In vitro screening of EPS‐producing Streptococcus thermophilus strains for their probiotic potential from Dahi

作者：Taj Robina; Masud Tariq; Sohail Asma; Sammi Shehla; Naz Rooma; Sharma Kh**** Bal Kumari; Nawaz Malik Adil

来源：Food Science & Nutrition, 2022, 10(7): 2347-2359.

DOI：10.1002/FSN3.2843

• antibiotic
• cell surface hydrophobicity
• cellular auto‐aggregation
• Dahi
• exopolysaccharide (EPS)
• gastrointestinal transit tolerance

Dahi is a very common and traditional fermented dairy product in Pakistan and its neighboring countries, it represents a rich source for the isolation of many new strains of lactic acid bacteria (LAB). The major objective of this study was to evaluate the probiotic potential of novel exopolysaccharide (EPS)‐producing strains of S. thermophilus isolated from Dahi, sold in the local markets of Rawalpindi and Islamabad, Pakistan. In this study, 32 isolates of S. thermophilus were initially isolated from Dahi and out of these, 10 identified strains were further screened for their EPS‐producing ability. Maximum EPS production was estimated for RIY strain (133.0?±?0.06), followed by RIH4 strain (103.83?±?0.76) and RIRT2 strain (95.77?±?0.22), respectively. Thereafter, in vitro studies revealed that these newly identified EPS‐producing strains of S. thermophilus fulfilled the basic requirements for probiotic functions; including resistance to harsh conditions of GIT, good cell surface hydrophobicity, auto‐aggregation, and co‐aggregation, especially against L. monocytogenes. Finally, the safety assessment displayed that these strains were also sensitive to clinical antibiotics, including vancomycin. Thus, these selected EPS strains of S. thermophilus act as potential candidates for biostabilizers in the preparation of consumer‐friendly fermented probiotic milk products.(#br)Dahi is a famous fermented dairy product in Pakistan used for LAB isolation. S. thermophilus EPS‐generating strains were isolated from Dahi obtained in the marketplaces of Rawalpindi and Islamabad, Pakistan. Ten S. thermophilus strains were chosen for EPS production testing. This was followed by selecting three strains RIY (133.00.06), RIH4 (103.830.76), and RIRT2 (95.770.22). We chose these three strains based on their antibiotic susceptibility and acid/bile tolerance. In RIRT2, L. monocytogenes ATCC19115 survived at 0.3 and 1.5 percent bile. RIY exhibited the best acid tolerance (69%) and survival (25%), followed by RIH4 (nearly 65%) and RIH5 (almost 20%). RIY had the highest bile tolerance (0.3%), followed by RIH4 (80%) and RIRT2 (>70%). On the heels of RIRT2, RIY (57.7B) and RIH4 (97.80.4). (56.8C). Antibiotic resistance was found in all three.

• 出版日期2022