Glucuronoarabinoxylans from bamboo shoots and the oligosaccharides obtained from them by enzymatic treatment, with potential application as prebiotics

VICTOR MARTIN ZELAYA; PAULA VIRGINIA FERNÁNDEZ; MARINA CIANCIA

Mar del Plata

Simposio; XVI Simposio Latinoamericano de Polímeros; 2018

Instituto de Investigaciones en Ciencia y Tecnología de Materiales (INTEMA, CONICET ? UNMDP).

Glucuronoarabinoxylans from bamboo shoots and the oligosaccharides obtained from them by enzymatic treatment, with potential application as prebioticsVíctor Martín Zelaya, Paula Virginia Fernández, Marina CianciaUniversidad de Buenos Aires, Facultad de Agronomía, Cátedra de Química de Biomoléculas, Consejo Nacional de Investigaciones Científicas y Técnicas- Centro de Investigación de Hidratos de Carbono (CIHIDECAR, CONICET-UBA) martinzelaya88@gmail.com INTRODUCTIONWoody bamboos comprise 1641 species, some of them utilized for their edible and palatable shoots, the new culms that arise from the rhizomes. Besides, shoot fiber is a common ingredient in many food products in some countries, but they are not used in Argentina. Previous studies suggested that xylo-oligosaccharides (XOS) can be applied as prebiotics, as they selectively enhance the growth of bacteria from human colon exhibiting beneficial health effects. Moreover, it was found that the most effective fraction of XOS contains short chains with DP=2?5, but presence of uronic acid residues can have a negative effect on their digestibility. XOS can resist heat up to 100 °C and they are stable at pH 2.5?8.0, In addition, they are moderately sweet compounds with no off-taste, and no cariogenic effect. XOS can be applied in foods and beverages1. Recently, the major hemicellulose fraction from shoots of Phyllostachys aurea was studied2, and now we present the chemical characteristics of those from Guadua chacoensis. Besides, experiments carried out to obtain oligosaccharide fractions through treatment of these polysaccharides with inexpensive enzyme mixtures (Driselase) gave products, which were separated using different GPC phases and analyzed. EXPERIMENTAL METHODSExtraction, fractionation, analyses and structural determination of glucuronoarabinoxylans from bamboo shoots were described before2. Treatment with Driselase®: 10 mg xylans/1mg de enzyme/1ml phosphate buffer pH=7.5 (66 h at 40ºC). Yield: 70-80%.Analytical fractionations were carried out on BioGel P-2 and P-6, and on Sephadex G-75 and G-100 columns (30x1 cm i.d.) suspended in water. Fractions of 3 mL were collected and analyzed for the presence of carbohydrates. Methylation analyses were carried out according to Mazumder and York3. NMR spectra were performed in standard conditions.RESULTS AND DISCUSSIONYoung shoots of Phyllostachys aurea and Guadua chacoensis (Poales) showed glucuronoarabinoxylans (GAX) as the major hemicellulosic components, being extracted in important quantities with 1M KOH (12.1% and 10.3% of the cell wall material, ratio Xyl:Ara:GlcA, 100:67:8 and 100:28:8, respectively). Their structure was determined by methylation analyses and NMR spectroscopy. The degree of ramification of both xylans was very different, so they were considered appropriate substrate models for enzymatic treatment. Yields of digestion with Driselase were 73% and 80%, respectively.The mixtures of oligosaccharides (OPhy and OGua) were chromatographed on BioGel P-2, using water as eluant. The fractions obtained in the exclusion volume (Ve) (OPhy1 and OGua1) were further chromatographed on BioGel P-6. Similar elution patterns were obtained for both samples, still showing an important amount of the samples in the corresponding Ve (OPhy2 and OGua2). The first important difference in the elution pattern was obtained by elution of OPhy2 and OGua2 on Sephadex G-75, which gave a cleaner separation for the former. On the other hand, the sample obtained from OGua2 in the Ve was finally chromatographed on Sephadex G-100 obtaining a good separation. Methylation analyses of the fractions was carried out, and showed i.e. for OGua1 a mixture of XOS of degree of polymerization (DP)=14, and ramification of 14%. Results from NMR spectra of this oligosaccharide complemented this information. CONCLUSIONThe major polysaccharide fraction from shoots of Guadua chacoensis comprises glucuronoarabinoxylans with relatively low degree of ramification. Mixtures of XOS were obtained by treatment with Driselase of this xylan, and that of Phyllostachys aurea2. Analysis of the oligosaccharides showed mixtures with different DP, including those potentially suitable for their use as prebiotics, a possible application of an underutilized row material in the food industry.REFERENCES1. Deutschmann R. & Dekker R.F.H., Biotechnol. Adv. 30, 1627?1640, 2012.2. Zelaya V.M. et al., Carbohydr. Polym. 167, 240?249, 2017.3. Mazumder K. & York W. S., Carbohydr. Resear. 345, 2183?2193, 2010.ACKNOWLEDGMENTSThis work was supported by the National Research Council of Argentina (CONICET) [PIP11220130100762CO 2014-2016 and PUE 22920160100068CO].