Monzur Morshed Ahmed

Screening of Lactobacillus spp. from Buffalo Yoghurt for Probiotic and Antibacterial Activity

Since the beneficial effects of viable probiotic bacteria as dietary supplements have gained huge research interest, Lactobacillus spp. with probiotic characteristics are widely used to prepare fermented dairy products such as yoghurts, milk-shakes etc. In this study, eight (08) homemade yoghurt samples were collected from different regions in the country for isolation of probiotic Lactobacillus spp. Among the samples, four (04) isolates were identified as Lactobacillus plantarum based on their growth and biochemical characteristics. The Isolates were resistant to NaCl (1-9%) and bilesalt (0.05-0.3%) and showed good growth in the acidic condition, while maximum growth was observed at pH around 6.0. The isolates were examined for their antibacterial activity against nine (09) different test pathogens and found all pathogens are inhibited their growth to some extent but maximum zone of inhibition was observed against Bacillus cereus (53.20 mm) and minimum was against Staphylococcus aureus (19 mm) after 72 hour incubation. The results of the present study indicate that, homemade yoghurts in Bangladesh are potential source of probiotic Lactobacillus spp. Further extensive research on isolation and characterization of probiotic organisms from local fermented foods and their growth optimization might be required for development of probiotic enriched food supplements in our country.

Stress tolerant virulent strains of Cronobacter sakazakii from food

BackgroundCronobacter sakazakii is considered as an emerging foodborne pathogen. The aim of this study was to isolate and characterize virulent strains of Cronobacter sakazakii from food samples of Bangladesh.ResultSix (6) Cronobacter sakazakii was isolated and identified from 54 food samples on the basis of biochemical characteristics, sugar fermentation, SDS-PAGE of whole cell protein, plasmid profile and PCR of Cronobacter spp. specific genes (esak, gluA, zpx, ompA, ERIC, BOX-AIR) and sequencing. These strains were found to have moderately high antibiotic resistance against common antibiotics and some are ESBL producer. Most of the C. sakazakii isolates were capable of producing biofilm (strong biofilm producer), extracellular protease and siderophores, curli expression, haemolysin, haemagglutinin, mannose resistant haemagglutinin, had high cell surface hydrophobicity, significant resistance to human serum, can tolerate high concentration of salt, bile and DNase production. Most of them produced enterotoxins of different molecular weight. The isolates pose significant serological cross-reactivity with other gram negative pathogens such as serotypes of Salmonella spp., Shigella boydii, Shigella sonnei, Shigella flexneri and Vibrio cholerae. They had significant tolerance to high temperature, low pH, dryness and osmotic stress.ConclusionSpecial attention should be given in ensuring hygiene in production and post-processing to prevent contamination of food with such stress-tolerant virulent Cronobacter sakazakii.

Antimicrobial and antioxidant activities of Saccharomyces cerevisiae IFST062013, a potential probiotic

BackgroundProbiotic yeast has become a field of interest to scientists in recent years.MethodsConventional cultural method was employed to isolate and identify yeast and standard methods were used to determine different probiotic attributes, antimicrobial and antioxidant properties.ResultsThis study reports potential probiotic properties of a strain of S. cerevisiae IFST 062013 isolated from fruit. The isolate is tolerant to a wide range of temperature and pH, high concentration of bile salt and NaCl, gastric juice, intestinal environment, α-amylase, trypsin and lysozyme. It can produce organic acid and showed resistance against tetracycline, ampicillin, gentamycin, penicillin, polymixin B and nalidixic acid. It can assimilate cholesterol, can produce killer toxin, vitamin B12, glutathione, siderophore and strong biofilm. It showed moderate auto-aggregation ability and cell surface hydrophobicity. The isolate can produce enzymes such as amylase, protease, lipase, cellulose, but unable to produce galactosidase. The isolate can’t produce gelatinase and DNase. The isolate showed moderate anti-microbial activity against bacteria and fungi and cell lysate showed better antimicrobial activity than whole cell and culture supernatant. Again, the isolate showed better anti-bacterial activity against gram negative bacteria than gram positive. The isolate showed strong antioxidant activity, reducing power, nitric oxide and hydroxyl radical scavenging activity, significant brine shrimp cytotoxicity and acute toxicity and metal ion chelating activity. The isolate did not induce any detectable change in general health of mice upon oral toxicity testing and found to be safe in mouse model. The isolate improve lymphocyte proliferation and cytokine production in treated mice.ConclusionsSuch isolate could be potential as probiotic to be used therapeutically.