http://archive.saulibrary.edu.bd/handle/123456789/4985 Thu, 04 Jun 2026 08:40:43 GMT 2026-06-04T08:40:43Z http://archive.saulibrary.edu.bd/handle/123456789/5263 STUDY ON ISOLATION, CHARACTERIZATION AND IDENTIFICATION OF LACTIC ACID BACTERIA DERIVED FROM FERMENTED DAIRY PRODUCTS RAHMAN, ABDUR Lactic acid bacteria (LAB) are important in dairy food fermentation which have beneficial health properties. The research was conducted to isolate, characterize and identify the LAB derived from fermented dairy products like dahi, borhani, matha, lassi, cheese and to assess their antibiotic susceptibility patterns. The bacteria were isolated based on their colony morphology on de Man, Rogosa, and Sharpe (MRS) agar and selected based on gram-staining properties, biochemical properties and molecular tests. Salt tolerance, sugar fermentation and growth at different temperatures and salt concentrations were observed for all isolates. PCR followed by 16S rDNA sequencing was done to identify the bacteria. All isolates survived at low (≤5%) NaCl concentration, but could not tolerate high (≥6%) NaCl concentration. All isolates can ferment glucose, sucrose, and lactose. All the tested isolates were sensitive to antibiotics like gentamicin, ciprofloxacin, tetracycline and ceftriaxone. Finally, the identified bacterial species were Lactobacillus rhamnosus from dahi, lassi and matha samples and Lactobacillus fermentum was identified from the cheese sample which are known as probiotic species. Ultimately, the research revealed two antibiotic-sensitive LAB species suitable for incorporation into fermented dairy product formulations. A thesis Submitted to the Department of Dairy Science Faculty of Animal Science and Veterinary Medicine Sher-e-Bangla Agricultural University, Dhaka in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE IN DAIRY SCIENCE Sat, 01 Jan 2022 00:00:00 GMT http://archive.saulibrary.edu.bd/handle/123456789/5263 2022-01-01T00:00:00Z http://archive.saulibrary.edu.bd/handle/123456789/5262 CHARACTERIZATION AND ANTIBIOGRAM STUDY OF SOME PATHOGENIC BACTERIA ISOLATED FROM FERMENTED DAIRY PRODUCTS IN DHAKA CITY SULTANA, MST. TASMIM This study aimed to investigate the microbiological quality of various fermented dairy products by isolating different pathogenic bacteria and antibiogram study. A total of 50 samples consisting packaged (n=30) and non-packaged (n=20) were aseptically collected and subjected to microbiological analysis. The samples were cultured on selective media to isolate and identify pathogenic bacteria based on morphological, biochemical, microscopic and molecular characteristics and finally antibiogram study was done for the isolated bacteria. From the study, it was found that the dahi had the highest titratable acidity, with mean values of 1.003%, while lassi, matha, and burhani had lower mean values of 0.51%, 0.63%, and 0.65%, respectively. The Total Viable Count (TVC) of all fermented dairy products ranged from 6 to 8 log CFU/ml, with the mean Total Coliform Count (TCC) being lowest in packaged dahi and highest in nonpackaged burhani. Furthermore, the Total Salmonella-Shigella Count (TSS) and Total Staphylococcal Count (TSC) is remarkable in non-packaged burhani and non-packaged dahi. Out of the 50 samples in total, 52% contained Escherichia coli, 10% had Staphylococcus, and 4% showed the presence of Salmonella species. In the current research, it was discovered that 52% of the samples contained at least one type of bacteria from three different genera: Staphylococcus, Escherichia coli, and Salmonella. The overall prevalence rate was lower in packaged products (30%) than non-packaged (85%) products. Almost all of the isolated bacteria were resistant to amoxicillin, tetracycline and erythromycin exhibiting less resistance pattern to ciprofloxacin, gentamicin and neomycin. This study revealed that in spite of having high acidity, fermented dairy products sold at different markets in Dhaka city were contaminated with multiple species of antibiotic resistant bacteria. Keywords: Characterization, pathogenic bacteria, fermentation, antibiogram, dairy products, A Thesis Submitted to the Department of Dairy Science Sher-e-Bangla Agricultural University, Dhaka in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE IN DAIRY SCIENCE Sat, 01 Jan 2022 00:00:00 GMT http://archive.saulibrary.edu.bd/handle/123456789/5262 2022-01-01T00:00:00Z