Prebiotic Galactooligosaccharides: Enzymatic Synthesis, Characterization and Bioactive studies

Gobinath, D. (2015) Prebiotic Galactooligosaccharides: Enzymatic Synthesis, Characterization and Bioactive studies. PhD thesis, University of Mysore.

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Abstract

Use of prebiotic oligosaccharides’ as nutraceutical food ingredients has increased rapidly in the recent years due to their important physiological and physicochemical attributes, which are known to improve the consumers’ health. Galactooligosaccharides (GOS) have gained special attention towards human nutrition owing to the presence of structurally related oligosaccharides, which bear a semblance to the human milk oligosaccharides. GOS are oligomers of galactose with either β(1'4), β(1'6), β(1'3) or β(1'2) linkages. They are produced from lactose through transgalactosylation using β-galactosidase. In India, 270 million kg of whey/annum is generated. It contains 16.2 million kg of valuable milk nutrients (lactose, protein, fat and minerals) and could be an ideal source of lactose. Efforts towards the use of whey have been made still, at present significant quantity is discarded as effluent. The present study focuses on the GOS production using selected microbial β- galactosidase from lactose as well as whey, from the point of view of value addition to an industrial by-product. Among the various microorganisms (78) evaluated, Lactobacillus plantarum MCC2156 was selected for the production of β-galactosidase, based on its transgalactosylating efficacy for GOS synthesis. Further, optimization of cultural and nutritional parameters resulted in 1.7 fold increase in β-galactosidase production. The β-galactosidase was purified to homogeneity using affinity chromatography, followed by size exclusion chromatography and was found to be a 66 kDa monomeric protein from SDS and native-PAGE analysis. In addition, Lactobacillus plantarum MCC2156 cells have been permeabilized for the use as whole cell biocatalyst. Optimization of process parameter resulted in a maximum GOS yield of 34.1% (w/w) by 10 h when purified β-galactosidase was used for transgalactosylation while 33.8% (w/w) GOS was obtained by 12 h in case of reaction with permeabilized cells, at an optimum lactose concentration of 40% (w/v), pH 7.0 at 50oC. The resultant GOS syrup contained (w/w): 38-45% monosaccharides (glucose and galactose); 28-20% lactose; 33-35% GOS. The oligomer composition of GOS syrup consists of 12- 14% GOS-2 (disaccharides), 15-17% GOS-3 (trisaccharides) and 3- 5% GOS-4 (tetrasaccharides). Besides, the comparative synthesis of GOS from untreated whey and deproteinized whey was carried out under optimized conditions using purified β-galactosidase which resulted in a maximum of 34.7 (w/w) and 34.4% (w/w) GOS, respectively. Further, the microbial fermentation process was found to be effective for the production of high purity GOS (91-93%) with a recovery of 81-84%. Whey protein components such as lactoferrin, BSA, α- and β-casein, α- and β- lactoglobulin were also retained, adding value to the GOS and high purity GOS synthesised from whey. In-vitro studies on prebiotic efficacy provided evidence towards the effective fermentation of GOS by probiotic lactic acid bacteria, whereas GOS did not support the growth of pathogenic bacteria. GOS was also found to have a profound influence on the organic acids such as lactic, acetic and butyric acids production profile in comparison with glucose. In addition, GOS significantly inhibited the adherence of E. coli and B. cereus to the human epithelial (HEp-2) cell lines by acting as receptor decoys. The results of in-vivo studies using female Wistar rats fed with GOS (10%, w/w) supplemented diet for four weeks have clearly indicated in an effective mobilization of calcium from Eleusine coracana (finger millet/ ragi) flour through gut microbial fermentation.

Item Type:	Thesis (PhD)
Uncontrolled Keywords:	prebiotic oligosaccharides, Lactobacillus plantarum, β-galactosidase, lactose
Subjects:	600 Technology > 08 Food technology > 10 Food Microorganisms 600 Technology > 08 Food technology > 16 Nutritive value > 05 Enzymes
Divisions:	Fermentation Technology and Bioengineering
Depositing User:	Food Sci. & Technol. Information Services
Date Deposited:	18 May 2016 12:10
Last Modified:	18 May 2016 12:10
URI:	http://ir.cftri.res.in/id/eprint/12165

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