Short communication Application of in vitro methods for selection of Lactobacillus casei strains as potential probiotics Vijendra Mishra * , D.N. Prasad Department of Microbiology, Bundelkhand University, Jhansi, India Dairy Microbiology Division, National Dairy Research Institute, Karnal 132 001, India Received 28 April 2003; received in revised form 15 April 2004; accepted 6 October 2004 Abstract Probiotics have established their efficacy as dietary adjuncts providing benefits to consumers, but the selection of probiotics before incorporation in diet requires close scrutiny in the form of in vitro as well as in vivo tests. The present study was undertaken to check different in vitro characteristics of seven Lactobacillus casei strains. The characteristics studied include acid and bile tolerance, adhesion and cell surface hydrophobicity, antimicrobial effect on common pathogens and cholesterol reduction. All strains were able to resist pH 3 for 3 h, though resistance to pH 2 was exhibited by NCDC 17, C1 and Y strains only. NCDC 63 and VT strains were able to tolerate 1% and 2% bile concentrations for 12 h. There was wide variation in ability of strains to adhere to isolated rat epithelial cells. The index was highest for C1 at 66%. The electron microscopic adhesion studies on the stainless steel chips did not reveal any specific attachment to surfaces by any of strains. The hydrophobic character for octane was highest for strain C1 at 54.06% and lowest for strain C2 at 4.65%. The ability to antagonize common pathogens was observed in all strains but this activity was attributed to production of organic acids and no specific compound caused the inhibitory effect. The cholesterol reducing ability varied not only for strains but also for time of incubation. NCDC 17 showed maximum reduction in cholesterol level after 48 h of incubation with buffalo plasma as the source of cholesterol. Overall there existed variations in different strains with respect to different characters of significance to be a probiotic. D 2005 Elsevier B.V. All rights reserved. Keywords: Probiotics; Lactobacillus casei ; In vitro properties 1. Introduction The science of probiotics, live microbial cultures which, when ingested in sufficient numbers, provide beneficial effects to the consumer beyond basic nutrition (Schaffsma, 1996), may be traced to Metchinikoff in 1907. The characteristics of a successful probiotic are acid and bile tolerance, antimicrobial activity against intestinal pathogens, and ability to adhere and colonize the intestinal tract. Probiotic organisms include Lactobacillus , lacto- cocci, bifidobacteria and Saccharomyces with several 0168-1605/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.ijfoodmicro.2004.10.047 * Corresponding author. Fax: +91 517 2320761,2330677. E-mail address: vijendra _ mishra@rediffmail.com (V. Mishra). International Journal of Food Microbiology 103 (2005) 109– 115 www.elsevier.com/locate/ijfoodmicro