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Study on the Utilization of Xylo-Oligosaccharides by Lactobacillus Sp. with an Emphasis on the Biochemical Characterization of a Xylanolytic Enzyme.

Lyned, D. Lasrado (2015) Study on the Utilization of Xylo-Oligosaccharides by Lactobacillus Sp. with an Emphasis on the Biochemical Characterization of a Xylanolytic Enzyme. PhD thesis, University of Mysore.

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Abstract

Xylo-oligosaccharides (XOS) are non-digestible oligosaccharides which are classified under emerging prebiotics. The ability to utilize XOS varies considerably among lactobacilli and is dependent on the efficiency of their xylanolytic enzymes and sugar transporters. The present study is envisaged to understand the utilization of XOS by Lactobacillus sp. by characterizing the major xylanolytic enzyme and identifying sugar transporters involved in the uptake of XOS. It also touches upon the health benefits of the synbiotic combination of XOS and lactobacilli in terms of antioxidant potential as well as cholesterol lowering property. XOS used in this study was isolated from wheat bran water unextractable portion. The major oligosaccharides in the XOS mixture were identified as, xylobiose (Xyl-(1→4) β-Xyl) and arabinoxylotriose (β-Xyl-(3→1-α-Ara)-1→4-β-Xyl). Among the seven strains of lactobacilli studied, Lactobacillus brevis NCDC 01 showed the highest efficiency to utilize XOS. Intracellular β-D-xylosidase was the major xylanolytic enzyme involved in the metabolism of XOS. Three sequential steps i.e. ultrafiltration, ion exchange chromatography and gel permeation chromatography were employed to purify the enzyme. The estimated molecular mass of the purified enzyme was found to be ~58 kDa. The temperature and pH optima of the enzyme were found to be 40°C and 6.0, respectively. The enzyme does not require any metal ion for stability or activity and under optimum conditions exhibited a Km and Vmax of 0.87 mM and 0.14 μmoles/min respectively. Presence of an intracellular β-Dxylosidase indicated that XOS may first be transported into the bacterial cell by sugar transporters and subsequently digested to xylose. Gene expression analysis by real-time quantitative PCR (qPCR) showed a significant upregulation of genes putatively coding for the components of the ATP-Binding Cassette (ABC transporter system). Synbiotic combination of XOS and Lactobacillus brevis NCDC 01 showed higher ability to reduce the cholesterol content in media and deconjugate bile salts compared to the combination of XOS and other tested strains. XOS was used in combination with selected Lactobacillus sp. in preparation of synbiotic fermented milk and their antioxidant potential was evaluated. Ferric reducing power as well as DPPH radical scavenging activity were significantly (p<0.05) higher in all the synbiotic samples as compared to that of probiotic samples. The findings of this study may have future implications for the design of novel synbiotics.

Item Type: Thesis (PhD)
Uncontrolled Keywords: Xylo-oligosaccharides, Lactobacillus sp, wheat bran
Subjects: 600 Technology > 08 Food technology > 16 Nutritive value > 05 Enzymes
600 Technology > 08 Food technology > 21 Cereals > 04 Wheat
Divisions: Dept. of Biochemistry
Depositing User: Food Sci. & Technol. Information Services
Date Deposited: 06 Nov 2015 07:00
Last Modified: 21 Dec 2016 12:43
URI: http://ir.cftri.com/id/eprint/11932

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