ORIGINAL PAPER Characterization of trehalose synthase from Corynebacterium nitrilophilus NRC Mohsen Mohamed Selim Asker Æ Mohamed Fawzy Ramadan Æ Samir Khalf Abd El-Aal Æ Ebtsam Mokhtar Mohamed El-Kady Received: 27 October 2008 / Accepted: 17 December 2008 / Published online: 6 January 2009 Ó Springer Science+Business Media B.V. 2009 Abstract Trehalose synthase (TSII) from Corynebacte- rium nitrilophilus NRC was successively purified by ammonium sulphate precipitation, ion exchange chroma- tography on DEAE-cellulose and gel filtration chroma- tography on Sephadex G-100 columns. The specific activity of the trehalose synthase was increased *200-fold, from 0.14 U mg -1 protein to 28.3 U mg -1 protein. TSII was found to be a monomeric protein with a molecular weight of 67–69 kDa. Characterization of the enzyme exhibited opti- mum pH and temperature were 7.5 and 35°C, respectively. The purified enzyme was stable from pH 6.6 to 7.8 and able to prolong its thermal stability up to 35°C. The enzyme activity was inhibited strongly by Zn 2? , Hg 2? and Cu 2? and moderately by Ba 2? , Fe 2? , Pb 2? and Ni 2? . Other metal ions Ca 2? , Mg 2? , Co 2? , Mn 2? and EDTA had almost no effect. Keywords Corynebacterium nitrilophilus NRC Á Trehalose synthase Á Characterization Á Purification Introduction Trehalose is a naturally occurring disaccharide which consists of two glucose molecules linked in a 1,1-position by an a-glycosidic bond. It is produced in bacteria, yeast, fungi, algae and a few higher plants. In many insects it is produced as a major blood sugar and as a reserve carbo- hydrate during periods of dehydration and freezing. Trehalose also occurs at low concentration in a number of foods which are consumed as part of a regular diet (Cardoso et al. 2004). Trehalose is stable under hot and acidic conditions and has affinity for lipids in biological membranes and proteins. It forms hydrogen bonds involved in protection of biological structures during freezing, des- iccation or heating (Roser 1991a; Richards et al. 2002). In addition, amorphous glasses of trehalose hold trapped biological molecules without essential changes of their native structure and in consequence limit damage to bio- logical materials during desiccation (Crove and Crove 2000). The natural functions, mechanisms of action and technical qualities of trehalose lend to several applications in the food, cosmetic and medical industries (Roser 1991b; Colaco and Roser 1995; Sugimoto 1995). Until recently, the major applications of trehalose have been for use in science, medicine and cosmetics. The limiting factor to the generalized use of trehalose in the food industry was cost (Sugimoto 1995). With the advent of a new manufacturing process, the production costs of trehalose have been dra- matically reduced. This permits its use in a wide variety of cost-sensitive applications including foods. Desirable properties for application of trehalose synthase (TS) in food processing are its mild sweetness, low carcinogenic- ity, good solubility in water, stability under low pH conditions, and reduction of water activity, low hygrosco- picty, depression of freezing point, high glass transition temperature and ability to protect proteins. This multi- functional food ingredient does not caramelize and does not undergo Maillard reactions, is safe for human consumption and has been accepted by the European M. M. S. Asker (&) Á E. M. M. El-Kady Department of Microbial Biotechnology, National Research Center, Dokki, Cairo, Egypt e-mail: mohsenmsa@yahoo.com M. F. Ramadan Biochemistry Department, Faculty of Agriculture, Zagazig University, Zagazig 44511, Egypt S. K. A. El-Aal Department of Microbial Genetic, National Research Center, Dokki, Cairo, Egypt 123 World J Microbiol Biotechnol (2009) 25:789–794 DOI 10.1007/s11274-008-9950-9