Membrane-assisted processing of xylooligosaccharide-containing liquors

Effect of addition of wheat bran hydrolysate on bread properties

Although the addition of bran to bread makes it healthier and more functional, it brings with it some technological problems. One way to eliminate these problems is hydrothermal pretreatment of wheat bran. In this study, five different ratios (10%, 20%, 30%, 50%, and 100%) of hydrolysates from hydrothermal pretreatment of wheat bran (150°C, 30 min) were substituted with dough-kneading water during dough kneading for bread making. The physical, chemical, functional, textural and important starch fractions of the bread produced were determined. The addition of hydrolysate in different amounts to the dough-kneading water resulted in similar physical properties (height, specific volume, and crust color) as the control bread. While the addition of hydrolysate decreased the hardness of the breads, it positively improved important starch fractions (increasing the amount of slowly digestible starch and decreasing the amount of rapidly digestible starch). It also increased antioxidant capacity (iron (III) reducing antioxidant power, ABTS, and DPPH (2,2-diphenyl-1-picrylhydrazyl) and reduced the starch hydrolysis index of the bread. It was shown that the hydrolysate obtained after the hydrothermal treatment of bran could be used in bread making to satisfy the demand for products preferred by consumers from both health and sensory points of view.

Isolation, purification and characterization of β-glucan from cereals - A review

β-glucans are soluble fibers found in cereal compounds, including barley, oats etc., as an active component. They are used as a dietary fiber to treat cholesterol, diabetes and cardiovascular diseases. These polysaccharides are important because they can provide many therapeutic benefits related to their biological activity in human like inhibiting tumour growth, anti-inflammatory action, etc. All these activities were usually attached to their molecular weight, structure and degree of branching. The present manuscript reviews the background of β-glucan, its characterization techniques, the possible ways to extract β-glucan and mainly focuses on membrane-based purification techniques. The β-glucan separation methods using polymeric membranes, their operational characteristics, purification methods which may yield pure or crude β-glucan and structural analysis methods were also discussed. Future direction in research and development related to β-glucan recovery from cereal were also offered.

Fractionation of functional oligosaccharides produced from sugarcane straw using serial nanofiltration membranes and their influence on prebiotic potential

Functional oligosaccharides are non-digestible by human gut enzymes and provide health benefits as fibers and prebiotics. The cello-oligosaccharides (COS) and xylooligosaccharides (XOS) are functional oligosaccharides obtained from xylan and cellulose, respectively, and are present in lignocellulosic material. The serial NF membranes process was performed to investigate the impact of the fractionation process on the prebiotic activity of oligosaccharides from xylan and cellulose. The NP030 (weight cut-off of 500-600 Da) and DK (weight cut-off of 150-300 Da) NF polymeric membranes were employed using defined operational conditions. The diafiltration (DF) was also investigated and it was determined that only a 1-time DF for NP030 was a more suitable strategy and improved the performance indices for short DP oligosaccharides. The short DP fractions obtained favored cell density for probiotic strains, which presented an increase on the optical density of up to 25 % after the fractionating process; enabling the use of short purified fractions in the food and pharmaceutical industry as a prebiotic ingredient.

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.

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.

Prebiotic effects of citrus pectic oligosaccharides

Citrus peel wastes, one of the major by-products of the agri-food industry, are a source of value-added compounds. In this work, a commercial pectin (PEC1) and one obtained by direct extraction from citrus fibre (PEC2), were hydrolysed and ultrafiltered at different cut-off (100, 50 and 30 kDa) and then tested in broth with four different probiotic strains: Lacticaseibacillus paracasei, Limosilactobacillus fermentum, Lacticaseibacillus rhamnosus and Bifidobacterium animalis subsp. paracasei. In addition, the probiotic strains selected for their growth rate with the fractions of the two pectins were tested for tolerance to different pH values and bile salts. This study demonstrated that POS2 (product from the enzymatic hydrolysis by PEC2) showed greater prebiotic activity than POS1 (product from the enzymatic hydrolysis by PEC1). The results confirmed that citrus pectic oligosaccharides could be used as emerging prebiotics with improved properties due to their antimicrobial and modulating-microbiota ability.

Potential Valorization of Hazelnut Shells through Extraction, Purification and Structural Characterization of Prebiotic Compounds: A Critical Review

Hazelnuts are one of the most widely consumed nuts, but their production creates large quantities of by-products, especially shells, that could be upcycled into much more valuable products. Recent studies have shown that hazelnut shell hemicellulose is particularly rich in compounds that are potential precursors of xylooligosaccharides and arabino-xylooligosaccharides ((A)XOS), previously defined as emerging prebiotics very beneficial for human health. The production of these compounds on an industrial scale-up could have big consequences on the functional foods market. However, to produce (A)XOS from a lignocellulosic biomass, such as hazelnut shell, is not easy. Many methods for the extraction and the purification of these prebiotics have been developed, but they all have different efficiencies and consequences, including on the chemical structure of the obtained (A)XOS. The latter, in turn, is strongly correlated to the nutritional effects they have on health, which is why the optimization of the structural characterization process is also necessary. Therefore, this review aims to summarize the progress made by research in this field, so as to contribute to the exploitation of hazelnut waste streams through a circular economy approach, increasing the value of this biomass through the production of new functional ingredients.

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.

Miscanthus×giganteus xylooligosaccharides: Purification and fermentation

A procedure was developed to recover xylooligosaccharides (XOS) from Miscanthus×giganteus (M×G) hydrolyzate. M×G hydrolyzate was prepared using autohydrolysis, and XOS rich fractions were acquired using activated carbon adsorption and stepwise ethanol elution. The combined XOS fractions were purified using a series of ion exchange resin treatments. The end product, M×G XOS, had 89.1% (w/w) total substituted oligosaccharides (TSOS) composed of arabinose, glucose, xylose and acetyl group. Bifidobacterium adolescentis and Bifidobacterium catenulatum (health promoting bacteria) were cultured in vitro on M×G XOS and a commercial XOS source, which was used as a comparison. B. adolescentis grew to a higher cell density than B. catenulatum in both XOS cultures. Total xylose consumption for B. adolescentis was 84.1 and 84.8%, respectively for M×G and commercial XOS cultures; and for B. catenulatum was 76.6 and 73.6%, respectively. The xylobiose (X2), xylotriose (X3) and xylotetraose (X4) were almost utilized for both strains. Acetic and lactic acids were the major fermentation products of the XOS cultures.

Production, Purification, and in Vitro Evaluation of the Prebiotic Potential of Arabinoxylooligosaccharides from Brewer's Spent Grain

Brewer's spent grain (BSG) samples were subjected to a two-step aqueous processing (starch extraction and autohydrolysis) in order to assess their potential as a raw material for obtaining a mixture of arabinoxylooligosaccharides (AXOS) suitable to be use as prebiotics for elderly. After hydrothermal treatment, the liquors were refined by a sequence of purification and conditioning steps including membrane filtration, enzymatic hydrolysis, and ion exchange. The presence of both substituted (degree of polimerization (DP) = 2-10) and unsubstituted (DP = 2-16) oligosaccharides made up of xylose and arabinose (AXOS) were confirmed in purified mixtures (in which total OS content = 84% w/w) by using chromatographic techniques and matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS). Finally, AXOS were evaluated for their prebiotic activity by in vitro fermentation assays using fecal inocula from elderly people, demonstrating that AXOS were slightly better substrates than FOS, in terms of bacterial population shifts as in the production of SCFA.

Purification, characterization, and prebiotic properties of pectic oligosaccharides from orange peel wastes

Pectic oligosaccharides (POS) were obtained by hydrothermal treatment of orange peel wastes (OPW) and purified by membrane filtration to yield a refined product containing 90 wt % of the target products. AraOS (DP 3-21), GalOS (DP 5-12), and OGalA (DP 2-12, with variable DM) were identified in POS mixtures, but long-chain products were also present. The prebiotic potential of the concentrate was assessed by in vitro fermentation using human fecal inocula. For comparative purposes, similar experiments were performed using orange pectin and commercial fructo-oligosaccharides (FOS) as substrates for fermentation. The dynamics of selected microbial populations was assessed by fluorescent in situ hybridization (FISH). Gas generation, pH, and short-chain fatty acid (SCFA) production were also measured. Under the tested conditions, all of the considered substrates were utilized by the microbiota, and fermentation resulted in increased numbers of all the bacterial groups, but the final profile of the microbial population depended on the considered carbon source. POS boosted particularly the numbers of bifidobacteria and lactobacilli, so that the ratio between the joint counts of both genera and the total cell number increased from 17% in the inocula to 27% upon fermentation. SCFA generation from POS fermentation was similar to that observed with FOS, but pectin fermentation resulted in reduced butyrate generation.

Pectic oligosacharides from lemon peel wastes: production, purification, and chemical characterization

Lemon peel wastes were extracted with water to remove free sugars and other soluble compounds, and the insoluble solid was employed as a substrate for the manufacture of pectin-derived oligosaccharides by processing with hot, compressed water. When water-extracted lemon peel wastes were treated with water at 160 °C, the oligomer concentration reached the maximum value (31 g/L). Autohydrolysis liquors were subjected to two membrane filtration stages (diafiltration followed by concentration), yielding a refined product containing about 98 wt % of oligomers at a global yield of 14 kg/100 kg oven-dry lemon peel. The concentrate contained oligogalacturonides (with DP in the range of 2-18) and arabinooligosaccharides (with DP in the range of 2-8).

Plant cell wall polysaccharides as potential resources for the development of novel prebiotics

Prebiotic oligosaccharides, with a degree of polymerization (DP) of mostly less than 10, exhibit diverse biological activities that contribute to human health. Currently available prebiotics are mostly derived from disaccharides and simple polysaccharides found in plants. Subtle differences in the structures of oligosaccharides can cause significant differences in their prebiotic proper-ties. Therefore, alternative substances supplying polysaccharides that have more diverse and complex structures are necessary for the development of novel oligosaccharides that have actions not present in existing prebiotics. In this review, we show that structural polysaccharides found in plant cell walls, such as xylans and pectins, are particularly potential resources supplying broadly diverse polysaccharides to produce new prebiotics.

Production of oligosaccharides and sugars from rye straw: a kinetic approach

Following the biorefinery philosophy, the non-isothermal autohydrolysis of rye straw (an agroindustrial byproduct) was carried out to obtain liquors containing substituted xylooligosaccharides and solids enriched in cellulose (suitable as substrates for further enzymatic hydrolysis). The effects of temperature (in the range 185-220 degrees C) on the composition of solids and liquid phases were evaluated, and kinetic models were developed. When operation was carried out at 208 degrees C, 69.2% of the initial xylan was converted into xylooligosaccharides, leading to reaction liquors containing up to 22.4 g oligosaccharides/L. The effects of treatments on the DP of the target products and on their substituents were also measured. At 208 degrees C, the percentages of XOS having DP2-4, DP5-6 and DP>6 were 24.8%, 22.4% and 54.8%, respectively. Under selected conditions, the molar ratio Xyl:Ac:UA of the oligomers was 10:1.54:0.50. Finally, when the solid was subjected to enzymatic hydrolysis, 70.6% of cellulose and 63.8% of xylan were saccharified after 48 h.

Production, refining, structural characterization and fermentability of rice husk xylooligosaccharides

Oligosaccharides produced by hydrothermal processing of rice husks (xylooligosaccharides and glucooligosaccharides) were refined by membrane processing (operating in diafiltration and concentration modes), subjected to xylanase treatment to reduce the average molar mass, and subjected to further purification by ultrafiltration (operating in concentration mode) and ion exchange. The purified products were assayed for composition, molar mass distribution and structural characterization by HPLC, HPAEC-PAD, HPSEC, MALDI-TOF-MS and NMR ((1)H and (13)C). The fermentability of the purified product by fecal inocula was assessed on the basis of the time courses of pH and oligosaccharide concentrations. Succinate, lactate, formiate, acetate, propionate and butyrate were the major products resulting from fermentation experiments.

Evaluation of ultra- and nanofiltration for refining soluble products from rice husk xylan

Liquors from water treatments of rice husks (containing soluble xylan-derived products) were processed with NF and UF membranes for concentrating and removing both monosaccharides and non-saccharide compounds. Among the commercial membranes assayed, the best results were achieved with the 4 kDa polymeric tubular ESP04 (PCI Membranes), and the 1 kDa ceramic monolithic Kerasep Nano (Novasep). Several trade-offs were identified both in membrane selection and in operating conditions. The ESP04 polymeric membrane provided the best fractionation, but lower recovery under comparable experimental conditions, while its fluxes were about half of those of the ceramic Kerasep Nano membrane. Increase in transmembrane pressure resulted in improved product recovery, at the expense of a lower purity. Additional data on product refining by coupling membrane processing with extraction and ion exchange are provided.

Assessment on the fermentability of xylooligosaccharides from rice husks by probiotic bacteria

Liquors from rice husk autohydrolysis, containing xylooligosaccharides (XOS), other saccharides, and nonsaccharide compounds, were refined by membrane processing to increase the proportion of substituted XOS in refined liquors. XOS were assayed for composition and degree of polymerization (DP) distribution and hydrolyzed with commercial enzymes for obtaining XOS with DP in the range of 2-6. Nanofiltered, hydrolyzed liquors were subjected to ion exchange processing to yield a final product containing monosaccharides, XOS (accounting for 55.6% of the nonvolatile solutes), and other nonvolatile compounds. The solution obtained after enzymatic hydrolysis with commercial xylanases (in which 82.8% of XOS were in the DP range of 2-6) was examined as a medium for promoting the growth of Bifidobacterium adolescentis CECT 5781, B. longum CECT 4503, B. infantis CECT 4551, and B. breve CECT 4839. The growth rate of B. adolescentis (0.58 h(-1)) was higher than the ones determined for B. longum, B. infantis, and B. breve (0.37, 0.30, and 0.40 h(-1), respectively). The percentage of total XOS consumption by B. adolescentis was 77% after 24 h, the highest percentage of utilization corresponding to xylotriose (90%), followed by xylobiose (84%), xylotetraose (83%), and xylopentaose (71%).

Effects of Eucalyptus globulus wood autohydrolysis conditions on the reaction products

Eucalyptus globulus wood samples were reacted in aqueous media (hydrothermal treatments) at 160 degrees C for 30-66 min. Liquors from the several experiments were analyzed by spectrophotometry, high-performance liquid chromatography, or gas chromatography-mass spectrometry for monosaccharides, oligosaccharides, oligosaccharide substituents (arabinose moieties, uronic acids, and acetyl groups), acetic acid, furfural, hydroxymethylfurfural, and dichloromethane-soluble compounds. Individual components of this latter fraction were identified and quantified. The molecular weight distribution of oligosaccharides was studied by high-performance size exclusion chromatography. The kinetics of xylan conversion into high-, medium-, and low-molecular-weight products was assessed in terms of the severity factor and by pseudohomogeneous kinetic models.

Enzymatic production of xylooligosaccharides from cotton stalks

Xylooligosaccharide (XO) production was performed from xylan, which was obtained by alkali extraction from cotton stalk, a major agricultural waste in Turkey. Enzymatic hydrolysis was selected to prevent byproduct formation such as xylose and furfural. Xylan was hydrolyzed using a commercial xylanase preparation, and the effects of pH, temperature, hydrolysis period, and substrate and enzyme concentrations on the XO yield and degree of polymerization (DP) were investigated. Cotton stalk contains about 21% xylan, the composition of which was determined as 84% xylose, 7% glucose, and 9% uronic acid after complete acid hydrolysis. XOs in the DP range of 2-7 (X6 approximately X5>X2>X3) were obtained with minor quantities of xylose in all of the hydrolysis conditions used. Although after 24 h of hydrolysis at 40 degrees C, the yield was about 53%, the XO production rate leveled off after 8-24 h of hydrolysis. XO yield was affected by all of the parameters investigated; however, none of them affected the DP of the end product significantly, except the hydrolysis period. Enzyme hydrolysis was maintained by the addition of fresh substrate after 72 h of hydrolysis, indicating the persistence of enzyme activity. The optimal hydrolysis conditions were determined as 40 degrees C, pH 5.4, and 2% xylan. The obtained product was fractionated via ultrafiltration by using 10, 3, and 1 kDa membranes. Complete removal of xylanase and unhydrolyzed xylan was achieved without losing any oligosaccharides having DP 5 or smaller by 10 kDa membrane. After a two-step membrane processing, a permeate containing mostly oligosaccharides was obtained.