Raman spectroscopy for the analysis of different exo-polysaccharides produced by bacteria Muhammad Tahir a , Muhammad Irfan Majeed a, ⁎, Haq Nawaz a, ⁎, Saqib Ali a , Nosheen Rashid b , Muhammad Kashif a , Iram Ashfaq c , Waqar Ahmad c , Komal Ghauri c , Fazal Sattar c , Iqra Jawad c , M.A. Ghauri c , Munir A. Anwar c a Department of Chemistry, University of Agriculture Faisalabad, 38040, Pakistan b Department of Chemistry, University of Central Punjab, Faisalabad campus, Faisalabad, Pakistan c Industrial Biotechnology Division, National Institute for Biotechnology and Genetic Engineering, Constituent College of Pakistan Institute of Engineering and Applied Sciences, PO Box 577, Jhang Road, Faisalabad, Pakistan abstract article info Article history: Received 19 November 2019 Received in revised form 8 April 2020 Accepted 21 April 2020 Available online xxxx Keywords: Raman spectroscopy Principal component analysis Exo-polysaccharides Bacteria In this study, Raman spectroscopy is employed for the characterization and comparison of two different classes of exo-polysaccharides including glucans and fructans which are produced by different bacteria. For this purpose, nine samples are used including five samples of glucans and four of fructans. Raman spectral results of all these polysaccharides show clear differences among various glucans as well as fructans showing the potential of this technique to identify the differences within the same class of the compounds. Moreover, these two classes are also compared on the basis of their Raman spectral data and can be differentiated on the basis of their unique Raman features. Multivariate data analysis techniques, Principle Component Analysis (PCA) is found very helpful for the comparison of the Raman spectral data of these classes of the carbohydrates. © 2020 Published by Elsevier B.V. 1. Introduction Polysaccharides produced by bacteria play an integral role in the ad- hesion and other processes like protection and coordination of the bac- teria. Moreover, many of these exopolysaccharides (EPSs) are gaining remarkable importance due to their applications in food and pharma- ceutical industries [1]. The structural features of these polysaccharides determine their physio-chemical properties and hence their applicabil- ity. Therefore, it is very important to have the good understanding of their complex structures. Usual ways of elucidation of these structures are either sugar and methylation analysis or application of advanced techniques. For the structural analysis and characterization of carbohy- drates (polysaccharides) the advanced techniques like Nuclear mag- netic resonance spectroscopy (NMR), Liquid chromatography and Calorimetric methods are mainly used. As most of the available tech- niques have sensitivity limitations, therefore it is very difficult to even differentiate between various capsular polysaccharides [2]. No doubt NMR and liquid chromatography are used for the characterization of polysaccharides but these have some disadvantages as these techniques require extensive sample preparation, are time consuming and costly. Moreover, use of calorimetric procedure is limited due to time con- sumption, require large sample quantity, require a lot of consumable and harmful reagents [3]. Raman spectroscopy has achieved a broader acceptance as an excel- lent analytical technique for the non-invasive, quick characterization and qualitative analysis. It distinguishes itself from other currently ap- plied techniques because it is easy to use, cost effective, rapid, and pro- vides high content information of the chemical or biochemical composition, structure and the interactions of biomolecules within the microorganisms [4]. This technique is also explored for the analysis of microbes or microbial products [1,3,5,6] and characterization of bacte- rial biofilms [6–8]. Moreover, although, this technique is explored for the characterization of different compounds produced by bacteria in- cluding bioactive metabolites, [9] bio-oil and bio char [10] but it has not yet been explored for the analysis of exo-polysaccharides produced by bacteria. In the present study, Raman spectroscopy is employed, for the first time to characterize the exopolysaccharides (EPSs,) including glucans and fructans, produced by bacteria. Moreover, the potential of Raman spectroscopy to distinguish between different classes of the EPSs is explored. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 237 (2020) 118408 ⁎ Corresponding authors. E-mail addresses: irfanmajeed2003@gmail.com (M.I. Majeed), haqchemist@yahoo.com (H. Nawaz). https://doi.org/10.1016/j.saa.2020.118408 1386-1425/© 2020 Published by Elsevier B.V. Contents lists available at ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa