Xylooligosaccharides as prebiotics from biomass autohydrolyzate

The way forward to produce nutraceuticals from agri-food processing residues: obstacle, solution, and possibility

Food matrices contain bioactive compounds that have health benefits beyond nutritional value. The bulk of bioactive chemicals are still present in agro-industrial by-products as food matrices. Throughout the food production chain, there is a lot of agro-industrial waste that, if not managed effectively, could harm the environment, company, and how nutritiously and adequately people eat. It's important to establish processes that maximise the use of agro-industrial by-products, such as biological technologies that improve the extraction and acquisition of bioactive compounds for the food and pharmaceutical industries. As opposed to nonbiological processes, biological procedures provide high-quality, bioactive extracts with minimum toxicity and environmental impact. Fermentation and enzymatic treatment are biological processes for obtaining bioactive compounds from agro-industrial waste. In this context, this article summarises the principal bioactive components in agro-industrial byproducts and the biological methods employed to extract them. In this review efficient utilization of bioactive compounds from agro-industrial waste more effectively in food and pharmaceutical industries has been described.

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.

Evaluating the In Vitro and In Vivo Prebiotic Effects of Different Xylo-Oligosaccharides Obtained from Bamboo Shoots by Hydrothermal Pretreatment Combined with Endo-Xylanase Hydrolysis

Xylo-oligosaccharides (XOS) enriched with high fractions of X2-X3 are regarded as an effective prebiotic for regulating the intestinal microflora. In this study, the original XOS solution was obtained from bamboo shoots through hydrothermal pretreatment under optimized conditions. Subsequently, enzymatic hydrolysis with endo-xylanase was performed on the original XOS solution to enhance the abundance of the X2-X3 fractions. The results demonstrated that hydrothermal pretreatment yielded 21.24% of XOS in the hydrolysate solution, and subsequent enzymatic hydrolysis significantly increased the proportion of the X2-X3 fractions from 38.87% to 68.21%. Moreover, the XOS solutions with higher amounts of X2-X3 fractions exhibited superior performance in promoting the growth of probiotics such as Bifidobacterium adolescentis and Lactobacillus acidophilus in vitro, leading to increased production of short-chain fatty acids. In the in vivo colitis mouse model, XOS solutions with higher contents of X2-X3 fractions demonstrated enhanced efficacy against intestinal inflammation. Compared with the colitis mice (model group), the XOS solution with higher X2-X3 fractions (S1 group) could significantly increase the number of Streptomyces in the intestinal microflora, while the original XOS solution (S2 group) could significantly increase the number of Bacteroides in the intestinal microflora of colitis mice. In addition, the abundances of Alcaligenes and Pasteurella in the intestinal microflora of the S1 and S2 groups were much lower than in the model group. This effect was attributed to the ability of these XOS solutions to enhance species diversity, reversing the imbalance and disorder within the intestinal microflora. Overall, this work highlights the outstanding potential of XOS enriched with high contents of X2-X3 fractions as a regulator of the intestinal microbiota and as an anti-colitis agent.

Xylooligosaccharides: A Bibliometric Analysis and Current Advances of This Bioactive Food Chemical as a Potential Product in Biorefineries' Portfolios

Xylooligosaccharides (XOS) are nondigestible compounds of great interest for food and pharmaceutical industries due to their beneficial prebiotic, antibacterial, antioxidant, and antitumor properties. The market size of XOS is increasing significantly, which makes its production from lignocellulosic biomass an interesting approach to the valorization of the hemicellulose fraction of biomass, which is currently underused. This review comprehensively discusses XOS production from lignocellulosic biomass, aiming at its application in integrated biorefineries. A bibliometric analysis is carried out highlighting the main players in the field. XOS production yields after different biomass pretreatment methods are critically discussed using Microsoft PowerBI® (2.92.706.0) software, which involves screening important trends for decision-making. Enzymatic hydrolysis and the major XOS purification strategies are also explored. Finally, the integration of XOS production into biorefineries, with special attention to economic and environmental aspects, is assessed, providing important information for the implementation of biorefineries containing XOS in their portfolio.

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.

Green Process for Xylooligosaccharides Production using an Eucalyptus Kraft Pulp

Xylooligosaccharides (XOS) are oligomers with recognized and important prebiotic properties, whose consumption is associated with several health benefits, including a positive impact on the immune system. In this work, XOS were produced through a green process of enzymatic hydrolysis performed directly on an intermediate product from a pulp and paper industry, Eucalyptus bleached kraft pulp. Focusing on an industrial, sustainable and more economical application, two goals were defined and validated: (i) no pretreatment of the substrate and (ii) the replacement of the commonly used buffer solution as reaction medium for only water. The influence of the most relevant operating conditions on the production of XOS as well as the respective yields obtained were very similar when using either buffer or water as the reaction medium. For the use of water, although the solution pH decreases during the enzymatic reaction, this change did not affect the production of XOS. For the optimized conditions, 80 °C and 100 U/g pulp, a maximum yield of 31.4 ± 2.6% per total xylan in the pulp was obtained, resulting in more than 50 kg of XOS per ton of pulp. The correspondent hydrolysate was mainly composed by xylobiose (66%) and xylotriose (29%), oligomers with the highest prebiotic effect.

Glutamic acid assisted hydrolysis strategy for preparing prebiotic xylooligosaccharides

Since the immune-boosting properties as well as the benefit of promoting the growth of gut bacteria, xylooligosaccharides as prebiotics have attracted considerable interest as functional feed additives around the world. A growing number of studies suggest that acidic hydrolysis is the most cost-effective method for treating xylan materials to prepare xylooligosaccharides, and organic acids were proved to be more preferable. Therefore, in this study, glutamic acid, as an edible and nutritive organic acid, was employed as a catalyst for hydrolyzing xylan materials to prepare xylooligosaccharides. Further, xylooligosaccharide yields were optimized using the response surface methodology with central composite designs. Through the response surface methodology, 28.2 g/L xylooligosaccharides with the desirable degree of polymerization (2-4) at a yield of 40.5 % could be achieved using 4.5% glutamic acid at 163°C for 41 min. Overall, the application of glutamic acid as a catalyst could be a potentially cost-effective method for producing xylooligosaccharides.

Preparation and nutritional properties of xylooligosaccharide from agricultural and forestry byproducts: A comprehensive review

Xylooligosaccharide (XOS) are functional oligosaccharides with prebiotic activities, which originate from lignocellulosic biomass and have attracted extensive attention from scholars in recent years. This paper summarizes the strategies used in the production of XOS, and introduces the raw materials, preparation methods, and purification technology of XOS. In addition, the biological characteristics and applications of XOS are also presented. The most commonly recommended XOS production strategy is the two-stage method of alkaline pre-treatment and enzymatic hydrolysis; and further purification by membrane filtration to achieve the high yield of XOS is required for prebiotic function. At the same time, new strategies and technologies such as the hydrothermal and steam explosion have been used as pre-treatment methods combined with enzymatic hydrolysis to prepare XOS. XOS have many critical physiological activities, especially in regulating blood glucose, reducing blood lipid, and improving the structure of host intestinal flora.

Manufacture and Prebiotic Potential of Xylooligosaccharides Derived From Eucalyptus nitens Wood

Mixtures of xylooligosaccharides (XOS) were manufactured from Eucalyptus nitens samples by hydrothermal processing. In order to obtain a product suitable to be used as a prebiotic, the liquors obtained were subjected to a refining sequence consisting of a two-step membrane filtration followed by anion exchange and freeze-drying. The process proposed allowed to obtain a highly refined product mainly made up of a mixture of substituted XOS with a degree of polymerization, DP3–10, which was evaluated for its prebiotic potential by in vitro fermentation assays. Their effects on the microbiota composition and the metabolic activity were assessed along the fermentation time and compared to fructooligosaccharides (FOS, a gold standard prebiotic), using fecal inocula from donors belonging to two age-groups (young and elderly). Significant and similar increases were observed in most of the bacterial groups considered (including Bifidobacterium spp. or several butyrate-producers) in both XOS and FOS in vitro interventions, although XOS resulted in significantly higher increases in total bacteria and lower rises in Clostridium clusters I and II than FOS. Regarding the metabolic activity, higher amounts of total organic acid (TOA; 150 vs. 110 mM) and higher total short-chain fatty acid (SCFA)/TOA ratio (0.88 vs. 0.70 mol/mol) were achieved at 28 h using XOS as a carbon source in comparison with FOS. Moreover, both substrates resulted in different metabolite profiles. Higher percentages of acetate and propionate were achieved when XOS were used as substrates, whereas FOS resulted in slightly higher concentrations of butyrate. No differences were found between both age-groups. Taking together these results, it can be concluded that XOS produced from E. nitens by a biorefinery-based approach led to, at least, similar prebiotic activity as that observed with FOS.

Production and Characterization of High Value Prebiotics From Biorefinery-Relevant Feedstocks

Hemicellulose, a structural polysaccharide and often underutilized co-product stream of biorefineries, could be used to produce prebiotic ingredients with novel functionalities. Since hot water pre-extraction is a cost-effective strategy for integrated biorefineries to partially fractionate hemicellulose and improve feedstock quality and performance for downstream operations, the approach was applied to process switchgrass (SG), hybrid poplar (HP), and southern pine (SP) biomass at 160°C for 60 min. As a result, different hemicellulose-rich fractions were generated and the chemical characterization studies showed that they were composed of 76-91% of glucan, xylan, galactan, arabinan, and mannan oligosaccharides. The hot water extracts also contained minor concentrations of monomeric sugars (≤18%), phenolic components (≤1%), and other degradation products (≤3%), but were tested for probiotic activity without any purification. When subjected to batch fermentations by individual cultures of Lactobacillus casei, Bifidobacterium bifidum, and Bacteroides fragilis, the hemicellulosic hydrolysates elicited varied responses. SG hydrolysates induced the highest cell count in L. casei at 8.6 log10 cells/ml, whereas the highest cell counts for B. fragilis and B. bifidum were obtained with southern pine (5.8 log10 cells/ml) and HP hydrolysates (6.4 log10 cells/ml), respectively. The observed differences were attributed to the preferential consumption of mannooligosaccharides in SP hydrolysates by B. fragilis. Lactobacillus casei preferentially consumed xylooligosaccharides in the switchgrass and southern pine hydrolysates, whereas B. bifidum consumed galactose in the hybrid poplar hydrolysates. Thus, this study (1) reveals the potential to produce prebiotic ingredients from biorefinery-relevant lignocellulosic biomass, and (2) demonstrates how the chemical composition of hemicellulose-derived sources could regulate the viability and selective proliferation of probiotic microorganisms.

Selective Production of Xylooligosaccharides by Xylan Hydrolysis Using a Novel Recyclable and Separable Furoic Acid

Xylooligosaccharides (XOS) have gained considerable attention worldwide as prebiotics due to their immune-strengthening activity and beneficial gut bacteria development and can be produced from xylan-rich resources by acid hydrolysis. The present study proved the organic acid hydrolysis to be beneficial for XOS yield. In this study, a recyclable and separable organic acid, i.e., furoic acid, was used for hydrolyzing xylan to produce XOS, and the response surface methodology design was applied to maximize the XOS yield; the results indicated that the quadratic model terms of the interaction between reaction temperature and hydrolysis time showed the most significant impact on XOS yields (P < 0.05). The predicted maximum yield of XOS was 49.0% with 1.2% furoic acid at 167°C for 33 min, being close to the experimental value (49.2%), indicating that the fitted models were in good agreement with the experimental results. Meanwhile, the primary byproducts, including xylose and furfural, were concurrently bio-oxidized into xylonic acid and furoic acid by Gluconobacter oxydans and separated by electrodialysis. Subsequently, the furoic acid with low solubility (<3.7%, 25°C) was recovered by natural crystallization. The above results indicate that the use of multi-steps contributes to sustainable XOS production by furoic acid.

An integrated process to produce prebiotic xylooligosaccharides by autohydrolysis, nanofiltration and endo-xylanase from alkali-extracted xylan

Alkali-extracted xylan from lignocellulosics is a promising feedstock for production of prebiotic xylooligosaccharides (XOS). An integrated process was established combining autohydrolysis, nanofiltration and xylanase hydrolysis. Results show that after autohydrolysis 48.37% of xylan was degraded into oligomers and dissolved into the autohydrolysate, of which 57.83% were XOS. By-products and xylose were removed by nanofiltration with discontinuous diafiltration, while high recovery yields of XOS (84.15%) and xylan (87.45%) were obtained. High yields of XOS were obtained by adding xylanase to the autohydrolysates; after enzymatic hydrolysis an XOS yield of 96-98% was obtained. The enzymatic hydrolysates showed positive prebiotic effects on B. adolescentis with an increase in cell concentration by 4.8-fold after fermentation for 24 h. The main products were short-chain fatty acids with carbon balanced during the whole fermentation process. This integrated strategy resulted in a final XOS conversion of 41.22% contrasted to the initial xylan in raw alkali-extracted xylan.

Aspergillus nidulans: A Potential Resource of the Production of the Native and Heterologous Enzymes for Industrial Applications

Aspergillus nidulans is a filamentous fungus that is a potential resource for industrial enzymes. It is a versatile fungal cell factory that can synthesize various industrial enzymes such as cellulases, β-glucosidases, hemicellulases, laccases, lipases, proteases, β-galactosidases, tannases, keratinase, cutinases, and aryl alcohol oxidase. A. nidulans has shown the potential to utilize low-cost substrates such as wheat bran, rice straw, sugarcane bagasse, rice bran, coir pith, black gram residue, and chicken feathers to produce enzymes cost-effectively. A. nidulans has also been known as a model organism for the production of heterologous enzymes. Several studies reported genetically engineered strains of A. nidulans for the production of different enzymes. Native as well as heterologous enzymes of A. nidulans have been employed for various industrial processes.

Hydrophobic resin treatment of hydrothermal autohydrolysate for prebiotic applications

∼30% of xylooligosaccharides (XOS) in autohydrolysate are likely bonded to lignin “tied,” contributing to loss during resin purification. Loss of “free” XOS depends on DP.