Journal of Basic Medical and Allied Sciences (JBMAS): 2011:1:34 Preliminary characterization of the thermostable dextranase producing microorganisms Prasada Rao Vallem 1 R. Nelson 2 , Abdallah M Jarari 3 Farag Elshaari 3 and Jagannadha Rao Peela 4 1. Department of Biotechnology JJ College of Arts and Sciences Pudukkottai, Tamilnadu, India, 2. Department of Botany Govt. Arts College, Ariyalur, Tamilnadu, India, 3. Department of Biochemistry Faculty of Medicine, Benghazi University, Benghazi, Libya. 4. Department of Biochemistry, Faculty of Medicine, Quest International University Perak,Ipoh,Malaysia. Corresponding Author: Dr.Prasada Rao Vallem , E-Mail:prasadvallem@yahoo.com Abstract A Gram- positive spore forming thermophilic strict anaerobic bacterium was isolated from enrichments at 65 o C with dextran as sole carbon and energy source. When compared with the total viable anaerobic micro flora, the proportion of these microbes from different areas varied over a wide range. Preliminary characterization of some of the dextranase producing microorganisms revealed a heterogeneous mixture of cell types with varying morphological and biochemical characteristics. Several bacterial isolates were identified as being members of the genus Bacillus. An additional isolate appeared to belong to the genus Bacteroides. The dextran degrading enzymes produced by these bacteria are extracellular, and a cell free preparation from one of the isolates has been shown to cause extensive endo- hydrolytic cleavage of high molecular weight dextrans. Key words: dextranase, dextrans, microoranism Introduction Dextrans are high molecular weight complex polysaccharides formed, of at least 50%, by α1-6 linked glucose units, with α - 1-3 branch linkage and may also contain other branch linkages such as α-1-2 or α-1-4. The approximate average molecular weight of dextran is 5 x 10 6 (Inkerman et al., 1980). Dextranases catalyze the hydrolysis of the α- l, 6 glucosidic bond of the polysaccharide dextran. The dextranases have often been classified as endo and exo dextranases based on the mode of action (Zevenhuizen et al., 1968). The dextran degrading enzymes have been isolated from a wide range of microorganisms with high substrate specificity. Dextranases have been obtained from a variety of sources. The dextranase producing genera include Pseudomonas, Brevebacterium, Streptococcus, Bacteroides, and Bacillus. The exoenzyme activity that releases glucose from dextran has been detected in animal tissues and bacteria (Rozenfel’d et al., 1964; Henrissat, 1991; Garcia et al., 2001).