Xylo-oligosaccharide microparticles with synbiotic potential obtained from enzymatic hydrolysis of sugarcane straw

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.

Enzymatic production of xylooligosaccharide from lignocellulosic and marine biomass: A review of current progress, challenges, and its applications in food sectors

Over the last decade, xylooligosaccharides (XOS) have attracted great attentions because of their unique chemical properties and excellent prebiotic effects. Among the current strategies for XOS production, enzymatic hydrolysis is preferred due to its green and safe process, simplicity in equipment, and high control of the degrees of polymerization. This paper comprehensively summarizes various lignocellulosic biomass and marine biomass employed in enzymatic production of XOS. The importance and advantages of enzyme immobilization in XOS production are also discussed. Many novel immobilization techniques for xylanase are presented. In addition, bioinformatics techniques for the mining and designing of new xylanase are also described. Moreover, XOS has exhibited great potential applications in the food industry as diverse roles, such as a sugar replacer, a fat replacer, and cryoprotectant. This review systematically summarizes the current research progress on the applications of XOS in food sectors, including beverages, bakery products, dairy products, meat products, aquatic products, food packaging film, wall materials, and others. It is anticipated that this paper will act as a reference for the further development and application of XOS in food sectors and other fields.

Efficient co-production of xylo-oligosaccharides and fermentable sugars from sugarcane bagasse by glutamic acid pretreatment

In the production of xylo-oligosaccharides (XOS) by organic acid pretreatment, it is often difficult to isolate organic acids from XOS. Here, an acidic amino acid, glutamic acid (GA), was used to pretreat sugarcane bagasse (SCB) to prepare XOS and fermentable sugars. The effects of GA concentration, hydrolysis temperature, and pretreatment time on the yield and polymerization distribution of XOS were investigated. After hydrolysis by 0.2 M GA at 140 °C for 30 min, the maximum yield of X2-5 was 53.3%, and the concentrations of xylose and furfural were 1.8 g/L and 0.1 g/L, respectively. Meanwhile, GA increased the pore size and porosity of SCB as well as the number of functional groups of amino acid residues, which improved the enzymatic efficiency and the maximum yield of glucose was 95.3%. Thus, GA pretreatment provides a more economical, environmentally friendly and sustainable method for the co-production of XOS and glucose from SCB.

Impact of adding xylooligosaccharides encapsulated in butter: Microstructural, optical, rheological and sensory aspects

This study investigated the microstructure, rheological properties, and sensory characteristics of butters produced with free and encapsulated xylooligosaccharides (XOS). Four formulations of butter were processed: BCONT: 0 % w/w XOS (control); BXOS: 20% w/w free XOS; BXOS-ALG: 20% w/w XOS microencapsulated with alginate (XOS-alginate ratio of 3:1 w/w); and BXOS-GEL: 20% w/w XOS microencapsulated with alginate-gelatin (XOS-alginate-gelatin ratio of 3:1:1.5 w/w). The microparticles showed a bimodal distribution, low size and low span values, demonstrating physical stability to be included in emulsions. The XOS-ALG presented surface weighted mean diameter (D3.2) of 90.24 µm, volume-weighted mean diameter (D4.3) of 131.8 µm, and Span of 2.14. In contrast, the XOS-GEL presented D3.2 of 82.80 µm, D4.3 of 141.0 µm, and a Span of 2.46. Products with XOS were characterized by higher creaminess, sweet taste, and lower salty taste than the control. However, the addition form significantly impacted the other evaluated parameters. The utilization of XOS in a free form (BXOS) resulted in smaller droplet sizes (1.26 μm) than encapsulated XOS and control (XOS-ALG = 1.32 µm / XOS-GEL = 1.58 µm, / BCONT = 1.59 µm), and changes in the rheological parameters (higher values of shear stress, viscosity, consistency index, rigidity (J0), and Newtonian viscosity (ηN) and lower elasticity (τ)). Furthermore, it changed the color parameters (more yellow and dark color, lower L* and higher b* values). On the other hand, the utilization of micropaticles of XOS (BXOS-ALG and BXOS-GEL) kept shear stress, viscosity, consistency index, rigidity (J0), and elasticity (τ) more similar to control. The products had a less intense yellow color (lower b* values) and was perceived with more consistency and butter taste. However, the presence of particles was perceived by consumers. The results suggest that consumers were more attentive to reporting flavor-related attributes than texture. In conclusion, adding microparticles of XOS could improve butter's rheological and sensory properties. In conclusion, adding microparticles of XOS could improve butter's rheological and sensory properties.

Rational enzyme design for controlled functionalization of acetylated xylan for cell-free polymer biosynthesis

Xylan O-acetyltransferase 1 (XOAT1) is involved in O-acetylating the backbone of hemicellulose xylan. Recent structural analysis of XOAT1 showed two unequal lobes forming a cleft that is predicted to accommodate and position xylan acceptors into proximity with the catalytic triad. Here, we used docking and molecular dynamics simulations to investigate the optimal orientation of xylan in the binding cleft of XOAT1 and identify putative key residues (Gln445 and Arg444 on Minor lobe & Asn312, Met311 and Asp403 on Major lobe) involved in substrate interactions. Site-directed mutagenesis coupled with biochemical analyses revealed the major lobe of XOAT1 is important for xylan binding. Mutation of single key residues yielded XOAT1 variants with various enzymatic efficiencies that are applicable to one-pot synthesis of xylan polymers with different degrees of O-acetylation. Taken together, our results demonstrate the effectiveness of computational modeling in guiding enzyme engineering aimed at modulating xylan and redesigning plant cell walls.

Heterologous Expression of Lignocellulose-Modifying Enzymes in Microorganisms: Current Status

Heterologous expression of the carbohydrate-active enzymes in microorganisms is a promising approach to produce bio-based compounds, such as fuels, nutraceuticals and other value-added products from sustainable lignocellulosic sources. Several microorganisms, including Saccharomyces cerevisiae, Escherichia coli, and the filamentous fungi Aspergillus nidulans, have unique characteristics desirable for a biorefinery production approach like well-known genetic tools, thermotolerance, high fermentative capacity and product tolerance, and high amount of recombinant enzyme secretion. These microbial factories are already stablished in the heterologous production of the carbohydrate-active enzymes to produce, among others, ethanol, xylooligosaccharides and the valuable coniferol. A complete biocatalyst able to heterologous express the CAZymes of glycoside hydrolases, carbohydrate esterases and auxiliary activities families could release these compounds faster, with higher yield and specificity. Recent advances in the synthetic biology tools could expand the number and diversity of enzymes integrated in these microorganisms, and also modify those already integrated. This review outlines the heterologous expression of carbohydrate-active enzymes in microorganisms, as well as recent updates in synthetic biology.