Food Biopreservation Research Articles

Evaluation of Soil Streptomyces Isolates from North-Western Ethiopia as Potential Inhibitors against Spoilage and Foodborne Bacterial Pathogens

The outbreak and spread of foodborne diseases is a serious concern for global healthcare and security. Finding novel antimicrobial agents with diverse mechanisms of action against the current spoilage and foodborne bacterial pathogens is a central strategy to overcome the problems of antibiotic resistance. Soil actinomycetes are the major antimicrobial producers with great biopreservative and medical value. This study was aimed at isolating Streptomyces from soil samples of northwestern Ethiopia against spoilage and foodborne bacterial pathogens. Thirty-six soil samples were collected at a depth of 5–10 cm in the rhizosphere and agricultural soils of soybean. A total of 118 actinomycete strains were isolated and screened primarily using the perpendicular streak plate method against 3 Gram-positive and 3 Gram-negative bacterial strains. Out of 118 isolates, 36/118 (30.50%) were active against at least two of the tested bacteria, of which 8 isolates were selected for their wide-spectrum antibacterial activities. During the disc diffusion assay, the eight in vitro ethyl acetate extract antibacterial activities range from 7 to 24 mm. The minimum inhibitory concentration and minimum bactericidal concentration values range from 0.10 to 0.25 μg/mL and 0.15 to 0.40 μg/mL, respectively. Following the morphological, physiological, biochemical, and molecular characteristics, eight potent isolates were identified as follows: Streptomyces fasciculus, Streptomyces roseochromogenes, Streptomyces ruber, Streptomyces glaucus, Streptomyces griseus, Streptomyces cellulosae, Streptomyces griseoflavus, and Streptomyces xanthophaeus. After the treatment of potent Streptomyces cell-free culture supernatant with proteinase K, papain, α-amylase, and lysozyme enzymes, their antagonistic effects were also observed. Most Streptomyces cell-free culture supernatant antibacterial activity was highly resistant to heat, acidity, organic solvents, and additives. Thus, the results of this investigation revealed that soil actinomycetes could be a valuable source for novel antibacterial agents applicable in food biopreservation and the treatment of spoilage and foodborne bacterial pathogens.

NOVEL RUMMELIIBACILLUS SP. ISOLATED FROM FERMENTED VEGETABLE PRODUCTS AS THE POTENTIAL PROBIOTICS

The novel lactic acid bacteria has potential probiotics which were selectively screened from different fermented vegetable products by antagonistic activity against Escherichia coli ATCC 25922 as a food-borne pathogenic bacteria. From 40 isolates on MRS agar, some isolates had anti-E. coli activity. Surprisingly, isolated STR 0103f and STR 0404f strains demonstrated bile salt-tolerance at 0.3% bile salt for 24 hours with survival rate of 67.77±0.38 and 68.72±0.45%, respectively. Both strains also survived under acidic conditions (pH 3-5) with 60.53±0.08-76.87±0.09% of survival rate. STR 0103f and STR 0404f strains elicited the broad spectrum against both Gram-negative (Pseudomonas aeruginosa ATCC 27853, Salmonella typhimurium ATCC 13311 and Salmonella paratyphi A) and Gram-positive (StaphylococcusS. aureus ATCC 25923) pathogenic strains which appeared inhibition zone of 7.33±0.58-8.33±0.58 mm and revealed a susceptibility to various antibiotics. Moreover, two selected strains were also able to adhere to stainless steel plates at least 30% of adhesion rate and without any detectable hemolytic activity. Morphological, biochemical characteristics and 16S rRNA gene sequences were used as a tool for bacterial identification. Both STR 0103f and STR 0404f isolates were identified as Rummeliibacillus sp. which are Rummeliibacillus pycnus STR 0103f and Rummeliibacillus stabekisii STR 0404f, respectively. Thus, R. pycnus STR 0103f and R. stabekisii STR 0404f would be the novel bacterial strains from fermented vegetable products that act as the potential probiotic candidates for safety food bio-preservation.

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.

Combined use of bacteriocins and bacteriophages as food biopreservatives. A review

Throughout history, humans have consistently developed strategies to prevent food-associated illnesses. However, despite our multiple technological advances, food safety is still an issue of concern. Moreover, there is a demand for gaining access to less processed and naturally preserved food. Food biopreservation, understood as the use of natural antimicrobials already present in food with a long history of safe consumption, is seen as a plausible strategy to reduce the intensity of current preservation technologies (e.g., presence of chemically synthesized food preservatives). In that sense, the combined use of several antimicrobial strategies, known as hurdle technology, has been often chosen as a means to improve the efficacy of food biopreservation. This review intends to summarize the most recent examples of the combined use of bacteriocins and bacteriophages to extend food shelf-life and reduce the risks associated with the presence of foodborne bacteria along the food chain. However, while the efficacy of bacteriocins has been extensively documented, bacteriophages have only started to be assessed as potential food biopreservatives more recently. Within this context, we would like to consider whether these two types of natural antimicrobials would help each other to overcome bottlenecks in food biopreservation.

Combined antimicrobial effect of bacteriocins with other hurdles of physicochemic and microbiome to prolong shelf life of food: A review

Bacteriocins are ribosomally synthesized peptides to inhibit food spoilage bacteria, which are widely used as a kind of food biopreservation. The role of bacteriocins in therapeutics and food industries has received increasing attention across a number of disciplines in recent years. Despite their advantages as alternative therapeutics over existing strategies, the application of bacteriocins suffers from shortcomings such as the high isolation and purification cost, narrow spectrum of activity, low stability and solubility and easy enzymatic degradation. Previous studies have studied the synergistic or additive effects of bacteriocins when used in combination with other hurdles including physics, chemicals, and microbes. These combined treatments reduce the adverse effects of chemical additives, extending the shelf life of food products while guaranteeing food quality. This review highlights the advantages and disadvantages of bacteriocins in food preservation. It then reviews the combined effect and mechanism of different hurdles and bacteriocins in enhancing food preservation in detail. The combination of bacterioncins and other hurdles provide potential approaches for maintaining food quality and food safety.

Lactobacillus plantarumprotective cultures to improve safety and quality of wheyless Domiati‐like cheese

This study aimed to isolate some lactic acid bacteria (LAB) with potential antimicrobial activity against Staphylococcus aureus (S. aureus) to be used as a protective culture for the manufacture of Domiati-like cheese. Eight isolates with anti-staphylococcal activity were identified as Lactobacillus plantarum (L. plantarum FFNL739 and FFNL1810) and one as Enterococcus faecium (E. farcium). Strains FFNL739 and FFNL1810 and their mixture were used as protective cultures to control S. aureus in Domiati like-cheese. The impact of both strains and their mixture on some ripening indices and sensory attributes of cheese was assessed during 8 weeks of refrigerated storage at 6±1°C. The inclusion of L. plantarum could suppress the growth of S. aureus and improve the overall acceptability, proteolysis, and lipolysis. Thus, it could be recommended to use the mixed culture of strains FFNL739 and FFNL1810 to improve the safety and quality of Domiati cheese. Practical applications There is a growing demand among consumers for chemical-free products especially those used as preservatives. Lactic acid bacteria can produce a wide variety of antimicrobial molecules, particularly bacteriocins. These natural antimicrobials are secure and could consider a good alternative to chemical preservatives. The application of bacteriocin-producing lactic acid bacteria is the main strategy of food bio-preservation. This approach is applicable, cheap, and efficient to extend the shelf-life of minimally processed and ready-to-eat products. Also, biopreservation proves to be able to improve quality, hygienic status, and improved safety of foods.

A novel bacteriocin against Staphylococcus aureus from Lactobacillus paracasei isolated from Yunnan traditional fermented yogurt: Purification, antibacterial characterization, and antibiofilm activity

Staphylococcus aureus and its biofilm have emerged as a significant threat to the safety of dairy products. In recent years, lactic acid bacteria (LAB) bacteriocins have been widely acknowledged as the potential natural antibacterial substance in food biopreservation due to their excellent antibacterial effects. However, few LAB bacteriocins with antibacterial and antibiofilm activity against S. aureus have been reported in dairy products. In the present study, a novel bacteriocin LSX01 of Lactobacillus paracasei LS-6 isolated from a traditional fermented yogurt produced in Yunnan, China, was purified and characterized extensively. The LSX01 possessed a molecular weight of 967.49 Da and an AA sequence of LDQAGISYT. The minimum inhibitory concentration of LSX01 against S. aureus_45 was 16.90 μg/mL, which was close to or lower than the previously reported bacteriocins. The LSX01 exhibited an extensive antimicrobial spectrum against both gram-positive and gram-negative bacteria. Moreover, LSX01 exhibited excellent tolerance to heat and acid-base treatments, and sensitivity to the proteolytic enzymes, such as pepsin and proteinase K. Furthermore, the treatment of S. aureus_45 planktonic cells with LSX01 significantly reduced their metabolic activity and disrupted the cell membrane integrity. Scan electron microscopy results demonstrated that LSX01 induced cytoplasmic content leakage and cell deformation. Additionally, biofilm formation of S. aureus_45 was also significantly inhibited by LSX01. Overall, the results suggested that the novel LAB bacteriocin LSX01 possessed antibacterial activity and antibiofilm activity against S. aureus and, hence, could have potential for improving safety of dairy products.

Inhibitory Effect of Lactic Acid Bacteria on Aflatoxin B1 Producing Aspergillus flavus Isolated from Garri

Among the potential benefits of probiotic lactic acid bacteria (LAB) is their practical use for biopreservation of foods, fungal decontamination, and novel biotherapy. A number of ready to eat foods hawked in streets of Nigeria such as garri are prone to contamination by mycotoxin-producing fungi. In this study the inhibitory effect of lactic acid bacteria (LAB) (sourced from local foods (nono and kunun- zaki)) and their bacteriocins-derivatives on aflatoxin B1 -producing Aspergelius flavus was conducted. Out of the five LAB isolates screened three (two strains of Lactococcus and one of Pediococcus sp had high indices of probiotic potentials and bacteriocins extracts were obtained from them and used for the inhibition study. Fourty samples of garri sold in Jos metropolis were screened for A. flavus and their abilities to produce Aflatoxin B1 using the Coconut Extract Agar (CEA) and Ammonia Vapour Test (AVP) methods. The three most probiotic LAB and their respective crude baterioncin extracts were used to test for their inhibitory effect on aflatoxin producing A. flavus isolates. The results of the study showed that while only 17 samples (42.50%) had A. flavus in them, only three of the fungi ((17.65%) demonstrated capacity to produce Aflatoxin B1, making (7.5% of the total number of garri samples that had aflatoxin-producing A. flavus. The inhibition of fungal growth by LAB and bacteriocins was dose dependent. At an inoculum concentration of 1 ml, Pediococcus sp had the highest mean zone of inhibition of 43.0 mm followed by Lactococcus sp (Strain LAC20G with radial diameter 38.0mm and Lactococcus sp (LAC20G) which had a radial diameter of 29.3mm respectively. The results of the study portend that the growth of aflatoxin producing Aspergillus flavus in ready to eat foods such as garri could be prevented by application of appropriate dosages of bacteriocins extracts from lactic acid bacteria.

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.

Study on the applicability of potentially probiotic strain Lactobacillus plantarum L4 to be included in the development of strategies for bio-preservation of food products

The antimicrobial activity of potentially probiotic strains is important for their possible application in the development of successful strategies for bio-preservation of different foods. The antimicrobial activity of the potentially probiotic strain Lactobacillus plantarum L4 against the pathogenic bacteria Salmonella abony; Staphylococcus aureus; Escherichia coli and the phytopathogenic fungi Aspergillus niger and Aspergillus flavus was determined using agar-diffusion assay with wells. Lb. plantarum L4 exhibited high antagonistic activity against all test microorganisms included in the study, which was due not only to the production and accumulation of lactic acid and other organic acids, but also to the production of other bioactive substances. The bioactive substances were then submitted to the action of different enzymes. This allowed to observe that they have protein nature, suggesting that they are likely bacteriocins or bacteriocin-like substances. The substances produced by Lb. plantarum L4 did not lose their antimicrobial activity during heat treatment at temperatures above 100 °С for 15 min and they exhibited high inhibitory activity against the test-microorganisms when pH ranged between 4 and 7. After further examination of the properties of the produced antimicrobial compounds, Lb. plantarum L4 can be used in the development of strategies for bio-preservation of different food products.

ISOLATION AND IDENTIFICATION OF LACTIC ACID BACTERIA (LAB) PRODUCING BACTERIOSIN-LIKE FROM SMOKED GIANT CATFISH (Arius thalassinus)

Bacteriocin was bacterial metabolite that have antimicrobial properties, so it had the potential to be used as food bio preservatives. Bacteriocin was produced by lactic acid bacteria (LAB), one of the sources of which was from smoked fish products. Some regions in Indonesia produce various types of smoked fish from various types of fish, which were thought to contain bacteriocin-producing lactic acid; one of them was giant cathfish (Arius thalassinus). This study aims to obtain LAB isolates that have strong antimicrobial activity and have the potential to produce bacteriocin-like from smoked giant catfish (Arius thalassinus). The research method used an experimental method that analyzed descriptively. Based on the results, there were 15 isolates LAB isolated from smoked giant catfish. Three selected isolates showed strong antimicrobial activity inhibiting E. coli and S. aureus bacteria, and the most effective inhibiting Salmonella sp. One selected LAB isolates identified Pediococcus acidilactici suspected to produce pediocin bacteriocin-like, while the other two isolates identified Lactobacillus plantarum sp 1 and Lactobacillus plantarum sp 2 which suspected to produce plantaricin bacteriocin. Bacteriocin from the three isolates of LAB had characteristics stable to temperatures up to 121oC, stable in pH range 2-6, and bacteriocin activity increased with the addition of SDS (Sodium Dodecyl Sulfate) and EDTA (Ethylenediaminetetraacetic acid) surfactants. The conclusion was that the bacteriocin produced was stable at high temperature, low pH, and resistence in the presence of surfactants, so it had the potential to be developed as biopreservatives material in preserving fish-based foods

A Novel Nano-Antimicrobial Polymer Engineered with Chitosan Nanoparticles and Bioactive Peptides as Promising Food Biopreservative Effective against Foodborne Pathogen E. coli O157-Caused Epithelial Barrier Dysfunction and Inflammatory Responses.

For food quality and safety issues, the emergence of foodborne pathogenic bacteria has further accelerated the spread of antibiotic residues and drug resistance genes. To alleviate the harm caused by bacterial infections, it is necessary to seek novel antimicrobial agents as biopreservatives to prevent microbial spoilage. Nanoantimicrobials have been widely used in the direct treatment of bacterial infections. CNMs, formed by chitosan nanoparticles and peptides, are promising antibiotic alternatives for use as excellent new antibacterial drugs against pathogenic bacteria. Herein, the current study evaluated the function of CNMs in the protection of foodborne pathogen Escherichia coli (E. coli) O157 infection using an intestinal epithelial cell model. Antibacterial activity assays indicated that CNMs exerted excellent bactericidal activity against E. coli O157. Assessment of the cytotoxicity risks toward cells demonstrated that 0.0125–0.02% of CNMs did not cause toxicity, but 0.4% of CNMs caused cytotoxicity. Additionally, CNMs did not induced genotoxicity either. CNMs protected against E. coli O157-induced barrier dysfunction by increasing transepithelial electrical resistance, decreasing lactate dehydrogenase and promoting the protein expression of occludin. CNMs were further found to ameliorate inflammation via modulation of tumor factor α, toll-like receptor 4 and nuclear factor κB (NF-κB) expression via inhibition of mitogen-activated protein kinase and NF-κB activation and improved antioxidant activity. Taken together, CNMs could protect the host against E. coli O157-induced intestinal barrier damage and inflammation, showing that CNMs have great advantages and potential application as novel antimicrobial polymers in the food industry as food biopreservatives, bringing new hope for the treatment of bacterial infections.

Recent developments in applications of lactic acid bacteria against mycotoxin production and fungal contamination

Post-harvest spoilage and toxicity of food products mainly occur by fungi, including Aspergillus, Penicillium, and Fusarium resulting in massive economic losses globally. Additionally, fungi produce an enormous number of allergenic spores and mycotoxins associated with human health issues. The inhibition of fungal growth in the cereal grain, foodstuff, and storage and reduction of food safety hazards are of utmost importance. Thus, the interest in the involvement of bacteria or their antimicrobial active metabolites for bio-protection properties has increased. Lactic acid bacteria (LAB) that present a wide range of genera are a broad class of Gram-positive, acid-tolerant, and immotile organisms. The LABs have a great potential for food bio-preservation since most LABs are GRAS, and they naturally dominate the microbiota of most of the foods. The LABs can control fungal growth by secreting antimicrobial compounds from the cell wall of the lactobacilli defense system to destroy the bacterial and fungal cells. Additionally, LABs are key ingredients of culture starters in the food industries to produce aroma, flavor, texture, color and prolong the shelf life. Therefore, this review is about the recent antifungal potential, mechanism of LABs against mycotoxin, and their potential use in various food applications against fungal contamination.

Antifungal Activity of Biocontrol Agents In Vitro and Potential Application to Reduce Mycotoxins (Aflatoxin B1 and Ochratoxin A).

Food bio-preservatives are requested as substituents of chemical pesticides in food. The aim of this study was to carry out a screening of twenty biocontrol agents (BCAs) for their potential fungicidal activity in vitro. Twenty BCAs were tested against ten pathogenic fungi. Some of the cell-free supernatants (CFS) tested showed in vitro antifungal activity versus pathogenic fungi. The highest fungicidal activity was observed in the fermented CFS of Paenibacillus chibensis CECT 375, Bacillus amyloliquefaciens CECT 493, and Pantoea agglomerans CECT 850, which showed a minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) values of 125 and 250 g/L, respectively. The compounds responsible for the antifungal activity, such as organic and phenolic acids, were determined. Lactic acid, acetic acid, benzoic acid, and phenyllactic acid among others can be related to antifungal activity. HPLC-MS/MS analysis showed a reduction of ochratoxin A (OTA) and aflatoxin B1 (AFB1) up to 26% (Paenibacillus alvei CECT 2) and 55% (Paenibacillus polymyxa CECT 155), respectively. The present study prompts that metabolism products of BCAs are propitious for the bioconservation of food, due to their ability to reduce the proliferation of mycotoxigenic fungi and mycotoxins production.

Improved antimicrobial spectrum of the N-acetylmuramoyl-L-alanine amidase from Latilactobacillus sakei upon LysM domain deletion.

The gene encoding N-acetylmuramoyl-L-alanine amidase in Latilactobacillus sakei isolated from a fermented meat product was cloned in two forms: its complete sequence (AmiC) and a truncated sequence without one of its anchoring LysM domains (AmiLysM4). The objective of this work was to evaluate the effect of LysM domain deletion on antibacterial activity as well the biochemical characterization of each recombinant protein. AmiC and AmiLysM4 were expressed in Escherichia coli BL21. Using a zymography method, two bands with lytic activity were observed, which were confirmed by LC-MS/MS analysis, with molecular masses of 71kDa (AmiC) and 66kDa (AmiLysM4). The recombinant proteins were active against Listeria innocua and Staphylococcus aureus strains. The inhibitory spectrum of AmiLysM4 was broader than AmiC as it showed inhibition of Leuconostoc mesenteroides and Weissella viridescens, both microorganisms associated with food decomposition. Optimal temperature and pH values were determined for both proteins using L-alanine-p-nitroanilide hydrochloride as a substrate for N-acetylmuramoyl-L-alanine amidase activity. Both proteins showed similar maximum activity values for pH (8) and temperature (50°C). Furthermore, structural predictions did not show differences for the catalytic region, but differences were found for the region called 2dom-AmiLysM4, which includes 4 of the 5 LysM domains. Therefore, modification of the LysM domain offers new tools for the development of novel food biopreservatives.

Insight into the pilot‐scale fed-batch fermentation for production of Enterococcus faecium CW3801 using molasses-based medium

Enterococcus sp. has been used as starters in food fermentation due to their probiotic and antimicrobial properties in food biopreservation. The antimicrobial properties were mainly contributed by the bacteriocin called enterocin. Hence, the availability of a cost-effective pilot-scale cultivation conditions is a necessity for the production of probiotic bacteria. This study aims to investigate optimization of medium composition using sugarcane molasses as a carbon source using response surface methodology and the potential use of fed-batch cultivation for improvement of the cell viability of Enterococcus faecium CW3801 for the use as a probiotic starter culture. Two feeding strategies (ramp and constant) were applied in fed-batch cultivation for enhancement of the production of E. faecium in a 2-L stirred tank bioreactor using the optimized medium and scaled up to a 15-L bioreactor. Optimized fermentation medium which comprised of 10% (v/v) of molasses and 10 g/L of yeast extract at pH 7 yielded maximum cell viability of 29.4 × 1011 CFU/mL with 3900 AU/mL of bacteriocin-like inhibitory substances (BLIS) activity. In the fed-batch, the cell viability (8.4 × 1013) and dry cell weight (6.34 g/L) reached the highest in optimized medium when the ramp (stepwise) feeding was applied. In scaling up to 15-L bioreactor, the growth of E. faecium was achieved at 2.3 × 1013 CFU/mL with the dry cell weight of 5.28 g/L under the same condition. The BLIS in 15-L bioreactor was 6% higher than the 2-L bioreactor. This study demonstrated that molasses and yeast extract are good feedstock for the growth of E. faecium. The E. faecium, a non-vancomycin resistant enterococcus (VRE) was successfully produced by a fed-batch cultivation approach and scaled up to a 15-L bioreactor using a ramp feeding strategy. Results from this study revealed that the fed-batch cultivation using molasses-based medium has industrial potential for the production of probiotics.

Antifungal activity of human gut lactic acid bacteria against aflatoxigenic Aspergillus flavus MTCC 2798 and their potential application as food biopreservative

AbstractWith the enhanced use of chemical preservatives and the survival of foodborne pathogens, lactic acid bacteria and its metabolic product have received increased attention as a potential food preservative. Even though the antibacterial property of lactic acid bacteria is well known, its antifungal property and application in food preservation have not been widely exploited. Considering these facts, this study was conducted to investigate the antifungal properties of three human gut lactic acid bacterial isolates, Lactobacillus plantarum AL1, Lactobacillus fermentum AL2, and Weissella confusa AL3 antifungal activity of the isolates were studied against the aflatoxigenic Aspergillus flavus MTCC 2798, using the agar overlay method and inhibition of fungal mycelium (co‐culture method). These LAB isolates were also potent producers of antimicrobial compounds like lactic acid, hydrogen peroxide, and diacetyl. GC–MS analysis of the methanolic extract of the three LAB isolates detected two antifungal bioactive compounds like cyclo (leucyloprolyl) and 1,2‐benzenedicarboxylic acid in extracts. The hemolysis results provided an important insight that the human gut lactic acid bacteria can be used as protective cultures in the biopreservation. The antifungal activity of human gut LAB AL1, AL2, and AL3 against aflatoxigenic Aspergillus flavus MTCC 2798 and its ability extend the shelf life of peanuts prove as a natural preservative for food products.

Physicochemical stability of antilisterial proteins from P. polymyxa Kp10 as potential food biopreservative

AbstractListeria monocytogenes has continuously become a significant threat to consumers worldwide. The use of chemical‐derived preservatives that are commonly associated with safety and nutritional issues has prompted the use of natural‐based preservatives as a better alternative. Many bacterial strains including Paenibacillus polymyxa Kp10 have been reported to produce various antimicrobial proteins and compounds that are considered more natural. However, their stability in various physicochemical conditions should be examined before being applied in various types of food. In this study, the stability of four previously identified antilisterial proteins in P. polymyxa Kp10 upon exposure to several physicochemical conditions was examined. More than 80% residual antilisterial activity is conserved upon heat and proteinase K treatment. But, sensitivity to 24 h trypsin digestion has been observed. P1 and P2 proteins (histone‐like DNA binding proteins HU) were sensitive to alkaline pH (pH 10‐12) as compared with other proteins. More than 70% and 97% residual antilisterial activity were recovered after incubation in raw beef homogenates and simulated meat gravy model, respectively. However, the antilisterial activity of most proteins was highly compromised in chicken and salmon meat homogenates, and UHT cow milk. Inoculation of these proteins into Listeria‐contaminated simulated meat gravy showed that all proteins exerted a bactericidal action against L. monocytogenes. P1 and P2 shared almost similar antilisterial activity rates, while P4 was the most potent antilisterial protein. The findings in this study could provide important preliminary data for future applications of these proteins as preservative in food products especially beef‐based meat products.

Phages and Enzybiotics in Food Biopreservation

Presently, biopreservation through protective bacterial cultures and their antimicrobial products or using antibacterial compounds derived from plants are proposed as feasible strategies to maintain the long shelf-life of products. Another emerging category of food biopreservatives are bacteriophages or their antibacterial enzymes called “phage lysins” or “enzybiotics”, which can be used directly as antibacterial agents due to their ability to act on the membranes of bacteria and destroy them. Bacteriophages are an alternative to antimicrobials in the fight against bacteria, mainly because they have a practically unique host range that gives them great specificity. In addition to their potential ability to specifically control strains of pathogenic bacteria, their use does not generate a negative environmental impact as in the case of antibiotics. Both phages and their enzymes can favor a reduction in antibiotic use, which is desirable given the alarming increase in resistance to antibiotics used not only in human medicine but also in veterinary medicine, agriculture, and in general all processes of manufacturing, preservation, and distribution of food. We present here an overview of the scientific background of phages and enzybiotics in the food industry, as well as food applications of these biopreservatives.

Dynamic Modeling of Carnobacterium maltaromaticum CNCM I-3298 Growth and Metabolite Production and Model-Based Process Optimization.

Carnobacterium maltaromaticum is a species of lactic acid bacteria found in dairy, meat, and fish, with technological properties useful in food biopreservation and flavor development. In more recent years, it has also proven to be a key element of biological time–temperature integrators for tracking temperature variations experienced by perishable foods along the cold-chain. A dynamic model for the growth of C. maltaromaticum CNCM I-3298 and production of four metabolites (formic acid, acetic acid, lactic acid, and ethanol) from trehalose in batch culture was developed using the reaction scheme formalism. The dependence of the specific growth and production rates as well as the product inhibition parameters on the operating conditions were described by the response surface method. The parameters of the model were calibrated from eight experiments, covering a broad spectrum of culture conditions (temperatures between 20 and 37 °C; pH between 6.0 and 9.5). The model was validated against another set of eight independent experiments performed under different conditions selected in the same range. The model correctly predicted the growth kinetics of C. maltaromaticum CNCM I-3298 as well as the dynamics of the carbon source conversion, with a mean relative error of 10% for biomass and 14% for trehalose and the metabolites. The paper illustrates that the proposed model is a valuable tool for optimizing the culture of C. maltaromaticum CNCM I-3298 by determining operating conditions that favor the production of biomass or selected metabolites. Model-based optimization may thus reduce the number of experiments and substantially speed up the process development, with potential applications in food technology for producing starters and improving the yield and productivity of the fermentation of sugars into metabolites of industrial interest.