Please cite this article in press as: C. Saravanan, P.K.H. Shetty, Int. J. Biol. Macromol. (2015), http://dx.doi.org/10.1016/j.ijbiomac.2015.02.007 ARTICLE IN PRESS G Model BIOMAC-4880; No. of Pages 7 International Journal of Biological Macromolecules xxx (2015) xxx–xxx Contents lists available at ScienceDirect International Journal of Biological Macromolecules j ourna l h o mepa ge: www.elsevier.com/locate/ijbiomac Isolation and characterization of exopolysaccharide from Leuconostoc lactis KC117496 isolated from idli batter Chinnashanmugam Saravanan, Prathap Kumar H. Shetty ∗ Department of Food Science and Technology, Pondicherry University, Pondicherry 605014, India a r t i c l e i n f o Article history: Received 25 November 2014 Received in revised form 8 January 2015 Accepted 8 February 2015 Available online xxx Keywords: Idli batter Leuconostoc lactis Exopolysaccharide a b s t r a c t Diverse exopolysaccharide (EPS)-producing isolates were isolated from an Indian acidic fermented food (Idli) based on the colony morphology. One of the EPS-producing microflora (Leuconostoc lactis KC117496) was selected for further characterization using FT-IR, HPTLC, AFM, SEM, TGA and XRD analysis. FT-IR spectroscopy revealed the -d-glucose nature of the EPS. HPTLC analysis confirmed the presence of only glucose monomers, indicating the glucan nature of EPS. NMR spectra revealed the presence of 95% -(1→6) and 5% branching -(1→3) linkages. The SEM and AFM showed smooth surfaces and com- pact structure. TGA results showed higher degradation temperature of 272.01 ◦ C. XRD analysis proved the 33.4% crystalline nature of the EPS. Water solubility index and water-holding capacity of EPS are 14.2 ± 0.208% and 117 ± 7.5%. All the above characteristics of the EPS produced by L. lactis showed that the EPS is of a good-quality polysaccharide with potential applications in the food industry. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Idli is a fermented product consumed widely in the Indian sub- continent made by steaming ground mixture of rice and black mung bean (Phaseolus mungo). Lactic acid bacteria (LAB) are the major group of microorganisms involved in the idli batter fermentation [1]. Exopolysaccharides (especially dextran) produced by LAB are reported to enhance the texture and sensory properties in many Indian fermented foods [2]. EPS production is well documented among various species of LAB belonging to Leuconostoc spp., Lac- tobacillus spp., Lactococcus spp., and Streptococcus spp. [5]. Some of the known EPS (exopolysaccharide) producing LAB species isolated from idli batter are Leuconostoc mesenteroides, Weissella confusa, Weissella cibaria, Pediococcus parvulus [3,4]. Homopolysaccharides secreted by Lactobacillus spp. contain glucose or fructose as sole monosaccharide and are classified as glucans (dextrans) and fruc- tans respectively [6]. Glucan produced by Leconostoc garium PR contains 95% of -(1→6) glucopyranose linkage carrying low con- tent branches of -(1→2), -(1→3) and -(1→4) linkage [7]. EPS are profusely used as bio-absorbents, bio-flocculants, encapsulat- ing constituents, heavy metal confiscating agents, drug distribution agents and ion-exchange resins [8]. Bacteria produce biofilms to defend the microbial community against the environmental stress ∗ Corresponding author. Tel.: +91 2656743; fax: +91 2656743. E-mail address: pkshalady@yahoo.co.uk (P.K.H. Shetty). [9]. Bacterial exopolysaccharides are the essential constituent of extracellular polymer form bio-film and mediate most of the cell- to-cell and cell-to-surface connections and stabilization in intestine [10]. The EPS produced by LAB act as an immuno-stimulator, anti- tumour agent, and blood cholesterol lowering agent. EPS are used as drug conjugates, coatings, and matrix agents to develop the specificity of drug release in colon cancer treatment [11]. Current research focused on the development of polymeric matrices with tuned characteristics such as transparency, barrier, mechanical properties, and biocompatibility or bioactivity. The polymer is also modified in vitro to form structured materials (e.g. nano-particles, scaffolds or hydrogels) for numerous industrial applications and also used as edible coatings in numerous food products [12–14]. EPS-producing cultures in dairy foods are known to promote vis- cosity and water binding functions [13]. EPS-producing microflora have been suggested as effective functional starter cultures for preparing fermented foods [14]. Present study is indented to screen and identify the EPS-producing lactic acid bacteria and characterize the EPS produced by a selected strain. 2. Materials and methods 2.1. Preliminary screening for EPS-producing isolates Idli batter (100 g) was collected from households in sterile containers thoroughly mixed. One gram of sample was homoge- nized in sterile phosphate buffer saline solution (pH-7.2) to get an http://dx.doi.org/10.1016/j.ijbiomac.2015.02.007 0141-8130/© 2015 Elsevier B.V. All rights reserved.