Source Of Lactic Acid Bacteria Research Articles

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

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

Antimicrobial Action of Lactobacillus spp. Isolated from Yoghurt against Escherichia coli, Salmonella Enteritidis and Listeria monocytogenes: A Pilot Study

Milk has been a dietary staple around the world for centuries. In recent years, consumer interest in healthy foods and organic products has increased due to their health-promoting properties. Fermented dairy products, including yoghurt, are receiving special attention for their properties and the presence of probiotic bacteria. The quantitative and qualitative (MALDI TOF MS) evaluation of lactic acid bacteria (LAB) in different types of yoghurt (with different shelf lives) was carried out. The effect of the Lactobacillus spp. strains isolated from yoghurts (with potential antimicrobial activity) against foodborne pathogenic bacteria (Escherichia coli, Salmonella Enteritidis and Listeria monocytogenes) was evaluated. The presence of Lactobacillus spp. (Lactobacillus rhamnosus and Lactobacillus paracasei) in the tested yoghurts was demonstrated. In the samples tested, not all the lactic acid bacteria (LAB) declared by the manufacturer were identified. The number of live bacteria present in the product was influenced by the type of yoghurt. The number of bacteria did not fall below the World Health Organization (WHO) recommended level by the last day of validity. It was shown that a mixed culture (L. rhamnosus and L. paracasei, isolated from tested yoghurts) had the most significant effect on changing the number of pathogenic microorganisms. The consumption of dairy products, which are a source of LAB, can reduce the risk of foodborne pathogen infections.

Probiotic Properties of Lactobacilluscasei and L. plantarum Isolated From Overripe Avocado Pear

Probiotics have been researched for their benefit to gut health. Research for sources of probiotic bacteria has moved from milk to plants, as they have been found to be an inexhaustible source of lactic acid bacteria (LAB). The probiotic properties of lactic acid bacteria isolated from Over ripe Avocado pear on selected bacterial species were assessed. Fifty Unripe Avocado pears were purchased from different markets and allowed to ferment. Enumeration of the microorganisms and pure culture isolation were done on MRS agar supplemented with1.0% CaCO3 at 37 oC for 48 hours; using the pour plate and streak plate methods respectively. The isolates were identified based on their microscopic, macroscopic, biochemical and molecular characteristics. They include Lactobacillus casei and L. plantarum. LAB isolates were tested for their phenol tolerance, bile salt tolerance, acid tolerance and antimicrobial activity. All the isolates were tolerant to simulated gastrointestinal conditions. Growth of the isolates was observed at different temperature between 15 oC to 60 oC. They exhibited tolerance to phenol ranging from 0.085±0.01% to 2.40±0.02%. Tolerance to bile salt ranged from 1.06x101± 0.96x101 to 3.04x103±1.15x102. The acid tolerance level of the LAB obtained ranged from 2.98x102±1.30x102 to 8.78x102±2.22x102. Agar-well diffusion method was used to determine the antimicrobial susceptibility of the bacterial species. The test showed that the isolates were susceptible to the LAB isolates as zones of inhibition were observed. The inhibition zones diameter obtained ranged from 8.35±1.34mm to 13.77±2.21mm. Avocado pear, asides from their high nutritional content, also have the potential to serve as source of probiotic bacteria.

THE USE OF PURPLE EGGPLANT FRUIT CALYX STEM (Solanum melongena L.) AS AN ALTERNATIVE SOURCE OF LACTASE-PRODUCING LACTIC ACID BACTERIA

Lactose intolerance is a condition where body is unable to digest lactose due to an enzyme lactase deficiency in digestive system, leading to various health problems ranging from bloating, diarrhea, and abdominal pain to severe problems that can result in stunting in children. One attempt to prevent stunting due to lactose intolerance is administration of low-lactose dairy products, such as yogurt. The production of yogurt requires a starter known as lactic acid bacteria (LAB). Starter bacteria are often derived from yeast or commercially available bacteria, which are relatively expensive. This research aims to utilize waste products, namely the purple eggplant (Solanum melongena L.) stalks, as a new source of LAB for lactase enzyme production. Fermenting cow's milk using purple eggplant stalks results in yogurt. Inoculating this yogurt onto MRS Broth and MRS Agar media confirms the presence of LAB from the milk fermentation. To test the lactase enzyme, bacterial cell wall degradation is achieved using sonication, allowing for lactase enzyme testing. Characterization test for lactase enzyme is conducted at various temperatures and pH levels to determine the optimum conditions for the lactase enzyme. The optimum temperature for lactase enzyme is at 70°C with a specific enzyme activity of 0.0061 U/mg, optimum pH is 7 with a specific enzyme activity of 0.0044 U/mg. This study demonstrates that purple eggplant stalks can be utilized as a new source of LAB to produce lactase enzyme as an alternative starter bacterium for yogurt production, particularly for lactose intolerance therapy in the future.

Probiotic Potential and Application of Indigenous Non-Starter Lactic Acid Bacteria in Ripened Short-Aged Cheese.

There are massive sources of lactic acid bacteria (LAB) in traditional dairy products. Some of these indigenous strains could be novel probiotics with applications in human health and supply the growing needs of the probiotic industry. In this work, were analyzed the probiotic and technological properties of three Lactobacilli strains isolated from traditional Brazilian cheeses. In vitro tests showed that the three strains are safe and have probiotic features. They presented antimicrobial activity against pathogenic bacteria, auto-aggregation values around 60%, high biofilm formation properties, and a survivor of more than 65% to simulated acid conditions and more than 100% to bile salts. The three strains were used as adjunct cultures separately in a pilot-scale production of Prato cheese. After 45days of ripening, the lactobacilli counts in the cheeses were close to 8 Log CFU/g, and was observed a reduction in the lactococci counts (around -3 Log CFU/g) in a strain-dependent manner. Cheese primary and secondary proteolysis were unaffected by the probiotic candidates during the ripening, and the strains showed no lipolytic effect, as no changes in the fatty acid profile of cheeses were observed. Thus, our findings suggest that the three strains evaluated have probiotic properties and have potential as adjunct non-starter lactic acid bacteria (NSLAB) to improve the quality and functionality of short-aged cheeses.

Cereus jamacaru DC. (mandacaru) fruit as a source of lactic acid bacteria with in vitro probiotic-related characteristics and its protective effects on Pediococcus pentosaceus during lyophilization and refrigeration storage

This study isolated and identified autochthonous lactic acid bacteria (LAB) from mandacaru fruit and evaluated their potential probiotic and technological aptitudes in vitro, as well as the protective effects of freeze-dried mandacaru fruit on the most promising LAB isolate during lyophilization and refrigeration storage. Initially, 212 colonies were isolated from mandacaru fruit, and 34 were preliminarily identified as LAB. Thirteen isolates identified by 16S-rRNA sequencing as Pediococcus pentosaceus were negative for DNase, gelatinase, hemolytic, and biogenic amine production. The selected isolates showed proteolytic activity, diacetyl and exopolysaccharide production, and good tolerance to different NaCl concentrations while having low cellular hydrophobicity and antagonistic activity against pathogens. The survival of isolates sharply decreased after 3 h of exposure to pH 2 and had a good tolerance to 1 % bile salt. A principal component analysis selected P. pentosaceus 57 as the most promising isolate based on the examined technological and probiotic-related physiological properties. This isolate was lyophilized with mandacaru fruit and stored under refrigeration for 90 days. P. pentosaceus 57 lyophilized with mandacaru fruit had high viable cell counts (9.69 ± 0.03 log CFU/mL) and >50 % of physiologically active cells at 90 days of refrigeration storage. The results indicate that mandacaru fruit is a source of P. pentosaceus with aptitudes to be explored as potential probiotic and technological characteristics of interest for the food industry, besides being a good candidate for use in lyophilization processes and refrigeration storage of LAB due to its cryoprotective effects.

Technological and Enzymatic Characterization of Autochthonous Lactic Acid Bacteria Isolated from Viili Natural Starters.

Viili, a Finnish ropy fermented milk, is traditionally manufactured through spontaneous fermentation, by mesophilic lactic acid bacteria and yeast-like fungi, or back-slopping. This study evaluated four natural viili starters as sources of lactic acid bacteria for dairy production. Back-slopping activation of the studied viili samples was monitored through pH and titratable acidity measurements and enumeration of mesophilic lactic acid bacteria. Sixty lactic acid bacteria isolates were collected, molecularly identified, and assayed for acidification performance, enzymatic activities, production of exopolysaccharides (EPSs), presence of the histidine decarboxylase (hdcA) gene of Gram-positive bacteria, and production of bacteriocins. A neat predominance of Lactococcus lactis emerged among the isolates, followed by Enterococcus faecalis, Enterococcus faecium, Enterococcus durans, Enterococcus lactis, and Lactococcus cremoris. Most isolates exhibited proteolytic activity, whereas only a few enterococci showed lipase activity. Five isolates identified as L. cremoris, L. lactis, and E. faecalis showed a good acidification performance. Most of the isolates tested positive for leucine arylamidase, whereas only one E. durans and two L. lactis isolates were positive for valine arylamidase. A few isolates also showed a positive reaction for beta-galactosidase and alpha- and beta-glucosidase. None of the isolates produced EPSs or bacteriocins. The hdcA gene was detected in five isolates identified as L. lactis and E. faecium. A few L. cremoris and L. lactis isolates for potential use as starter or adjunct cultures for dairy processing were finally identified.

Evaluation of Probiotic Bacteria Isolated from Indigenous Honeybee Species of Pakistan

The honey bee gut is inhabited by many useful bacteria such as Lactic Acid Bacteria (LAB). These LAB possess active probiotic properties that are beneficial to other animals and even humans. The LAB is declared as generally recognized as safe (GRAS). The LAB is non-pathogenic and produces different metabolites having antimicrobial potential. In the current study LAB species isolated from four honey bee species (Apis melifera, Apis dorsata, Apis cerana, and Apis florae) prevalent in Pakistan were identified and investigated for their probiotic potential. The strains were identified using morphological, biochemical, and molecular techniques as genus Lactobacillus and Lactococcus. Current results confirmed that the honey bee gut has a rich source of lactic acid bacteria. Isolated strains were further evaluated for their ability to resist physiological stresses encountered in the human gastrointestinal tract. Safety testing of the isolates such as hemolytic assay revealed that these isolates have γ-hemolytic activity and were adjudged to be safe. Hence the present study concluded that honey bee gut is thesource of potential probiotic bacteria and can be used in pharmaceuticals, fermented foods, and nutraceuticals and may be used as a natural food preservative

Recycling of animal protein wastes in the formulation of feed for Labeo rohita and Mystus vittatus—a comparative evaluation

Lactic acid bacteria (LAB) are key players in the fermentation of organic wastes and their recycling as feedstuff for fish. Whey, a common dairy byproduct in India, is a cheap source of LAB and can be used to ferment animal byproducts. An experimental study was designed to explore whether the whey fermented animal protein blend (WFAPB) could be used as a fishmeal replacer in the formulation of feed for both stomach-less carp fish Labeo rohita and stomach-bearing catfish Mystus vittatus. Experiments were performed with five isoproteinous, isolipidous, and isoenergetic feeds with WFAPB replacing fishmeal (FM) by 0% (T1), 25% (T2), 50% (T3), 75% (T4), and 100% (T5). Fifteen days of laboratory experiments with these experimental feeds revealed that more than 50% FM replacement level could result in excess postprandial absorption (6 h) of some essential and non-essential amino acids in the plasma of both fish. The postprandial absorption was more in M. vittatus than L. rohita. Ninety-day experiments were conducted in outdoor cement vats to measure growths and deposition of amino acids (AA) in muscle. Regression analysis was performed to find the optimal FM replacement based on four growth parameters and fifteen AA deposition in muscle. A two-phase fuzzy methodology was used to obtain Pareto-optimal replacement levels for each fish. The results demonstrated that FM replacement levels were 7.63% and 36.79% respectively for L. rohita and M. vittatus when only four growth parameters were considered. However, based on the FM replacement level that maximized deposition of 15 amino acids and growth parameters, it was found that 12.23% and 40.02% replacement of FM by the WFAPB was ideal respectively for L. rohita and M. vittatus. The results revealed that only a fraction of both essential and non-essential amino acids absorbed in plasma could be converted into protein and deposited as bound amino acids in the muscle. It is concluded that fermentation by whey is an inexpensive, easily available, and environmentally sustainable technique to recycle animal protein in the formulation of feed for fish, and the stomach-bearing carnivorous fish are more efficient in utilizing fermented animal protein blend than the stomach-less carps.

Identification of safe putative probiotics from various food products.

The objective of this study was to isolate, identify, and assess the safety and functionality in vitro of putative probiotic bacterial strains. Isolation procedures were based on standard methods using elective and selective media. The isolates were identified by comparative 16S rRNA sequencing analysis while their safety was determined according to the safety tests recommended by the FAO/WHO such as antibiotic resistance, hemolysin, and biogenic amine production. Most of the isolates did not pass the in vitro safety tests; therefore, only Lactiplantibacillus plantarum (from ant intestine and cheese), Lacticaseibacillus paracasei (from goat milk and kimchi), Enterococcus faecium (from chili doenjang and vegetables with kimchi ingredients), Limosilactobacillus fermentum (from saliva), and Companilactobacillus alimentarius (from kimchi) were identified and selected for further studies. The isolates were further differentiated by rep-PCR and identified to the strain level by genotypic (16S rRNA) and phenotypic (Gen III) approaches. Subsequently, the strain tolerance to acid and bile was evaluated resulting in good viability after simulated gastrointestinal tract passage. Adhesion to mucin in vitro and the presence of mub, mapA, and ef-tu genes confirmed the adhesive potential of the strains and the results of features associated with adhesion such as hydrophobicity and zeta potential extended the insights. This study reflects the importance of fermented and non-fermented food products as a promising source of lactic acid bacteria with potential probiotic properties. Additionally, it aims to highlight the challenges associated with the selection of safe strains, which often fail in the in vitro tests, thus hindering the possibilities of "uncovering" novel and safe probiotic strains.

Utilization of Inulin from Mangrove Apple and Pineapple Juice as Prebiotic Drink to Recovery Covid-19 Patients

Amidst the COVID-19 pandemic, some individuals have turned to functional foods in an effort to bolster their immune systems. One such functional option is prebiotic drinks. These beverages are crafted from fermented sugars, which serve as a carbon source for lactic acid bacteria. To enhance their functional properties, prebiotic drinks often incorporate inulin—a type of prebiotic. Traditionally, these drinks are milk-based, but for those who cannot tolerate dairy, alternatives have emerged. For instance, pineapple-based prebiotic drinks enriched with inulin from mangrove apples have gained popularity. The process involves extracting inulin from mangrove apples and combining it with pineapple to create a probiotic drink. The resulting beverage derives its sweetness from the natural sugars found in pineapples and mangrove apples. Pineapple contains approximately 2.32% glucose, 1.42% fructose, and 7.89% sucrose, while mangrove apples boast 5.08% inulin, 9.67% soluble dietary fiber, and 0.66% FOS. These sugars serve as nourishment for lactic acid bacteria, ultimately stimulating the production of IgG and IgM antibodies. In summary, the combination of inulin-rich mangrove apples and pineapple’s total soluble solids can contribute to fortifying the body’s immune system during the COVID-19 pandemic.

Changes in bacterial composition and metabolite profiles during kimchi fermentation with different garlic varieties

Garlic, a key ingredient in kimchi, is an indispensable source of lactic acid bacteria, which are essential for fermentation. This study explored the effects of various garlic varieties on kimchi fermentation, focusing on changes in microbial communities and metabolite profiles. We observed that the type of garlic used did not significantly alter the microbial community. However, the presence of garlic itself made a significant difference. Specifically, kimchi with garlic showed higher abundance of Leuconostoc and Weissella, which are bacteria primarily responsible for kimchi fermentation. Additionally, kimchi containing garlic had increased levels of mannitol and fructose, which significantly influence taste; however, lactic acid and putrescine levels were decreased. Therefore, the addition of garlic directly contributes to the flavor profile of kimchi. Sixty-two metabolites were identified using gas chromatography and mass spectrometry. The variety of garlic added influenced the metabolite profiles of kimchi, particularly in the later stages of fermentation. These profiles were categorized based on the garlic's origin, whether from southern or northern ecotypes (R2X = 0.933, R2Y = 0.986, Q2 = 0.878). These findings confirm that both the presence and the variety of garlic significantly impact the microbial ecology and metabolites during kimchi fermentation, underscoring its essential role in the process.

Potential of Animal Excreta as a Source of Probiotic Lactic Acid Bacteria for Aflatoxin B1 Detoxification by the Surface Binding Mechanism

Aflatoxins (AFs) are the most potent and ubiquitously found mycotoxins, capable of causing contamination in agricultural products. Aflatoxin B1 (AFB1) is the most toxic and primarily produced Aflatoxin and will be a real threat to the safety of food and feeds. The current study searched for the potential of Lactic acid bacteria (LAB) isolated from animal excreta for AFB1 mitigation. Three LAB out of 56 isolates were found to exhibit more than 50% sorbent action with AFB1 in phosphate-buffered saline (PBS) and were identified as Lactococcuslactis strain CF_6 (OP183481) (65.38%), Lacticaseibacillus casei strain CW_3 (OP183482)(52.63%) and Lactobacillus acidophilus strain CE_4 (OP183483)(63.13%). More than 60% of the total AFB1 removal was observed in 2 hr of incubation, and maximum sorbent action was found at a pH 6-7 range at 37oC for 24 hours. In the Scanning Electron Microscope (SEM) analysis, heat-killed cells showed a significant increase in cell surface binding area, which improved the surface binding for all isolates except L. casei strain CW_3; however, it proves that LAB surface binding is strain-specific rather than heat treatment. Moreover, the rise in AFB1 concentration improved the rate of the sorbent action but did not observe any substantial changes in total AFB1 detoxification. So, it is concluded that the animal excreta may be a versatile source of probiotic LAB for AFB1 detoxification by surface binding.

Isolation and screening of lactic acid bacteria and yeast starters from ersho (traditional Ethiopian sourdoughs) and evaluation of their role in bread production

SummaryErsho is a well‐known as a source of lactic acid bacteria (LAB) and yeasts in Ethiopia. However, the utilisation of yeasts and LAB for bread production has not been previously studied. Therefore, the objective of the current study was to screen yeasts and LAB from ersho samples and determination of their bread production efficiency using a laboratory based experiment. Three LAB (1A, 13E, and 55A) and three yeasts (4A, 14D, and 54A) were screened and used to develop sourdough starters (4A13E, 14D55A, 54A1A, and 54A13E). The properties of BS4 bread made with 54A13E sourdough starter had more improved. The protein, TVC (total viable count), TFC (total fungal count), and shelf life of control bread were 13.38%, 3.1, 2.1 log cfu g−1, and 4 days, respectively. The protein, TVC, TFC, and shelf life of BS4 bread were 15.52%, 2.0, 1.4 log cfu g−1, and 7 days, respectively. Colour, texture, taste, odour, and overall acceptability mean scores of control bread were 6.6, 6.7, 6.9, 7.1, and 6.9, respectively. Colour, texture, taste, odour, and overall acceptability mean scores of BS4 bread were 8.6, 8.6, 6.4, 8.1, and 7.7, respectively. The results suggest that the use of sourdough starter in place of bakery yeast would be preferable when baking bread.

Functional and Probiotic Characterization of Newly Isolated Strains from Infant Feces and Breast Milk

Infant feces and breast milk are sources of lactic acid bacteria with interesting functional and technological properties. Therefore, we focused on the isolation and characterization of new potential probiotic strains from infant feces and breast milk. Nine strains were identified based on 16S rRNA sequences of Lacticaseibacillus rhamnosus, Limosilactobacillus reuteri, and Lactobacillus gasseri. Subsequently, these isolates were evaluated for their safety (antibiotic resistance, hemolytic, and enzymatic activity) and functional properties (gastrointestinal condition tolerance, hydrophobicity, auto-aggregation, adhesion to Caco-2/HT-29 cell lines, antimicrobial and antioxidant properties, and the production of exopolysaccharides). All the isolates were non-hemolytic and resistant to streptomycin, kanamycin, and vancomycin. They also demonstrated antimicrobial activity against five selected pathogens (Staphylococcus aureus, Bacillus cereus, Escherichia coli, Salmonella sp., and Enterococcus faecalis) and the production of exopolysaccharides. Isolates Lacticaseibacillus rhamnosus S1F and S6C together with Lactobacillus gasseri M8C showed the highest ability to survive 3.0 g/L of bile salts and a good adhesion property, which is important for gastrointestinal tract (GIT) colonization or the inhibition of pathogens. Following in vivo characterization, three strains S1F and S6C from infant feces, and M6C from breast milk, showed probiotic properties with potential applications in the food industry.

A new bacteriocin- like-inhibitory substance from Egyptian dairy products isolated from Enterococcus faecium with anti-SARS-CoV-2 activity

Bacteriocins generated by lactic acid bacteria have increased in popularity due to their safety and versatility of application. Dairy products are rich sources of lactic acid bacteria. This work screened 31 Egyptian dairy product isolates for antimicrobial activity. Two bacteriocinogenic isolates, Enterococcus faecium CH019 and Enterococcus faecium CM019, were identified using molecular techniques. The production conditions of Bacteriocin-like inhibitory substances (BLIS) were optimized. The physical and chemical properties of the Enterococcus faecium CM019 bacteriocin-like compound were analyzed. Cytotoxic and antiviral properties against SARS-CoV-2 were evaluated. Enterococcus faecium CM019 produces bacteriocin-like substances most effectively in MRS broth with a pH of 6.5 and incubation temperature of 35 °C for 24 h. In the presence of surfactant, solvent, and high temperature, the bacteriocin-like substance activity was persistent, but it was eliminated by proteinase K, trypsin, and lipase. The BLIS proved effective against Listeria monocytogenes and Staphylococcus aureus. The CC50 of the bacteriocin-like compound was 108.3 µg/ml, while the IC50 against SARS-CoV-2 was 22.9 µg/ml. With an acceptable toxicity limit, BLIS generated by Enterococcus faecium CM019 isolated from Egyptian dairy products has a broad antimicrobial spectrum and can be employed as an antibacterial agent against Gram-positive bacteria and anti-SARS-CoV-2.

Agave bagasse cookies as a carbon source for lactic acid bacteria

AbstractCurrently, the Agave genus has a high economic importance because due to the products that can be obtained from these plants, with alcoholic beverage production being the most common use. The principal storage carbohydrates of agave are fructans. In this study, the utilization of Agave salmiana (green agave) and Agave atrovirens (ashy agave) bagasse cookies as a carbon source by lactic acid‐producing bacteria (LAB), as well as the acceptability of cookies by consumers was evaluated. The cookies were manufactured and digested in vitro, and fermentation by LAB was performed to evaluate pH changes, bacterial growth, and relative carbohydrate intake. The results showed that the bacteria assimilated the digested agave cookies as a carbon source, and there was no significant difference in the pH of both agave bagasse and the growth of Lacticaseibacillus casei. The highest bacterial growth of the L. lactis was observed at 12 h with green bagasse cookies. The results obtained in the present study demonstrate the potential of agave bagasse to be used as functional food ingredients.

Comparison of Activity of Commercial Protective Cultures and Thermophilic Lactic Acid Bacteria against Listeria monocytogenes: A New Perspective to Improve the Safety of Sardinian PDO Cheeses.

Listeria monocytogenes contamination that occurs during and post-processing of dairy products is a serious concern for consumers, and bioprotective cultures can be applied to control the growth of the pathogen in sheep milk cheeses. However, to respect specifications provided for protected designation of origin (PDO) cheeses, only autochthonous microorganisms can be used as bioprotective cultures in these products. This in vitro study aimed to evaluate thermophilic lactic acid bacteria (LAB) isolated from sheep milk as bio-preservative agents to control L. monocytogenes growth in PDO cheese. Results were compared with those obtained with a commercial protective culture (cPC) composed of a Lactiplantibacillus plantarum bacteriocin producer designed to inhibit L. monocytogenes growth in cheese. The in vitro antilisterial activities of n.74 autochthonous LAB and a cPC were tested against 51 L. monocytogenes strains using an agar well diffusion assay. In addition, 16S rRNA sequencing of LAB isolates with antilisterial activity was conducted and strains of Lactobacillus helveticus, Lactobacillus delbrueckii subsp. indicus, Lactobacillus delbrueckii subsp. sunkii, Lactobacillus delbrueckii subsp. lactis and Enterococcus faecalis were identified. In this study, 33.6% (74/220) bacterial strains isolated from milk had characteristics compatible with thermophilic LAB, of which 17.6% (13/74) had in vitro antilisterial activity. These results demonstrate that raw sheep milk can be considered an important source of autochthonous thermophilic LAB that can be employed as protective cultures during the manufacturing of Sardinian PDO cheeses to improve their food safety. The use of bioprotective cultures should be seen as an additional procedure useful to improve cheese safety along with the correct application of good hygienic practices during manufacturing and the post-processing stages.

Brazilian Table Olives: A Source of Lactic Acid Bacteria with Antimycotoxigenic and Antifungal Activity.

Food and feed contamination by fungi, especially by toxigenic ones, is a global concern because it can pose serious health problems when the production of mycotoxins is involved. Lactic acid bacteria (LAB), well-known for fermenting foods, have been gaining attention for their antifungal and anti-mycotoxin properties. This work tested 14 LAB strains isolated from naturally fermented Brazilian table olives for growth inhibition of Aspergillus flavus, Aspergillus carbonarius, Penicillium nordicum, and Penicillium expansum. The strains Lacticaseibacillus paracasei subsp. paracasei CCMA 1764, Levilactobacillus brevis CCMA 1762, and Lactiplantibacillus pentosus CCMA 1768 showed the strongest antifungal activity, being more active against P. expansum. Aflatoxin B1 (AFB1), ochratoxin A (OTA), and patulin (PAT) production was reduced essentially by mycelia growth inhibition. The main organic acids detected in the cell free supernatant (CFS) were lactic and acetic acids. Tested LAB exhibited adsorption capacity against AFB1 (48-51%), OTA (28-33%), and PAT (23-24%). AFB1 was converted into aflatoxin B2a (AFB2a) by lactic and acetic acids produced by the strain CCMA 1764. A similar conversion was observed in solutions of these organic acids (0.1 M). These findings demonstrate the potential of isolated LAB strains as natural agents to control toxigenic fungi and their mycotoxins in fermented products, such as table olives.

Prevalence of macrolide-lincosamide-streptogramin resistant lactic acid bacteria isolated from food samples.

Lactic acid bacteria (LAB) being a reservoir of antibiotic resistance genes, tend to disseminate antibiotic resistance that possibly pose a threat to human and animal health. Therefore, the study focuses on the prevalence of macrolide-lincosamide-streptogramin- (MLS) resistance among LAB isolated from various food samples. Diverse phenotypic and genotypic MLS resistance were determined among the LAB species (n = 146) isolated from fermented food products (n = 6) and intestine of food-producing animals (n = 4). Double disc, triple disc diffusion and standard minimum inhibitory concentration (MIC) tests were evaluated for phenotypic MLS resistance. Specific primers for MLS resistance genes were used for the evaluation of genotypic MLS resistance and gene expressions using total RNA of each isolate at different antibiotic concentrations. The isolates identified are Levilactobacillus brevis (n = 1), Enterococcus hirae (n = 1), Limosilactobacillus fermentum (n = 2), Pediococcus acidilactici (n = 3), Enterococcus faecalis (n = 1). The MIC tests along with induction studies displayed cMLSb, L phenotype, M phenotype, KH phenotype, I phenotype resistance among MLS antibiotics. Genotypic evaluation tests revealed the presence of ermB, mefA/E, msrA/B and msrC genes. Also, gene expression studies displayed increased level of gene expression to the twofold increased antibiotic concentrations. In the view of global health concern, this study identified that food samples and food-producing animals represent source of antibiotic resistant LAB that can disseminate resistance through food chain. This suggests the implementation of awareness in the use of antibiotics as growth promoters and judicious use of antibiotics in veterinary sectors in order to prevent the spread of antibiotic resistance.