Presumptive Lactic Acid Bacteria Research Articles

Selection of starter lactic acid bacteria capable of forming biofilms on wooden vat prototypes for their future application in traditional Sicilian goat's milk cheese making

In this study, 327 presumptive lactic acid bacteria (LAB) were isolated from goats' milk acid curds produced at a Sicilian dairy farm with the aim to identify potential starter cultures for traditional cheeses. All isolates were first processed by randomly amplified polymorphic DNA (RAPD)-PCR analysis. This approach identified 63 distinct strains which were evaluated for their acidifying capacity. Only 15 strains specifically stood out for their acidification capacity and were identified through 16S rRNA gene sequencing as Lactococcus lactis (11 strains) Enterococcus faecalis (three strains), and Ligilactobacillus animalis (one strain). Notably, all 15 LAB isolates produced bacteriocin-like inhibitory substances and anti-biofilm compounds, against both planktonic and biofilm forms of Listeria monocytogenes, Salmonella Enteritidis, Escherichia coli, and Staphylococcus aureus, albeit at varying levels. Among these 15 LAB, En. faecalis RGM25 and Lc. lactis RGM55, susceptible to five antibiotics tested, were put in contact with wooden vat prototypes, because all equipment used in traditional cheese production in Sicily are made of wood. Scanning electron microscopy and bacterial plate counts of the wooden vat prototypes showed the development of biofilms at levels of approximately 6.0 log CFU/cm2. Overall, this study contributes to establishing a custom-made LAB starter cultures with bio-preservatives properties for Sicilian cheese productions.

Biodiversity and biotechnological properties of lactic acid bacteria isolated from traditional Moroccan sourdoughs.

The present study aimed at characterizing lactic acid bacteria (LAB) strains isolated from traditional sourdoughs collected in different regions of Morocco. Isolated strains were firstly identified using Gram staining and catalase reaction test. Presumptive LAB strains were then checked for various phenotypical properties including growth at 45°C, resistance to NaCl, enzyme production, acidification capacity, diacetyl and exopolysaccharide (EPS) production, and antifungal activity. Finally, selected LAB strains were identified using 16S rDNA sequencing. Results showed that 32.1% of the isolates were thermophilic (45°C) and 83.9% were resistant to NaCl (6.5%). Moreover, 51.7 and 37.5% were able to produce diacetyl and EPS, respectively. Regarding enzyme production, 55.3 and 7.1% of the isolates showed lipolytic and proteolytic activities, respectively. Low pH values (3.37-3.76) were obtained after 24h of incubation of LAB strains in de Man, Rogosa and Sharpe (MRS) broth. Antifungal activity test against Aspergillus flavus, Aspergillus niger and Penicillium spp. showed an inhibition rate up to 50%. Bacterial DNA sequencing showed that LAB isolates belong to seven species, chiefly Levilactobacillus brevis, Lentilactobacillus parabuchneri, Lactiplantibacillus plantarum, Pediococcus pentosaceus, Enterococcus hirae, Bifidobacterium pseudocatenulatum, and Companilactobacillus paralimentarius. These findings, for the first time in Moroccan sourdoughs, indicate that the isolated LAB strains have good multifunctional properties and could be suitable as good starters for sourdough bread production under controlled conditions.

Isolation and in vitro screening of the probiotic potential of microorganisms from fermented food products

IntroductionSeveral human health benefits have been ascribed to probiotics, while traditional fermented foods have been acknowledged as rather important sources of these microorganisms. The objective of this study was the isolation of microorganisms from fermented food products of both animal and plant origin and the evaluation of their probiotic potential.MethodsMicrobial isolation was performed from milk kefir and table olives, while an olive mill waste sample also was analyzed given its anticipated association with the autochthonous microbiota of olive drupes. Among the 16 macroscopically distinct recovered microorganisms, 14 microbial isolates were identified as presumptive lactic acid bacteria (LAB), whereas two isolates corresponded to yeasts. The microbial isolates exhibiting a reproducibly robust growth profile in appropriate culture broth media (11 out of the 16 isolates) were assessed for their probiotic potential based on a set of in vitro assays: resistance to low pH; autoaggregation; biofilm formation; antioxidant activity; and safety assessment through evaluation of hemolytic activity.Results and discussionBased on the collective evaluation of the results of the abovementioned assays, five presumptive LAB as well as the two yeast isolates were identified as exhibiting desirable in vitro probiotic traits. Hence, these microbial isolates could be regarded as good candidates for inclusion in further studies aiming, ultimately, at their potential utilization in novel functional food products.

METABOLISM AND FUNCTIONAL HETEROGENEITY OF FERMENTED MILK ORIGIN LACTIC ACID BACTERIA FOR LACTOSE INTOLERANCE

Lactic acid bacteria (LAB) are cosmopolitan in distribution with multiple ecological niches. LAB shows diverse applications in improvement of health by biochemical interference or imuno modulation to overcome several clinical circumstances. Lactose intolerance (LI) is one such situation, where individual show lactose maldigestion after the consumption of dairy products. It is necessary to overcome such a condition by employing indigenous beneficial bacteria or their products. Therefore, in this study we have isolated and characterized LAB from fermented milk samples, from remote villages of districts of south India. Traditionally fermented milk samples (68) were collected, cultivated on MRS medium, identified by biochemical and carbohydrate metabolic activity and correlated with Bergey's manual of systematic bacteriology. When matched with other LAB, Lactiplantibacillus isolates were able to reduced pH of medium significantly and reached pH of 4.6 in 48 hours. On MRS agar, 450 different bacterial isolates were isolated, recognized as presumptive LAB and classified up to the level of genera as Lactiplantibacillus (285), Lactococcus (70), Pediococcus (19), Streptococcus (20), and Enterococcus (16). Later, β-galactosidase screening was carried out using MRS/X-gal agar medium. Out of 450 LAB isolates only Lactiplantibacillus isolates were potential β-galactosidase producers. GRAS organisms such as LAB are multifaceted diverse group of bacteria localized in varieties of fermented foods/in the intestine and recognized as probiotics. Distinct contribution of LAB in health care and disorder management made this organism as a choice for alternate therapy; hence functionality of LAB can be promoted for LI management.

Antibiotic Susceptibility and Antimicrobial Activity of Lactic Acid Bacteria from Malaysian Fermented Foods Against Biofilm-Forming Escherichia coli Strains

Lactic acid bacteria (LAB) are frequently employed in the food industry as food preservatives and starter cultures due to their potentially advantageous properties. Their ability to promote numerous health benefits in fermented foods has received increased attention. However, few studies have investigated the antibacterial activity of LAB and their susceptibility to antibiotics when combating biofilm-forming Escherichia coli strains. In this study, four fermented food samples were screened for presumptive LAB cultures, including Maman pickle (M5Bi), fermented fish (PB4iii), fermented durian (T6Aiii), and fermented glutinous rice (Ta2Ai), using the API 50 CHL method. The isolates were subsequently identified as Lactobacillus plantarum, L. plantarum, Pediococcus pentosaceus, and Lactobacillus pentosus, respectively, through molecular analysis of the 16S rDNA sequencing. The isolates were then assessed for antibiotic susceptibility to amoxicillin (25 µg), chloramphenicol (30 µg), tetracycline (30 µg), and erythromycin (10 µg) using the disc diffusion method. Moreover, the antibacterial activity of LAB against eight biofilm-forming E. coli strains was evaluated using the well diffusion method. The results showed that L. plantarum from the Maman pickle sample exhibited the most significant inhibitory zone against biofilm-forming E. coli strains. Importantly, all detected LAB were resistant to the four main antibiotics tested, indicating that the safety and efficacy of probiotics must be ensured before they can be developed and commercialized.

Electrochemical detection of lactate produced by foodborne presumptive lactic acid bacteria

The detection of lactate is an important indicator of the freshness, stability, and storage stability of products as well as the degree of fermentation in the food industry. In addition, it can be used as a diagnostic tool in patients' healthcare since it is known that the lactate level in blood increases in some pathological conditions. Thus, the determination of lactate level plays an important role in not only the food industry but also in health fields. As a result, biosensor technologies, which are quick, cheap, and easy to use, have become important for lactate detection. In the current study, amperometric lactate biosensors based on lactate oxidase immobilization (with Nafion 5% wt) were designed and the limit of detection, linear range, and sensitivity values were determined to be 31μM, 50-350μM, and 0.04μAμM-1cm-2, respectively. Then, it was used for the measurement of lactic acid that produced by six different and morphologically identified presumptive lactic acid bacteria (LAB) which are isolated from different naturally fermented cheese samples. The biosensors were then used to successfully perform lactate measurements within 3min for each sample, even though a few of them were out of the limit of detection. Thus, electrochemical biosensors should be used as an alternative and quick solutions for the measurement of lactate metabolites rather than the traditional methods which require long working hours. This is the first study to use a biosensor to measure lactate produced by foodborne LAB in a real sample.

Dietary soy galactooligosaccharides affect the performance, intestinal function, and gut microbiota composition of growing chicks

The objective of this experiment was to investigate the effects of the dietary soy galactooligosaccharides (GOS), raffinose and stachyose, on performance, gastrointestinal health, and systemic stress in young broilers. Birds were fed a GOS-devoid diet based on soy protein isolate (SPI) or the SPI diet with 0.9, 1.8, 2.7, or 3.6% added stachyose and raffinose in a ratio of 4:1 at the expense of corn starch. These 5 treatments were administered to 10 replicate cages of 8 birds. Performance was measured weekly and excreta moisture, N retention, apparent metabolizeable energy, and complete blood cell counts were determined at 14 and 21 d. At 21 d, 2 birds per cage were orally gavaged with fluorescein isothiocyanate-dextran (FITC-d) and serum samples were analyzed for FITC-d as a marker of gut leakage. Additionally, intestinal morphology, crop presumptive lactic acid bacteria (LAB) counts, crop and cecal pH, and cecal microbiota via16S rRNA microbial sequencing were evaluated at 21 d. From 0 to 21 d, feed intake increased linearly (P < 0.01) as dietary GOS increased, whereas BWG increased (P < 0.05) quadratically. Feed conversion ratio increased (P < 0.01) linearly as GOS increased. There were linear increases (P < 0.05) in excreta moisture as dietary GOS increased at 14 and 21 d, as well as dose-dependent responses (P < 0.05) in N retention, AME, and AMEn. There was a quadratic increase (P < 0.05) in crop LAB recovery and a linear decrease (P < 0.01) in ceca pH as GOS increased. At 14 d, a linear increase (P < 0.05) in blood heterophil to lymphocyte ratio was observed as dietary GOS increased. Serum concentrations of FITC-d increased quadratically (P < 0.01) to dietary GOS. Increasing levels of GOS influenced alpha and beta diversities and composition of gut microbiota, including the abundance of Ruminococcus and Bifidobacterium. Results from this trial indicate that soy-derived GOS exert dose-dependent effects on nutrient utilization and intestinal health in young broilers.

Psychobiotic Potential of Gamma-Aminobutyric Acid–Producing Marine Enterococcus faecium SH9 from Marine Shrimp

Psychobiotics are a novel class of probiotics with potential to confer mental wellness via production of neuroactive compounds such as gamma-aminobutyric acid (GABA). The demand for new biological sources of GABA has increased steadily. Therefore, the current study reports the isolation of 17 presumptive lactic acid bacteria (LAB) from marine samples and their screening for GABA synthesis from monosodium glutamate (MSG) using thin-layer chromatography (TLC). The isolate SH9 was selected as a high GABA producing strain. The GABA content of SH9 cell free supernatant (CFS) was quantitatively determined by high performance liquid chromatography (HPLC) to be 0.97 g/L. SH9 was identified biochemically and molecularly as Enterococcus faecium (identity 99%). Moreover, SH9 demonstrated promising probiotic potentials; it gave no signs of hemolysis and could survive at low pH values and high bile salt concentrations. It also exhibited antimicrobial activity against highly pathogenic strains and the ability to grow at 6.5% NaCl. In addition, SH9 CFS showed anti-inflammatory and antioxidant properties. The glutamate decarboxylase (GAD) gene was detected in SH9 by using specific primers. Product of 540 bp was obtained, sequenced, and analyzed (accession number: MW713382). The inferred amino acid sequence was 99.3% identical to Lactobacillus plantarum M-6 gadB gene. The findings of this study suggest that the marine isolate E. faecium SH9 could be used as a novel psychobiotics in the development of GABA rich healthy products.

Identification, safety and technological characteristics of Weissella strains from traditional Southwestern Algerian kaddid

Kaddid is a dry-fermented meat product traditionally produced in North Africa by spontaneous fermentation. As a reservoir of natural biodiversity, the identification and relevant traits of lactic acid bacteria (LAB) were carried out from South-western Algeria homemade samples. After a preliminary physiological and biochemical screening, 19 presumptive LAB isolates were selected on the basis of antimicrobial compounds production. The isolates were identified by 16S rRNA gene sequencing as Weissella cibaria, W. confusa, W. paramesenteroides, Pediococcusacidilactici, and Enterococcus hirae. As predominant, the safety and technological characterization of Weissella strains were performed. The production of antimicrobial and antifungal compounds was observed, while neither H2S, biogenic amines nor hemolytic activity were detected; antibiotic resistance was exhibited, however several strains were more susceptible to assayed antibiotics. Technological characterization of Weissella strains showed high acidification rates even in the presence of up to 10 % NaCl, autolytic and proteolytic capacity however, no EPS production and lipolytic activity were observed. Strains characterization led to the selection of W. cibaria BK2, W. confusa BK6 and BK11 as well as W. paramesenteroides BK8 to be considered as possible candidates for use as starter culture for kaddid fermentation to improve and standardize this traditional meat product.

In Vitro and in Vivo Activity of Lactobacillus Sakei L14 Strain Against Campylobacter Jejuni DC3 Strain.

IntroductionDomestic poultry is a natural reservoir of Campylobacter, the host–pathogen interaction being predominantly asymptomatic. This study investigated whether chickens remain asymptomatic partly because of lactic acid bacteria (LAB).Material and MethodsCampylobacter spp. and LAB were isolated from the gut of poultry chickens using enrichment and screening assays and were identified via rDNA sequencing. The C. jejuni DC3 isolate was grown in different cell-free supernatants (CFS) generated from a priority LAB isolate. An in vivo challenge involving the C. jejuni and LAB isolates using a chicken model was performed to confirm the in vitro findings.ResultsTwelve presumptive LAB isolates had anti-C. jejuni activity based on cross-streak and agar plug assays, with Lactobacillus sakei L14 isolate exhibiting the highest activity. Inhibition by L. sakei L14 CFS of the growth of C. jejuni occurred in a dose-dependent manner. Campylobacter jejuni DC3 inhibition was most evident in CFS harvested at 72 h and produced by co-culture with the pathogen. Neutralisation of the CFS abrogated the observed inhibition. Co-infection with C. jejuni DC3 and L. sakei L14 in vivo, however, failed to inhibit C. jejuni colonisation in chickens.ConclusionThe results suggest that the anti-C. jejuni effect of L. sakei L14 in chickens may be due to mechanisms other than direct inhibition of growth.

Potential of a Techno-Functional Sourdough and Its Application in Sugar-Reduced Soft Buns

Functional lactic acid bacteria (LAB) as starter cultures used in sourdough fermentation have been researched for years. This study evaluated the LAB strains Leuconostoc citreum DCM65 (mannitol, exopolysaccharide producing, antifungal activity) and Lactiplantibacillus plantarum subsp. plantarum MA418 (amylolytic activity) and their potential as single or co-culture starters in sourdough fermented buns containing different levels of sugar (control 9% and reduced 0, 3, 6%). Cell counts, pH development, and organic acids were determined before and after sourdough fermentation (30 °C, 24 h) and physical properties (color, volume, pore structure, and texture) of buns produced thereof were determined after baking. Sourdoughs started with DCM65 and/or MA418 developed up to log 9.2 CFU/g presumptive LAB after 24 h, assertiveness of the added starter cultures species was confirmed by MALDI-TOF MS. Acetic acid and mannitol were only detected in sourdough fermented with DCM65 (single or co-culture) up to 2.5 mg/g and 9.8 mg/g, respectively. The starter cultures applied influenced physical properties of buns. Sourdough buns started with MA418 had higher volume and slice area, and softer crumb; in contrast, buns fermented with DCM65 had a finer pore structure. In summary, both starter cultures showed high potential in sourdough buns with reduced sugar content.

Characterization and Evaluation of the Probiotic Potential In Vitro and In Situ of Lacticaseibacillus paracasei Isolated from Tenate Cheese

The objectives of this investigation were (i) to isolate bacteria from various foods (dairy products, fruits, and vegetables) and evaluate their probiotic potential and (ii) to select, identify, and characterize the bacterial strain(s) with the highest probiotic potential. From 14 food samples, 117 bacterial strains were isolated; however, only 42 (T1 to T42) had the correct characteristics (gram positive, coccoid, and bacilliform) and were catalase and oxidase negative to be considered presumptive lactic acid bacteria (LAB). The antagonistic activity of the 42 strains was evaluated against Escherichia coli (O157:H7E09), Listeria monocytogenes (ATCC 19115), Staphylococcus aureus (ATCC 25923), and Salmonella enterica serotype Typhimurium (ATCC 14028). The nine strains with the highest antagonistic activity were recovered from the following foods: pulque (T1), sprouted beans (T26), Ranchero cheese (T30, T31, T32, T33, T35, and T36), and Tenate cheese (T40). The inhibition zones on culture and sensitivity plates were 17.0 ± 1.2 to 19.3 ± 2.8 mm in diameter. Based on the antagonistic activity against pathogenic bacteria and resistance to low pH and bile salts, strain T40 had the highest probiotic potential. A 16S rRNA technique was used to identify strain T40 as Lacticaseibacillus paracasei (renamed from Lactobacillus paracasei in April 2020). This strain had no resistance to ampicillin, gentamicin, erythromycin, and tetracycline. The antagonistic activity was evaluated in situ (fresh cheese) against pathogenic bacteria, supporting the probiotic potential of L. paracasei. Isolates of this LAB recovered from Tenate cheese had characteristics of a probiotic microorganism with high potential for use in food technology.

Non-Alcoholic Pearl Millet Beverage Innovation with Own Bioburden: Leuconostoc mesenteroides, Pediococcus pentosaceus and Enterococcus gallinarum.

The appropriate solution to the problem of quality variability and microbial stability of traditional non-alcoholic pearl millet fermented beverages (NAPMFB) is the use of starter cultures. However, potential starter cultures need to be tested in the production process. We aimed to identify and purify bioburden lactic acid bacteria from naturally fermented pearl millet slurry (PMS) and assess their effectiveness as cultures for the production of NAPMFB. Following the traditional Kunun-zaki process, the PMS was naturally fermented at 37 °C for 36 h. The pH, total titratable acidity (TTA), lactic acid bacteria (LAB), total viable count (TVC) and the soluble sugar were determined at 3 h interval. The presumptive LAB bacteria were characterized using a scanning electron microscope, biochemical tests and identified using the VITEK 2 Advanced Expert System for microbial identification. The changes in pH and TTA followed a non-linear exponential model with the rate of significant pH decrease of 0.071 h−1, and TTA was inversely proportional to the pH at the rate of 0.042 h−1. The Gompertz model with the mean relative deviation modulus, 0.7% for LAB and 2.01% for TVC explained the variability in microbial growth during fermentation. The LAB increased significantly from 6.97 to 7.68 log cfu/mL being dominated by Leuconostoc, Pediococcus, Streptococcus and Enterococcus with an optimum fermentation time of 18 h at 37 °C and 4.06 pH. L. mesenteroides and P. pentosaceus created an acidic environment while E. gallinarum increased the pH of the pearl millet extract (PME). Innovative NAPMFB was produced through assessment of LAB from PMS to PME fermented with L. mesentoroides (0.05%) and P. pentosaceus (0.025%) for 18 h, thereby reducing the production time from the traditional 24 h.

Effect of Echinostoma caproni on Presumptive Lactic Acid Bacteria Abundance and Salmonella enterica Serovar Typhimurium Colonization in the Mouse Gut.

Co-infections of mammalian hosts with intestinal helminths and bacterial pathogens are common, especially in areas with inadequate sanitation. Interactions between co-infecting species and host microbiota can cause significant changes in host immunity, disease severity, and pathogen transmission, requiring unique treatment for each case. A greater understanding of the influences of parasite-bacteria co-infections will improve diagnosis and therapeutic approaches to control infectious diseases. To study the influence of the trematode parasite Echinostoma caproni on commensal and pathogenic bacteria in the mouse gut, we examined the abundance of intestinal lactic acid bacteria and Salmonella enterica serovar Typhimurium in control mice not exposed to E. caproni (P-) or S. Typhimurium (S-), E. caproni-infected (P+S-), S. Typhimurium-infected (P-S+), and E. caproni-S. Typhimurium co-infected (P+S+) mice, and determined bacterial burdens in the livers and spleens of the P-S+ and P+S+ mice. We also examined a subset of P+S- and P+S+ mice for survival and the relative location of E. caproni in the small intestine. The numbers of presumptive lactic acid bacteria were significantly higher in the P+S+ and P-S+ mice compared to the uninfected mice, and S. Typhimurium colonization in the liver and spleen was significantly reduced in the P+S+ mice compared to the P-S+ mice. Echinostoma caproni were located anteriorly in the intestine of P+S- mice, while in the P+S+ mice, the parasites were distributed more posteriorly. Survival of E. caproni was unaffected in either group. The results of our study suggest that E. caproni facilitates a higher abundance of presumptive lactic acid bacteria in the mouse intestine and reduces colonization of S. Typhimurium in the liver and spleen of the co-infected host.

Strain-level Identification of Beneficial Lactobacilli of Dairy Origin using 16S rRNA Sequencing: A Biotechnology Approach

Aim: This study investigated the cultural method and 16S rRNA gene analysis to reveal the composition and diversity of lactic acid bacteria (LAB) from dairy origin (spontaneous fermented cow milk) in Nigeria.&#x0D; Methods: Six dairy samples which includes two raw cow milk, two raw goat milk and two fermented cow milk (nono) were collected and subjected to standard microbiological investigation using both cultural and molecular methods. The dairy samples were cultured on MRS media, and the isolates were identified using physiological and biochemical parameters. DNA of four selected probiotic LAB isolates from nono were amplified using PCR while the amplicons were electrophoresed in agarose gel, pre-stained with ethidium bromide and characterized by 16S rRNA gene analysis. The result of the DNA sequencing were analyzed using NCBI BLAST. &#x0D; Results: A total of 55 presumptive LAB were isolated. Twenty nine (29) Lactobacillus plantarum representing 52.7%, Pediococcus acidilactici 15(27.2%), Lactobacillus casei and Lactobacillus brevis 4(7.3%) while Lactobacillus fermentum 3(5.5%) were recorded respectively. Result of the gel electrophoresis revealed DNA size of approximately 1500bp. The selected probiotic LAB from nono used in this study were confirmed as Lactobacillus plantarum N17, Lactobacillus plantarum N24, Lactobacillus brevis N10 and Lactobacillus casei N1 based on 16S rRNA gene sequence analysis while the phylogenetic analysis revealed a 98-100% similarity with a high homology level which affirms the strain of the organism.&#x0D; Conclusion: This study has demonstrated the diversity of LAB existing in dairy samples known as fermented cow milk (nono) which could be harnessed as valuable sources for LAB isolation and potential probiotic organisms.

Monitoring Commercial Starter Culture Development in Presence of Red Grape Pomace Powder to Produce Polyphenol-Enriched Fresh Ovine Cheeses at Industrial Scale Level

Red grape Nero d’Avola cultivar grape pomace powder (GPP) was applied during fresh ovine cheese production in order to increase polyphenol content. Before cheeses were produced, the bacteria of a freeze-dried commercial starter culture were isolated and tested in vitro against GPP. Two dominant strains, both resistant to GPP, were identified. Thestarter culture was inoculated in pasteurized ewe’s milk and the curd was divided into two bulks, one added with 1% (w/w) GPP and another one GPP-free. GPP did not influence the starter culture development, since lactic acid bacteria (LAB) counts were 109 CFU/g in both cheeses at 30 d. To exclude the interference of indigenous LAB, the pasteurized milk was analyzed, and several colonies of presumptive LAB were isolated, purified and typed. Four strains were allotted into Enterococcus and Lacticaseibacillus genera. The direct comparison of the polymorphic profiles of cheese bacteria evidenced the dominance of the starter culture over milk LAB. The addition of GPP increased cheese total phenolic compounds by 0.42 g GAE/kg. Sensory evaluation indicated that GPP-enriched cheese was well appreciated by the judges, providing evidence that GPP is a suitable substrate to increase the availability of total phenolic content in fresh ovine cheese.

A novel combination of sodium metabisulfite and a chemical mixture based on sodium benzoate, potassium sorbate, and sodium nitrite for aerobic preservation of fruit and vegetable discards and lactic acid fermentation in a total mixed ration for ruminants.

ObjectiveOur recent findings confirmed the effectiveness of sodium metabisulfite (SMB) in controlling the growth of undesirable microorganisms in fruit and vegetable discards (FVD); however, lactic acid bacteria (LAB) are susceptible to its antibacterial effects. Two series of experiments were conducted to enable the survivability of LAB during silage fermentation of a total mixed ration (TMR) containing SMB-treated FVD.MethodsIn Exp. 1, the objective was to isolate a strain of LAB tolerable to the toxic effect of SMB. In Exp. 2, the SMB load was minimized through its partial replacement with a chemical mixture (CM) based on sodium benzoate (57%), potassium sorbate (29%), and sodium nitrite (14%). FVD was treated with SMB + CM (2 g each/kg biomass) and added to the TMR at varying levels (0%, 10%, or 20%), with or without KU18 inoculation.ResultsThe KU18 was screened as a presumptive LAB strain showing superior tolerance to SMB in broth medium, and was identified at the molecular level using 16S rRNA gene sequence analysis as Lactobacillus plantarum. Inoculation of KU18 in TMR containing SMB was not successful for the LAB development, biomass acidification, and organoleptic properties of the resultant silage. In Exp. 2, based on the effectiveness and economic considerations, an equal proportion of SMB and CM (2 g each/kg FVD) was selected as the optimal loads for the subsequent silage fermentation experiment. Slight differences were determined in LAB development, biomass acidification, and sensorial characteristics among the experimental silages, suggesting the low toxicity of the preservatives on LAB growth.ConclusionAlthough KU18 strain was not able to efficiently develop in silage mass containing SMB-treated FVD, the partial substitution of SMB load with the CM effectively alleviated the toxic effect of SMB and allowed LAB development during the fermentation of SMB + CM-treated FVD in TMR.

Investigation of the microbiota associated with ungerminated and germinated Norwegian barley cultivars with focus on lactic acid bacteria

The microbial community of ungerminated and germinated barley grains from three different cultivars grown at four different locations in Norway was investigated by culture dependent and culture independent methods. Lactic acid bacteria (LAB) was focused in this study and was isolated from germinated barley. The number of LAB ranged between 2.8 and 4.6 log cfu/g in ungerminated grains and between 4.9 and 6.3 log cfu/g in germinated grains. In total 66 out of 190 isolates were Gram+, catalase-negative and presumptive LAB. The LAB isolates were by 16S rRNA sequencing identified to be Carnobacterium maltaromaticum (6), Lactococcus lactis (2), Enterococcus sp. (1) and Leuconostoc sp. (57). Germination significantly influenced the bacterial composition. Regarding the different cultivars and growth places no significant difference in bacterial composition was seen. The most abundant bacterial genus was Pantoea (18.5% of the total sequences), followed by Rhizobium (10.1%) and Sphingomonas (9.9%). Fungal composition was significantly influenced by the germination process and the cultivation place, but no significant difference in fungal composition was detected between the 3 cultivars. The most abundant fungal genera were Cryptococcus (43.8% of all the sequences), Cladosporium (8.2%), Pyrenophora (7.4%) and Vagicola (6.3%). This study revealed knowledge of barley grain associated microbes of Norwegian barley that can be useful to control the malt quality. Germination affected both bacterial and fungal microbiota composition. No difference in bacterial microbiota composition was seen regarding cultivars and cultivation place, however, the fungal microbiota composition was significantly influenced by the cultivation place. Differences in fungal community of ungerminated and germinated barley samples of different geographical locations were more pronounced than differences in bacterial communities.

Microbial dynamics in rearing trials of Hermetia illucens larvae fed coffee silverskin and microalgae

In the present study, Hermetia illucens larvae were reared on a main rearing substrate composed of a coffee roasting byproduct (coffee silverskin, Cs) enriched with microalgae (Schizochytrium limacinum or Isochrysis galbana) at various substitution levels. The microbial diversity of the rearing substrates, larvae, and frass (excrement from the larvae mixed with the substrate residue) were studied by the combination of microbial culturing on various growth media and metataxonomic analysis (Illumina sequencing). High counts of total mesophilic aerobes, bacterial spores, presumptive lactic acid bacteria, coagulase-positive cocci, and eumycetes were detected. Enterobacteriaceae counts were low in the rearing diets, whereas higher counts of this microbial family were observed in the larvae and frass. The microbiota of the rearing substrates was characterized by the presence of lactic acid bacteria, including the genera Lactobacillus, Leuconostoc and Weissella. The microbiota of the H. illucens larvae fed Cs was characterized by the dominance of Paenibacillus. H. illucens fed diets containing I. galbana were characterized by the presence of Enterococcus, Lysinibacillus, Morganella, and Paenibacillus, depending on the algae inclusion level, while H. illucens fed diets containing S. limacinum were characterized by high relative abundances of Brevundimonas, Enterococcus, Paracoccus, and Paenibacillus, depending on the algae inclusion level. Brevundimonas and Alcaligenes dominated in the frass from larvae fed I. galbana; the predominance of Brevundimonas was also observed in the frass from larvae fed Schyzochitrium-enriched diets. Based on the results of the present study, an effect of algae nutrient bioactive substances (e.g. polysaccharides, high-unsaturated fatty acids, taurine, carotenoids) on the relative abundance of some of the bacterial taxa detected in larvae may be hypothesized, thus opening new intriguing perspectives for the control of the entomopathogenic species and foodborne human pathogens potentially occurring in edible insects. Further studies are needed to support this hypothesis. Finally, new information on the microbial diversity occurring in insect frass was also obtained.

Lactic acid bacteria isolated from the Stingless bee Scaptotrigona mexicana and partial characterization of their probiotic activity

The objective of this study was to isolate lactic acid bacteria (LAB) from honey produced by the stingless bee Scaptotrigona mexicana from southern of Mexico, and to evaluate their probiotic potential. From fresh and fermented honey, 18 strains were isolated. Of these, 10 had presumptive LAB biochemical characteristics. Their ability to grow at different pH values and different temperatures, susceptibility to antibiotics, and ability to inhibit Salmonella sp. and Escherichia coli were assessed. All the strains tested were resistant or moderately susceptible to penicillin, dicloxacillin, and ampicillin. The strains that showed tolerance to pH 2.5 were the bacteria labeled FIM1 and FIM2, and only strains OP3 and TUX5 were able to grow at 5 °C. Although none of the supernatant growth media of the strains inhibited the development of pathogenic bacteria, other tests should be done to verify the probiotic nature of the strains that exhibited some characteristic of interest.