Carbohydrates valorization of Quinoa (Chenopodium quinoa) stalk in xylooligosaccharides and carotenoids as emergent biomolecules

Quinoa (Chenopodium quinoa) stalk (QS) is an unvalued and renewable lignocellulosic waste. Aiming to its valorization, autohydrolysis process (178 °C and 10 bar) for xylooligosaccharides (XOS) production and enzymatic hydrolysate of residual solid for carotenoids production by Rhodotorula glutinis were evaluated. The highest yield of XOS (79 mg/g of biomass) containing mainly xylotetraose (X4) to xylohexaose (X6) was achieved in 20 min of process, while high xylobiose (X2, 18 mg/g of QS) and xylotriose (X3, 18 mg/g of QS) contents were observed in 45 min. In ultrafiltration-UF using membrane with nominal MWCO of 10 kDa, higher permeate flux was observed at pH 6.6 than at lower pH values (3.6, 4.6, and 5.6). In the retentate after nanofiltration-NF (150–300 Da), 56 % of total XOS (X2-X6) was recovered. Finally, 4.1 mg of carotenoids/g of dry cells weight, corresponding to 6.27 mg of carotenoids/g of total sugar consumed, were produced by the yeast using residual solids hydrolysate. Therefore, quinoa stalk was shown as an interesting source for high value biomolecules production.