The purpose of this study was to explore Lactobacillus species from yogurt and cheese that can be used as potential probiotics. In this study, a total of twenty five samples, fifteen from cheese and ten from yogurt were collected from local markets, Dhaka city during May-July, 2016. Single colonies were isolated by enriching in MRS broth and subsequent streaking on MRS agar plate. Total twenty five isolated bacteria were identified as Lactobacillus species by morphological, gram staining and short biochemical tests. All isolated strains were characterized for probiotic properties including acid and salt tolerance, phenol tolerance, sugar fermentation, lactose fermentation and proteolytic activity. Acid tolerance test was performed at pH 2, 3, 4, 5, 6, 7 and 8 in MRS broth. Results showed all isolates survived in highly acidic pH, however most of the strains also survived in alkaline media (pH 8). Salt tolerance test was performed at 2%, 4% and 8% NaCl in MRS broth. All isolates survived in 2% and 4% NaCl concentrations. Phenol tolerance test was performed in MRS broth with 0.1%, 0.2%, 0.3% and 0.4% phenol concentration. All strains survived in 0.1% and 0.2% phenol concentrations. Sugars such as glucose, fructose, sucrose, xylose and lactose were used for fermentation tests. Results of fermentation test showed that most isolates fermented all sugars. All strains digested casein by producing protease enzyme in skim milk agar plate. This study indicated that Lactobacillus species from yogurt and cheese samples have potential probiotic properties. Further study is needed to find specific probiotics with specific benefit from yogurt and cheese.

Abstract:We studied soil samples from Dhaka municipality area to isolate and characterize bacteria having potential biochemical and pharmacological importance. Total twenty five soil samples were collected from fish, vegetables and fruits dump area from Dhaka City. Bacterial population was sub-cultured in trypticase soya agar (TSA) plate.Nineteen colonies were isolated, cultured and characterized by gram staining and biochemical tests. Six isolates were found to be gram negative while thirteen were gram positive. All isolates were positive in oxidase, catalase, citrate, and protease tests. Eight isolates showed coagulase negative and nine were coagulase positive. It was found that all bacterial isolates were sensitive to tetracycline, chloramphenicol, gentamycin, ciprofloxacin, azithromycin and ceftriaxone. About 95% of the bacterial isolates were resistant to penicillin-G and ampicillin. About 89%, 26%, 21% and 11% of the bacterial isolates were resistant to amoxicillin, co-trimoxazole, nalidixic acid and erythromycin, respectively. It was found that bacterial isolates produce chemical(s) inhibitory to other bacterial strains including both gram positive and gram negative bacteria. Further studies are needed to characterize the potential antibacterial factor(s) and other bioactive compound (s) present in these bacterial isolates from soil samples.