research and application in food processing.

Evaluation of the Microbial Load and pH of Pap Produced from Selected Cereals

The aim of this work was to evaluate the microbial load of pap samples made from three commonly utilized cereal grains namely: maize (Zea mays), millet (Pennisetum typhoideum) and guinea corn (Sorghum bicolor). Exactly 2 kg each of the aforementioned grains was steeped in 1000 ml of clean water for 3 days at 30±20C temperature. The water was disposed and the cereal grain separately washed thoroughly using clean water. The grains were then wet milled and the resulting paste mixed with1000 ml of clean water. The slurry was filtered with the aid of the muslin cloth. The filtrate was then allowed to stand for a period of 24 hours and the supernatant disposed. Microbiological analysis to determine microbial load on the various samples were carried using standard procedures. Guinea corn based pap had the highest lactic acid bacteria count of 9×103 CFU/g at 0 hr of fermentation which decreased to 6.6×105 CFU/g at the 72nd hr. On the other hand, the composite of the three cereals had the lactic acid bacteria count of 4.2×104 CFU/g at 0 hr of fermentation which increased to 8.6×105 CFU/g at the 72nd hr, the highest value recorded for all samples studied. Total coliform count on all samples maintained a uniform trend of increase at the 24th and 48th hr and a decrease at the 72nd hr. Millet based pap had the highest fungi count of 2.3×101CFU/g at 0hr of fermentation which increased progressively to 4.9×101 at the 72nd hr. However, pap derived from the composite of the cereals presented the lowest fungi count of 0.52×102 at 0hr which however increased progressively to record the highest count of 1.4×101at the 72nd hr. In conclusion, there is need to optimize the growth of lactic acid bacteria in the production of pap, this may enhance its acid production potential and consequent inhibition and/destruction of potential harmful microorganisms in fermented foods.

Bioinformatics investigation of CRISPR/Cas systems in Bifidobacterium longum

Bifidobacterium longum is one of the most important probiotics used in the food industries. These bacteria are also applied for the treatment or prevention of gastrointestinal and gynecological diseases as well the regulation of immune system. On the other hand, the discovery of clustered regularly interspaced short palindromic repeats (CRISPR) systems has revolutionized gene therapy approaches and provided a novel tool for gene editing. Several investigators are seeking for potential CRISPR sequences as well the CRISPR-associated (Cas) proteins in various microorganism. Considering the importance of B. longum and its safe application in food industry, the aim of the present study is to investigate the presence and characteristics of CRISPRs in this bacterium via in silico study in 96 strains of the bacteria. According to the results obtained in this study, nine B. longum strains demonstrated high occurrence of CRISPR arrays. These arrays could probably form four RNA secondary structures. Since the bacterium B. longum have been widely used as a safe microorganism in foods, the first report on the probable presence of CRISPR sequences may provide the opportunity to introduce the bacteria as a gene editing tool.

Production of Organic Acid and Short-Chain Fatty Acids (SCFA) from Lactic Acid Bacteria Isolate on Oligosaccharide Media

The growth of microorganisms in food, one of which is lactic acid bacteria (LAB), can produce metabolites beneficial to health. It is essential to study the results of LAB metabolism to improve the quality of a functional food product. This study aimed to evaluate the isolates Lactobacillus acidophilus FNCC 0051 and Lactobacillus rhamnosus R23 to metabolize oligosaccharides as a carbon source so that the final fermentation product can benefit health especially in lowering cholesterol. In vitro testing was carried out on MRS media with or without oligosaccharides, either singly or in a combination consisting of galactooligosaccharides (GOS), fructooligosaccharides (FOS), inulin (IN), inulin hydrolyzate (HI), or their combination as prebiotics by adding 0.3 % oxbile (bile salt) and inoculated with 1% v/v LAB isolate culture and incubated at 37°C for 24 hours. The results showed that the main product of oligosaccharide metabolism by L. acidophilus FNCC 0051 and L. rhamnosus R23 produced several organic acids (lactic acid), including short-chain fatty acids (SCFA) (acetic acid, propionic acid, and butyric acid). The single and combined carbon sources affected the proportion of lactic acid and acetic acid produced by L. acidophilus FNCC0051 (p<0.05). However, they did not affect the proportions of propionic acid and butyric acid. While in L. rhamnosus R23 (p<0.05), the presence of a single carbon source significantly affected the proportions of lactic acid, acetic acid, propionic acid, and butyric acid, while the combination of oligosaccharides affected the proportions of lactic acid and butyric acid produced. SCFA is the main product of prebiotic metabolism, but the characteristics of the acid produced have not been identified. The fermentation pattern is thought to be related to molecular weight, chain length, and oligosaccharide structure. Short-chain molecules, such as FOS generally ferment more rapidly than long-chain molecules such as inulin. The results of this study indicate that both isolates can be used as probiotics in the development of symbiotic products with the addition of oligosaccharides, which have a physiological effect in lowering cholesterol levels.

Plant hydrolates – Antioxidant properties, chemical composition and potential applications

Hydrolates, are by-products of the hydrodistillation of plants. They consist of the distillation water in which very small amounts of essential oils remain dispersed. Hydrosols are widely used in cosmetics. One of the greatest challenges in skin care, whether it is healthy or affected by a pathological condition, is how to minimize oxidative stress. Extract also lend themselves to applications in the agri-food industry, to inhibit the development of pathological microorganisms in food and to remove biofilms constituting a threat to public health in food, pharmaceuticals and beauty products. Therefore, the aim of this study was to analyze the antioxidant potential of hydrosols available in the cosmetics market, taking into account for the first time in scientific literature not only plant species, but also origin (country, farming system, part of plant) and method of preservation. Antioxidant activity, expressed as percentage inhibition of DPPH (1,1-diphenyl-2-picrylhydrazyl), ferric ion reducing antioxidant power (FRAP) and content of polyphenolic compounds (Folin-Ciocalteu method), was determined in seventeen hydrosols by spectrophotometric methods. Antioxidant potential was in the range of 4.43–39.87% of DPPH radical inhibition and 1325.65–5794.38 µM Fe(II)/L. Total phenolic content (TPC) in the hydrosols amounted to 9.33–44.23 mg GAE/L, while total flavonoid content (TFC) ranged from 1.48 to 14.82 mg rutin/L. The hydrosols had a pH in the range of 3.31–5.42. Conclusions: Plant hydrosols appear to have a high antioxidant potential, which depends on not only the plant species, but also its origin, part of the plant from which the hydrosol was obtained and the preservation method used in the finished product.

Validation of process technologies for enhancing the safety of low-moisture foods: A review.

The outbreaks linked to foodborne illnesses in low-moisture foods are frequently reported due to the occurrence of pathogenic microorganisms such as Salmonella Spp. Bacillus cereus, Clostridium spp., Cronobacter sakazakii, Escherichia coli, and Staphylococcus aureus. The ability of the pathogens to withstand the dry conditions and to develop resistance to heat is regarded as the major concern for the food industry dealing with low-moisture foods. In this regard, the present review is aimed to discuss the importance and the use of novel thermal and nonthermal technologies such as radiofrequency, steam pasteurization, plasma, and gaseous technologies for decontamination of foodborne pathogens in low-moisture foods and their microbial inactivation mechanisms. The review also summarizes the various sources of contamination and the factors influencing the survival and thermal resistance of pathogenic microorganisms in low-moisture foods. The literature survey indicated that the nonthermal techniques such as CO2 , high-pressure processing, and so on, may not offer effective microbial inactivation in low-moisture foods due to their insufficient moisture content. On the other hand, gases can penetrate deep inside the commodities and pores due to their higher diffusion properties and are regarded to have an advantage over thermal and other nonthermal processes. Further research is required to evaluate newer intervention strategies and combination treatments to enhance the microbial inactivation in low-moisture foods without significantly altering their organoleptic and nutritional quality.

Characterization of biosurfactants derived from probiotic lactic acid bacteria against methicillin-resistant and sensitive Staphylococcus aureus isolates

Metabolites of lactic acid bacteria (LAB) are gaining renewed interest as postbiotics to curb the growth of undesirable microorganisms in food and pharmaceutical industries. The present study was aimed to extract and characterize the biosurfactants (BS) of Lactobacillus acidophilus NCFM and Lacticaseibacillus rhamnosus GG. Acceptable levels of emulsification index and oil displacement ability of cell-free supernatant as well as considerable cell surface hydrophobicity of LGG and NCFM confirmed the BS production. The cell wall-bound and extracellular BS were extracted by solvent extraction method. Chemical group characterization of BS through Fourier-Transform Infrared Spectroscopy specified the amalgamation of carbohydrates, lipids, and proteins in NCFM, whereas only the proteins and carbohydrates in LGG. Gas chromatography-mass spectrometry analysis of BS (NCFM) revealed hexadecanoic acid, 9-octadecenoic acid, and methyl stearate as principal fatty acids. BS showed dose-dependent antibacterial and antibiofilm activities against methicillin-resistant and sensitive staphylococcal isolates. Upon visual inspection through scanning electron microscopy confirmed the cell death via alternations in the cell surface coherence. Overall, our findings suggest that BS from LGG and NCFM may be the potential candidates to abrogate staphylococcal biofilms, and therefore further technology intervention to scale up the production process could be noteworthy.

Modeling and validation of delivered fluence of a continuous Dean flow pilot scale UV system: monitoring fluence by biodosimetry approach

The inactivation of pathogenic microorganisms in water and high transmittance liquid foods has been studied extensively. The efficiency of the process is relatively low for treating opaque liquid foods using traditional UV systems. This study evaluated the ability of UV-C light to inactivate foodborne pathogens in a simulated opaque fluid (6.5 to 17 cm−1) at commercial relevant flow rates (31.70, 63.40, 95.10 gph) using a pilot-scale Dean Flow UV system. In this study, a mathematical model for the prediction of delivered fluence was developed by the biodosimetry method. The results revealed that increased Reduction equivalent fluence (REF) rates were observed with increased flow rates due to additional turbulence. The experimental and calculated REF were well correlated with the UV-C absorption coefficient range of 6.5 to 17 cm−1 indicating efficient mixing in the reactor. REF scaled up linearly at experimental conditions as an inverse function of flow rate and absorption coefficient, and a linear mathematical model (R2 > 0.99, p < 0.05) to predict delivered REF was developed. The model was tested and validated against independent experiments using Salmonella Typhimurium and Bacillus cereus endospores. The predicted and experimental REF values were in close agreement (p > 0.05). It is demonstrated that the developed model can predict the REF, thus microbial inactivation of microbial suspensions in simulated fluid with the absorption coefficient of 6.5–17 cm−1 and flow rates of 31.70–95.10 gph. The pilot system will be field-tested against microorganisms in highly absorbing and scattering fluids.

Influence of drying conditions, food composition, and water activity on the thermal resistance of Salmonella enterica

Salmonella contamination of low-water activity (aw) foods poses a serious concern worldwide. The present study was conducted to assess the effects of drying conditions, food composition, and water activity on the desiccation tolerance and thermal resistance of S. Enteritidis FUA1946, S. Senftenberg ATCC43845 and S. Typhimurium ATCC13311 in pet food, binder formulation, and skim milk powder. The samples were wet inoculated with the individual Salmonella strains and were equilibrated to aw 0.33 and 0.75, followed by an isothermal treatment at 70 °C. The thermal inactivation data was fitted to the Weibull model. Irrespective of the aw, food composition and physical structure of the selected foods, strain S. Enteritidis FUA1946 displayed the highest desiccation and thermal resistance, followed by S. Senftenberg ATCC43845 and S. Typhimurium ATCC13311. The food matrix and strain type significantly (p < 0.05) influenced the thermal resistance of microorganisms in foods along with aw change during thermal treatments. To further study the effect of food composition, an additional set of experiments using dry inoculation of the resistant Salmonella strain in the low-aw foods was designed. Significant (p < 0.05) matrix-dependent interaction on Salmonella reduction was observed. The water adsorption isotherms of selected low-aw foods were measured at 20 and 70 °C to relate the thermal inactivation kinetics with the change in the aw. The characterization of thermal resistance of the Salmonella serovars in low-aw products with different compositions and aw in this study may be used for the validation of thermal challenge studies.

Recent trends in bacterial decontamination of food products by hurdle technology: A synergistic approach using thermal and non-thermal processing techniques

Researchers are continuously discovering varied technologies for microbial control to ensure worldwide food safety from farm-to-fork. The microbial load and virulence of spoilage causing microorganisms, including bacteria, fungi, yeasts, virus, and protozoa, determines the extent of microbial contamination in a food product. Certain pathogenic microbes can cause food poisoning and foodborne diseases, and adversely affect consumers' health. To erade such food safety-related problems, various traditional and novel food processing methods have been adopted for decades. However, some decontamination techniques bring undesirable changes in food products by affecting their organoleptic and nutritional properties. Combining various thermal and non-thermal food processing methods is an effective way to impart a synergistic effect against food spoilage microorganisms and can be used as an alternative way to combat certain limitations of food processing technologies. The combination of different techniques as hurdles put the microorganisms in a hostile environment and disturbs the homeostasis of microorganisms in food temporarily or permanently. Optimization and globalization of these hurdle combinations is an emerging field in the food processing sector. This review gives an overview of recent inventions in hurdle technology for bacterial decontamination, combining different thermal and non-thermal processing techniques in various food products.

Antibiotic resistance and plasmid analysis of Enterobacteriaceae isolated from retail meat in Lagos Nigeria

BackgroundThe presence of antibiotic resistant microorganisms in food is of great concern globally. This research was carried out to detect and characterize plasmid carriage and profiles among members of Enterobacteriaceae from different meat types in Nigeria.MethodFrom a total of 80 meat samples comprising of mutton, pork, beef and chicken, organisms belonging to the family Enterobacteriaceae were isolated by standard procedures and identified by API 20E system. Antibiotics susceptibilities testing (AST) against selected classes of antimicrobial agents and plasmid extraction was carried out by disc diffusion and alkaline lysis methods respectively.ResultsOne-hundred and ten Enterobacteriaceae were isolated, species identification revealed isolates belonging to 7 genera comprising of Escherichia, Enterobacter, Klebsiella, Citrobacter, Proteus, Salmonella and Serratia. Overall resistance of the organisms to amoxycillin/clavulanic acid was 91 (82.7%), streptomycin 85 (75.7%) and perfloxacin 74 (67.2%) while ofloxacin had the highest susceptibility rate (91.8%). Plasmids profiling revealed ranges of plasmids from1 to 3 copies with estimated sizes range of 700bp to 1.1kb among E. coli, K. pneumoniae, E. aerogenes and Proteus mirabilis. All the isolates with plasmids were multidrug resistant and were isolated from chicken except a strain of E. coli from pork which harboured a single plasmid copy suggesting these meat as reservoirs for antibiotic resistant bacteria. ConclusionOur findings revealed high level of meat contamination with antibiotic resistant Enterobacteriaceae harbouring resistant plasmids. An integrated surveillance system and safety practice must be ensured among the processors and retailers.

The Microbiota of Modified-Atmosphere-Packaged Cooked Charcuterie Products throughout Their Shelf-Life Period, as Revealed by a Complementary Combination of Culture-Dependent and Culture-Independent Analysis.

Although refrigeration and modified-atmosphere packaging (MAP) allow for an extended shelf life of cooked charcuterie products, they are still susceptible to bacterial spoilage. To obtain better insights into factors that govern product deterioration, ample information is needed on the associated microbiota. In this study, sliced MAP cooked ham and cooked chicken samples were subjected to culture-dependent and culture-independent microbial analysis. In total, 683 bacterial isolates were obtained and identified from 60 samples collected throughout the storage period. For both charcuterie types, lactic acid bacteria (LAB) constituted the most abundant microbial group. In cooked ham, Brochothrix thermosphacta was highly abundant at the beginning of the shelf-life period, but was later overtaken by Leuconostoc carnosum and Lactococcus piscium. For cooked chicken products, Latilactobacillus sakei was most abundant throughout the entire period. Additionally, 13 cooked ham and 16 cooked chicken samples were analyzed using metabarcoding. Findings obtained with this method were generally in accordance with the results from the culture-dependent approach, yet they additionally demonstrated the presence of Photobacterium at the beginning of the shelf-life period in both product types. The results indicated that combining culture-dependent methods with metabarcoding can give complementary insights into the evolution of microorganisms in perishable foods.

A Brief Review on the Food Irradiation Process: Radiolysis of Water by Irradiation

Nowadays food irradiation process is an engrained technology for the preservation of foods and food products. It is the process of exposing food or food product to ionizing radiation such as ℽ-rays which is emitted from the radio-isotopes Cobalt-60 and Caesium-137, or electron beams and X-rays. In the food irradiation process, ionizing radiation is use to destroy the harmful biological micro-organisms in food which is recognized as a safe and well-proven process found with many beneficial applications.

Evaluation of nutritional value and microbiological safety in commercial dog food

In addition to properly balancing nutritional value in accordance with the needs of a dog, estimating the microbiological quality of dog food is crucial in providing healthy and safe foods. The aim of this study was to examine the quality of dry food for adult dogs, with particular reference to: (1) evaluating the nutritional value and compliance with nutritional guidelines for dogs, (2) comparing the nutritional value of dog foods, with particular emphasis on the division into cereal and cereal-free foods, and (3) evaluating their microbiological safety. All thirty-six evaluated dry dog foods met the minimum European Pet Food Industry FEDIAF requirement for total protein and fat content. The total aerobic microbial count in the analyzed dry dog foods ranged from 2.7 × 102 to above 3.0 × 107 cfu/g. In five (14%) dog foods the presence of staphylococci was detected; however, coagulase positive Staphylococcus (CPS) was not found. Mold presence was reported in one cereal-free dog food and in six cereal foods. In none of the analyzed foods Enterobacteriaceae were found, including coliforms, Escherichia coli and Salmonella spp. Bacteria of the genus Listeria and Clostridium as well as yeasts were also not detected. In conclusion, the evaluated dry dog foods had varied microbiological quality. The detected number of microorganisms may have some implications for long-term consumption of contaminated food. The lack of European Commission standards regarding the permissible amounts of microorganisms in pet food may result in insufficient quality control of these products.

Resistance profile of Staphylococcus sp. isolates from tilapia fillet samples Oreochromis niloticus from the northwestern region of Paraná state, Brazil / Perfil de resistência de Staphylococcus sp. isolados de amostras de filete de tilápia Oreochromis niloticus da região noroeste do estado do Paraná, Brasil

Staphylococcus sp. are responsible for several clinical problems in fish farming and humans. This microorganism has a high risk associated with its presence in large numbers, as they have the ability to produce, under certain conditions, thermostable enterotoxins, which, when ingested, cause poisoning and various foodborne diseases. Present in aquaculture environments, Staphylococcus sp, have great potential to acquire antibiotic resistance, due to the use of such substances in the indiscriminate treatment and prophylaxis of bacterial diseases. The presence of food resistant Staphylococcus sp is a current problem in food production and marketing and is a potential danger to human health and a risk to the world fish industry. One hundred tilapia fillet samples were used for isolation of Staphylococccus sp., obtained from fishes located in northwestern Paraná state. It was submitted to antimicrobial susceptibility testing with ten antibiotics. Regarding the 100 samples analyzed, all showed resistance: Tetracycline 18%, Penicillin 31%, Enrofloxacin 14%, Erythromycin 12%, Vancomycin 15%, Gentamicin 14%, Oxacillin 20%, Ampicillin 28% and Cephalothin 11%. The emergence of resistant microorganisms in food is worrying as it can cause serious infections, hospitalizations, and death.

Acetate Activates Lactobacillus Bacteriocin Synthesis by Controlling Quorum Sensing.

Bacteriocins are useful for controlling the composition of microorganisms in fermented food. Bacteriocin synthesis is regulated by quorum sensing mediated by autoinducing peptides. In addition, short-chain fatty acids, especially acetic acid, reportedly regulate bacteriocin synthesis. Five histidine kinases that regulated the synthesis of bacteriocins were selected to verify their interactions with acetate. Acetate activated the kinase activity of PlnB, SppK, and HpK3 in vitro and increased the yield of their cognate bacteriocins plantaricin EF, sakacin A, and rhamnosin B in vivo. The antimicrobial activity against Staphylococcus aureus of the fermentation supernatants of Lactobacillus plantarum, Lactobacillus sakei, and Lactobacillus rhamnosus with addition of acetate increased to 298%, 198%, and 289%, respectively, compared with that in the absence of acetate. Our study elucidated the activation activity of acetate in bacteriocin synthesis, and it might provide a potential strategy to increase the production of bacteriocin produced by Lactobacillus. IMPORTANCE Bacteriocins produced by lactic acid bacteria (LAB) are particularly useful in food preservation and food safety. Bacteriocins might increase bacterial competitive advantage against the indigenous microbiota of the intestines; at the same time, bacteriocins could limit the growth of undesired microorganisms in yogurt and other dairy products. This study confirmed that three kinds of histidine kinases were activated by acetate and upregulated bacteriocin synthesis both in vitro and in vivo. The increasing yield of bacteriocins reduced the number of pathogens and increased the number of probiotics in milk. Bacteriocin synthesis activation by acetate may have a broad application in the preservation of dairy products and forage silage.