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

FERNADEZ, PAULA VIRGINIA; ZELAYA, VICTOR MARTÍN; CIANCIA, MARINA

Mar del Plata

Simposio; XVI Simposio Latinoamericano de Polímeros - XIV Congreso Iberoamericano de Polímeros; 2018

CONICET - Universidad Nacional de Mar del Plata

INTRODUCTION Woody bamboos comprise 1641 species, some of themutilized for their edible and palatable shoots, the newculms that arise from the rhizomes. Besides, shootfiber is a common ingredient in many food products insome countries, but they are not used in Argentina.Previous studies suggested that xylo-oligosaccharides(XOS) can be applied as prebiotics, as they selectivelyenhance the growth of bacteria from human colonexhibiting beneficial health effects. Moreover, it wasfound that the most effective fraction of XOS containsshort chains with DP=2?5, but presence of uronic acidresidues can have a negative effect on theirdigestibility. XOS can resist heat up to 100 °C and theyare stable at pH 2.5?8.0, In addition, they aremoderately sweet compounds with no off-taste, andno cariogenic effect. XOS can be applied in foods andbeverages1.Recently, the major hemicellulose fraction from shootsof Phyllostachys aurea was studied2, and now wepresent the chemical characteristics of those fromGuadua chacoensis. Besides, experiments carried outto obtain oligosaccharide fractions through treatmentof these polysaccharides with inexpensive enzymemixtures (Driselase®) gave products, which wereseparated using different GPC phases and analyzed.EXPERIMENTAL METHODSExtraction, fractionation, analyses and structuraldetermination of glucuronoarabinoxylans frombamboo shoots were described before2.Treatment with Driselase®: 10 mg xylans/1mg deenzyme/1ml phosphate buffer pH=7.5 (66 h at 40ºC).Yield: 70-80%.Analytical fractionations were carried out on BioGel P-2and P-6, and on Sephadex G-75 and G-100 columns(30x1 cm i.d.) suspended in water. Fractions of 3 mLwere collected and analyzed for the presence ofcarbohydrates. Methylation analyses were carried outaccording to Mazumder and York3. NMR spectra wereperformed in standard conditions.RESULTS AND DISCUSSIONYoung shoots of Phyllostachys aurea and Guaduachacoensis (Poales) showed glucuronoarabinoxylans(GAX) as the major hemicellulosic components, beingextracted 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 structurewas determined by methylation analyses and NMRspectroscopy. The degree of ramification of both xylanswas very different, so they were consideredappropriate substrate models for enzymatic treatment.Yields of digestion with Driselase® were 72% and 80%,respectively.The mixtures of oligosaccharides (OPhy and OGua)were chromatographed on BioGel P-2, using water aseluant. The fractions obtained in the exclusion volume(Ve) (OPhy1 and OGua1) were furtherchromatographed on BioGel P-6. Similar elutionpatterns were obtained for both samples, still showingan important amount of the samples in thecorresponding Ve (OPhy2 and OGua2). The firstimportant difference in the elution pattern wasobtained by elution of OPhy2 and OGua2 on SephadexG-75, which gave a cleaner separation for the former.On the other hand, the sample obtained from OGua2 inthe Ve was finally chromatographed on Sephadex G-100 obtaining a good separation. Methylation analysesof the fractions was carried out, and showed i.e. forOGua1 a mixture of XOS of degree of polymerization(DP)=14, and ramification of 14%. Results from NMRspectra of this oligosaccharide complemented thisinformation.CONCLUSIONThe major polysaccharide fraction from shoots ofGuadua chacoensis comprises glucuronoarabinoxylanswith relatively low degree of ramification. Mixtures ofXOS were obtained by treatment with Driselase® of thisxylan, and that of Phyllostachys aurea2. Analysis of theoligosaccharides showed mixtures with different DP,including those potentially suitable for their use asprebiotics, a possible application of an underutilizedrow material in the food industry.