Extraction of Glucuronoarabinoxylan from Quinoa Stalks (Chenopodium quinoa Willd.) and Evaluation of Xylooligosaccharides Produced by GH10 and GH11 Xylanases

Abstract

Byproducts from quinoa are not yet well explored sources of hemicellulose or products thereof. In this work, xylan from milled quinoa stalks was retrieved to 66% recovery by akaline extraction using 0.5 M NaOH at 80 °C, followed by ethanol precipitation. The isolated polymer eluted as a single peak in size-exclusion chromatography with a molecular weight of >700 kDa. Analysis by Fourier transform infrared spectroscopy and nuclear magnetic resonance (NMR) combined with acid hydrolysis to monomers showed that the polymer was built of a backbone of β(1 → 4)-linked xylose residues that were substituted by 4-O-methylglucuronic acids, arabinose, and galactose in an approximate molar ratio of 114:23:5:1. NMR analysis also indicated the presence of α(1 → 5)-linked arabinose substituents in dimeric or oligomeric forms. The main xylooligosaccharides (XOs) produced after hydrolysis of the extracted glucuronoarabinoxylan polymer by thermostable glycoside hydrolases (GHs) from families 10 and 11 were xylobiose and xylotriose, followed by peaks of putative substituted XOs. Quantification of the unsubstituted XOs using standards showed that the highest yield from the soluble glucuronoarabinoxylan fraction was 1.26 g/100 g of xylan fraction, only slightly higher than the yield (1.00 g/100 g of xylan fraction) from the insoluble fraction (p < 0.05). No difference in yield was found between reactions in buffer or water (p > 0.05). This study shows that quinoa stalks represent a novel source of glucuronoarabinoxylan, with a substituent structure that allowed for limited production of XOs by GH10 or GH11 enzymes.

Exopolysaccharides Production by Cultivating a Bacterial Isolate from the Hypersaline Environment of Salar de Uyuni (Bolivia) in Pretreatment Liquids of Steam-Exploded Quinoa Stalks and Enzymatic Hydrolysates of Curupaú Sawdust

“…is a highly-nutritive, widely-cultivated crop with origins in the Andean region, including Bolivia, with annual local production of 60,000 tons between 2010 and 2018 [26,27]. Its non-edible parts, e.g., stalks, constitute a very interesting, yet unused, renewable raw material for the production of value-added materials [28,29]. Curupaú (Anadenanthera colubrina) is a hardwood species widely available in South America and used in timber production.…”

Novel xylan degrading enzymes from polysaccharide utilizing loci ofPrevotella copriDSM18205

“…Low amounts of hydrolysed products were observed with arabinoxylan as substrate, exposing the need of additional debranching enzymes for an effective degradation of this substrate. Release of xylose by the action of the GH10 enzymes has previously been reported for related endo-xylanases, evidencing ability to act on low molecular weight XOS (Chapla, Pandit, and Shah 2012;Rahmani et al 2019;Salas-Veizaga et al 2017). The apparent lack of generation of xylose by GH10 (1), despite presence of xylooligosaccharides with a DP between 2 to 5 ( Figure 4A), gives to the GH10 (PUL 15) endo-1,4-β-xylanase from P. copri DSM18205 a significant biotechnological potential for oligosaccharides production with prebiotic activity (Linares-Pasten, Rahmani et al 2019;Samanta et al 2015).…”

Multilayer Bixin Microcapsules: The Impact of Native Carbohydrates on the Microencapsulation Efficiency and Dispersion Stability

“…After that, the samples were filtered with a 0.22 μm membrane filter, diluted 20 times with ultra-pure water, and analyzed with high-performance anion exchange chromatography with pulse amperometric detectior (HPAEC-PAD) (Sunnyvale, CA, USA). A PA-20 column was used with NaOH as the mobile phase, as described in [31,33]. Standards of glucose, galactose, manose, xylose, and arabinose were prepared in concentration from 0.5 to 20 μg/mL.…”