Lactic Acid Bacteria Strains Research Articles

Pistacia terebinthus MEYVESİ: GIDA BOZULMASINI ÖNLEMEK İÇİN BİR ALTERNATİF

The aim of this work was to investigate the usage possibilities of P. terebinthus fruit, which has a limited usage area, in the food industry. Antimicrobial activity of hexane extract obtained from P. terebinthus fruits from Adıyaman (Turkey) was determined by disc diffusion and micro-dilution assays against test microorganisms. In addition, the antibacterial activity of the extract on Escherichia coli O157:H7, one of the most important food-borne pathogens, was determined by viable cell count using a macro-dilution assay. The potential for use of the extract with probiotic candidate lactic acid bacteria (LAB) strains was also investigated. The hexane extract presented antimicrobial activity against all the tested microorganisms, with good inhibition zone diameters between 10.51 mm and 18.02 mm. MIC and MFC or MBC values of P. terebinthus fruit extract were determined as 5-80 µg/µL against all tested microorganisms. The lowest MIC and MBC values (5 µg/µL) of the extract were obtained against E. coli O157:H7. Macro-dilution assay results indicated that the P. terebinthus extract at various concentrations (5-10-20 mg/mL) inhibited the growth of E. coli O157:H7 more than the control group after all of the incubation hours. No viable E. coli O157:H7 cells were detected after 48 hours at all concentrations. The extract showed low antimicrobial activity, and relatively high bactericidal concentration on probiotic candidate LAB strains. This shows that P. terebinthus hexane extract at appropriate concentrations can be used together with probiotic strains as a natural preservative and biopreservative to prevent food spoilage and extend shelf life.

Impact of lactic acid bacteria strains against Listeria monocytogenes biofilms on various food-contact surfaces.

Listeria monocytogenes is one of the most important foodborne pathogens, causing listeriosis, a disease characterized by high mortality rates. This microorganism, commonly found in food production environments and transmitted to humans by consuming contaminated food, has the ability to form biofilms by attaching to a wide variety of surfaces. Traditional hygiene and sanitation procedures are not effective enough to completely remove L. monocytogenes biofilms from food-contact surfaces, which makes them a persistent threat to food safety. Alternative approaches to combating Listeria biofilms are needed, and the use of lactic acid bacteria (LAB) and their antimicrobial compounds shows promise. The present study investigated the effect of Lactobacillus strains, previously isolated from various foods and known to possess antimicrobial properties, on the biofilm formation of L. monocytogenes on three different food-contact surfaces. To study L. monocytogenes IVb ATCC 19115 type, culture was preferred to represent serotype IVb, which is responsible for the vast majority of listeriosis cases. The results demonstrated that cell-free supernatants (CFSs) of LAB strains inhibited biofilm formation by up to 51.57% on polystyrene, 60.96% on stainless steel, and 30.99% on glass surfaces. Moreover, these CFSs were effective in eradicating mature biofilms, with reductions of up to 78.86% on polystyrene, 73.12% on stainless steel, and 72.63% on glass surfaces. The strong inhibition rates of one strain of L. curvatus (P3X) and two strains of L. sakei (8.P1, 28.P2) used in the present study imply that they may provide an alternate technique for managing Listeria biofilms in food production environments.

Effect of lactic acid bacteria fermentation on bioactive components of black rice bran (Oryza sativa L.) with different milling fractions

This study investigated the impact of fermentation using lactic acid bacteria (LAB) on the bioactive compounds and antioxidant properties of black rice bran (BRB) with varying fractions of milling. The BRB was divided into four fractions through the milling process, resulting in the outermost layer BRB-1 and the innermost layer BRB-4, and each fraction accounted for 4.14 %, 4.38 %, 3.50 %, and 3.31 % (W/W) of the whole grain, respectively. The suitable Lactobacillus plantarum for fermentation of BRB was selected from nine different LAB strains. Additionally, the changes in pH and total titratable acidity (TTA) were monitored throughout the fermentation process. Notably, the fermentation process with LAB significantly increased the total phenolic content in three milled fractions of BRB, while the total flavonoid and anthocyanin contents exhibited opposite trends. The in vitro antioxidant capacity assessment revealed that the antioxidant activity of the four fractions of BRB was enhanced by 15.94 %–98.69 % after fermentation. Additionally, the high-performance liquid chromatography (HPLC) analysis demonstrated a substantial increase in the levels of certain phenolic acids and a notable decrease in the levels of individual anthocyanins as a result of fermentation. These findings offer momentous insights regarding the potential application of fermentation techniques for enhancing the utilization of BRB.

СОВРЕМЕННЫЕ ЗАДАЧИ НАУЧНЫХ ИССЛЕДОВАНИЙ В ОБЛАСТИ ВИНОДЕЛИЯ

The article presents the results of research activities for 2023 of the Federal State Budget Scientific Institution All-Russian National Research Institute of Viticulture and Winemaking Magarach of the RAS in the field of winemaking, carried out in accordance with the Program of Fundamental Scientific Research in the Russian Federation for the long term (2021-2030). The methodology of wine quality management with ecostatus has been created, aimed at revealing the individual characteristics of wines caused by natural factors and reducing the risks of negative effects on humans. Promising yeast strains have been identified: Steinberg, Champanskaya G-14, ShM-30, Novocimlyanskaya 3 with a description of their taxonomic affiliation, morphological and physiological-biochemical properties. Two strains of O. oeni active acid-reducing agents are recommended for practical use. The application of technology for the production of young sparkling wines of Crimean autochthonous grape The article presents the results of research activities for 2023 of the Federal State Budget Scientific Institution All-Russian National Research Institute of Viticulture and Winemaking Magarach of the RAS in the field of winemaking, carried out in accordance with the Program of Fundamental Scientific Research in the Russian Federation for the long term (2021-2030). The methodology of wine quality management with ecostatus has been created, aimed at revealing the individual characteristics of wines caused by natural factors and reducing the risks of negative effects on humans. Promising yeast strains have been identified: Steinberg, Champanskaya G-14, ShM-30, Novocimlyanskaya 3 with a description of their taxonomic affiliation, morphological and physiological-biochemical properties. Two strains of O. oeni active acid-reducing agents are recommended for practical use. The application of technology for the production of young sparkling wines of Crimean autochthonous grape varieties: Kokur belyi, Sary Pandas, Soldaiya and Kefesiya is justified. The system of criteria indicators for assessing the quality of grapes for the production of high-quality cognac distillates and cognacs is substantiated. A working collection of 63 natural strains of lactic acid bacteria has been formed. The optimal technological factors of the process of single-stage extraction by infusing with a food water-alcohol solution of green grape shoots of the Vitis vinifera, Vitis abrusca species have been established, allowing to increase the yield of total polyphenols by at least 2.6 times for the production of functional products. The most optimal technological modes of cold treatment of dry and fortified wine materials have been established to substantiate the constructive solution of an energy-saving installation for the purpose of cold treatment of wine materials based on the study of the main factors affecting the mass transfer process of potassium bitartrate crystallization. The obtained results of research work contribute to improving the quality of domestic wine products and expanding its production, including winemaking with ecological and geographical statuses, the production of domestic cognac and grape processing products of a functional orientation. The introduction of scientific developments into production will increase the competitiveness of domestic wine products, accelerate import substitution and ensure the country's food independence.

Characterization of phyllosphere endophytic lactic acid bacteria reveals a potential novel route to enhance silage fermentation quality.

The naturally attached phyllosphere microbiota play a crucial role in plant-derived fermentation, but the structure and function of phyllosphere endophytes remain largely unidentified. Here, we reveal the diversity, specificity, and functionality of phyllosphere endophytes in alfalfa (Medicago sativa L.) through combining typical microbial culture, high-throughput sequencing, and genomic comparative analysis. In comparison to phyllosphere bacteria (PB), the fermentation of alfalfa solely with endophytes (EN) enhances the fermentation characteristics, primarily due to the dominance of specific lactic acid bacteria (LAB) such as Lactiplantibacillus, Weissella, and Pediococcus. The inoculant with selected endophytic LAB strains also enhances the fermentation quality compared to epiphytic LAB treatment. Especially, one key endophytic LAB named Pediococcus pentosaceus EN5 shows enrichment of genes related to the mannose phosphotransferase system (Man-PTS) and carbohydrate-metabolizing enzymes and higher utilization of carbohydrates. Representing phyllosphere, endophytic LAB shows great potential of promoting ensiling and provides a novel direction for developing microbial inoculant.

Protective effects of oral administration of lactic acid bacteria strains against methylmercury-induced intestinal toxicity in a murine model

The utilization of lactic acid bacteria has been proposed to mitigate the burden of heavy metal exposure through processes probably involving chelation and reduced metal bioaccessibility. We evaluated the effects of daily intake of two strains of lactobacilli (Lactobacillus intestinalis LE1 or Lactobacillus johnsonii LE2) on intestinal toxicity during methylmercury (MeHg) exposure through drinking water (5 mg/L) for two months in mice. MeHg exposure resulted in inflammation and oxidative stress at the colon, as well as an increase in intestinal permeability accompanied by decreased fecal short-chain fatty acids (SCFA). The administration of the strains resulted in a differential protective effect that, based on their chelation capacity, supported the existence of additional mechanisms of action besides chelation. Both strains reduced IL-1β levels and oxidative stress, while LE1 lowered TNF-α, diminished MeHg-induced mucus over-secretion triggered by the IL-4/IL-13/STAT6 pathway, reduced intestinal permeability, and ameliorated inflammation and oxidative stress, probably by acting on the Keap1/Nrf2/ARE pathway. Administration of LE1 partially restored SCFA contents, which could be partly responsible for the positive effects of this strain in alleviating MeHg toxicity. These results demonstrate that lactobacilli strains can be useful tools in reducing the intestinal toxicity of MeHg, the main mercurial form conveyed by food.

A circular economy approach: A new formulation based on a lemon peel medium activated with lactobacilli for sustainable control of post-harvest fungal rots in fresh citrus fruit

The aim of the study was to develop an effective bio-formulation for preventing post-harvest fungal rots in fresh citrus fruit through a multi-step process that includes isolation and characterization of lactic acid bacteria (LABs) from citrus fruit peel, selection of LAB strains with high antifungal activity, chemical characterization of cell free supernatants (CFS), formulation of a lemon peel powdery-based medium (LM) activated with LAB fermentates, chemical characterization of fermented LM, and evaluation of the efficacy of the new bio-formulation against blue mold. Thirteen LABs were recovered from the rind of citrus fruit and identified by the peptide mass fingerprinting method. The antifungal activity of LABs, isolated from citrus fruit, as well as cell free supernatants (CFSs), obtained from their liquid cultures, was tested against diverse plant pathogenic fungi and oomycetes, using the dual-culture overlay and the diffusion agar assays, respectively. Two isolates designated as N3B2 and M2B2, both identified as Lactiplantibacillus plantarum, were selected among the others for their relevant antifungal activity. Both isolates showed a broad spectrum antagonistic activity comprising also major postharvest pathogens of citrus fruit, such as Penicillium digitatum and P. italicum, the causal agents of green and blue moulds, respectively, Alternaria alternata, Colletotrichum gloeosporioides, C. karsti, Phytophthora citrophthora and Ph. nicotianae. The N3B2 and M2B2 isolates were used as starter cultures to ferment a lemon peel powder medium enriched with a nutrient water solution (LM). The two formulations obtained by fermenting LM with the N3B2 and M2B2 isolates showed a strong in vitro inhibitory activity on the same broad range of pathogens used in the preliminary screening of LABs. Moreover, the two LM-based formulations reduced the severity of blue mold infection and inhibited the sporulation of P. italicum on artificially inoculated lemon fruit. The chemical analysis of LM-based bioformulations revealed their antifungal activity was very probably due to the LAB-derived acidic components, including lactic, acetic, DL-3-phenyllactic, 3-4-dihydroxyhydrocinnamic, salicylic acid vanillic acids. These innovative LM-based bioformulations activated with LAB-derived antifungal compounds will be exploited as edible and biodegradable fruit coatings to prolong the shelf-life and prevent post-harvest rots of fresh citrus fruit.

Oral Administration of Alcohol-Tolerant Lactic Acid Bacteria Alleviates Blood Alcohol Concentration and Ethanol-Induced Liver Damage in Rodents.

Excessive alcohol consumption can have serious negative consequences on health, including addiction, liver damage, and other long-term effects. The causes of hangovers include dehydration, alcohol and alcohol metabolite toxicity, and nutrient deficiency due to absorption disorders. Additionally, alcohol consumption can slow reaction times, making it more difficult to rapidly respond to situations that require quick thinking. Exposure to a large amount of ethanol can also negatively affect a person's righting reflex and balance. In this study, we evaluated the potential of lactic acid bacteria (LAB) to alleviate alcohol-induced effects and behavioral responses. Two LAB strains isolated from kimchi, Levilactobacillus brevis WiKim0168 and Leuconostoc mesenteroides WiKim0172, were selected for their ethanol tolerance and potential to alleviate hangover symptoms. Enzyme activity assays for alcohol dehydrogenase (ADH) and acetaldehyde dehydrogenase (ALDH) were then conducted to evaluate the role of these bacteria in alcohol metabolism. Through in vitro and in vivo studies, these strains were assessed for their ability to reduce blood alcohol concentrations and protect against alcohol-induced liver damage. The results indicated that these LAB strains possess significant ethanol tolerance and elevate ADH and ALDH activities. LAB administration remarkably reduced blood alcohol levels in rats after excessive alcohol consumption. Moreover, the LAB strains showed hepatoprotective effects and enhanced behavioral outcomes, highlighting their potential as probiotics for counteracting the adverse effects of alcohol consumption. These findings support the development of functional foods incorporating LAB strains that can mediate behavioral improvements following alcohol intake.

Efficient Screening and Enhanced Exopolysaccharide Production by Functional Lactic Acid Bacteria (LAB) in Lactose Supplemented Media

Exopolysaccharides (EPS) produced by lactic acid bacteria (LAB) can be considered as natural biological thickeners that have attracted considerable attention in the food industry. This study aimed to evaluate and select potentially EPS-producing strains LAB and to assess the influence of carbon source and aeration on EPS production. Nine LAB strains were assessed as potential EPS producers, and Rahnella aquatilis ATCC 55046 was employed as the positive control strain for EPS. The compaction test and the observation of viscous colonies in a solid medium did not yield sufficient evidence for the presence of EPS. The assessment of capsules through staining provided evidence of EPS presence only for Rahnella aquatilis ATCC 55046. The EPS yield was subsequently assessed in De-Man Rogosa and Sharpe (MRS) broth medium supplemented with 2% (w/w) fructose (MRS-f) or lactose (MRS-l), as well as in whey (Whey) and whey supplemented with 2% (w/w) lactose (Whey-l). The EPS production in the various culture media under study ranged from 194 to 1,187 mg of EPS/g of polymer dry mass (PDM). These results suggest that the culture medium and carbon sources had an impact on the EPS production of the different strains. Bifidobacterium animalisBb12 achieved the highest EPS production in MRS-f. In the case of MRS-l, the control strain recorded the highest EPS value, along with Lactobacillus acidophilus LAC-1. Regarding Whey, Lentilactobacillus Kefir NCFB 2753 exhibited the highest EPS production, while in Whey-l, Lacticaseibacillus paracasei LCS-1 emerged as the top performer in terms of EPS production. This suggests that certain strains exhibit potential for use in the production of novel fermented EPS products, whether dairy or non-dairy.

Growth Control of Listeria monocytogenes in Raw Sausage via Bacteriocin-Producing Leuconostoc carnosum DH25.

The current study addresses the critical issue of Listeria monocytogenes growth in raw sausage/meat products leading to human infections, most commonly listeriosis, which is known for its high fatality rate. This research focuses on the isolation, identification, and screening of lactic acid bacteria from various meat and fish products in Switzerland. In total, 274 lactic acid bacteria strains were isolated from 30 different products and were screened for their ability to inhibit Listeria monocytogenes growth, with 51 isolates demonstrating anti-Listeria activity at 8 °C, 15 °C, 25 °C, and 37 °C. Further experiments, using a meat model and a raw sausage challenge test, demonstrated that Leuconostoc carnosum DH25 significantly inhibited Listeria monocytogenes growth during the ripening and storage of the tested meat/sausage. This inhibitory effect was found to be attributed to the bacteriocins produced by Leuconostoc carnosum DH25 rather than factors like pH or water activity. The stability of the anti-Listeria substances was examined, revealing their resistance to temperature and pH changes, making Leuconostoc carnosum DH25 a promising protective culture for raw sausages. The genome sequencing of this strain confirms its safety, with no antibiotic resistance genes or virulence factors detected, and reveals the presence of the structural genes for the production of the bacteriocin LeucocinB-Ta11a. This study underscores the potential of LAB strains and their bacteriocins as effective tools for enhancing food safety and preventing Listeria monocytogenes growth in meat products, offering valuable insights into biocontrol strategies in the food industry.

Sodium carboxymethyl celluloses as a cryoprotectant for survival improvement of lactic acid bacterial strains subjected to freeze-drying

This study investigated the possibility of sodium carboxymethyl celluloses (Na-CMC) in protecting the viability of lactic acid bacteria (LAB) against freeze-drying stress. 1 % concentration of Na-CMC with a 0.7 substitution degree and viscosity of 1500 to 3100 (MPa.s) was found to protect Lactobacillus delbrueckii subsp. bulgaricus CICC 6098 best, giving a high survival rate of 23.19 ± 0.88 %, high key enzymatic activities, and 28-day storage stability. Additionally, Na-CMC as cryoprotectant provided good protection for other 7 lactic acid bacterial strains subjected to freeze-drying. The highest survival rate was 48.79 ± 0.20 U/mg for β-GAL, 2.75 ± 0.15 U/mg for Na+-K+-ATPase, and 2.73 ± 0.41 U/mg for Ca2+-Mg2+-ATPase as 48.48 ± 0.46 % for freeze-dried Pediococcus pentosaceus CICC 22228. It was Interesting to note that the presence of Na-CMC reduced the freezable water content of the lyophilized powders containing the tested strains through its hydroxyl group, and supplied micro-holes and fibers for protecting the integrated structure of LAB cell membrane and wall against the freezing damage. It is clear that addition of Na-CMC should be promising as a new cryoprotective agent available for processing the lyophilized stater cultures of LAB strains.

Antigen surface display in two novel whole genome sequenced food grade strains, Lactiplantibacillus pentosus KW1 and KW2

BackgroundUtilization of commensal bacteria for delivery of medicinal proteins, such as vaccine antigens, is an emerging strategy. Here, we describe two novel food-grade strains of lactic acid bacteria, Lactiplantibacillus pentosus KW1 and KW2, as well as newly developed tools for using this relatively unexplored but promising bacterial species for production and surface-display of heterologous proteins.ResultsWhole genome sequencing was performed to investigate genomic features of both strains and to identify native proteins enabling surface display of heterologous proteins. Basic characterization of the strains revealed the optimum growth temperatures for both strains to be 35–37 °C, with peak heterologous protein production at 33 °C (KW1) and 37 °C (KW2). Negative staining revealed that only KW1 produces closely bound exopolysaccharides. Production of heterologous proteins with the inducible pSIP-expression system enabled high expression in both strains. Exposure to KW1 and KW2 skewed macrophages toward the antigen presenting state, indicating potential adjuvant properties. To develop these strains as delivery vehicles, expression of the mycobacterial H56 antigen was fused to four different strain-specific surface-anchoring sequences.ConclusionAll experiments that enabled comparison of heterologous protein production revealed KW1 to be the better recombinant protein production host. Use of the pSIP expression system enabled successful construction of L. pentosus strains for production and surface display of an antigen, underpinning the potential of these strains as novel delivery vehicles.

Comparative genomics and fermentation flavor characterization of five selected lactic acid bacteria provide predictions for flavor biosynthesis metabolic pathways in fermented muskmelon puree

AbstractFive species of plant‐derived lactic acid bacteria (LAB), including Pediococcus pentosaceus, Lactococcus garvieae, Lactiplantibacillus paraplantarum, Weissella paramesenteroides, and Lactococcus lactis, were used for muskmelon fermentation to improve flavor characteristics. Comparative genomic analysis showed that a high proportion of annotated genes were related to carbohydrate metabolism and amino acid metabolism in all five strains. L. lactis P‐1 (Ll1) contained the highest proportion (2.02%) of genes from the glycoside hydrolase family associated with carbohydrate metabolism. Gas chromatography–mass spectrometry results showed that 89 volatile compounds in muskmelon purees were identified; the largest number of volatile compounds was detected in fermented muskmelon puree (FMP) inoculated with W. paramesenteroides FL3, followed by L. paraplantarum FL‐8. A total of 25 key volatile compounds were screened in muskmelon puree, and some unique key volatile compounds (e.g., β‐damascenone, phenylacetaldehyde, and 3‐penten‐2‐one) and taste compounds (e.g., mannitol) were produced by different LAB strains. L. garvieae Pa‐2 and Ll1 were considered to have greater potential due to their ability to produce a greater category of pleasant key aromas. Based on the correlations of potential pathways analyzed using comparative genomics and detected flavor profiles, flavor synthesis pathways in FMP were predicted. Some carbohydrate, amino acid, and fatty acid metabolism pathways, including tricarboxylic acid cycle, glycolysis, and cysteine and methionine metabolism pathways, are common to all five LAB strains. Furthermore, differences in the predicted flavor biosynthesis metabolic pathways in monoterpenoid biosynthesis, phenylalanine metabolism, fatty acid biosynthesis, and fructose and mannose metabolism pathways explained the differences in volatile profiles produced by different strains.

Gut Microbiome Derived Lactic Acid Bacteria (GM-d-LAB) from Dwarf Goats (Capra aegagrus hircus) Inhibit the Resident Multiple Antibiotics Resistance Bacterial pathogens

Background: The global health threat posed by antimicrobial resistance (AMR) has created an urgent need for developing alternative treatment methods. Probiotics, especially Lactic Acid Bacteria (LAB), are gaining interest in this context, as they demonstrate health-enhancing effects and potent antimicrobial activities. The intestines of goats could be a potential origin for developing new probiotics applications in animal feed and human health. Hence this study was carried out to determine the antibiotic resistance profiles of LAB and pathogens within the intestines of Nigerian dwarf goats (Capra aegagrus hircus), the antimicrobial activity of LAB against resident MDR pathogens, and subsequent identification of bioactive LAB isolated from goat faeces in Nigeria as potential probiotics in animal feed and human health.
 Method: Selective isolation of the LAB was carried out using de Mann Rogosa Sharpe (MRS) agar while enteric pathogens were isolated on MacConkey agar. Preliminary identification was carried out based on Gram reaction, and morphological, colonial, and biochemical characteristics of each isolate. Antibiotic susceptibility profiles of all isolates were determined using the Kirby-Bauer disc diffusion method. The agar overlay method was used to test the most resistant LAB isolates for antimicrobial activity against enteric pathogens. Selected LAB isolates were identified by 16SrRNA sequencing. 
 Results: The antibiotics susceptibility profile showed that a majority (77%) of LAB isolates and minimal (҇≤10%) of enteric pathogens demonstrated resistance to at least three classes of antibiotics, indicating a pattern of multi-drug resistance. Over half (62%) of these LAB isolates displayed significant antimicrobial activity against at least five of the resident-resistant pathogens, illustrating their potential role in controlling these pathogens. The sequencing results identified the most active LAB isolates, revealing a mix of strains including Pediococcus lolli (46%), Pediococcus pentosaceus (23%), Weissella confusa (8%), Enterococcus faecium (8%), Enterococcus hirae (8%), and Lactobacillus sanfranciscensis (8%).
 Conclusion: The discovery of a diverse range of LAB strains in goat intestines with significant antimicrobial activity against resident enteric pathogens is valuable. This finding suggests the potential use of these bacteria as natural alternatives to traditional antibiotics, especially in the context of growing AMR in animal husbandry.

Physicochemical properties of whole grain foxtail millet sourdough and steamed bread quality: Co-fermentation of lactic acid bacteria and yeast in whole grain fermented foods

Four strains of lactic acid bacteria (LAB) were selected to explore the physicochemical properties of whole grain foxtail millet (Setaria italica) sourdough and steamed bread quality. Both sourdough properties and steamed bread qualities were determined and compared. The results showed that LAB fermentation released bioactive polyphenol compounds. The pasting properties (PV, BD, FV, SB) decreased. T21 and T23 migrated to semi-bound water T22 and reduced the rheological G′ and G″ during the fermentation process (p < 0.05). LAB fermentation can significantly improve the steamed bread texture characteristics, and enrich the aroma of volatile compounds, especially esters, hydrocarbons, and others. The endogenous metabolites 2-methoxy-4-vinylphenol and 2,4-di-tert-butylphenol were found in the flavor profile and may play a functional effect. These results indicated that the LAB fermentation for whole grain foxtail millet functional steamed bread was practical and useful, which may lead to future innovations in the area of whole grain functional products.

Characteristics of Lactic Acid Bacteria as Potential Probiotic Starters and Their Effects on the Quality of Fermented Sausages.

The aim of this study was to explore the potential of commercial lactic acid bacteria (LAB) as probiotic starters in fermented sausages. We initially investigated the growth activity, acid production capability, and tolerance to fermentation conditions of Lactobacillus sakei, Lactiplantibacillus plantarum, and Pediococcus pentosaceus. All three LAB strains proved viable as starters for fermented sausages. Subsequently, we explored their potential as probiotics based on their antibacterial and antioxidant capabilities. L. plantarum exhibited stronger inhibition against Escherichia coli and Staphylococcus aureus. All three strains displayed antioxidant abilities, with cell-free supernatants showing a higher antioxidant activity compared to intact cells and cell-free extracts. Moreover, the activities of superoxide dismutase, glutathione peroxidase, and catalase were stronger in the cell-free supernatant, cell-free extract, and intact cell, respectively. Finally, we individually and collectively inoculated these three LAB strains into sausages to investigate their impact on quality during the fermentation process. External starters significantly reduced pH, thiobarbituric acid reactive substances, and sodium nitrite levels. The improvements in color and texture had positive effects, with the L. plantarum inoculation achieving higher sensory scores. Overall, all three LAB strains show promise as probiotic fermentation starters in sausage production.

Isolation of Lactic Acid Bacteria (LAB) from Salmonids for Potential Use as Probiotics: In Vitro Assays and Toxicity Assessment of Salmo trutta Embryonated Eggs.

This research investigates the potential of lactic acid bacteria (LAB) from freshwater salmonids as prospective probiotics for application in aquaculture. LAB and pathogenic bacteria were obtained from mucus and tissues of Oncorhynchus mykiss and Salmo trutta from fish farms in northeast Spain that had not used antibiotics for the six months preceding the study. Isolates were identified using Gram staining and sequencing of 16S rRNA and ITS-1. To assess the safety of the LAB, antibiotic susceptibility tests (ASTs) against 23 antimicrobials were performed. In vitro antagonism assays were conducted to evaluate the inhibitory effects of living LAB using the agar diffusion test method and their metabolites using the agar well diffusion method. The assays targeted six specific pathogens: Aeromonas salmonicida subsp. salmonicida, Carnobacterium maltaromaticum, Vagococcus salmoninarum, Yersinia ruckeri, Lactococcus garvieae, and the marine pathogen Vibrio jasicida. Additionally, a toxicity assay was conducted on embryonic eggs of S. trutta. The ASTs on probiotic LAB candidates revealed varied responses to antimicrobials, but no resistance to oxytetracycline or florfenicol, which are two antibiotics commonly used in aquaculture, was detected. The in vitro assays indicate that LAB exhibit antagonistic effects against pathogens, primarily when directly stimulated by their presence. In applications involving embryonic eggs or larvae, certain live strains of LAB were found to have adverse effects, with some isolates resulting in higher mortality rates compared to the control group or other isolates. Furthermore, the potential pathogenicity of certain LAB strains, typically considered safe in salmonids, warrants deeper investigation.

Biocontrol of L. monocytogenes with Selected Autochthonous Lactic Acid Bacteria in Raw Milk Soft-Ripened Cheese under Different Water Activity Conditions.

The effect of selected autochthonous Lactic Acid Bacteria (LAB) against Listeria monocytogenes was evaluated in two elaborations of soft-ripened cheese performed under high and low relative humidity (RH) elaborations, to achieve aw ranging from 0.97 to 0.94 in ripened cheeses. Two selected autochthonous strains of Lacticaseibacillus casei 31 and 116 were used. In each elaboration, 8 batches were physicochemically and microbiologically evaluated throughout the ripening process. The aw and pH decreased during ripening to final values ranging from 0.944 to 0.972 aw and 5.0 to 5.3 pH, respectively. LAB was the only microbial group that increased throughout the ripening in high and low RH elaborations. In batches that were uninoculated with LAB strains, L. monocytogenes was either maintained at the initial inoculation level or showed a slight reduction by the end of the ripening process. However, in LAB-inoculated batches in the two elaborations, steady decreases of L. monocytogenes were observed throughout maturation. L. casei 31 alone or in combination with strain 116 provoked reductions of 2 to 4 log CFU/g in L. monocytogenes over 60 days of ripening, which could be enough as a strategy for biocontrol to deal with the usual contamination by L. monocytogenes during cheese processing.

Preliminary Study on Screening and Genetic Characterization of Lactic Acid Bacteria Strains with Cadmium, Lead, and Chromium Removal Potentials

Due to industrial development, heavy metal pollution has become a severe global health hazard. The bioadsorption method represented by the adsorption of lactic acid bacteria (LAB) has been widely employed. The purpose of this study is to screen LAB strains that can remove cadmium, lead, and chromium. Through the heavy metal resistance tests, four strains with significant growth inhibition rate were identified. After 16S rDNA sequencing, these resistant strains were identified by Lactobacillus helveticus KD-3 (Cd2+ removal rate 37.54 ± 0.85%), Limosilactobacillus fermentum B27 (Pb2+ removal rate 69.41 ± 0.19%), Lacticaseibacillus rhamnosus 7469 (Cr6+ removal rate 71.13 ± 0.97%), and Lb. helveticus K5. Three encoding genes were identified in our screen strains, namely resistance gene czcD, chromium resistance gene chrA, and lead resistance gene pbrT. L.helveticus KD-3 exhibited the best comprehensive performance. Given the diverse types of heavy metal pollution at present, the current research mainly focuses on the removal of a single heavy metal by one strain. The four strains enrich the absorption resources of LAB for heavy metals, paving a new way for the biosorption of various heavy metals in food by LABs.

Screening of Lactiplantibacillus plantarum NML21 and Its Maintenance on Postharvest Quality of Agaricus bisporus through Anti-Browning and Mitigation of Oxidative Damage.

Browning and other undesirable effects on Agaricus bisporus (A. bisporus) during storage seriously affect its commercial value. In this study, a strain, Lactiplantibacillus plantarum NML21, that resists browning and delays the deterioration of A. bisporus was screened among 72 strains of lactic acid bacteria (LAB), and its preservative effect was analyzed. The results demonstrated that gallic acid, catechin, and protocatechuic acid promoted the growth of NML21, and the strain conversion rates of gallic acid and protocatechuic acid reached 97.16% and 95.85%, respectively. During a 15 d storage of the samples, the NML21 treatment displayed a reduction in the browning index (58.4), weight loss (2.64%), respiration rate (325.45 mg kg-1 h-1), and firmness (0.65 N). The treatment further inhibited Pseudomonas spp. growth and polyphenol oxidase activity, improved the antioxidant capacity, reduced the accumulation of reactive oxygen species, and reduced the malonaldehyde content and cell membrane conductivity. Taken together, the optimized concentrations of NML21 may extend the shelf life of A. bisporus for 3-6 d and could be a useful technique for preserving fresh produce.