International Journal of Genetic Engineering and Biotechnology. ISSN 0974 3073 Volume 5, Number 2 (2014), pp. 201-208 © International Research Publication House http://www.irphouse.com Antimicrobial Activity of Casein Fermentate of Probiotic Lactobacillus Spp. Shilpa Vij 1 , Priyanka Chandra 2 , and Prashant Ramrao Bachanti Dairy Microbiology Division, National Dairy Research Institute, Karnal, India Abstract Of the total 34 Lactobacillus cultures 12 were selected on the basis of maximum proteolytic activity. Among these Lb 24 and Lb 19 were highly proteolytic and Lb 63 was least proteolytic. All the 12 proteolytic Lactobacillus were assessed for probiotic attributes. Las 1, Lb 141 were having maximum resistance to acid at pH 1.0 for 3 h of treatment. La 1, Lb 19, Lb 22 and Lb141 were highly bile resistant at 1-2% level. Lb 25, Lb 63, Lb 141 and Lb 307 showed maximum cell surface hydrophobicity (i.e. 59.35-77.21%). Almost all the lactobacilli were resistant to vancomycin and sensitive to erythromycin, whereas, for other antibiotic variation in sensitivity was seen. Cell free supernatant of Lactobacillus was tested for antimicrobial activity and it was found that Lb 25, Lb 63, Lb141 and Lb288 were showing maximum antimicrobial activity. Sodium caseinate was prepared for fermentation and the fermentate was tested for antimicrobial activity against gram positive and gram negative bacteria, yeast and mold cultures. Lb 141 had maximum antimicrobial activity as compared to other Lactobacillus and selected for further studies.100 μg / ml of the fermentate of Lb141 showed maximum antimicrobial activity against bacterial cultures whereas 120 and 150 μg / ml was inhibitory to mold and yeast, respectively. Keywords: Antimicrobial activity, Bioactive peptides, Lactobacillus, Probiotic attributes, Proteolytic activity. 1. INTRODUCTION Milk naturally contains an array of bioactivities due to lysozyme immunoglobulin and growth factors. A number of bioactive peptides have been identified in milk proteins, such as casein and whey proteins, where they are present in encrypted form, stored as