Specific Lactic Acid Bacteria Research Articles

Adding rumen microorganisms to improve fermentation quality, enzymatic efficiency, and microbial communities of hybrid Pennisetum silage

Hybrid Pennisetum, a top biomass energy source, faces usage limitations because of its scarce lactic acid bacteria and high fiber content. This study assessed the influence of rumen fluid pretreatment on hybrid Pennisetum’s silage, with focus on silage duration and rumen fluid effects on quality and fiber decomposition. Advanced third-generation sequencing was used to track microbial diversity changes and revealed that rumen fluid considerably enhanced dry matter, crude protein, and water-soluble carbohydrates, thus improving fermentation quality to satisfactory pH levels (3.40–3.67). Ideal results, including the highest fiber breakdown and enzymatic efficiency (47.23 %), were obtained with 5 % rumen fluid in 60 days. The addition of rumen fluid changed the dominant species, including Paucilactobacillus vaccinostercus (0.00 % vs. 18.21 %) and Lactiplantibacillus plantarum (21.03 % vs. 47.02 %), and no Enterobacter was detected in the high-concentration treatments. Moreover, strong correlations were found between specific lactic acid bacteria and fermentation indicators, revealing the potential of achieving efficient and economically beneficial hybrid Pennisetum production.

Screening of Yoghurt Produced by Local Strains of Lactic Acid Bacteria Isolated from Locally Fermented Yoghurt “Kindirmo” For Flavour Compounds

Study’s Novelty/Excerpt This study presents comprehensive screening of local strains of lactic acid bacteria (LAB) isolated from "Kindirmo" for their potential to produce flavor-enhancing compounds in yoghurt. The research uniquely identifies specific LAB strains, such as Leuconostoc mesenteroides dextranicum and Lactobacillus acidophilus, and demonstrates their capacity to produce a variety of volatile flavor compounds using GC–MS analysis. The findings suggest the potential application of these isolates in improving the taste of "Kindirmo" and other food products, thereby contributing valuable insights to the field of food microbiology and fermentation. Full Abstract Yoghurt is known as cultured milk which is derived from the action of bacteria on lactose to produce lactic acid, carbon dioxide (CO2), acetic acid, diacetyl, acetaldehyde, and other flavor compounds. The aim of this research was to screen yoghurt produced by local strains of lactic acid bacteria isolated from locally fermented yoghurt “Kindirmo” for the production of flavor-enhancing compounds. A total of five “Kindirmo” samples were collected from two farmhouses located in Daura local government of Katsina State, Nigeria. The samples were collected and transported in ice containers. Serial dilutions of the “Kindirmo” samples were made and plated using the pour-plate method on de Man, Rogosa, and Sharpe (MRS) agar and incubated anaerobically at 37°C for 72 hours, followed by bacterial identification using Vitek system. Thereafter, yoghurt was produced using the isolated lactic acid bacteria and volatile flavor compounds in the yoghurt were determined using GC–MS analysis. Out of all the five (5) samples analyzed, only two (2) were positive for Lactic acid bacteria. The lactic acid bacteria identified were leuconostoc mesenteroides dextranicum and Lactobacillus acidophilus. While Lactobacillus acidophilus produced 14 volatile flavor compounds, leuconostoc mesenteroides dextranicum produced only 12. Butanoic acid, Hexanoic acid, Acetaldehyde, Propane, Acetone, ethyl ester, Lactic acid, and Diacetone were some of the flavor compounds detected. The research shows the potentials of the isolated LAB to produce flavor compounds, which could be used to enhance the taste of Kindirmo. It is recommended that the isolates should be used for further study on how to produce Kindirmo with single and co-culture of the LAB, or rather on how to produce the flavor enhancers for application in other foods or food products.

Identification of volatile and odor-active compounds in pea protein fractions obtained by a modified extraction method using fermentation.

This study investigates the aromatic composition of pea albumin and globulin fractions obtained through either fermentation or conventional acidification using hydrochloric acid (control) toward the isoelectric point of pea globulins. Different lactic acid bacteria were used including S. thermophilus (ST), L. plantarum (LP), and their coculture (STLP). The volatile compounds were extracted by solvent-assisted flavor evaporation technique and quantified by gas chromatography-mass spectrometry (GC-MS). Odor-active compounds (OAC) were further characterized by gas chromatography-olfactometry (GC-O). In total, 96 volatile and 36 OACs were identified by GC-MS and GC-O, respectively. The results indicated that the protein fractions obtained by conventional acidification were mainly described by green notes for the presence of different volatile compounds such as hexanal. However, the samples obtained by fermentation had a lower content of these volatile compounds. Moreover, protein fractions obtained by coculture fermentation were described by volatile compounds associated with fruity, floral, and lactic notes. PRACTICAL APPLICATION: The insights from this study on pea protein aroma could find practical use in the food industry to enhance the sensory qualities of plant-based products. By utilizing fermentation methods and specific lactic acid bacteria combinations, manufacturers may produce pea protein with reduced undesirable green notes, offering consumers food options with improved flavors. This research may contribute to the development of plant-based foods that not only provide nutritional benefits but also meet consumer preferences for a more appealing taste profile.

Screening the Protective Agents Able to Improve the Survival of Lactic Acid Bacteria Strains Subjected to Spray Drying Using Several Key Enzymes Responsible for Carbohydrate Utilization.

The aim of this study was to identify the most effective protectants for enhancing the viability of specific lactic acid bacteria (LAB) strains (Lactobacillus delbrueckii subsp. bulgaricus CICC 6097, Lactiplantibacillus plantarum CICC 21839, Lactobacillus acidophilus NCFM) by assessing their enzymatic activity when exposed to spray drying (inlet/outlet temperature: 135 °C/90 °C). Firstly, it was found that the live cell counts of the selected LAB cells from the 10% (w/v) recovered skim milk (RSM) group remained above 107 CFU/g after spray drying. Among all the three groups (1% w/v RSM group, 10% w/v RSM group, and control group), the two enzymes pyruvate kinase (PK) and lactate dehydrogenase (LDH) were more sensitive to spray drying than hexokinase (HK) and β-galactosidase (β-GAL). Next, transcriptome data of Lb. acidophilus NCFM showed that 10% (w/v) RSM improved the down-regulated expressions of genes encoding PK (pyk) and LDH (ldh) after spray drying compared to 1% (w/v) RSM. Finally, four composite protectants were created, each consisting of 10% (w/v) RSM plus a different additive-sodium glutamate (CP-A group), sucrose (CP-B group), trehalose (CP-C group), or a combination of sodium glutamate, sucrose, and trehalose (CP-D group)-to encapsulate Lb. acidophilus NCFM. It was observed that the viable counts of strain NCFM (8.56 log CFU/g) and enzymatic activity of PK and LDH in the CP-D group were best preserved compared to the other three groups. Therefore, our study suggested that measuring the LDH and PK activity could be used as a promising tool to screen the effective spray-dried protective agent for LAB cells.

Insights into fermentation with lactic acid bacteria on the flavonoids biotransformation of alfalfa silage

BackgroundOxidative stress is currently one of the main threats to animal health, and flavonoids in forage have good antioxidant activity. However, the impact of fermentation on flavonoids and their antioxidant activity in forage is still unclear. This study aims to investigate the effect of lactic acid bacteria inoculation on the biological transformation of flavonoids in alfalfa silage fermentation and its relationship with antioxidant activity.ResultsCompared with the raw materials, silage fermentation can increase the total flavonoid content of alfalfa. The addition of Pediococcus pentosaceus (CP115739.1) and Lactiplantibacillus plantarum (CP115741.1) can significantly increase the total flavonoid content in alfalfa silage (P < 0.05). The addition of lactic acid bacteria significantly improved the antioxidant capacity of alfalfa silage (P < 0.05). Pearson correlation analysis showed a significant correlation between total flavonoids and DPPH (R = 0.62, P < 0.05), and a highly significant correlation between total flavonoids and FRAP (R = 0.70, P < 0.01). Compared with natural silage fermentation, the addition of lactic acid bacteria leads to changes in the biological transformation process of flavonoids in alfalfa. Its unique products, 3,7,4′-trioxyflavonoids, as well as acacetin and taxifolin 7-O-rhamnoside, are significantly positively correlated with antioxidant activity.ConclusionsSilage fermentation contributes to the transformation of flavonoids, and inoculation with certain lactic acid bacteria can increase the content of flavonoids (including apigenin, luteolin, and other free flavonoids). It is worth noting that after fermentation, the antioxidant capacity of alfalfa is significantly improved, which may be attributed to the biotransformation of flavonoids related to acacetin, 3,7,4′-trihydroxyflavonoids, and taxifolin 7-O-rhamnoside. This study provides a potential pathway for obtaining value-added silage fermentation products by selecting specific lactic acid bacteria inoculants.Graphical

Assessment of probiotic intervention for control of biofilm former Escherichia coli isolates of animal‐origin foods

AbstractThe study investigates the efficacy of lactic acid bacteria (LAB) strains (Lactobacillus rhamnosus and Lactobacillus casei) in combating Escherichia coli biofilms by determining antibacterial, anti‐biofilm activity, auto‐aggregation, and co‐aggregation assay. The study included 115 E. coli isolates from milk (n = 36), chicken meat (n = 33), and chicken eggs (n = 46). Among 115 E. coli isolates, 22.61% were strong biofilm formers. The LAB strain, L. rhamnosus exhibited a 28.47 mm mean antibacterial inhibition zone, an average reduction of 51.22% in biofilm growth, 55.46% auto‐aggregation, and 41.57% co‐aggregation with E. coli. Similarly, L. casei demonstrated a 21.55 mm mean antibacterial inhibition zone, an average reduction of 36.74% in biofilm growth, 45.23% auto‐aggregation, and 38.74% co‐aggregation with E. coli isolates. Both strains individually and in combination demonstrate substantial reductions in biofilm growth, with L. rhamnosus observed to be more effective than L. casei. Scanning electron microscopy provides valuable insights into the structural aspects of the probiotic impact on diminishing E. coli biofilm. Probiotics' ability to auto‐aggregate and co‐aggregate with pathogenic strains serves as an initial screening method for identifying suitable probiotic bacteria. In conclusion, the results underscore the efficacy of specific LAB strains in combating E. coli biofilm formation. This study provides a basis for future investigations into LAB's capacity to mitigate biofilm‐related hurdles and strengthen microbial management protocols within food processing settings or relevant food substrates.

Detection of the lactic acid bacterial community in small scale white cheese processing facility using shotgun metagenomics and culturomics

This study aims to characterize lactic acid bacteria (LAB) community in small-scale white cheese processing facility highly favored by consumers. Shotgun metagenomics and culturomics based on MALDI-TOF MS approaches were employed. Samples from various production stages and equipment surfaces were collected. Dominant phyla in dairy and equipment samples were Firmicutes (63–70%) and Proteobacteria (84–89%), respectively. Lactococcus was the most abundant LAB genus across all samples, with Lactococcus lactis as dominant species followed by Streptococcus, Enterococcus, and Lactobacillus, indicating LAB community diversity contributing to product characteristics. Culturomics identified 12 LAB species, including Enterococcus faecalis and Lactobacillus delbrueckii. Metagenomics provided insights into microbial composition and dynamics in dairy environment, while culturomics identified specific LAB species. The combined approach offers a comprehensive view of dairy microbial communities, aiding industrial development by informing starter culture combinations for improved dairy products and processes.

Characterization of four peptides from milk fermented with kombucha cultures and their metal complexes-in search of new biotherapeutics.

The most common skin diseases include eczema, psoriasis, acne, and fungal infections. There is often no effective cure for them. Increasing antimicrobial drug resistance prompts us to search for new, safe, and effective therapeutics. Among such interesting candidates are peptides derived from milk fermented with specific lactic acid bacteria or with kombucha cultures, which are a potential treasure trove of bioactive peptides. Four of them are discussed in this article. Their interactions with zinc and copper ions, which are known to improve the well-being of the skin, were characterized by potentiometry, MS, ITC, and spectroscopic methods, and their cytostatic potential was analyzed. The results suggest that they are safe for human cells and can be used alone or in complexes with copper for further testing as potential therapeutics for skin diseases.

Cultivable microbial diversity, peptide profiles, and bio-functional properties in Parmigiano Reggiano cheese.

Lactic acid bacteria (LAB) communities shape the sensorial and functional properties of artisanal hard-cooked and long-ripened cheeses made with raw bovine milk like Parmigiano Reggiano (PR) cheese. While patterns of microbial evolution have been well studied in PR cheese, there is a lack of information about how this microbial diversity affects the metabolic and functional properties of PR cheese. To fill this information gap, we characterized the cultivable fraction of natural whey starter (NWS) and PR cheeses at different ripening times, both at the species and strain level, and investigated the possible correlation between microbial composition and the evolution of peptide profiles over cheese ripening. The results showed that NWS was a complex community of several biotypes belonging to a few species, namely, Streptococcus thermophilus, Lactobacillus helveticus, and Lactobacillus delbrueckii subsp. lactis. A new species-specific PCR assay was successful in discriminating the cheese-associated species Lacticaseibacillus casei, Lacticaseibacillus paracasei, Lacticaseibacillus rhamnosus, and Lacticaseibacillus zeae. Based on the resolved patterns of species and biotype distribution, Lcb. paracasei and Lcb. zeae were most frequently isolated after 24 and 30 months of ripening, while the number of biotypes was inversely related to the ripening time. Peptidomics analysis revealed more than 520 peptides in cheese samples. To the best of our knowledge, this is the most comprehensive survey of peptides in PR cheese. Most of them were from β-caseins, which represent the best substrate for LAB cell-envelope proteases. The abundance of peptides from β-casein 38-88 region continuously increased during ripening. Remarkably, this region contains precursors for the anti-hypertensive lactotripeptides VPP and IPP, as well as for β-casomorphins. We found that the ripening time strongly affects bioactive peptide profiles and that the occurrence of Lcb. zeae species is positively linked to the incidence of eight anti-hypertensive peptides. This result highlighted how the presence of specific LAB species is likely a pivotal factor in determining PR functional properties.

A systematic assessment on the influence of probiotics on patients with Inflammatory Bowel Disorder

Inflammatory bowel disease (IBD) causes persistent mucosal inflammation, and mounting evidence points to the intestinal microbiota's critical involvement in this process. New molecular techniques have also helped to identify dysbiosis in these individuals. Many potential probiotic product action mechanisms counteract IBD etiological causes. The study aimed to explain the benefits of probiotics for IBD and thoroughly evaluate current trials using probiotics to treat IBD in grownups. A specific search was done using specified keywords on October 1, 2011, using the supplied date range. Only English-language, full-text articles on clinical results for adult patients were addressed. Based on disease type and disease activity, the 41 eligible studies were classified. Pooled odds ratios were calculated only when there were many available randomized controlled trials per probiotic for a particular patient group. According to well-designed randomized controlled studies, few probiotics are effective in treating IBD at this time. It was only feasible to conduct meta-analyses on a limited number of studies, which yielded an overall risk ratio of 2.70 for inducing remission in active U.C. with Bifido fermented milk versus placebo or no adjuvant treatment. Very Specific Lactic Acid Bacteria (VSL#3) enables people to go into remission active U.C. compared to placebo. To support the favorable outcomes for inactive ulcerative colitis (U.C.), it is still a need to conduct better-conducted investigations in regard to the variety of drug VSL#3 in patients with both active and dormant U.C. U.C. based on intention-to-treat analyses by many independent research organizations. According to the existing data, probiotic usage in Crohn’s Disease (CD) has yet to be shown. The location and subtypes of certain diseases should be the focus of future research. Selecting probiotic strains for certain disease entities and illness sites will be easier with more knowledge of the mechanisms of probiotic strains and the etiology of IBD.

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.

Selective influence of garlic as a key ingredient in kimchi on lactic acid bacteria in a fermentation model system

Garlic is an essential ingredient added to kimchi, a fermented vegetable, in small amounts owing to its sensory and antibacterial properties. This study aimed to elucidate the complex relationship between garlic and specific lactic acid bacteria (LAB) and the resulting metabolite changes in a controlled kimchi model system using nine strains as mixed and individual starters. The group without garlic using mixed starters showed the highest LAB growth activity, which influenced lactic acid production, pH, and titratable acidity. The group without garlic also showed differences in the composition of bacteria, such as Latilactobacillus sakei, Levilactobacillus brevis, unclassified Leuconostoc, and Weissella koreensis, during the fermentation period. In addition, the altering patterns of metabolites in the group without garlic during fermentation differed from those in the group with garlic. In addition, the metabolic profile of L. brevis group was mostly different from that of the other strains in the controlled model kimchi system using individual starters, suggesting that changes in LAB composition by garlic could subsequently affect metabolites during fermentation. This study provides valuable insights into the complex interactions among food ingredients, LAB succession, and metabolite production during fermentation.

FERMENTATION OF BAMBARA FLOUR: EXPLORING MICROBIAL ECOLOGY DYNAMICS AND EFFECTS ON ANTI-NUTRITIONAL FACTORS

The fermentation of Bambara flour represents a crucial step in traditional food processing, modulating its nutritional profile and sensory attributes. This study investigates the microbial ecology dynamics during Bambara flour fermentation and its impact on anti-nutritional factors. A diverse consortium of lactic acid bacteria was employed to ferment Bambara flour under controlled conditions. Through molecular and biochemical analyses, we characterized the shifts in microbial populations and the degradation of anti-nutritional compounds throughout the fermentation process. Our findings reveal intricate microbial interactions, including the dominance of specific lactic acid bacteria species and their role in mitigating anti-nutritional factors. Furthermore, we elucidate the potential health benefits conferred by the fermentation process, highlighting its significance in enhancing the nutritional quality and safety of Bambara flour-based products.

Comparative Structure Analysis of the Multi-Domain, Cell Envelope Proteases of Lactic Acid Bacteria.

Lactic acid bacteria (LAB) have an extracellular proteolytic system that includes a multi-domain, cell envelope protease (CEP) with a subtilisin homologous protease domain. These CEPs have different proteolytic activities despite having similar protein sequences. Structural characterization has previously been limited to CEP homologs of dairy- and human-derived LAB strains, excluding CEPs of plant-derived LAB strains. CEP structures are a challenge to determine experimentally due to their large size and attachment to the cell envelope. This study aims to clarify the prevalence and structural diversity of CEPs by using the structure prediction software AlphaFold 2. Domain boundaries are clarified based on a comparative analysis of 21 three-dimensional structures, revealing novel domain architectures of CEP homologs that are not necessarily restricted to specific LAB species or ecological niches. The C-terminal flanking region of the protease domain is divided into fibronectin type-III-like domains with various structural traits. The analysis also emphasizes the existence of two distinct domains for cell envelope attachment that are preceded by an intrinsically disordered cell wall spanning domain. The domain variants and their combinations provide CEPs with different stability, proteolytic activity, and potentially adhesive properties, making CEPs targets for steering proteolytic activity with relevance for both food development and human health.

The Occurrence of Folate Biosynthesis Genes in Lactic Acid Bacteria from Different Sources.

Lactic acid bacteria (LAB) are known to produce folate. However, this ability is highly strain-dependent. Folate synthesis in specific LAB strains is affected by the availability of folate, which can be consumed by other LAB under certain conditions. Moreover, differences in folate synthesis capabilities are related to the presence of folate biosynthesis-related genes and regulation of this pathway. As basic information to better understand the regulation of folate biosynthesis among different LAB species and strains, folate biosynthetic genes were screened and identified in folate-producing and non-folate-producing LAB isolated from various local food sources in Indonesia. The extracellular folate productivity amounts of the isolates were analyzed using high-performance liquid chromatography with a diode array detector (HPLC-DAD). Eleven of the thirteen tested LAB isolates had all of the eight genes involved in folate biosynthesis (folE, folQ, folB, folK, folP, folC1, folA and folC2). Furthermore, these isolates produced extracellular folate ranging from 10.37 to 31.10 µg/mL. In contrast, two non-folate-producing isolates lacked several folate biosynthetic genes, such as folQ, folP and folA, which is possibly the reason for their inability to synthesize folate de novo. Phylogenetic tree construction revealed that the folate biosynthetic genes (excluding folK and folP) from six distinct species of folate-producing LAB isolates were monophyletic with homologous genes from other LAB species in the database. In this study, the distribution of folate biosynthetic genes in various LAB species was determined. The findings from this research support the use of folate biosynthesis marker genes in the genotypic screening for folate-producing LAB.

Reviewing the Potential Therapeutic Approaches Targeting the Modulation of Gastrointestinal Microflora in Schizophrenia.

Schizophrenia (SCZ) is a severe brain disorder characterized by an intriguing clinical panel that has begun to gain interest due to its particular phenotype. Having considered the role of gut microflora in psychiatry, the latest discoveries might offer further insight into the underlying mechanisms. Thus, we aimed to offer an updated overview of the therapeutic potential of microorganism-derived supplements alongside dedicated protocols that target the re-establishment of the host's eubiosis. Based on combinations of specific keywords, we performed searches in four databases (PubMed/Medline, ISI Web of Knowledge, Scopus, and ScienceDirect) for the established interval (2018-2022) and identified twenty two eligible cases, restricted only to human patients' experiences. Up until the writing of this manuscript, it has been revealed that the administration of specific lactic acid bacteria strains (Lactobacillus and Bifidobacterium), or those combined with vitamin D and selenium, maintain the integrity of the gut flora, preventing antagonistic effects including inflammation, antipsychotic-related body weight gain (olanzapine) and other metabolic dysfunctionalities. However, there are multiple antipsychotics that exert a potent effect upon gut flora, influencing a plethora of pathways and creating a dysbalance ratio between beneficial and opportunistic pathogens. Risperidone, amisulpride, and clozapine are just a few examples, but the current literature is unfortunately inconsistent and reported data is contradictory, which is why we support additional studies in this context. Moreover, we further argue the utility of studying how distinct controlled substances influence microbial communities, considering that ketamine is proved to alleviate depressive-like behavior as opposed to amphetamine and phencyclidine, which are known substances to trigger SCZ-like symptoms in experimental models. Probiotics may be regarded as the most consequential vehicle through which the gut flora can be successfully influenced, in adequate doses exerting a beneficial role as an alternative approach to alleviate SCZ symptoms.

3-Phenyllactic acid generated in medicinal plant extracts fermented with plant-derived lactic acid bacteria inhibits the biofilm synthesis of Aggregatibacter actinomycetemcomitans.

In the present study, the effect of PLA on a periodontic pathogen, Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans), the biofilm, and virulence-related genes was investigated. We confirmed that two lactic acid bacteria (LAB) strains isolated from plant sources, Lactiplantibacillus plantarum MSC-C2 and Pediococcus pentosaceus K40, secrete PLA into the de Man, Rogosa & Sharpe (MRS) broth when supplemented with phenyl pyruvic acid (PPA) as a precursor to PLA. Moreover, PLA was generated in the fermentation broths of two medicinal plant extracts, Paeonia lactiflora Pall (PR) and Carthamus tinctorius (CT), when used by each LAB strain and each extract supplemented with PPA. We determined that the minimum inhibitory concentration (MIC) of PLA against A. actinomycetemcomitans was 20 mM. PLA significantly decreased biofilm formation and suppressed the transcription of pgA, ltxA, and cdtB genes, which encode the poly-N-acetylglucosamine (PGA) polysaccharide of biofilm matrix and exotoxins leukotoxin and cytolethal distending toxin (CDT), respectively. The PLA produced by the MSC-C2 and K40 strains was increased several times by the addition of PPA to the MRS broth. The anti-biofilm effect of the extracts from the fermentation broth was proportional to the increasing PLA concentration, while a cumulatively higher effect than that of PLA alone suggested a combinational effect of PLA and the other metabolites, such as lactic acid (LA). Among the two medicinal plants, PLA, produced after the addition of PPA, was higher in PR extract in case of both the LAB strains. PLA production by the MSC-C2 strain in the PR extract reached 4.8 ± 0.23 mM, which was obviously higher than that in the MRS broth (3.88 ± 0.12 mM) supplemented with 1 mg/ml PPA. The activity to inhibit biofilm formation in the fermented PR extract was clearly high. PLA formed in the fermented PR extract downregulated the dispersin B encoding the dspB gene together with pgA, ltxA, and cdtB. In conclusion, this study shows a promising activity of PLA against the A. actinomycetemcomitans biofilm and virulence genes. In addition, the combinational effect of PLA and the medicinal plant extract can be achieved by fermentation with a specific plant-derived LAB strain.

프로바이오틱스 안전성 평가를 위한 항생제 저항성 유전자의 생물정보학적 분석법 비교

The detection of the genome-based antibiotic resistance gene is an essential analysis process for the purpose of verifying the safety of probiotic strains, including lactic acid bacteria. In this study, 4 analysis platforms (AMRFinderPlus, staramr, rgi, ABRicate) were used for cross-comparison of 782 genomes corresponding to 19 kinds of probiotic species notified as functional foods. As a result of the analysis, the relatively fewest number of antibiotic resistance genes were detected in strains belonging to the order Lactobacillales, and antibiotic resistance genes were detected in 322 genomes used in the case of 2 types of Enterococcus genus. In addition, the presence and type of antibiotic resistance gene detection showed a lot of difference even for the same genome sequence depending on the database and analysis algorithm used by the analysis platform. These results can be confused in evaluating the potential for transmission of antibiotic resistance genes inherent in specific lactic acid bacteria and predicting potential risks that may occur in the future. Accordingly, it is judged that the antibiotic resistance gene-related analysis criteria need to be established more clearly and specifically in the safety evaluation of probiotic bacteria.

Use of Autochthonous Lactic Acid Bacteria as Starter Culture of Pasteurized Milk Adobera Cheese

Adobera, a genuine, brick-shaped, lightly ripened, unstretched pasta filata-like cheese from Western México, is one of the most important market-share wise but is usually made with raw milk and prepared following artisanal procedures. A pasteurized milk cheese is needed to assess its safety and guarantee standardized quality features. However, no commercial Adobera cheese culture is available, as specific lactic acid bacteria relevant for its production have not been thoroughly identified. This study is aimed at comparing the technological and quality features of Adobera cheeses made with pasteurized milk inoculated with a mixture of autochthonous lactic acid bacteria (Lactobacillus and Leuconostoc strains) to those of traditional raw milk cheeses, hypothesizing that no significant differences would be found between them. Milk pasteurization promoted water retention into the cheese matrix, impacting its texture and color profiles. Raw milk cheeses were harder, more cohesive, and less elastic than pasteurized milk cheeses. Ripening markers were significantly higher in raw milk cheeses at all sampling times, although its evolution over time showed that the starter culture could exhibit similar proteolytic activity than that of native milk microbiota under favorable ripening conditions. The principal component analysis revealed apparent overall differences between raw Adobera cheeses and those made with pasteurized cheese milk.

Effects of LAB Inoculants on the Fermentation Quality, Chemical Composition, and Bacterial Community of Oat Silage on the Qinghai-Tibetan Plateau.

Lactic acid bacteria (LAB) have been proposed for the control of undesirable fermentation and, subsequently, aerobic deterioration due to their ability to produce antimicrobial metabolites in silage mass. To investigate the effect of specific LAB on the silage fermentation characteristics and bacterial community composition of oat in cold regions, silages were treated without (control) or with three LAB strains (LB, Lentilactobacillus buchneri; nLP, low temperature tolerant Lactiplantibacillus plantarum; pLP, phenyllactic acid-producing Lactiplantibacillus plantarum), and then stored at ambient temperature (−2.63 ± 5.47–14.29 ± 5.48 °C) for 30, 60, and 90 days. Compared with control, inoculation of LAB decreased the final pH value, butyric acid content, ammonia-N of total N and dry matter loss of silage. Treatments with nLP and pLP increased (p < 0.05) lactic acid content, whereas LB increased (p < 0.05) acetic acid content of silage. Lactiplantibacillus and Leuconostoc dominated in the silages with relative abundance of 68.29–96.63%. A prolonged storage period enhanced the growth of Leuconostoc in pLP-treated silage. In addition, pLP increased (p < 0.05) the aerobic stability of silage as compared with nLP. In conclusion, inoculation of LAB improved silage fermentation and/or delayed aerobic deterioration by shifting bacterial community composition during ensiling. Phenyllactic acid-producing Lactiplantibacillus plantarum as an inoculant exhibited potential for high quality silage production.