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Xylanase from Ragi Malt and It’s Use in the Preparation of Xylo-Oligosaccharides from Cereal Brans

Chithra, M. (2007) Xylanase from Ragi Malt and It’s Use in the Preparation of Xylo-Oligosaccharides from Cereal Brans. PhD thesis, University of Mysore.

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Abstract

Xylanases (EC 3.2.1.8) are the major enzymes which bring about the depolymerization of heteroxylan, the major hemicellulosic component of plant cell walls. Xylanases from plant sources still remains unexplored and hence the present study. It focuses on the characterization of purified xylanase from finger millet (Ragi; Eleusine coracana, Indaf-15) malt and its utilization in obtaining xylo-oligosaccharides. Xylanase was purified to apparent homogeneity from 96 h ragi malt by a three step purification procedure via ammonium sulphate fractionation, DEAE-cellulose ion exchange and Sephadex G-75 gel filtration chromatographies with a recovery of 4.0 % and fold purification of 60. Xylanase, having a molecular weight of 29.5 kDa was found to be monomeric on SDS-PAGE. pH optimum of the enzyme was found to be in the range of pH 5.0-5.5. Xylanase showed maximum stability at 35°C in a pH range of 5.0-6.0. Km and Vmax of purified xylanase were found to be 0.2 % and 4.5 Cmoles min-1 respectively. Metal ions such as Ca2+, Mg2+, Mn2+, Cu2+, Fe2+, Ag2+ and Ni2+ enhanced xylanase activity at 5 mM concentration. P-chloromercuribenzoate (PCMB), citric, oxalic and boric acids inhibited the enzyme in concentration dependent manner. Purified ragi xylanase hydrolyzed wheat and ragi bran soluble polysaccharides (SP) yielding xylooligosaccharides which were purified on Biogel P-2 column followed by HPLC and their composition was determined by GLC. The oligosaccharides consisted of arabinose and xylose. The purified oligosaccharides were characterized by ESI-MS and H1NMR. Wheat bran SP yielded four oligosaccharides (WO-1, WO-2, WO-3 and WO-4). WO-1 and WO-2 were identified as arabinose containing xylotetraose and xylotriose respectively whereas, WO-3 and WO-4 were identified as unsubstituted xylotriose and xylobiose respectively. Ragi bran SP yielded only one oligosaccharide (RO-1), identified as xylobiose. The xylo-oligosaccharides liberated from both wheat and ragi brans were proved to be prebiotic by in vitro fermentation experiments using Bifidobacteria, Lactobacilli and Pediococci spp. in terms of growth characteristics such as absorbance (600 nm) and pH of the culture broth and dry cell mass. Acetic acid was the major short chain fatty acid (SCFA) liberated due to in vitro oligosaccharide fermentation. The thesis ends with summary and conclusions succeeded by references quoted.

Item Type: Thesis (PhD)
Uncontrolled Keywords: Xylanases xylo-oligosaccharides finger millet wheat bran ragi bran cereal bran
Subjects: 600 Technology > 08 Food technology > 16 Nutritive value > 05 Enzymes
600 Technology > 08 Food technology > 21 Cereals > 05 Ragi (Finger Millet)
Divisions: Dept. of Biochemistry
Depositing User: Food Sci. & Technol. Information Services
Date Deposited: 07 May 2009 04:52
Last Modified: 28 Dec 2011 10:07
URI: http://ir.cftri.com/id/eprint/8923

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