Anaerobe 13 (2007) 215–219 Food microbiology Screening of bifidobacteria with acquired tolerance to human gastrointestinal tract Ziyu Liu, Zhijie Jiang, Kang Zhou, Pinglan Li à , Guorong Liu, Bolin Zhang College of Food Science and Nutritional Engineering, China Agricultural University, Room 420, 17# Qinghua East Road, East District, Beijing 100083, China Received 23 December 2006; received in revised form 27 April 2007; accepted 10 May 2007 Available online 21 May 2007 Abstract Tolerance capabilities of 38 Bifidobacterium strains were achieved by simulating the micro-environment of human gastrointestinal tract using modified MRSC broth (pH 3.0). Fourteen strains of them with high viability were obtained in MRSC with 0.3% bile salts. Sequently, six strains of bifidobacteria with higher survivability were picked in MRSC broth (pH 3.0) supplemented with 1–20 mg/ml bile salt. Finally, strain A04 with the optimal ability was chosen for further studies. It had been seen that Bifidobacterium breve A04 had better survival capability to 0.5% pepsin (w/v) or 1% pancreatin (w/v) than other bifidobacteria, and viable bacteria were above 8.00 log cfu/ml after incubation for 24 h. Meanwhile, it had higher adhesive capability to HT-29 cells in vitro and average adhesive bacteria numbers reached 12.870.9 for each HT-29 cell. The results indicated that the ability to tolerate gastroenteric environment and the adhesive capacity to HT-29 cells among Bifidobacterium strains was different. B. breve A04 has several aspects of advantages and may be regarded as potential probiotics. r 2007 Elsevier Ltd. All rights reserved. Keywords: Bifidobacteria; Tolerance; Adhesion; Screening 1. Introduction Bifidobacteria are predominant bacteria in human intestinal microflora and colonize neonatal intestines for the first week after birth and inhabit the gastrointestinal tract throughout life [1]. They are considered to have beneficial effects on the host of all age groups by improving intestinal microbial balance [2,3] because bifidobacteria have beneficial physiological effects, such as inhibiting growth of several potentially pathogenic microbial groups [4–6], reducing colon cancer, improving lactose intolerance, preventing gut inflammation [7], enhancing natural im- munity [8] and reducing serum cholesterol [9]. However, bifidobacteria decline in human intestine with the ageing of human, the pollution of environment and the use of antibiotics, which will result in the disorder of intestinal microflora. It is essential that health products with claims meet the criterion of a minimum 10 6 /ml probiotic bacteria at the expiry phase because the mini- mum therapeutic dose per day is suggested to be 10 8 –10 9 cells [10]. To exert their functions, these bacteria must overcome biological barriers including gastric juice, hydro- lytic enzymes and bile salts in small intestine. So it is imperative to have probiotics enough to survive and achieve characteristic strains with both adherence to epithelial surfaces and persistence in human gastrointest- inal tract. It has been known that the resistance to acid and bile salts varies widely among bifidobacteria species even strains. Lan-szu and Bart [11] had substantiated that strains selected as probiotic bacteria should tolerate acid and bile salts for at least 90 min, attach to the epithelium and grow in the intestinal tract before they can provide any health benefits. The purpose of this study is to screen bifidobacteria with tolerance to human gastrointestinal tract and higher adhesive capability to HT-29 cell among 38 bifidobacterium strains. ARTICLE IN PRESS www.elsevier.com/locate/anaerobe 1075-9964/$ - see front matter r 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.anaerobe.2007.05.002 à Corresponding author. Tel.: +86 10 62737664; fax: +86 10 62737604. E-mail address: lipinglan420@126.com (P. Li).