Diversity and probiotic potentials of lactic acid bacteria isolated from gilaburu,a traditional Turkish fermented European cranberrybush (Viburnum opulus L.) fruit drink

The aim of the present study was to characterize lactic acid bacteria (LAB) strains isolated from traditional fermented gilaburu fruit juice and their probiotic potential. The LAB counts of the fermented gilaburu fruit juice were in the range of 3.92–8.30 log cfu/g. Total of 332 isolates belonging to Lactobacillus and Leuconostoc species were characterized from traditional fermented gilaburu juice by genotypic methods. It was also determined that the major LAB strains belong to Lactobacillus plantarum (173 isolates), Lactobacillus casei (52 isolates) and Lactobacillus brevis (24 isolates), while Lactobacillus buchneri, Lactobacillus parabuchneri, Lactobacillus pantheris, Leuconostoc pseudomesenteroides and Lactobacillus harbinensis were the least in isolated LAB strains. In terms of the probiotic potentials, Lb. plantarum strains were able to grow at pH 2.5, but 3 of Lb. casei strains, one of each Lb. brevis and Lb. buchneri strains could not grow at the same pH. All selected LAB stains were resistant to bile salt at ≤ 0.3% concentration. While all the LAB species grew at 15 °C, two Lactobacillus hordei strains could also grow at 45 °C. The highest cell hydrophobicity degrees were for Lb. casei (G20a) and Lb. plantarum (G19e) as 87.5 and 86.0%, respectively. Listeria monocytogenes and Bacillus cereus were the most sensitive bacteria against the selected LAB strains, while Escherichia coli and Staphylococcus aureus were the most resistant. Again all the isolated LAB species were resistant to three antibiotics; kanamycin, streptomycin and vancomycin. Characterization and probiotic potentials of the LAB isolated from fermented gilaburu (Viburnum opulus) juice were studied first time, and further research needs to be done on their behaviors in similar food formulations as a probiotic.     

Effect of cryoprotectants,prebiotics and microencapsulation on survival of probiotic organisms in yoghurt and freeze-dried yoghurt

The survival of probiotic microorganisms including Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus rhamnosus and Bifidobacterium spp. was evaluated in yoghurt and freeze-dried yoghurt after processing and storage. The effectiveness of microencapsulating probiotic organisms as well as adding cryoprotectants and prebiotics in improving their viability was also investigated. The viability of Bifidobacterium infantis 17930 and L. rhamnosus GG was reduced by 0.07 log, while that of L. casei 1520 and Bifidobacterium longum 1941 was reduced by 0.28 and 0.39 log, respectively. There was a 7% improvement in the viability of L. casei 1520 when cryoprotectant ‘Unipectine™ RS 150’ was added at 2.5% (w/v). The prebiotic ‘Raftilose^®P95’ when added at 1.5% w/v to yoghurt improved the viability of the combined selected probiotic organisms by 1.42 log during four weeks of storage at 4 °C. Microencapsulation with alginate improved viability of combined selected probiotic organisms by 0.31 log in freeze-dried yoghurt stored at 21 °C.     

Survival and activity of selected probiotic organisms in set-type yoghurt during cold storage

The growth and metabolism of two probiotic organisms (L. acidophilus LAFTI^® L10 and Lactobacillus casei LAFTI^® L26) and a regular yoghurt culture (L. delbrueckii ssp. bulgaricus Lb1466 and Streptococcus thermophilus St1342) were studied in yoghurt containing 0.5%, 1.0%, and 1.5% (w/v) of high amylose corn starch powder (Hi-maize^®) or inulin. Viable cell counts of probiotic organisms, their metabolites and proteolytic activities, and viscosity of the yoghurts were determined during refrigerated storage for 28 d at 4 ^oC. In the presence of inulin, cultures showed better retention of viability (8.0 log cfu g⁻¹) in comparison with that of Hi-maize, which had a reduction by one log cycle. Lower concentrations of 0.5–1.0% Hi-maize improved (P<0.05) the production of propionic acid and also increased proteolytic activity of probiotic organisms substantially. A greater release of free amino acids may have sustained better growth of the organisms in yoghurts. Supplementation with either Hi-maize or inulin increased the viscosity of probiotic yoghurts significantly (P<0.05).     

Antibiotic resistance and susceptibility to some food preservative measures of spoilage and pathogenic micro-organisms from spices

Antibiogram of 84 strains of Bacillus cereus, 26 strains of Clostridium perfringens, four strains of Staphylococcus aureus, 51 strains of Enterobacteriaceae, two strains of each of Salmonella and Shigella; isolated from spices, were studied against 20 different antibiotics that are commonly used against foodborne diseases, mainly gastroenteritis. All the tested strains of B. cereus, Cl. perfringens, Staph. aureus, Escherichia coli, Salmonella and Shigella were found resistant to at least 3, 4, 7, 6, 10 and 9 antibiotics, respectively. In brain–heart infusion broth supplemented with glucose, the D_100°C-values for B. cereus were 3.5–5.9 min, and the z-values were 17–18°C. The D_100°C-values for Cl. perfringens in fluid thioglycolate medium were higher (10.0–19.8 min) than those of B. cereus. The minimum inhibitory concentrations (MICs) of sodium chloride were 45–80 mg ml⁻¹. While the MIC of benzoic acid for Cl. perfringens, tested on perfringens agar (pH 7.3) plates by incubating anaerobially at 35°C for 24 h, was 1.9–2.2 mg ml⁻¹, for others, tested on nutrient agar (pH 6.8) plates by incubating at 35°C for 18 h in static aerobic condition, it was much less. Similarly, the MIC of sorbic acid for all the tested isolates, excepting Cl. perfringens, was 0.6–1.1 mg ml⁻¹. Of the eight isolates of Cl. perfringens, only three were inhibited at 2.0 mg sorbic acid ml⁻¹, while others were resistant. Sixty percent and 75% of the respective strains of B. cereus and Cl. perfringens were resistant to 5000 IU Nisaplin ml⁻¹, whereas the MIC values of Staph. aureus were between 3000 and 5000 IU ml⁻¹. While studying combined effect of selected hurdles on the growth of enterotoxigenic Cl. perfringens 16-C2, the judicious combination considered was low acid (pH 6.0), 30 mg sodium chloride ml⁻¹ and 1.25 mg benzoic acid ml⁻¹.     

Effects of probiotic administration in swine

In the present work we evaluated the effects of probiotic strains administration in pigs. On the 35th day of age, 30 pigs were distributed into 2 groups: the non-treated control group (initial average BW: 8.3 ± 0.6 kg) and a probiotic supplemented fed group (initial average BW: 8.7 ± 0.4 kg). Each experimental group was fed ad libitum on a commercial diet with free access to tap water for 35 days. A mixed probiotic culture (10⁸ CFU/ml) was orally delivered, every day, to the animals of the probiotic supplemented fed group. Body weight (BW), feed intake (FI), efficiency (BW: Feed), and faecal microflora, were studied before and throughout the experimental trial. At the end of the fifth week, 5 animals of each dietary treatment were slaughtered and intestinal samples were taken for histology. The results obtained showed that the group receiving probiotic bacteria exhibited lower FI values and better efficiency than control group (P ≤ 0.05), but mean final BW values were not significantly different. Only significant changes (P ≤ 0.05) were found in enterobacteria population between control and probiotic supplemented fed group during the experimental period. By histological techniques it was observed that the treatment group has intestinal morphological structures more preserved than control group. These results suggest that probiotic bacteria administrated in this study could be used widespread as a way to improve growth performance parameters of animals avoiding the use of antibiotics as growth-promoting factors.     

Isolation of Fungal Species from Fermentating Pearl Millet Gruel and Determination of their Antagonistic Activities against Indicator Bacterial Species

The mycological and physicochemical qualities (pH and titratable acidity) of fermenting pearl millet gruel were evaluated using routine methods. Several species of yeasts and moulds were isolated and the mould species identified based on their observable macroscopic and microscopic characteristics. The moulds identified included: Penicillium sp (FM1), Rhizopus spp (FM2, FM3 and FM6), Aspergillus flavus (FM7) and Aspergillus niger (FM8). These isolates were screened for production of antimicrobial compounds using agar well diffusion method. Escherichia coli, Staphylococcus aureus, Bacillus cereus, Bacillus lichieniformis, Salmonella spp., Pseudomonas fluorescens, Pseudomonas aeruginosa, Pseudomonas syringae, Proteus sp. and Serratia sp. were utilized as indicator organisms. Secondary metabolites were also extracted from the respective moulds and the antimicrobial properties of these metabolites were tested against pure cultures of E. coli, S. aureus, P. flourescens and B. lichieniformis. All the moulds exhibited antimicrobial activity against P. flourescens while the metabolic extract of Aspergillus flavus (FM7) displayed the highest zone of inhibition (24 mm) against an overnight culture of P. flourescens.     

Safety aspects of probiotic bacterial strains Lactobacillus rhamnosus HN001 and Bifidobacterium animalis subsp. lactis HN019 in human infants aged 0–2 years

Given the relatively immature state of the neonatal gut and gut-associated immune system, the safety of probiotic strains for use as ingredients in infant milk formulae must be demonstrated in infant populations. As part of a double-blind placebo-controlled clinical trial of two commercially available probiotic strains in the reduction of risk for infant eczema, a number of safety outcomes were measured. Infants received daily doses of Lactobacillus rhamnosus HN001 (6 × 10⁹ cfu day^?1) or Bifidobacterium animalis subsp. lactis HN019 (9 × 10⁹ cfu day^?1), or placebo from birth to 24 months. Mothers received the same treatment from 35 weeks gestation, for up to 6 months postnatally while breastfeeding. No statistically significant differences were observed between the treatment groups for study withdrawal, incidence of adverse events, morphometric data, wheeze, and antibiotic use over the treatment period. We conclude that probiotics strains HN001 and HN019 were safe and well tolerated in infants, and did not affect normal growth.     

Probiotic properties of folate producing Streptococcus thermophilus strains

This study aimed at assessing the probiotic potential of two high folate producing Streptococcus thermophilus strains (RD102 and RD104) isolated from Indian fermented milk products by both in vitro and in vivo tests. These strains were able to survive at pH 2.5 and 2% bile with a good bile salt hydrolase activity, cell surface hydrophobicity and sensitivity to most of the clinically important antibiotics. On evaluation for gastrointestinal transit tolerance these showed a viable count of 5 log cfu mL^?1 and 7 log cfu mL^?1, respectively in simulated gastrointestinal juice of pH 2.0 and 2% bile. During the in vivo feeding trial in mice the strains showed a viable count of about 7 log cfu g^?1 faeces and 6 log cfu g^?1 of large intestine, respectively. These strains were hence observed to possess favorable strain specific probiotic properties and have the potential to be a source of novel probiotics.     

Yacon (Smallanthus sonchifolius) and Lactobacillus acidophilus CRL 1014 reduce the early phases of colon carcinogenesis in male Wistar rats

The modifying effects of aqueous yacon extract (AYE) and Lactobacillus acidophilus CRL 1014 against colon carcinogenesis induced by 1,2-dimethylhydrazine (DMH) in male Wistar rats were investigated. Animals were allocated into five groups: G1: untreated group; G2: DMH-treated group; G3: DMH + L. acidophilus-treated group; G4: DMH + AYE-treated group; G5: DMH + L. acidophilus and AYE-treated group. A significant reduction (p < 0.05) in leukocyte DNA damage and in colonic cell proliferation was observed after the first DMH administration in G3 (probiotic), G4 (prebiotic) and G5 (synbiotic) groups. In this moment, a significant increase (p < 0.05) in colonic apoptosis was also observed in G3 (probiotic) and G5 (synbiotic) groups. In special, at five months after DMH administrations, a significant reduction (p < 0.05) in ACF development was observed in G3 (probiotic), G4 (prebiotic) and G5 (synbiotic) groups. Incidence of colon tumors was lower at five months in G4 (prebiotic) and G5 (synbiotic) groups but not in eight months after DMH administrations. In conclusion, the findings suggest that the oral treatments have potential effects as a chemopreventive agent against colon carcinogenesis on an early stage of tumor development.     

Kefir yeasts enhance probiotic potentials of Lactobacillus paracasei H9: The positive effects of coaggregation between the two strains

This study investigated pure Lactobacillus paracasei H9 tolerance to simulated gastrointestinal juices and adhesion to intestinal mucosa cells without yeasts, with viable yeasts (VY) and with different pretreated yeasts. Three models including gastric secretion tolerance (GST), intestinal juice tolerance (IJT) and sequential gastrointestinal tolerance (SGT) were respectively employed to assay the tolerance of L. paracasei H9, whilst Caco-2 cell line was used to investigate the bacterial adhesion. Particularly, the co-aggregation ability of the two strains at pH values of 2.0, 8.0 and 7.2 was originally carried out to study relations to the bacterial probiotic potentials. Results showed that yeast counts in the range from 3.0 to 5.0 log CFU mL^? 1 could gradually increase the viability of L. paracasei H9 in SGT. The bacterial viability in the three tolerance models and the adherent number to Caco-2 cells were significantly improved with addition of VY (P < 0.05). The L. paracasei H9 with VY in gastric juice at pH 2.0 and intestinal juice at pH 8.0, respectively, exhibited higher aggregation percentage compared with that of single L. paracasei H9 at 37 °C (P < 0.05). The aggregation ability of L. paracasei H9 with VY at pH 7.2, which might contribute to increase the adhesion of the bacteria, also excelled that of L. paracasei H9 (P < 0.05). It is deduced that proteins of the bacterial cell surface and polysaccharides in yeast cell walls play important roles in co-aggregation of the two strains and the microbial adhesion specificity to Caco-2 cells. The co-aggregation of the two strains also contributes to enhancing probiotic potentials of L. paracasei H9.     

Proteolytic pattern and organic acid profiles of probiotic Cheddar cheese as influenced by probiotic strains of Lactobacillus acidophilus,Lb. paracasei,Lb. casei or Bifidobacterium sp.

Cheddar cheeses were produced with starter lactococci and Bifidobacterium longum 1941, B. lactis LAFTI^® B94, Lactobacillus casei 279, Lb. paracasei LAFTI^® L26, Lb. acidophilus 4962 or Lb. acidophilus LAFTI^® L10 to study the survival of the probiotic bacteria and the influence of these organisms on proteolytic patterns and production of organic acid during ripening period of 6 months at 4 °C. All probiotic adjuncts survived the manufacturing process of Cheddar cheese at high levels without alteration to the cheese-making process. After 6 months of ripening, cheeses maintained the level of probiotic organisms at >8.0 log₁₀ cfu g⁻¹ with minimal effect on moisture, fat, protein and salt content. Acetic acid concentration was higher in cheeses with B. longum 1941, B. lactis LAFTI^® B94, Lb. casei 279 and Lb. paracasei LAFTI^® L26. Each probiotic organism influenced the proteolytic pattern of Cheddar cheese in different ways. Lb. casei 279 and Lb. paracasei LAFTI^® L26 showed higher hydrolysis of casein. Higher concentrations of free amino acids (FAAs) were found in all probiotic cheeses. Although Bifidobacterium sp. was found to be weakly proteolytic, cheeses with the addition of those strains had highest concentration of FAAs. These data thus suggested that Lb. acidophilus 4962, Lb. casei 279, B. longum 1941, Lb. acidophilus LAFTI^® L10, Lb. paracasei LAFTI^® L26 and B. lactis LAFTI^® B94 can be applied successfully in Cheddar cheese.     

Development of probiotic beads similar to fish eggs

Probiotic foods are mainly restricted to dairy and soy products. This study aimed to develop a new probiotic beads similar to fish eggs, commonly used in oriental cuisine. Beads were produced by the extrusion encapsulation technique with calcium alginate, added to one of the following cultures: Lactobacillus rhamnosus GG ATCC 53103 and Bifidobacterium animalis DN-173 010 and stored for 30 days at 4 °C. The beads were characterized by the size, weight, morphology and viability of the probiotic strains in different storage temperatures and in simulated gastric juice adjusted to different pH values. The beads were also evaluated by a sensorial affective hedonic scale. The beads present a 2.8 mm diameter and a weight of 0.01 g (p > 0.05). Free and encapsulated cells were tolerant to pH 3.0. At pH 2.5 only of the encapsulated cells presented counts above 6 Log colony-forming units per gram (CFU/g). Beads containing L. rhamnosus showed higher viability 10⁷ CFU/g in storage for 30 days under refrigeration. The beads may be stored at abusive temperature for 5 h without loss of viability cells. The probiotic product developed showed an 82.2% acceptability index of overall characteristics and good market potential as a new probiotic product.     

Biofilm formation,virulence gene and multi-drug resistance in Salmonella Kentucky isolated in Tunisia

Food-borne diseases caused by Salmonella enterica are a significant public health concern around the world. Since 2002, S. enterica serovar Kentucky has shown an increase in several countries with the concurrent emergence of multidrug-resistant isolates. The spread of such strains in the environment poses a major public health problem. A total of 57 Salmonella Kentucky strains isolated from different sources during the period 2005 to 2008 in Tunisia, were characterized by their antimicrobial and mercury resistance profiles; ability to form a biofilm; virulence invA/spvC genes and quorum sensing sdiA gene. A total of 10.6% of the isolates demonstrated multidrug-resistance against 3 to 13 antibiotics with ciprofloxacin resistance occurring in 33% of human isolates. In addition, 37% of the isolates exhibited minimum inhibitory concentrations value to mercuric chloride, ranging from 8 to 32 μg ml^?1 and were considered as resistant strains. The majority of strains tested were able to form a biofilm, especially for environmental and animal derived isolates. Therefore, the biofilm seems to comprise a normal and favorable capability in the life of Salmonella Kentucky in the environment. Interestingly, all the isolates possessed the sdiA gene, 87.7% of isolates possessed the invA gene, and no isolate harbored the spvC gene.The emergence of resistance to ciprofloxacin in human Salmonella Kentucky isolates, added to the presence of invA and sdiA genes, and the production of biofilm could be the decisive factors in the dissemination of S. Kentucky strains on a large scale.     

Volatile constituents from the leaves of Polygonum cuspidatum S. et Z. and their anti-bacterial activities

Volatile substances extracted from leaves of Polygonum cuspidatum S. et Z. by simultaneous steam distillation and solvent extraction (SDE) were investigated in terms of their inhibitory activities against six foodborne micro-organisms using Bioscreen C. The SDE extracts from P. cuspidatum S. et Z. obtained after 1.5 or 2.0 h at pH 4.5 exhibited strong growth inhibition upon the six micro-organisms tested; their volatile contents were 5.74 and 8.89 μl/100 g, respectively. Anti-bacterial activities against the bacterial strains examined increased upon reducing SDE pH from 6.5 to 3.5 and by increasing the extraction time from 0.5 to 2.0 h. The major volatile components of the SDE extracts obtained after 1.5 h at pH 4.5 were 2-hexenal (73.36%), 3-hexen-1-ol (6.97%), n-hexanal (2.81%), 1-penten-3-ol (2.55%), 2-penten-1-ol (2.21%), and ethyl vinyl ketone (1.13%) by Gas chromatography. The addition of 10% (v/v) of the SDE extracts to broth completely inhibited the growth of Bacillus cereus and of Vibrio parahaemolyticus for 72 h.     

Addition of probiotic bacteria in a semi-hard goat cheese (coalho): Survival to simulated gastrointestinal conditions and inhibitory effect against pathogenic bacteria

In this study, the survival of the probiotics Lactobacillus acidophilus (LA-5), Lactobacillus casei subsp. paracasei (L. casei 01) and Bifidobacterium lactis (BB12) incorporated in a Brazilian semi-hard goat cheese (coalho) when exposed to in vitro simulated conditions of digestion was assessed. The inhibitory effects of these probiotic bacteria were also evaluated against Listeria monocytogenes and Staphylococcus aureus in the goat coalho cheese during refrigerated storage. At the end of the in vitro digestion, all of the probiotic tested strains presented decreased (p < 0.05) viable cell counts (5.5–6.0 log cfu/g) with respect to those determined before exposure to the mouth conditions (7–8 log cfu/g). L. casei subsp. paracasei presented inhibition rate of 7.87% and 23.63% against S. aureus on the 14th and 21st day of storage at 10 °C, respectively; against L. monocytogenes these values were 12.96 and 32.99%. Positive inhibition rates of B. lactis toward S. aureus were found on the 1st, 14th and 21st days of storage (16.32%, 10.12% and 3.67%, respectively); and against L. monocytogenes only on the 1st day of storage (3.28%). From these results, goat coalho cheese could be an interesting carrier of probiotic strains of L. acidophilus, L. casei subsp. paracasei and B. lactis. Moreover, L. casei subsp. paracasei, could be used as protective culture for delaying the growth of S. aureus and L. monocytogenes in goat coalho cheese.     

Effect of temperature on growth and metabolism of probiotic bacteria in milk

The growth and metabolism of six probiotic strains with documented health effects were studied in ultra-high temperature (UHT) treated milk supplemented with 0.5% (w/v) tryptone or 0.75% (w/v) fructose at different temperatures. The probiotic strains were Lactobacillus acidophilus La5, Lb. acidophilus 1748, Lb. johnsonii LA1, Lb. rhamnosus GG, Lb. reuteri SD 2112 and Bifidobacterium animalis BB12. Fermentation was followed for 48 h at 20, 30, 37 and 45 °C and the samples were analysed for pH, log cfu mL⁻¹, volatile compounds, organic acids and carbon dioxide. All six probiotic strains showed very different profiles of metabolites during fermentation, however, the two Lb. acidophilus strains were the most alike. All strains, except Lb. reuteri SD 2112, showed viable cell numbers above 6.5 log cfu mL⁻¹ after 48 h fermentation at 30, 37 and 45 °C. The probiotic strains produced different amounts of metabolic products according to temperature and fermentation time illustrating the importance of controlling these parameters.     

Phytochemical and Antimicrobial Evaluation of Aqueous and Organic Extracts of Calotropis procera Ait Leaf and Latex

The aqueous and ethanol extract of Calotropis procera leaf and latex were investigated. The leaves and latex from the plant were tested for antimicrobial activities. The bioactive constituents extracted from the leaf and latex were tested against pathogenic organisms (Eschericia coli, Salmonella typhi, Bacillius subtilis, Candida albicans, Aspergillus niger) using the Agar well diffusion method. The ethanolic latex extract showed significant activity against all the test organisms. The results revealed that ethanol is a more effective extractive solvent for antimicrobial activity of leaf and latex of C. procera. The ethanol extract of the latex gave the widest zone of inhibition (21 mm) against B. subtilis. All the extracts inhibit the growth of all the organisms except B. subtilis of which the aqueous extract has no effect. The Minimum Inhibitory Concentration (MIC) for the latex extract was between 3 and 7.5 mg/ml for bacteria, and 5.0 to 7.0 mg/ ml for fungi. For the leaf extract the MIC for bacteria was between 5.0 and 10.5 mg/ml and 11 and 15 mg/ml for fungi. The results also showed an increase in antimicrobial activity with increase in temperature. This study therefore revealed that C. procera latex extract demonstrated strong and better inhibitory activity on the test organisms than the leaf extract. These findings therefore provide an explanation for the traditional medicinal use of C. procera extracts.     

Development of potentially synbiotic fresh-cut apple slices

The aim of this study was, to develop potentially synbiotic fresh-cut apple wedges by applying probiotic bacteria (Lactobacillus rhamnosus GG) and prebiotics in the form of oligofructose and inulin. An assessment of the quality, sensory, polyphenol and volatile attributes of synbiotic and probiotic samples was also undertaken. Fructan analysis showed that all prebiotics remained stable over the 14 days storage period and an intake of 100 g of apple supplies 2–3 g of prebiotics. All samples sets contained ca. 10⁸ cfu/g over the test period, which is sufficient for a probiotic effect, and is comparable to counts of probiotic bacteria in commercially available dairy products. Browning index, firmness, acidity and dry matter remained stable throughout the 14 days compared to the control while applying prebiotic coatings resulted in an increase in soluble solids. Sensory assessment indicated acceptable quality of probiotic and synbiotic apple wedges. HPLC analysis showed levels of decrease in polyphenolic compounds. No difference was found between O₂ and CO₂ headspace concentration and volatile production of synbiotic samples and samples only treated with probiotics.     

Antibiotic Susceptibility Profile and Survival of Bifidobacterium adolescentis and Bifidobacterium catenulatum of Human and Avian Origin in Stored Yoghurt

Bifidobacteria are categorized as health-promoting microorganisms (probiotics) in the gastrointestinal tracts of humans and animals. Antibiotic susceptibility is a key criterion for probiotic agent selection. Good survival of probiotics during storage at selected storage temperature(s) is highly desirable. Bifidobacteria isolated from human and chicken were thus characterized phenotypically by their ability to produce fructose-6-phosphoketolase enzyme. Eight selected isolates were then characterized on molecular basis employing genus-specific and species-specific 16S rRNA gene primers, and their antibiotic susceptibilities were also evaluated. Isolates were confirmed to be strains of B. catenulatum (4) and B. adolescentis (4). Studied strains were resistant to streptomycin, gentamycin, cloxacillin and cotrimoxazole but susceptible to chloramphenicol, augmentin, amoxicillin and erythromycin. Three strains (B. catenulatum HM2, B. catenulatum HM3 and B. catenulatum HM5) showed atypical tetracycline resistance. B. catenulatum HM2, B. adolescentis CH2 and B. adolescentis CH3 showed significant reduction in counts (p < 0.05) and survived in adequate amount in yoghurt stored at 4°C and -18°C for 4 weeks. In addition to presenting acceptable antibiotic susceptibility profile and exhibiting good survival in stored yoghurt, the bifidobacteria isolates inhibited Staphylococcus aureus ATCC 25925 and Escherichia coli ATCC 25922 in-vitro and demonstrated potential for application as probiotic agents for human and agricultural purposes.     

Identification of bioactive peptides in commercial Cheddar cheese

This study examined the presence of antimicrobial, antioxidant and antihypertensive peptides in three commercially available Australian Cheddar cheeses. Peptide extracts as well as fractionated peptide extracts were examined. Commercial cheese A peptides exhibited the greatest inhibition against Bacillus cereus and also commercial cheese A fractionated peptides greater than 10 kDa showed the highest inhibition against B. cereus. Commercial cheese A peptides also showed the highest inhibition of 2,2-diphenyl-1-picrylhydrazyl (DPPH), a free radical used to measure antioxidant activity. All cheese fractionated peptides greater than 10 kDa demonstrated higher inhibition of DPPH after fractionation. Antihypertensive peptides were determined by inhibition of the angiotensin-converting enzyme (ACE). Overall, commercial cheese A had the lowest concentration required to inhibit ACE and commercial cheese A fractionated peptides lower than 5 kDa had the lowest inhibition after fractionation. These preliminary findings suggest that peptide extracts of three commercial Australian Cheddar cheeses exhibit antimicrobial, antihypertensive and antioxidant properties.