Proteolytic profiles of yogurt and probiotic bacteria |
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| Affiliation: | 1. Food Science and Technology Programme, Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore;2. National University of Singapore (Suzhou) Research Institute, No. 377 Linquan Street, Suzhou Industrial Park, Suzhou, Jiangsu, 215123, China;1. Department of Food Science, University of Guelph, Canada;2. R&D Parmalat Canada, London, Ontario, Canada;1. Istinye University, Vocational School, Programme of Food Science and Technology, Istanbul, Turkey;2. Yildiz Technical University, Faculty of Chemical and Metallurgical Engineering, Department of Food Engineering, Istanbul, Turkey;1. Student Research Committee, Department of Food Science and Technology, National Nutrition and Food Technology Research Institute, Faculty of Nutrition Science and Food Technology, Shahid Beheshti University of Medical Sciences, Tehran, Iran;2. Department of Food Technology Research, National Nutrition and Food Technology Research Institute, Faculty of Nutrition Science and Food Technology, Shahid Beheshti University of Medical Sciences, Tehran, Iran;3. Department of Food Science and Technology, National Nutrition and Food Technology Research Institute, Faculty of Nutrition Science and Food Technology, Shahid Beheshti University of Medical Sciences, Tehran, Iran;2. Research and Development Center for University-Industry Public Relations (USKIM), Microbiology and Microbial Genetics Laboratory, and Kahramanmaraş Sutcu İmam University, 46060/Avsar, Kahramanmaras, Turkey;3. Faculty of Agriculture, Department of Agricultural Biotechnology, Kahramanmaraş Sutcu İmam University, 46060/Avsar, Kahramanmaras, Turkey |
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| Abstract: | Nine strains of Streptococcus thermophilus, 6 strains of Lactobacillus delbrueckii ssp. bulgaricus, 14 strains of Lactobacillus acidophilus and 13 strains of Bifidobacterium spp. were screened for proteolytic, amino-, di-, tri- and endopeptidase activity by using the o-pthaldialdehyde-based spectrophotometric assay. Strains showing the highest and lowest proteolytic activity were further studied for their peptidase activities at the extracellular and intracellular levels. The amounts of free amino groups released by S. thermophilus, L. delbrueckii ssp. bulgaricus and L. acidophilus strains were higher than that by Bifidobacterium strains. Aminopeptidase activity was detected for all bacterial strains both at the extracellular and intracellular levels. The specific activity towards the six substrates studied was higher at the intracellular level for all strains. High dipeptidase activity was demonstrated by all bacterial strains for L. delbrueckii ssp. bulgaricus, L. acidophilus, and Bifidobacterium spp. whereas S. thermophilus had greater dipeptidase activity at the extracellular level. All bacterial cultures tested were able to hydrolyse large biologically active peptides, bradykinin, Ala–Ala–Ala–Ala–Ala and the tripeptide substrate Gly–Ala–Tyr at both the extracellular and intracellular levels. However, with the substrates ending with a C-terminal of phenylalanine, the hydrolysis only occurred at the intracellular level. |
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