Mixed Lactic Acid Bacteria Research Articles

Kefir Culture-Mediated Fermentation to Improve Phenolic-Linked Antioxidant, Anti-Hyperglycemic and Human Gut Health Benefits in Sprouted Food Barley

The bioprocessing strategy is an effective approach to improve bioavailability and stability of bioactive compounds for designing functional foods and ingredients. In this study, food barley was bio-transformed to improve functional bioactives by sprouting, coupled with beneficial lactic acid bacteria (LAB)-based fermentation. Dairy Kefir culture with mixed beneficial LAB strains was targeted to ferment aqueous slurries of sprouted hulless food barley flour (unpigmented, purple, and black barley) for 72 h, and modulation of phenolic-linked antioxidant and anti-hyperglycemic functionalities were evaluated using in vitro assay models. The biochemical parameters analyzed were total soluble phenolic (TSP) content, profile of phenolic compounds, total antioxidant activity, and anti-hyperglycemic property-relevant α-amylase and α-glucosidase enzyme inhibitory activities. Furthermore, human gut health benefits of relevant properties of fermented slurries of barley flour were also evaluated based on growth of Kefir culture and subsequent determination of anti-bacterial potential against pathogenic human ulcer causing bacteria Helicobacter pylori. Kefir culture-mediated fermentation of 48-h sprouted barley flours improved the TSP content and associated antioxidant and anti-hyperglycemic functionalities. Additionally, anti-bacterial potential against H. pylori and sustaining active growth of viable LAB cells above the minimum level required for probiotic activity were also observed in fermented food barley flour slurries.

Production and Purification of Novel Hypocholesterolemic Peptides from Lactic Fermented Spirulina platensis through High Hydrostatic Pressure-Assisted Protease Hydrolysis

This research focuses on the proteolytic capacity of Spirulina platensis and their hypocholesterolemic activity via the 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase (HMGR) inhibitory activity. To select suitable proteases for releasing peptides with high HMGR-inhibiting activity from S. platensis, eight commonly used commercial proteases were used in protease hydrolysis under high hydrostatic pressure (HHP, 100 MPa or 0.1 MPa) at 50 °C for 24 h. The Peptidase R group had the highest inhibitory capacity (67%). First, S. platensis was fermented with seven mixed lactic acid bacteria for 5 h at 42 °C. This was followed by the addition of Peptidase R under high hydrostatic pressure (100 MPa at 50 °C) for 0–6 h of enzymatic hydrolysis (HHP-FH-PR6) to determine the hydrolytic capacity of S. platensis protein. As the hydrolysis time extended to 6 h, the peptide content increased from 96.8 mg/mL to 339.8 mg/mL, and the free amino acid content increased from 24 mg/mL to 115.2 mg/mL, while inhibition of HMGR increased from 67.0% to 78.4%. In an experimental simulation of in vitro gastrointestinal digestion, the IC50 of HHP-FH-PR6G on HMGR was 3.5 μg peptide/mL. Peptides with inhibitory activity on HMGR were purified, and their sequences were identified as Arg-Cys-Asp and Ser-Asn-Val (IC50: 6.9 and 20.1 μM, respectively).

Purification and Identification of Cholesterol Micelle Formation Inhibitory Peptides of Hydrolysate from High Hydrostatic Pressure-Assisted Protease Hydrolysis of Fermented Seabass Byproduct.

This research focuses on the proteolytic capacity of sea bass byproduct (SB) and their hypocholesterolemic activity via the cholesterol micelle formation (CMF) inhibition. SB was fermented with seven mixed lactic acid bacteria for 5 h at 42 °C. The lactic fermented SB was hydrolyzed with Protease N for 6 h under HHP to obtain the SB hydrolysates (HHP-assisted Protease N hydrolysis after fermentation, F-HHP-PN6). The supernatant was separated from the SB hydrolysate and freeze-dried. As the hydrolysis time extended to 6 h, soluble protein content increased from 187.1 to 565.8 mg/g, and peptide content increased from 112.8 to 421.9 mg/g, while inhibition of CMF increased from 75.0% to 88.4%. Decreasing the CMF inhibitory activity from 88.4% to 42.1% by simulated gastrointestinal digestion (FHHP-PN6 was further hydrolyzed by gastrointestinal enzymes, F-HHP-PN6-PP) reduced the CMF inhibitory activity of F-HHP-PN6. Using gel filtration chromatography, the F-HHP-PN6-PP was fractioned into six fractions. The molecular weight of the fifth fraction from F-HHP-PN6-PP was between 340 and 290 Da, and the highest inhibitory efficiency ratio (IER) on CMF was 238.9%/mg/mL. Further purification and identification of new peptides with CMF inhibitory activity presented the peptide sequences in Ser-Ala-Gln, Pro-Trp, and Val-Gly-Gly-Thr; the IERs were 361.7, 3230.0, and 302.9%/mg/mL, respectively.

Protective Effect of Prunus mume Fermented with Mixed Lactic Acid Bacteria in Dextran Sodium Sulfate-Induced Colitis.

The fruit of Prunus mume (PM) is widely cultivated in East Asia, and it has been used as a folk medication for gastrointestinal disorders, e.g., diarrhea, stomach ache and ulceration. In this study, the pectinase-treated PM juice (PJ) was fermented with Lactobacillus strains containing fundamental organic acids and free amino acids. The PJ fermented with Lactobacillus plantarum and L. casei (FP) was investigated for its protective effect in dextran sodium sulfate (DSS)-induced colitis mice model. The administration of FP reduced lipid peroxidation and histopathological colitis symptoms, e.g., shortening of the colon length, depletion of mucin, epithelial injury and ulceration, in colonic tissues. The FP-supplemented group showed the alleviation of pro-inflammatory cytokines. Compared with the DSS control group, the supplementation of FP significantly reduced the levels of serum interferon-γ (IFN-γ), interleukin (IL)-1β, IL-6, IL-12 and IL-17 as well as colonic tumor necrosis factor-α, IFN-γ, IL-12 and IL-17. Furthermore, the DSS-induced TUNEL-positive area was significantly reduced by the FP supplementation. These results show that the supplementation of FP fermented with mixed lactic acid bacteria, L. plantarum and L. casei, elucidated the protective effect in DSS-induced colitis mice. Hence, this study suggests that FP can be utilized as a natural therapeutic agent for colitis and intestinal inflammation.

Antioxidant activity and chemical characteristics in egg albumen fermented by lactid acid bacteria

Research on fermentation time and the addition of milk powder to egg albumen is still limited. The purpose of this study was to determine the antioxidant activity and chemical characteristics of fermented egg albumen using different levels of full cream milk powder and different microbial fermentation times. This study used a completely randomized factorial pattern design, 4 x 5 treatments with 4 replications. Research materials include egg albumen, full cream milk powder and mixed Lactic Acid Bacteria (L. bulgaricus, L.achidopillus, and Streptococcus thermopillus). The research treatments were the addition of powdered milk in different level (%) including, 0, 2, 4 and 6. Fermentation times were 0, 12, 24, 36, and 48 h, respectively. The results showed that the addition of powdered milk in different level and fermentation time had no significant effect on the antioxidant activity. The addition of different-level powdered milk was not significant on the glucose content and total protein, but it was very significant (P<0.01) on water content. The fermentation time had a very significant effect (P<0.01) on glucose levels and total protein, but it had no significant effect on the water content of albumen fermentation. Antioxidant activity did not change during the fermentation time and the addition of different-level milk powder. The 24 h fermentation time could reduce the total protein and glucose levels of egg albumen. Adding 2% milk powder could reduce the water content of egg albumen fermentation.

Effects of combining two lactic acid bacteria as a starter culture on model kimchi fermentation

This study aimed to establish a mixed starter culture to standardize the flavor of kimchi, a traditional Korean food. Leuconostoc mesenteroides and Lactobacillus sakei were selected for the culture based on their key roles in kimchi fermentation. The effects of various starter culture mixing ratios on the overall fermentation process were investigated. Fermentation was carried out at 15 °C for 72 h. In the microbial community analysis, a similar ratio to the initial mixed inoculated ratio was observed in the microbial environments. Treatment with high-rate L. mesenteroides inoculation, exhibiting hetero-fermentative characteristics, led to the production of mannitol (1393.11 mg/100 g), acetic acid (57.70 mg/kg), and lactic acid (1141.90 mg/kg), in addition to the induction of a rapid increase in the number of viable cells, thereby reducing the pH (pH 3.9). Conversely, treatment with high-rate L. sakei inoculation, exhibiting homo-fermentative characteristics, led to the production of less mannitol and acetic acid, with more lactic acid. Principal component analysis score plots showed a distinct difference in kimchi metabolites depending on the lactic acid bacteria (LAB) starter culture. Therefore, by using mixed LAB starter strains, this study demonstrated the value of various characteristics and standardized manufacturing of kimchi. LAB types and inoculation ratios greatly affected the types and concentration of metabolites in kimchi fermentation.

Preparation of yogurt-flavored bases by mixed lactic acid bacteria with the addition of lipase

Yogurt-flavored bases are widely used in food industry for enhancing flavors. In this study, yogurt-flavored bases by mixed lactic acid bacteria with or without lipase were investigated, which included Streptococcus lactis ACCC 11093 (SL) and Lactobacillus casei subsp. rhamnosus 6013 (LCR), SL and Lactobacillus acidophilus 1.1878 (LAP), and SL and Lactobacillus plantarum DMDL 9010 (LP), respectively. Compared with the combination of SL and LCR and the combination of SL and LAP, the combination of SL and LP had higher production of total amino acids, volatile acids and esters, suggesting that the combination of SL and LP was more efficient to produce yogurt-flavored bases. In addition, lipase significantly increased the production of amino acids associated with sweet and bitter flavors, and resulted in rougher milk globule surface and tighter network structure compared with fermentations without the addition of lipase. Furthermore, a total of 54 volatile compounds were detected in yogurt-flavored bases. The production of volatile compounds in fermentations with and without the addition of lipase, was mainly affected by acids and esters, respectively. Therefore, the lipase is a favorable supplement for producing yogurt-flavored bases.

In Vitro Hypoglycemic Potential of Dietary Fiber From Fermented Seaweed

Dietary fiber can regulate metabolic activity of the body by affecting enzyme activity in the intestine. It cut down the speed of digestion to relieve the release of glucose, so blood sugar can be controlled in the optimal range. In this study, seaweed was used to prepare dietary fiber by microbial transformation of Lactobacillus rhamnosus and Lactobacillus plantarum. The experiment showed that the content of soluble dietary fiber (SDF) increased significantly after the action of the mixed lactic acid bacteria, and the increments rate was 21.1%. The inhibition rate of α-amylase and α-glucosidase increased by 25.9% and 16.6% respectively after fermentation. Therefore, after fermentation seaweed can enhance the soluble dietary fiber and improve inhibition rate of enzyme activity related to digestion. Dietary fiber of seaweed has potential of hypoglycemic.

Antifungal and antibacterial effects of newly created lactic acid bacteria associations depending on cultivation media and duration of cultivation

BackgroundThe newly created associations of lactic acid bacteria (LAB) isolated from Armenian dairy products (yoghurt, sour cream and different varieties of cheese), as well as from the gastrointestinal tract of honeybees were screened according to their antifungal and antibacterial activity.ResultsLAB strains were mixed at equal proportions (1:1) according to mathematical planning of experiments. Antifungal and antibacterial effects of different combinations (associations) were determined in different media, employing well-diffusion and total diffusion into agar methods. A number of fungal and bacterial test-organisms, including pathogenic ones, were used. Pure LAB strain cultures were used as a control. The antifungal effect of the most active strain Lactobacillus rhamnosus MDC 9661 in the associations with other LAB strains was partly decreased. At the same time, some mixed LAB cultures in DeMan, Rogosa and Sharpe (MRS) medium demonstrated significant antibacterial activity against wide spectra of test-organisms only in the case of simultaneous cultivation of LAB strains. On the other hand, in the case of different LAB strains cultivated in MRS with 24-h time break between mix formations by different strains, no inhibitory activity was revealed. But the inhibitory effect of many LAB associations against test-organisms was significantly increased in the case of separated cultivation in milk.ConclusionThe inhibitory effect of mixed LAB associations showed stronger dependence on the cultivation media and on the duration of cultivation with respect to each other. The co-cultivation of some strains, like L. rhamnosus MDC 9661, could lead to changed antagonistic activity. Consequently, the results are significant for creation and further investigation of LAB associations, as effective probiotics, and for their probable application in the production of antimicrobial preparations.

Effects of mixed lactic acid bacteria on intestinal microbiota of mice infected with Staphylococcus aureus

BackgroundThe stability of intestinal microorganisms plays an important role in human health, as the intestines perform important functions in the human body. Staphylococcus aureus is a Gram-positive, facultative anaerobic bacteria, it causes human infection worldwide, and is a major pathogen that causes intestinal infection. Mixed lactic acid bacteria (LAB) may have potential in the prevention and treatment of S. aureus infection. In the present study, we examined the effects of mixed LAB treatment on intestinal microbiota modulation in mice infected with S. aureus.ResultsHigh-throughput sequencing of the V3-V4 region of the bacterial 16S rRNA gene showed that the mixed LAB maintained the richness and diversity of the microbiota in the mouse intestine. By establishing operational taxonomic units and using rarefaction analysis, rank-abundance distribution curves, heat maps, Venn diagrams, bacterial community structures, and hierarchical clustering analysis, Bacteroidales, Lachnospiraceae, Bacteroides and Prevotellaceae were the most abundant taxa in the samples, we found that the composition of the intestinal microbiota was similar between the protection group administered mixed LAB and the negative control group.ConclusionsStaphylococcus aureus destroys the stable intestinal microbiota structure of mice, treatment with mixed LAB could prevent S. aureus infection in mice and improve the structure of the intestinal microbiota.

THE EFFECT OF STORAGE CONDITION ON VIABILITY OF LACTIC ACID BACTERIA IN PROBIOTIC PRODUCT

Objective: The aim of this study was to determine the effect of storage condition on viability of lactic acid bacteria (LAB) in probiotic product.Methods: Four different of probiotic products used were A (Lacto B), B (Rillus), C (Interlac), and D (Lacbon) containing single or mixed LAB. The product was stored at temperature of 4°C and 28°C for 28 days. Viability test of LAB was done by counting a number of colony bacteria that live on de man, Rogosa, and Sharpe Agar.Results: The results of the study showed that counts of the LAB colonies in product A were less at the label (5.04×107 cfu/sachet), whereas in products B, C, and D were matching with the label. Storage at a temperature of 28°C for 28 days showed significant loss on the viability of LAB in product C (p<0.05).Conclucion: Storage temperature affecting on viability of LAB in probiotic product where storage at temperature 4°C is higher than 28°C for 28 days.

Changes in folate characteristics and its identification in broccoli (Brassica oleracea Italica) extract fermented by Lactic Acid Bacteria Mixed Culture (LAB)

Broccoli (Brassica oleracea Italica) was fermented by cultures of lactic acid bacteria (LAB) as a potential source of natural folic acid. This study aimed to evalte characteristic changes and to identify folate compounds from broccoli extract, fermented by mixed LAB cultures (L. bulgaricus, S. thermophulus, L.acidophilus, Bd. bifidum). The formulation of broccoli extract was fermented with variation of LAB starter culture with concentrations of 10 and 20%(v/v), and the change of characteristic of folic acid compound during fermentation (0 to 48 hours) with an interval of 8 hours was evaluated. The results showed that the fermentation of broccoli extract with different concentration of LAB culture had an effect on the concentration of folic acid produced, as well as the change of concentration of folic acid during the fermentation time interval. The optimum condition was obtained based on the highest folic acid concentration of 6.74%, at culture concentration of 20% during 24 hour fermentation with the value of folic acid concentration of 72.11 μg/mL, pH value of 4.29, total sugars of 34.61%, total acids of 0, 97%, dissolved protein of 14.64 mg/mL and total LAB of log 13.02 + 0.05 cfu / ml.

Ability of lactobacilli isolated from traditional cereal-based fermented food to produce folate in culture media under different growth conditions

Folates are essential vitamins (B9). Lactic acid bacteria (LAB) can be used to increase the folate levels in foods during fermentation. Here, 151 LAB strains isolated from fermented food were screened for folate production. Folates were extracted by heat treatment coupled with enzymatic extraction. Total, extra- and intracellular folate were quantified by microbiological assay. Most Lactobacillus plantarum and Lactobacillus fermentum strains synthesized folate, Pediococcus pentosaceus strains consumed folate, and Pediococcus acidilactici strains either consumed or produced. Seven strains were further examined for their ability to synthesize or consume folate during growth in rich folate medium (MRS) and folate-free medium (FACM). For most strains, the differences observed in MRS were attenuated in FACM. L. fermentum 8.2 and L. plantarum 6.2 produced the highest levels of folates in MRS (97 and 93 ng·mL−1) and FACM (29 and 44 ng·mL−1). In most cases, production reached a maximum from 9 or 11 h to 24 h. Incubations in FACM with mixed LAB cultures showed that folate production is not additive. We demonstrated how biosynthesis of folate by LAB depends on species, strains, and is highly influenced by time and medium composition. Characterized LAB strains can be further explored for novel folate bio-enriched functional food.

Immobilization of lactic acid bacteria and application of bacteriocin for preservation of fruit juices and bacteriocin production

<p>Lactic acid bacteria are generally recognized as safe (GRAS) organisms producingbacteriocins that help in inhibiting foodborne pathogens. However, its narrow spectrum activity is a major limitation for food applications. Thus, a combination of different methods were attemptedto broaden the antimicrobial spectrum of bacteriocins produced using lactic acid bacteria. Initially, the antimicrobial activity of bacteriocin from various combinations of mixed lactic acid bacteria and single culture were determined after 56 hours at 35ºC to select the desirable combination with maximum antimicrobial activity. Combination of bacteriocin produced by <em>Lactobacillus plantarum </em>DFR4<em>, Enterococcus faecalis </em>DFR4 and<em> E.Faecalis </em>DFRP1 showed maximumactivity against <em>Listeria monocytogenes</em> with zone of 31.24±0.33 mm in agar disc diffusion assay. The specific activity and purification of bacteriocins produced by these isolates werefound to be highest in gel permeation chromatography whereas, the yield was highest in 80 percent acetone precipitation. The partially purified bacteriocins were further investigated for the effect of pH, enzymes and temperature stability and were found to be thermostableand active at pH range of 3 to 5. Proteolytic enzymes such as protease and papain inactivedthe bacteriocinswhile amylase had no inhibitory effect. The antimicrobial activity of bacteriocin produced from bamboo (<em>Bambusa vulgaris</em>) fibre immobilized <em>Lactobacillus plantarum</em> DFR4 was found to be more (zone size=20.91±0.35 mm) in comparison to free cells (zone size=8.52±0.26 mm) after 24 h of incubation at 37°C. Further, immobilization of <em>Lactobacillus plantarum </em>DFR4<em>, Enterococcus faecalis </em>DFR4 and<em> E. Faecalis </em>DFRP1 using bamboo fibre aided in faster production of bacteriocins in 24 h.Mosambi juice (<em>Citrus limetta</em>) supplemented with bacteriocins (produced from mixed bacterial isolates) had a shelf life of 26 days at 5ºC. </p>

Protective effects of a cocktail of lactic acid bacteria on microcystin-LR-induced hepatotoxicity and oxidative damage in BALB/c mice

The aim of this study was to investigate the effects of mixed lactic acid bacteria (LAB) against microcystin-LR-exposed hepatotoxicity and oxidative stress in BALB/c mice.

Mixed Lactobacillus plantarum Strains Inhibit Staphylococcus aureus Induced Inflammation and Ameliorate Intestinal Microflora in Mice.

Objective. Staphylococcus aureus is an important pathogen that causes intestinal infection. We examined the immunomodulatory function of single and mixed Lactobacillus plantarum strains, as well as their impacts on the structure of the microbiome in mice infected with Staphylococcus aureus. The experiment was divided into three groups: protection, treatment, and control. Serum IFN-γ and IL-4 levels, as well as intestinal sIgA levels, were measured during and 1 week after infection with Staphylococcus aureus with and without Lactobacillus plantarum treatment. We used 16s rRNA tagged sequencing to analyze microbiome composition. IFN-γ/IL-4 ratio decreased significantly from infection to convalescence, especially in the mixed Lactobacillus plantarum group. In the mixed Lactobacillus plantarum group the secretion of sIgA in the intestine of mice (9.4–9.7 ug/mL) was significantly higher than in the single lactic acid bacteria group. The dominant phyla in mice are Firmicutes, Bacteroidetes, and Proteobacteria. Treatment with mixed lactic acid bacteria increased the anti-inflammatory factor and the secretion of sIgA in the intestine of mice infected with Staphylococcus aureus and inhibited inflammation.

A large factory-scale application of selected autochthonous lactic acid bacteria for PDO Pecorino Siciliano cheese production

The main hypothesis of this study was that the autochthonous lactic acid bacteria (LAB) selected for their dairy traits are able to stabilize the production of PDO (Protected Denomination of Origin) Pecorino Siciliano cheese, preserving its typicality. The experimental plan included the application of a multi-strain lactic acid bacteria (LAB) culture, composed of starter (Lactococcus lactis subsp. lactis CAG4 and CAG37) and non starter (Enterococcus faecalis PSL71, Lactococcus garviae PSL67 and Streptococcus macedonicus PSL72) strains, during the traditional production of cheese at large scale level in six factories located in different areas of Sicily. The cheese making processes were followed from milk to ripened cheeses and the effects of the added LAB were evaluated on the microbiological, chemico-physical and sensorial characteristics of the final products. Results highlighted a high variability for all investigated parameters and the dominance of LAB cocci in bulk milk samples. The experimental curds showed a faster pH drop than control curds and the levels of LAB estimated in 5-month ripened experimental cheeses (7.59 and 7.27 Log CFU/g for rods and cocci, respectively) were higher than those of control cheeses (7.02 and 6.61 Log CFU/g for rods and cocci, respectively). The comparison of the bacterial isolates by randomly amplified polymorphic DNA (RAPD)-PCR evidenced the dominance of the added starter lactococci over native milk and vat LAB, while the added non starter LAB were found at almost the same levels of the indigenous strains. The sensory evaluation showed that the mixed LAB culture did not influence the majority of the sensory attributes of the cheeses and that each factory produced cheeses with unique characteristics. Finally, the multivariate statistical analysis based on all parameters evaluated on the ripened cheeses showed the dissimilarities and the relationships among cheeses. Thus, the main hypothesis of the work was accepted since the quality parameters of the final cheeses were stabilized, but all cheeses maintained their local typicality.

발효된 물김치인 동치미에서 분리한 혼합 젖산균의 생리활성 증진에 대한 연구

The aim of this study was to investigate the efficacy of enhanced physiological activities in cultures isolated from Korean fermented watery Kimchi, Dongchimi, of single lactic acid bacteria (LAB), and when these three are mixed LAB as probiotics. Using the BIOLOG system and 16S rRNA sequencing, the isolates were characterized, and identified and assigned to Leuconostoc mesenteroides DK-3, Leuconostoc dextranicum DK-6, and Lactobacillus curvatus DK-13, respectively. Growth rate and pH changes, production of organic acids as metabolites, and physiological activities of the single and mixed LAB cultures, were monitored and compared. In mixed LAB cultures after 72 h of incubation, the maximum concentrations of lactic acid and acetic acid were approximately 340.5 mM and 191.9 mM, respectively, and pH changed from 7.00 to 3.62. Mixed LAB cultures were able to eliminate 96.3% of nitrite. Activities of antioxidant and β-galactosidase were 60.3% and 16.8 units/mg, respectively. Significant antibacterial activity of the concentrated supernatants was demonstrated against several food-poisoning bacteria. Physiological activities obtained from the mixed LAB cultures have been shown to be considerably higher than those of single LAB cultures. In conclusion, these studies demonstrate that compared to the single cultures, all physiological activities in mixed LAB cultures are significantly enhanced.

English

The antagonistic effect of mixed lactic acid bacterial cultures against foodborne pathogens (Staphylocuccus aureus ATCC 25923, Shigella boydii clinical isolate, Pseudomonas aeruginosa ATCC 25853) was evaluated in pasteurized ayib stored at room temperature. The lactic acid bacteria (LAB) were tested for acid tolerance at pH 2.0, 2.5, 3.0 and 3.5 for three and six h and for bile tolerance for 24 and 48 h at 0.3% (w/v) bile salt concentration. Their antimicrobial effect on selected foodborne pathogens was assessed by co-culturing assays in laboratory medium. The effect of mixed LAB cultures against the foodborne pathogens tested was followed in ayib stored at ambient conditions for 9 days. Only 11 LAB isolates were isolated upon their survival at a pH value of 3.5. Out of the 11 LAB isolates selected from a total of 60 based on their survival at pH 3.5, 6 isolates showed survival at pH 2.5 and pH 3.0 for 3 h with survival rates of 1.03-22% and 5-100%, respectively. The same 6 LAB isolates displayed tolerance to 0.3% bile salt concentration for up to 48 h. In the presence of acid-bile tolerant LAB isolates as compared to the control (without any LAB bacteria), Ps. aeruginosa was inhibited by all six to varying degree while, Sh. boyidii and S. aureus were inhibited by five of the LAB in laboratory medium. The mixed LAB culture was inoculated in to pasteurized ayib which was stored at ambient temperature for nine days and completely eliminated Ps. aruginosa, S. aureus and Sh. boyidii from day 5, 6, and 7, respectively. The result indicates that the mixed acid-bile tolerant LAB cultures eliminated the test pathogens in both laboratory medium and in ayib. The mixed acid-bile tolerant LAB culture could possibly be used as candidate potential protective starter culture for preparation of ayib. Key words: Ayib, lactic acid bacteria, foodborne pathogens, acid-bile tolerance, inhibition

Evaluation of mono or mixed cultures of lactic acid bacteria in type II sourdough system

ABSTRACTThe aim of this study was to evaluate the use of mono and mixed lactic acid bacteria (LAB) cultures to determine suitable LAB combinations for a type II sourdough system. In this context, previously isolated sourdough LAB strains with antimicrobial activity, which included Lactobacillus plantarum PFC22, Lactobacillus brevis PFC31, Pediococcus acidilactici PFC38, and Lactobacillus sanfranciscensis PFC80, were used as mono or mixed culture combinations in a fermentation system to produce type II sourdough, and subsequently in bread dough production. Compared to the monoculture fermentation of dough, the use of mixed cultures shortened the adaptation period by half. In addition, the use of mixed cultures ensured higher microbial viability, and enhanced the fruity flavor during bread dough production. It was determined that the combination of L. plantarum PFC22 + P. acidilactici PFC38 + L. sanfranciscensis PFC80 is a promising culture mixture that can be used in the production of type II sourdough systems, and that may also contribute to an increase in metabolic activity during bread production process.