Evaluation of hydrothermal sugarcane bagasse treatment for the production of xylooligosaccharides in different pressures

Recent developments in xylooligosaccharides: Sustainable production, characterization, beneficial properties and applications

Xylooligosaccharides (XOS) are functional oligosaccharides with prebiotic activity, offering exceptional nutritional and health benefits and a wide range of applications. The increasing market demand for healthy products has driven interest in XOS, as they are low-dose prebiotics with high added value, fostering developments in their production. In a sustainable production context, XOS can be obtained from low-cost lignocellulosic raw materials, which require adapted pretreatment techniques to produce high-quality XOS with high process efficiency. One- and two-step methodologies are discussed in terms of increasing XOS production while aiming to limit the co-production of toxic compounds. Autohydrolysis and enzymatic hydrolysis with xylanases stand out as a promising technology for XOS production with high yields. Purification and characterization methodologies are also two important steps to achieve mixtures of XOS with high purity, specific degree of polymerization and substitution to improve their beneficial properties and, consequently, their applications. This review presents the potential of XOS as prebiotics, describing the recent technological production routes, along with advancements in the development of new production processes using alternative substrates, as well as the beneficial effects of their consumption, addressing their latest applications that justify the pursuit of their consolidation in the industrial prebiotic market.

Green Process for Producing Xylooligosaccharides by Using Sequential Auto-hydrolysis and Xylanase Hydrolysis

Xylooligosaccharides (XOS), as prebiotic oligomers, are increasingly receiving attention as high value-added products produced from lignocellulosic biomass. Although the XOS contains a series of different degrees of polymerization (DP) of xylose units, DP 2 and 3 (xylobiose (X2) and xylotriose (X3)) are regarded as the main active components in food and pharmaceutical fields. Therefore, in the study, in order to achieve the maximum production of XOS with the desired DP, a combination strategy of sequential auto-hydrolysis and xylanase hydrolysis was developed with corncob as raw material. The evidences showed that the hemicellulosic xylan could be effectively decomposed into various higher DP saccharides (> 4), which were dissolved into the auto-hydrolysate; sequentially, the soluble saccharides could be rapidly hydrolyzed into XOS with desired DP by xylanase hydrolysis. Finally, a maximum XOS yield of 56.3% was achieved and the ratio of (X2 + X3)/XOS was over 80%; meanwhile, the by-products could be controlled at lower levels. Overall, this study provides solid data that support the selective and precise preparation of XOS from corncob, vigorously promoting the application of XOS as functional sugar products.

Sugarcane Straw as a Source of Arabinoxylans: Optimization and Economic Viability of a Two-Step Alkaline Extraction

Sugarcane processing produces a significant amount of byproducts in the form of straw and bagasse, which are rich in cellulose, hemicellulose, and lignin. This work aims to provide a valorization approach to sugarcane straw by optimizing a two-step alkaline extraction of arabinoxylans by a response surface methodology to evaluate a potential industrial-scale production. Sugarcane straws were delignified using an alkaline-sulfite pretreatment, followed by alkaline extraction and precipitation of arabinoxylan, a two-step process optimized using a response surface methodology. A KOH concentration of (2.93-17.1%) and temperature (18.8-61.2 °C) were chosen as independent variables, and the arabinoxylan yield (%) as a response variable. The model application shows that KOH concentration, temperature, and the interaction between both independent variables are significant in extracting arabinoxylans from straw. The best-performing condition was further characterized by FTIR, DSC, and chemical and molecular weight evaluation. The straws arabinoxylans presented high purities levels, ca. 69.93%, and an average molecular weight of 231 kDa. The overall estimated production cost of arabinoxylan from straw was 0.239 €/g arabinoxylan. This work demonstrates a two-step alkaline extraction of the arabinoxylans method, as well as their chemical characterization and economic viability analysis, that can be used as a model for industrial scale-up production.

Hydrothermal pretreatment for the production of prebiotic oligosaccharides from tobacco stem

Tobacco stem is an abundant and inexpensive renewable source to produce prebiotics by circular economy. In this study, hydrothermal pretreatments were evaluated on the release of xylooligosaccharides (XOS) and cello-oligosaccharides (COS) from the tobacco stem by a central composite rotational design associated with response surface methodology to evaluate the effects of temperature (161.72 to 218.3 °C) and solid load (SL) (2.93 to 17.07%). XOS were the main compounds released to the liquor. Desirability function was performed to maximize the production of XOS and minimize the effects of release of monosaccharides and degradation compounds. The result indicated yield of 96% w[XOS]/w[xylan] for 190 °C-2.93% SL. The highest value for COS and total oligomers content (COS + XOS) was 6.42 g/L and 17.7 g/L, respectively, for 190 °C-17.07% SL. The mass balance for the best yield XOS condition predicted 132 kg of XOS (X2-X6) from 1000 kg of tobacco stem.