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Optimization of Probiotic Activity of Lactobacillus Acidophilus Characterized from Commercial Yoghurt

Md. Ashrafuzzaman
Department of Genetic Engineering and Biotechnology, Shahjalal University of Science and Technology, Sylhet, Bangladesh

Farhana Momtaz
Laboratory of Virology, ICDDR,B, Dhaka, Bangladesh

Md. Javed Foysal
Department of Genetic Engineering and Biotechnology, Shahjalal University of Science and Technology, Sylhet, Bangladesh

Md. Hazrat Ali
Department of Genetic Engineering and Biotechnology, Shahjalal University of Science and Technology, Sylhet, Bangladesh

Md. Mahbubur Rahman
Department of Biotechnology, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur, Bangladesh

Abstract/ Executive Summary:

In this study, five (5) Lactobacillus acidophilusisolates characterized from local yoghurt sample after enrichment in MRS broth using biochemical and morphological examination. Two of the five, isolate LA002 and LA005, posed best probiotic activity on test organisms.Al of the L. acidophilusisolates grew best at 37°C with an initial pH 5. However, the best activity ofL. acidophilus was observed in pH 6. The two lactic acid bacterial isolates, LA₀₀₂ and LA₀₀₅ demonstrated potent antimicrobial activity against different multi drug resistant isolates of Escherichia coli, Klebsiella pneumonia and Salmonella typhimorium. The L. acidophilus was found to be the most potent antagonistic microbe against E. coli and activity was much higher than onion and garlic. K. pneumonia also significantly inhibited by L. acidophilusisolates. However, L. acidophilus isolates can not considerably inhibit the growth of S. typhimorium.These results demonstrated that L. acidophilus bacteria can support a healthy digestive tract and can be used as a probiotic supplementation.

Keywords: Yoghurt, Lactobacillus acidophilus,Antibacterial activity, Probiotics

Location: Bogra, Sylhet and Dhaka

Start Date:

End Date:

Program Area: Quality and Nutrition

Non-commodity: Performance

Objectives:

The present study was conducted to determine an optimized growth condition of L.acidophilus in culture that showed a potent activity against human clinical samples and thus can be used as potential probiotic.

Methodology:

Curd collection - A total of 20samples were collected aseptically from three different sources: Bogra, Sylhet and Dhaka. After collection, the samples were immediately brought to the laboratory in cold condition and processed within an hour. Preparation of media - Curd is the best source for lactobacillus spp. among the other dairy products such as milk, buttermilk etc. Curd istaken in sterilized flask. Under the aseptic conditions curd was serially diluted from 10-1 to 10- 14 from this 14 dilutions 10-5 10-7 10-9 are selected. For this 3 tubes spread plate technique further with streak plate technique is done on MRS medium. They are incubated in incubator at 37⁰C which is optimum temperature for lactobacillus species for 24 hours. After the period of incubation 3 isolated colonies were grown. Colony characterization is done for this 3 colonies found to be lactobacillus species. 1 colony shows 100% resemblance with lactobacillus acidophilus. Further catalase test was done. Selected colonies were purified by streak plate method. The purified bacterial isolates were stored at -80C in sterile reconstituted skim milk 12.5 (w/v) supplemented with 15% glycerol. Determination of acid tolerance - Percent survival of the three strains was determined after exposure to pH 2.5 for 2 h and 4 hat 37°C. For this, overnight grown cultures were inoculated in MRS broth adjusted to pH 2.5. The samples were plated onto MRS agar at the end ofexposure time. The plates were incubated for 24 h at37°C and total viable count was determined. Uninoculatedbroth served as negative control while set of test organisms inoculated in MRS broth (pH6.2) was used as positive. Determination of bile tolerance - Bile tolerance of L. acidophilus cultures was examined by inoculating them in MRS broth containing oxgall (Central Drug House, New Delhi,India) at the concentrations of 0.2%, 0.3% and 0.5%.The control comprised of MRS broth without bilesalt. Bacterial growth was monitored by measuring absorbance at 600 nm after incubation for 24 h at37°C. Antimicrobial activity - Using in-vitro agar well diffusion method,antimicrobial activity experiments were carried out. The probiotic activity of Lactobacillus strains was tested against three common human pathogens (1) Escherichia coli (2) Salmonella typhi and (3) Klebsiellapneumoniae cultured earlier in nutrient agar (NA) broth. Overnight grown cultures of L. acidophilus strains were inoculated in the wells of nutrient agar where test microorganisms were inoculated by pour plate technique. The plates were incubated at 37ºC for 24h. The inhibition zones were measured at the end of incubation period. Antibiotic susceptibility assay - A disc diffusion assay was performed to study antibiotic susceptibility of L. acidophilus strains. The cultures were inoculated in MRS agar using pourplate technique. The antibiotics were supplied in the form of dodeca discs (Hi Media, India) which include dnalidixic acid, norfloxacin, cotrimoxazole, gentamycin, ampicillin, cephalexin, mecillinam, chloramphenicol, tetracycline, kanamycin, amikacinand streptomycin. The zones of inhibition weremeasured after incubation at 37ºC for 24 h. The strains were cultivated on control plates (MRS agar without antibiotic discs) under identical conditions.

Source of Information: International Journal of Biosciences | IJB |; ISSN: 2220-6655 (Print), 2222-5234 (Online); Vol. 7, No. 5, p. 94-99, 2015

Article Link (Online Journal): http://www.innspub.net; http://dx.doi.org/10.12692/ijb/7.5.94-99

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

It is concluded from the present study that the Lactobacillus species isolated from the yogurt appeared strong antagonistic against E. coli isolates while inhibiting, Klebsiella pneumoniae too. However, Lactobacillus acidophilus can not strongly inhibit Salmonella typhi in culture media. Thus, Lactobacillus acidophilus contain yogurt can be used a probiotics in regular healthy diet.

Knowledge Management: Journal