American-Eurasian J. Agric. & Environ. Sci., 14 (3): 193-198, 2014 ISSN 1818-6769 © IDOSI Publications, 2014 DOI: 10.5829/idosi.aejaes.2014.14.03.83282 Corresponding Author: Md. Ibrahim Khalil, Department of Biochemistry and Molecular Biology, Jahangirnagar University, Savar, Dhaka-1342, Bangladesh. Tel: (+8802) 7708478-85/1379, Fax: (+8802) 7708069. 193 Antagonism of Lactic Acid Bacteria Against Selected Pathogenic Bacteria and Spoilage Fungi Khandakar Md. Rayhanul Kabir, Md. Rafiqul Islam, 1 1 Md. Sabir Hossain, Sudip Paul and Md. Ibrahim Khalil 2 2 2 Department of Biotechnology and Genetic Engineering, 1 Islamic University, Kushtia 7003, Bangladesh Department of Biochemistry and Molecular Biology, 2 Jahangirnagar University, Savar, Dhaka 1342, Bangladesh Abstract: Lactic acid bacteria (LAB) have been studied for many years to be used as biopreservative due to production of various antimicrobial compounds. This study was carried out for the determination of natural antimicrobial activity of LAB isolated from curd samples. LAB were screened for antagonistic activity against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus and Bacillus subtilis. The inhibitory activity was determined by a disc diffusion method. Strong (+++) and moderate (++) inhibition were found for E. coli and weak (+) inhibition was found for S. aureus. No zone of inhibition was found for B. subtilis. Studies were made to compare the production of antibiotic components by LAB in different nutrient media (LAPT broth with different supplements). The media LAPT with riboflavin (1.5 mg/l) and LAPT with vitamin B mixture (1.5 mg/l) showed the positive result. LAB were also screened for antagonism against spoilage fungi isolated from potato samples and showed antifungal activity against Aspergillus niger. This study led to suggest that food-derived LAB strains could be selected for biotechnological application to control pathogenic bacteria and spoilage fungi. Key words: Biopreservative Antagonism Lactic Acid Bacteria Pathogenic Bacteria Spoilage Fungi INTRODUCTION Lactic acid bacteria (LAB) are a group of The search for alternative bioproducts to replace negative bacteria, which excrete lactic acid as major end chemicals and toxic pesticides, has found growing interest product and generally recognized as safe (GRAS) in recent times because the extensive use of synthetic organisms [5]. They are also selected as probiotic, which chemicals and pesticides in food and agriculture may are able to promote health and prevent infections pose a health risk for human and animals and affect the against enteropathogenic bacteria [6, 7]. Different ecological equilibrium of the environment [1]. For this Lactobacillus spp. isolated from yoghurt samples purpose, using bacteria or natural compounds which collected from different regions of Bangladesh showed exhibit the same inhibitory effect on pathogenic and variation in probiotic properties [8]. LAB usually spoilage microbes was not only shown to be efficient in harbor in carbohydrate-rich environments and are found storage life extension and nutritive and safety value in various food products such as milk, plant, meat, retention, of food products but also the environment intestinal mucosa of human and animals [6, 9] but safeguarding [2, 3]. Such bacteria are known as especially proliferate in different fermented foods [10]. “biological control agents” [4]. Owing to particular physiological and biochemical traits, Gram-positive, nonspore forming, immobile and catalase