112 Journal of Basic Microbiology 2008, 48, 112 – 117 © 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.jbm-journal.com Research Paper Screening of Aspergillus species for occurrence of lectins and their characterization Ram Sarup Singh 1 , Ashok Kumar Tiwary 2 and Ranjeeta Bhari 1 1 Carbohydrate and Protein Biotechnology Laboratory, Department of Biotechnology, Punjabi University, Patiala – 147 002, Punjab, India 2 Department of Pharmaceutical Sciences and Drug Research, Punjabi University, Patiala – 147 002, Punjab, India Ten species of Aspergillus were screened for occurrence of lectins. Each of the species was investigated for the occurrence of extracellular, surface-bound and intracellular lectin ac- tivities. As many as four species namely, Aspergillus niger, Aspergillus versicolor, Aspergillus rugu- losus and Aspergillus nidulans, were found to possess intracellular lectin activities, while none of the species showed extracellular or surface-bound lectin activities. Each of the lectin was characterized with respect to blood group and carbohydrate specificities. All the lectins were found to agglutinate human erythrocytes, irrespective of their blood group and pig erythro- cytes. However, they did not show agglutination with sheep or goat erythrocytes. Of the various carbohydrates tested, all lectins were found to be specific for inulin, mucin, asia- lofetuin, N-acetyl galactosamine, melibiose, D-ribose, L-fucose, D-arabinose, D-sucrose and D-mannitol. The minimum inhibitory concentration of each of the specific sugars was also determined. The lectins were partially purified using ammonium sulfate precipitation tech- nique. Each of the lectin was found to be precipitated at 40 – 50% saturation of ammonium sulfate, yielding about 80% of lectin activity. Keywords: Lectin / Aspergillus / Haemagglutination / Carbohydrate specificity Received: October 09, 2007; accepted November 16, 2007 DOI 10.1002/jobm.200700314 Introduction * Lectins are polyvalent or univalent oligomeric proteins of non-immune origin [1]. They bind reversibly with specific sugars and are capable of precipitating polysac- charides, glycoproteins and glycolipids bearing specific sugars and play a role in cell recognition [2]. Lectins have found many clinical applications such as blood typing, carriers of chemotherapeutic agents, as mito- gens and taxonomic markers of specific microorgan- isms [3]. These have been found to be associated with murine lymphocyte ‘homing receptor’ MeL 14 [4] and human leukocyte adhesion molecule ELAM-1 [5]. Lec- tins bind to specific carbohydrate moieties present on Correspondence: Dr. R. S. Singh, Department of Biotechnology, Pun- jabi University, Patiala – 147 002, Punjab, India E-mail: rssingh11@lycos.com Phone: +91 175 304 6262 Fax: +91 175 2283073 the apposing cells. This specificity of lectin-carbo- hydrate binding has been exploited for targeting drugs or diagnostic agents to normal and diseased tissues. The role of lectins for drug targeting has been reviewed in several publications [6, 7]. Lectins are widely distributed in nature and have been reported in almost all groups of organisms like viruses, bacteria, fungi, invertebrates, vertebrates and plants [1]. Amongst the microbes, lectins in bacteria and protozoa have been extensively studied [8 – 12]. Although there are several reports on fungal lectins found in fruiting bodies [13 – 19], but only few reports are there on mycelial lectins [20]. Amongst the fungi belonging to genus Aspergillus, lectins have been re- ported in Aspergillus fumigatus [21, 22] and Aspergillus oryzae [23]. Aspergillus species are highly aerobic and are found in almost all oxygen-rich environments, where as a result of the high-oxygen tension, they commonly grow as molds on the surface of substrates. Aspergillus