Production of xylooligosaccharides from corncob xylan by fungal xylanase and their utilization by probiotics

Extraction, purification, structural characterization and bioactivity of maize oligosaccharides: a review

Maize (Zea mays L.), as a globally significant food and economic crop, has attracted considerable attention from both the academic and industrial sectors due to its rich nutrient components and wide-ranging application value. In recent years, maize oligosaccharides have exhibited remarkable bioactivities in regulating gut microbiota, lowering blood glucose levels, and improving lipid metabolism, thus emerging as a research hotspot. Numerous scholars have conducted relatively in-depth studies on maize oligosaccharides. However, the relevant research findings are fragmented, lacking a systematic summary, which is detrimental to their high-value-added development and utilization. In view of this, this study intends to systematically review the research progress of maize oligosaccharides in aspects such as extraction, separation and purification, structural characterization, bioactivity, and application, analyze the existing problems and deficiencies, and put forward suggestions for future research directions. The aim is to provide theoretical support for the in-depth development and application of maize oligosaccharides and promote their high-value-added development in fields such as food, pharmaceuticals, and health products.

Synergistic effects of multi-enzyme supplementation on nutrient digestion and absorption in the foregut and hindgut

This study was conducted to investigate the effect of dietary multi-enzyme (MCPC) supplementation on synergistically enhancing the functions of both the foregut and hindgut, ultimately improving the nutrient digestion and utilization throughout the gastrointestinal tract. In vitro results demonstrated that MCPC increased the phosphorus and reducing sugar levels in the supernatant during enzymatic hydrolysis. Furthermore, during the fermentation of the enzymatic hydrolysis products, MCPC significantly increased the FRD0 value of the enzymatic hydrolysis products from both the positive control (PC) and negative control 1 (NC1) diets (p < 0.05). MCPC reduced the T1/2 value of in vitro fermentation products from the PC diet (p < 0.01), and decreased the VF (p = 0.082) and K (p < 0.05) values for the NC1 diet. Additionally, 72 crossbred barrows [Duroc × (Landrace × Yorkshire)], weighing 25 kg, were fed one of six diets until their live weight approached 50 kg. The basal diets consisted of PC, NC1 and negative control 2 (NC2), while the remaining three diets were prepared by adding 100 mg/kg MCPC to the respective basal diets. The results showed that MCPC supplementation significantly upregulated the expression of solute carrier family 17 member 4 (SLC17A4) and vitamin D receptor (VDR) genes in the duodenum (p < 0.05), while downregulating the expression of Calbindin-D28k (CaBP-D28K) and solute carrier family 1 member 4 (SLC1A4) genes (p < 0.05) in growing pigs. Moreover, MCPC supplementation significantly upregulated the expression of VDR, glucose transporter 2 (GLUT2) and intestinal fatty acid binding protein (FABP2) genes in the jejunum of growing pigs. Furthermore, MCPC supplementation significantly increased the relative abundances of Bacteroidota, Prevotella and Phascolarctobacterium (p < 0.05), while reducing the relative abundances of Verrucomicrobiota and Clostridium_sensu_stricto_1 (p < 0.05) in the colon of growing pigs. In conclusion, MCPC enhances nutrient digestion and absorption in the foregut, provides fermentable substrates for hindgut microbial fermentation, and improves gut microbiota composition. This improves hindgut fermentation and supports the synergistic interaction between the foregut and hindgut, ultimately improving nutrient utilization and benefiting animal health.

Phenotypic and genomic characterization of Levilactobacillus brevis YT108: a potential probiotic strain capable of metabolizing xylo-oligosaccharides

Levilactobacillus brevis YT108, identified for its ability to metabolize prebiotic xylo-oligosaccharides (XOS), emerges as a candidate for probiotic use in synbiotic food formulations. This study aimed to investigate the metabolic and genomic traits associated with XOS metabolism in YT108 and to assess its probiotic attributes through whole genome sequencing and in vitro assays. Strain YT108 exhibited robust growth kinetics on XOS as the sole carbon source, with a growth profile comparable to that on glucose, achieving a pH reduction to 4.68 and an OD600nm of 1.603 after 48 h. Three key gene clusters (xylCDEPFRT, xylHTG, and xylABT) and key enzymes (1,4-β-xylosidase) were identified as potentially involved in XOS metabolism. In vitro assays confirmed the strain's remarkable physiological properties, including tolerance to acid, bile, heat, and NaCl, as well as resistance to simulated gastrointestinal juices and antioxidant capacity. Furthermore, strain YT108 was sensitive to five commonly used antibiotics and lacked transferable resistance genes. Taken together, these results highlight the potential of L. brevis YT108 as a probiotic candidate with beneficial traits for XOS utilization, suggesting its promising application in the formulation of next-generation synbiotic products.

pH-controlled acetic acid pretreatment for coproduction of low degree of polymerization xylo-oligosaccharides and glucose from corncobs

Acetic acid (HAc) pretreatment has been widely used for the production of xylo-oligosaccharides (XOS), requiring harsh reaction conditions because XOS are intermediates during the xylan degradation process. This complexity makes the pretreatment process difficult to regulate. In this study, a pH-controlled HAc pretreatment using sodium hydroxide (NaOH) was proposed to enhance the yield of XOS and to reduce its degree of polymerization (DP) from corncobs (CC). By employing this method (0.3 M-2.7), 49.7 % of XOS with DP 2-6 was obtained, alongside a notable increase in the fraction of XOS with DP 2-4 (10.1 g/L). This performance significantly surpassed that of the HAc alone (0.3 M). Moreover, the glucose yield from CC via pH-controlled HAc pretreatment was as high as 93.1 % after 72-h enzymatic hydrolysis. These results suggested that the pH-controlled HAc pretreatment could be a promising strategy for the coproduction of low-DP XOS and fermentable sugars.

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.

Improvement of combined cross-linked enzyme aggregates of cyclodextrin glucanotransferase and maltogenic amylase by functionalization of cross-linker for maltooligosaccharides synthesis

Combined cross-linked enzyme aggregates of cyclodextrin glucanotransferase (CGTase) and maltogenic amylase (Mag1) from Bacillus lehensis G1 (Combi-CLEAs-CM) were successfully developed to synthesis maltooligosaccharides (MOS). Yet, the poor cross-linking performance between chitosan (cross-linker) and enzymes resulting low activity recovery and catalytic efficiency. In this study, we proposed the functionalization of cross-linkers with the integration of computational analysis to study the influences of different functional group on cross-linkers in combi-CLEAs development. From in-silico analysis, O-carboxymethyl chitosan (OCMCS) with the highest binding affinity toward both enzymes was chosen and showed alignment with the experimental result, in which OCMCS was synthesized as cross-linker to develop improved activity recovery of Combi-CLEAs-CM-ocmcs (74 %). The thermal stability and deactivation energy (205.86 kJ/mol) of Combi-CLEAs-CM-ocmcs were found to be higher than Combi-CLEAs-CM (192.59 kJ/mol). The introduction of longer side chain of carboxymethyl group led to a more flexible structure of Combi-CLEAs-CM-ocmcs. This alteration significantly reduced the Km value of Combi-CLEAs-CM-ocmcs by about 3.64-fold and resulted in a greater Kcat/Km (3.63-fold higher) as compared to Combi-CLEAs-CM. Moreover, Combi-CLEAs-CM-ocmcs improved the reusability with retained >50 % of activity while Combi-CLEAs-CM only 36.18 % after five cycles. Finally, maximum MOS production (777.46 mg/g) was obtained by Combi-CLEAs-CM-ocmcs after optimization using response surface methodology.

Preparation of xylooligosaccharides from rice husks and their structural characterization, antioxidant activity, and probiotic properties

Rice husks are rich in xylan, which can be hydrolyzed by xylanase to form xylooligosaccharides (XOS). XOS are a functional oligosaccharide such as improving gut microbiota and antioxidant properties. In this study, the structure and functional characteristics of XOS were studied. The optimal xylanase hydrolysis conditions through response surface methodology (RSM) were: xylanase dosage of 3000 U/g, hydrolysis time of 3 h, hydrolysis temperature of 50 °C. Under this condition, the yield of XOS was 150.9 mg/g. The TG-DTG curve showed that XOS began to decompose at around 200 °C. When the concentration of XOS reached 1.0 g/L, the clearance rate of DPPH reached 65.76 %, and the scavenging rate of OH reached 62.10 %, while the clearance rate of ABTS free radicals reached 97.70 %, which was equivalent to the clearance rate of VC. XOS had a proliferative effect on four probiotics: Lactobacillus plantarum, Lactobacillus brucelli, Lactobacillus acidophilus, and Lactobacillus rhamnosus. However, the further experiments are needed to explore the improvement effect of XOS on human gut microbiota, laying a foundation for the effective utilization of XOS. XOS have a wide range of sources, low price, and broad development prospects. The reasonable utilization of XOS can bring greater economic benefits.

In vitro evaluation of the application of an optimized xylanase cocktail for improved monogastric feed digestibility

Xylanases from glycoside hydrolase (GH) families 10 and 11 are common feed additives for broiler chicken diets due to their catalytic activity on the nonstarch polysaccharide xylan. This study investigated the potential of an optimized binary GH10 and GH11 xylanase cocktail to mitigate the antinutritional effects of xylan on the digestibility of locally sourced chicken feed. Immunofluorescence visualization of the activity of the xylanase cocktail on xylan in the yellow corn of the feed showed a substantial collapse in the morphology of cell walls. Secondly, the reduction in the viscosity of the digesta of the feed by the cocktail showed an effective degradation of the soluble fraction of xylan. Analysis of the xylan degradation products from broiler feeds by the xylanase cocktail showed that xylotriose and xylopentaose were the major xylooligosaccharides (XOS) produced. In vitro evaluation of the prebiotic potential of these XOS showed that they improved the growth of the beneficial bacteria Streptococcus thermophilus and Lactobacillus bulgaricus. The antibacterial activity of broths from XOS-supplemented probiotic cultures showed a suppressive effect on the growth of the extraintestinal infectious bacterium Klebsiella pneumoniae. Supplementing the xylanase cocktail in cereal animal feeds attenuated xylan's antinutritional effects by reducing digesta viscosity and releasing entrapped nutrients. Furthermore, the production of prebiotic XOS promoted the growth of beneficial bacteria while inhibiting the growth of pathogens. Based on these effects of the xylanase cocktail on the feed, improved growth performance and better feed conversion can potentially be achieved during poultry rearing.

Bioengineered xylanase from Misiones Argentina rainforest: A bakery enhancement approach

In this study, we pursued the heterologous expression of the xylanase gene from Trichoderma atroviride, a native fungus in the province of Misiones, and used it to enhance the textural properties of baked goods through varying enzymatic concentrations. This marks the inaugural exploration into its functionality in the context of bread production. The recombinant xylanase exhibited improved activity, reaching 36,292 U L-1, achieved by supplementing the culture medium with dextrose. Following the optimization of recombinant xylanase concentration, promising results emerged, notably reducing hardness and chewiness parameters of bread significantly. Our findings underscore the potential of this native fungal enzyme for industrial processes, offering a sustainable and efficient means to enhance the quality of baked goods with broad implications for the food industry. No prior research has been documented on the heterologous expression of the xylanase gene derived from T. atroviride, from the Misiones rainforest, expressed in Kluyveromyces lactis. PRACTICAL APPLICATION: This research, focusing on the isolation and cloning of xylanase enzyme from Trichoderma atroviride, a native fungus in the province of Misiones, offers a valuable tool for improving the texture of bakery products. By optimizing enzyme concentrations, our findings present a practical approach for the food industry, offering a viable solution to improve the overall quality and consumer satisfaction of bakery products.

Exploring the efficacy of a novel prebiotic-like growth promoter on broiler chicken production performance

This study attempts to isolate a candidate growth promoter from the ovine paunch waste and scrutinize its effects on the production performance of broiler chickens as compared to mannan-oligosaccharide (MOS), a prebiotic, and lincomycin, an antibiotic growth promoter (AB). The paunch waste collected from slaughtered sheep was processed to remove particulate matter. The clarified liquid was then added to an excess of ethanol (1:9 ratio), and the resultant precipitate {(novel growth-promoting paunch extract (NGPE)} was collected, dried, and stored. In vitro increase in cell density for probiotic bacteria viz. Lactobacillus rhamnosus and Enterococcus faecalis (Log10 CFU/ml) were significantly higher (P < 0.01) in NGPE supplemented media (2.78 ± 0.11 and 2.77 ± 0.10) as compared to that on MOS (1.28 ± 0.05 and 2.49 ± 0.09) and glucose (1.09 ± 0.04 and 1.12 ± 0.04) supplemented media. In the in-vivo trial of six weeks duration with broiler chickens (Cobb-400), NGPE supplementation resulted in significantly higher growth in weeks IV (P < 0.05) and VI (P < 0.01) of age in comparison to MOS and AGP supplemented groups, a lower (P < 0.01) cumulative feed conversion ratio in comparison to MOS supplemented groups, and a higher (P < 0.01) cumulative protein efficiency ratio compared to MOS and AGP supplementation. NGPE supplementation also lowered lipid peroxidation (P < 0.01), increased reduced glutathione activity (P < 0.01) in chicken erythrocytes, and boosted the lactic acid bacteria count in the cecal contents (P < 0.01). This is the first report of the isolation of a paunch waste extract that increased the in vitro growth of probiotic bacteria and improved the production performance of broiler chickens.

Transformation of corncob into high-value xylooligosaccharides using glycoside hydrolase families 10 and 11 xylanases from Trichoderma asperellum ND-1

Effective production of xylooligosaccharides (XOS) with lower proportion of xylose entails unique and robust xylanases. In this study, two novel xylanases from Trichoderma asperellum ND-1 belonging to glycoside hydrolase families 10 (XynTR10) and 11 (XynTR11) were over-expressed in Komagataella phaffii X-33 and characterized to be robust enzymes with high halotolerance and ethanol tolerant. Both enzymes displayed strict substrate specificity towards beechwood xylan and wheat arabinoxylan. (Glu153/Glu258) and (Glu161/Glu252) were key catalytic sites for XynTR10 and XynTR11. Notably, XynTR11 could rapidly degrade xylan/XOS into xylobiose without xylose via transglycosylation. Direct degradation of corncob using XynTR10 and XynTR111 displayed that while XynTR10 yielded 77% xylobiose and 25% xylose, XynTR11 yielded much less xylose (11%) and comparable amounts of xylobiose (63%). XynTR10 or XynTR111 has great potential as a catalyst for bioconversion of xylan-containing agricultural waste into high-value products (biofuel or XOS), which is of significant benefit for the economy and environment.

Gene cloning, expression, and characterization of two endo-xylanases from Bacillus velezensis and Streptomyces rochei, and their application in xylooligosaccharide production

Endo-xylanase hydrolyzing xylan in cellulosic residues releasing xylobiose as the major product at neutral pH are desirable in the substitute sweeteners industry. In this study, two endo-xylanases were obtained from Streptomyces rochei and Bacillus velezensis. SrocXyn10 showed the highest identity of 77.22%, with a reported endo-xylanase. The optimum reaction temperature and pH of rSrocXyn10-Ec were pH 7.0 and 60°C, with remarkable stability at 45°C or pHs ranging from 4.5 to 11.0. rBvelXyn11-Ec was most active at pH 6.0 and 50°C, and was stable at 35°C or pH 3.5 to 10.5. Both rSrocXyn10-Ec and rBvelXyn11-Ec showed specific enzyme activities on wheat arabinoxylan (685.83 ± 13.82 and 2809.89 ± 21.26 U/mg, respectively), with no enzyme activity on non-xylan substrates. The Vmax of rSrocXyn10-Ec and rBvelXyn11-Ec were 467.86 U mg-1 and 3067.68 U mg-1, respectively. The determined Km values of rSrocXyn10-Ec and rBvelXyn11-Ec were 3.08 g L-1 and 1.45 g L-1, respectively. The predominant product of the hydrolysis of alkaline extracts from bagasse, corncob, and bamboo by rSrocXyn10-Ec and rBvelXyn11-Ec were xylooligosaccharides. Interestingly, the xylobiose content in hydrolysates by rSrocXyn10-Ec was approximately 80%, which is higher than most reported endo-xylanases. rSrocXyn10-Ec and rBvelXyn11-Ec could be excellent candidates to produce xylooligosaccharides at neutral/near-neutral pHs. rSrocXyn10-Ec also has potential value in the production of xylobiose as a substitute sweetener.

Optimization of Xylooligosaccharides Production by Native and Recombinant Xylanase Hydrolysis of Chicken Feed Substrates

Poultry production faces several challenges, with feed efficiency being the main factor that can be influenced through the use of different nutritional strategies. Xylooligosaccharides (XOS) are functional feed additives that are attracting growing commercial interest due to their excellent ability to modulate the composition of the gut microbiota. The aim of the study was to apply crude and purified fungal xylanases, from Trichoderma harzianum, as well as a recombinant glycoside hydrolase family 10 xylanase, derived from Geobacillus stearothermophilus T6, as additives to locally produced chicken feeds. A Box-Behnken Design (BBD) was used to optimize the reducing sugar yield. Response surface methodology (RSM) revealed that reducing sugars were higher (8.05 mg/mL, 2.81 mg/mL and 2.98 mg/mL) for the starter feed treated with each of the three enzymes compared to the treatment with grower feed (3.11 mg/mL, 2.41 mg/mL and 2.62 mg/mL). The hydrolysis products were analysed by thin-layer chromatography (TLC), and high-performance liquid chromatography (HPLC) analysis and showed that the enzymes hydrolysed the chicken feeds, producing a range of monosaccharides (arabinose, mannose, glucose, and galactose) and XOS, with xylobiose being the predominant XOS. These results show promising data for future applications as additives to poultry feeds.

Green Downstream Processing Method for Xylooligosaccharide Purification and Assessment of Its Prebiotic Properties

Xylooligosaccharides (XOS) obtained from lignocellulosic biomass after autohydrolysis primarily consist of lignin-derived impurities and autogenerated inhibitors like furfural, hydroxymethylfurfural, and acetic acid. In this study, graphene oxide-mediated purification (GOMP), a novel and environmentally friendly downstream processing method, was developed for the purification of XOS from hydrolysate obtained after ozone-assisted autohydrolysis of wheat bran. GOMP resulted in appreciable recovery of total XOS from the hydrolysate (73.87 ± 4.25%, DP2-6) with near complete removal of autogenerated inhibitors (furfural 85.42%, HMF 87.38%, and acetic acid 84.0%). Recovery of XOS by GOMP was higher than the conventional membrane purification technique (44.07 ± 0.92%) and activated charcoal treatment (72.76 ± 0.84%) along with comparatively higher removal of inhibitor compounds. GOMP results in the selective adsorption of inhibitors on the graphene oxide matrix from the XOS-rich hydrolysate, resulting in its purification and concentration. The prebiotic function of the obtained XOS fractions (DP2-4.48%, DP3-39.69%, DP4-36.13%, DP5-8.38%, and DP6-13.10%) was evaluated, indicating the growth stimulation of tested probiotic cultures and differential utilization of XOS oligomers DP3 and DP4 and complete consumption of DP2, DP5, and DP6 along with short-chain fatty acids as a major fermentation product. These findings suggest that GOMP, which employs a common substance (i.e., graphene oxide) used in water treatment, exhibits potential as an efficient and economically viable single-step methodology for XOS purification.

Production, Characterization and Prebiotic Potential of Xylooligosaccharides Produced from Wheat Bran using Enterobacter hormaechei KS1 Xylanase

In the present investigation, xylooligosaccharides were produced from wheat bran and wheat bran extracted xylan through enzymatic hydrolysis using xylanase from novel Enterobacter hormaechei KS1. Xylooligosaccharides/reducing sugars production from wheat bran was found maximum (374 mg/g) when 4.0% of wheat bran was treated with 375 units (IU/mL) of Enterobacter hormaechei KS1 xylanase at pH 6.0 and incubated at 50 °C for 24 h of incubation. In case of wheat bran extracted xylan 419 mg/g of xylooligosaccharides were produced when 3% of extracted xylan was incubate for 8 h. Analysis of the enzymatic hydrolysate through high performance liquid chromatography equipped with refractive index detector showed the presence of xylose, xylopentose and xylohexose. The decrease in pH with 1.0% dose of xylooligosacchaides produced from extracted xylan hydrolysis using E. hormaechei KS1 xylanase showed more decrease with L. rhamnosus (6.72 to 5.94) followed by L. brevis (6.71 to 6.15) and L. plantarum (6.71 to 6.41). In case of increase in optical density both wheat bran and wheat bran extracted xylan generated xylooligosaccharides exhibited similar pattern i.e., L. rhamnosus > L. plantarum > L. brevis.

Effects of prebiotic supplement on gut microbiota, drug bioavailability, and adverse effects in patients with colorectal cancer at different primary tumor locations receiving chemotherapy: study protocol for a randomized clinical trial

BACKGROUND

The prevalence of colorectal cancer (CRC) worldwide is a huge challenge to human health. Primary tumor locations found to impact prognosis and response to therapy. The important role of gut microbiota in the progression and treatment of CRC has led to many attempts of alleviating chemotherapy-induced adverse effects using microecologics. However, the underlying mechanism of the difference in the prognosis of different primary tumor locations and the synergistic effect of prebiotics on chemotherapy need to be further elucidated. This study aims to explore the differences in tumor microbiota and examine the effectiveness of xylooligosaccharides (XOS) on gut microbiota, adverse effects, and bioavailability of chemotherapy drugs in CRC patients at different primary tumor locations.

METHODS

This is a double-blinded, randomized, parallel controlled clinical trial. Participants with left-sided CRC (LSCRC, n = 50) and right-sided CC (RSCC, n = 50) will randomly allocated to prebiotic group (n = 25) or control group (n = 25) and will receive either a daily XOS (3 g/day) or placebo, respectively, for 12 weeks. The primary outcomes will be the differences in the mucosa microbiota composition at different tumor locations and differences in gut microbiota composition, adverse effects, and blood concentration of capecitabine posttreatment. The secondary outcomes will include other blood indicators, short-chain fatty acids (SCFAs) concentration, quality of life, and mental health.

DISCUSSION

This study will reveal the potential benefits of prebiotic for improving the gut microbiota composition, alleviating the adverse effects, and improving the efficacy of chemotherapy in patients with CRC. In addition, this study will provide data on the different distribution of tumor microbiota and the different changes of gut microbiota during treatment in LSCRC and RSCC, which may provide novel insights into personalized cancer treatment strategies based on primary tumor locations and gut microbiota in the future.

TRIAL REGISTRATION

Chinese Clinical Trial Registry ( www.chictr.org.cn ): ChiCTR2100046237. Registered on 12 May 2021.

Xylan extraction from hardwoods by alkaline pretreatment for xylooligosaccharide production: A detailed fractionation analysis

In the last decades, the production of value-added products from lignocellulosic biomass (LCB) has gained relevance. Xylans, which are the main hemicellulose compounds in LCB, may be extracted by alkaline pretreatment and employed for xylooligosaccharide (XOS) production. However, xylan extraction currently works as a black box due to the lack of characterization of the involved streams. Therefore, the appropriate operational conditions often remain unclear, especially in hardwoods. In this study, alkaline/thermal pretreatments at different operational conditions were evaluated for xylan extractions from Chilean Nothofagus species sawdust, determining the chemical compositions of the fractions at each step of the process. Results indicated that increasing alkali concentration (NaOH) leads to a higher xylan extraction, but also to high salt production during the acid neutralization step, decreasing xylan's purity and therefore XOS production. In this context, decreasing NaOH concentration and neutralizing it by membrane filtration, allow extracting xylans (62.5 %) of higher-purity (77 %).

Effects of fungal based bioactive compounds on human health: Review paper

Since the first years of history, microbial fermentation products such as bread, wine, yogurt and vinegar have always been noteworthy regarding their nutritional and health effects. Similarly, mushrooms have been a valuable food product in point of both nutrition and medicine due to their rich chemical components. Alternatively, filamentous fungi, which can be easier to produce, play an active role in the synthesis of some bioactive compounds, which are also important for health, as well as being rich in protein content. Therefore, this review presents some important bioactive compounds (bioactive peptides, chitin/chitosan, β-glucan, gamma-aminobutyric acid, L-carnitine, ergosterol and fructooligosaccharides) synthesized by fungal strains and their health benefits. In addition, potential probiotic- and prebiotic fungi were researched to determine their effects on gut microbiota. The current uses of fungal based bioactive compounds for cancer treatment were also discussed. The use of fungal strains in the food industry, especially to develop innovative food production, has been seen as promising microorganisms in obtaining healthy and nutritious food.

A novel cold-active GH8 xylanase from cellulolytic myxobacterium and its application in food industry

Although xylanase have a wide range of applications, cold-active xylanases have received less attention. In this study, a novel glycoside hydrolase family 8 (GH8) xylanase from Sorangium cellulosum with high activity at low temperatures was identified. The recombinant xylanase (XynSc8) was most active at 50 °C, demonstrating 20% of its maximum activity and strict substrate specificity towards beechwood and corncob xylan at 4 °C with V_max values of 968.65 and 1521.13 μmol/mg/min, respectively. Mesophilic XynSc8 was active at a broad range of pH and hydrolyzed beechwood and corncob xylan into xylooligosaccharides (XOS) with degree of polymerization greater than 3. Moreover, incorporation of XynSc8 (0.05-0.2 mg/kg flour) provided remarkable improvement (28-30%) in bread specific volume and textural characteristics of bread compared to commercial xylanase. This is the first report on a novel cold-adapted GH8 xylanase from myxobacteria, suggesting that XynSc8 may be a promising candidate suitable for bread making.

14 year applications of chemical fertilizers and crop straw effects on soil labile organic carbon fractions, enzyme activities and microbial community in rice-wheat rotation of middle China

Traditional fertilization management can damage soil structure and lead to severe soil erosion. The practice of crop straw returning to the field reduces the negative impact of straw burning and improves soil quality. We investigated the effects of these agricultural practices on soil organic carbon components, enzyme activities, and soil microorganisms over 14 years of field experiments. Specifically, we studied four management strategies: no fertilizer or crop straw returning (CK), traditional chemical fertilization (NPK), crop straw returning (S), and crop straw returning with chemical fertilizer (NPKS). We found NPKS treatments significantly (P < 0.05) increased the dissolved organic carbon (DOC), microbial biomass carbon (MBC), particulate organic carbon (POC) and readily oxidized organic carbon (ROC) concentrations by 79.32 %, 82.16 %, 92.46 %, and 104.32 % relative to CK. Furthermore, under NPKS, the activities of soil enzymes related C, N, and P (α-glucosidase (αG), β-glucosidase (βG), cellulase (CBH), xylanase (βX), acetyl β-glucosaminidase (NAG), leucine aminopeptidase (LAP), and acid phosphate (AP)) were increased by 54.66 %, 113.26 %, 76.73 %, 52.41 %, 45.74 %, 56.69 %, and 68.92 % relative to CK, respectively. Redundancy analysis and structural equation modelling showed that straw returning had positive effects on soil microbial community diversity and richness, and also improved microbial activity which is favorable in the degradation of soil carbon. Furthermore, we found that soil fungi were more sensitive than bacteria to changes in soil carbon composition and enzyme activities following straw returning. These results suggest that straw returning combined with chemical fertilizer can be an effective strategy to improve soil labile organic carbon components, enzyme activities, and ecological function of microorganisms.

Production of Xylooligosaccharide from Cassava Pulp’s Waste by Endo-β-1,4-D-Xylanase and Characterization of Its Prebiotic Effect by Fermentation of Lactobacillus acidophilus

This study explores the production of prebiotic xylooligosaccharide (XOS) from cassava pulp waste and its effectiveness for the growth of Lactobacillus acidophilus (L. acidophilus). We successfully produced and characterized XOS from cassava pulp xylan using a Bacillus sp. endo-β-1,4-D-xylanase. The XOS was added to modify the MRS medium (MRSm) in various concentrations (0, 1, 3 and 5%) in which the L. acidophilus was inoculated. The growth of L. acidophilus was observed every 12 h for 2 days, and the fermentation products were analyzed for pH, sugar content, and short-chain fatty acids (SCFA) in terms of types and amount. The study showed that L. acidophilus grew well in MRSm. The optimum XOS concentration in MRSm was 5%, indicated by the highest growth of L. acidophilus (8.61 log CFU mL−1). The profile of SCFA products is 14.42 mM acetic acid, 0.25 mM propionic acid, 0.13 mM isobutyric acid, 0.41 mM n-butyric acid, 0.02 mM n-valeric acid, 0.25 mM isovaleric acid, and 25.08 mM lactic acid.

A sustainable process for co-production of xylooligosaccharides and ethanol from alkali treated sugarcane bagasse: A strategy towards waste management

Present study aims at sustainable utilization of sugarcane bagasse (SCB) for production of valuable prebiotic xylooligosaccharides (XOS) along with second generation ethanol. Fractionation of SCB into hemicellulose rich liquid fraction and cellulose rich solid residue was achieved using alkaline treatment. Carbohydrate rich precipitate obtained from liquid fraction was utilized for XOS production using inhouse produced endoxylanase. XOS production from SCB xylan was optimized by employing response surface methodology. Under optimized conditions, maximum XOS yield was 227.72 mg/g of carbohydrate rich precipitates. The solid residue obtained after alkaline pretreatment was used for ethanol fermentation by prehydrolysis and simultaneous saccharification and fermentation (P-SSF) process using cellulolytic enzyme cocktail and Saccharomyces cerevisiae SM1. Maximum ethanol concentration, productivity and yield were 79.76 ± 0.16 g/L, 0.83 g/L/h and 69.38%, respectively by employing P-SSF process. Based on the experimental data it can be predicted that bioconversion of 100 g raw SCB can yield 6.26 g of XOS (DP 2-DP 5), 15.95 g ethanol and 1.44 g of xylitol. Present investigation reports an integrated process for effective bioconversion of SCB into value added products by maximum utilization of cellulosic and hemicellulosic fractions simultaneously using indigenously produced fungal enzymes.

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.

Characterization and application of a novel xylanase from Halolactibacillus miurensis in wholewheat bread making

The presence of arabinoxylan in wholewheat flour affects its quality significantly. Here, an efficient arabinoxylan hydrolytic enzyme, Hmxyn, from Halolactibacillus miurensis was identified and heterologously expressed in pichia pastoris. Moreover, its relevant properties, including potential application in the wholewheat bread were evaluated. Recombinant Hmxyn exhibited maximal activity at 45°C and pH 6.5, and was stable at mid-range temperature (&lt;55°C) and pH (5.5–8.0) conditions. Hmxyn had a clear hydrolysis effect on wheat arabinoxylan in dough and caused the degradation of the water-unextractable arabinoxylan, which increased the content of wheat soluble arabinoxylan of dough. The fermentation characteristics results and microstructure analysis revealed that Hmxyn improved the organizational structure and air holding capacity of fermented dough, thus promoting the dough expansion. Baking experiments further showed that Hmxyn significantly increased specific volume- and texture-linked properties of wholewheat breads. This study indicates the application potential of Hmxyn in the preparation of wholewheat bread.

Extraction, Isolation, and Purification of Value-Added Chemicals from Lignocellulosic Biomass

This review covers the operating conditions for extracting top value-added chemicals, such as levulinic acid, lactic acid, succinic acid, vanillic acid, 3-hydroxypropionic acid, xylitol, 2,5-furandicarboxylic acid, 5-hydroxymethyl furfural, chitosan, 2,3-butanediol, and xylo-oligosaccharides, from common lignocellulosic biomass. Operating principles of novel extraction methods, beyond pretreatments, such as Soxhlet extraction, ultrasound-assisted extraction, and enzymatic extraction, are also presented and reviewed. Post extraction, high-value biochemicals need to be isolated, which is achieved through a combination of one or more isolation and purification steps. The operating principles, as well as a review of isolation methods, such as membrane filtration and liquid–liquid extraction and purification using preparative chromatography, are also discussed.

A Comparative Analysis for the Production of Xylooligosaccharides via Enzymatic Hydrolysis from Sugarcane Bagasse and Coconut Coir

Xylooligosaccharides are known prebiotics that various foods and feed industries can utilize. In the present study, the xylan was extracted from sugarcane bagasse and coconut coir by NaOH treatment and it was further structurally characterized by FTIR. Furthermore, Thermomyces lanuginosus VAPS-24 was used to produce endo-xylanase, which induced the production of XOS from both of these substrates. The maximum production of XOS in 8 h using 20U enzyme concentration and 2% substrate concentration was found as 10.10 mg/ml, 5.43 mg/ml for sugarcane bagasse and coconut coir, respectively. Further, the produced XOS was structurally characterized by the NMR, HPLC and FTIR analysis. This study gives a clue that the sugarcane bagasse can be used as the potent producer for the xylooligosaccharides as compared to the coconut coir and can be utilized at the industrial level.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12088-022-01010-3.

Comparison of the Biochemical Properties and Roles in the Xyloglucan-Rich Biomass Degradation of a GH74 Xyloglucanase and Its CBM-Deleted Variant from Thielavia terrestris

Xyloglucan is closely associated with cellulose and still retained with some modification in pretreated lignocellulose; however, its influence on lignocellulose biodegradation is less understood. TtGH74 from Thielavia terrestris displayed much higher catalytic activity than previously characterized fungal GH74 xyloglucanases. The carbohydrate-binding module 1 (CBM1) deleted variant (TtGH74ΔCBM) had the same optimum temperature and pH but an elevated thermostability. TtGH74 displayed a high binding affinity on xyloglucan and cellulose, while TtGH74ΔCBM completely lost the adsorption capability on cellulose. Their hydrolysis action alone or in combination with other glycoside hydrolases on the free xyloglucan, xyloglucan-coated phosphoric acid-swollen cellulose or pretreated corn bran and apple pomace was compared. CBM1 might not be essential for the hydrolysis of free xyloglucan but still effective for the associated xyloglucan to an extent. TtGH74 alone or synergistically acting with the CBH1/EG1 mixture was more effective in the hydrolysis of xyloglucan in corn bran, while TtGH74ΔCBM showed relatively higher catalytic activity on apple pomace, indicating that the role and significance of CBM1 are substrate-specific. The degrees of synergy for TtGH74 or TtGH74ΔCBM with the CBH1/EG1 mixture reached 1.22–2.02. The addition of GH10 xylanase in TtGH74 or the TtGH74ΔCBM/CBH1/EG1 mixture further improved the overall hydrolysis efficiency, and the degrees of synergy were up to 1.50–2.16.

Chemometric optimisation of enzymatic hydrolysis of beechwood xylan to target desired xylooligosaccharides

Generation of specific xylooligosaccharides (XOS) is attractive to the pharmaceutical and food industries due to the importance of their structure upon their application. This study used chemometrics to develop a comprehensive computational modelling set to predict the parameters maximising the generation of the desired XOS during enzymatic hydrolysis. The evaluated parameters included pH, temperature, substrate concentration, enzyme dosage and reaction time. A Box-Behnken design was combined with response surface methodology to develop the models. High-performance anion-exchange chromatography coupled with triple-quadrupole mass spectrometry (HPAEC-QqQ-MS) allowed the identification of 22 XOS within beechwood xylan hydrolysates. These data were used to validate the developed models and demonstrated their accuracy in predicting the parameters maximising the generation of the desired XOS. The maximum yields for X2-X6 were 314.2 ± 1.2, 76.6 ± 4.5, 38.4 ± 0.4, 17.8 ± 0.7, and 5.3 ± 0.2 mg/g xylan, respectively. These values map closely to the model predicted values 311.7, 92.6, 43.0, 16.3, and 4.9 mg/g xylan, respectively.

Identification and Characterization of a Novel Endo-β-1,4-Xylanase from Streptomyces sp. T7 and Its Application in Xylo-Oligosaccharide Production

A xylanase-producing strain, identified as Streptomyces sp. T7, was isolated from soil by our lab. The endo-β-1,4-xylanase (xynST7) gene was found in the genome sequence of strain T7, which was cloned and expressed in Escherichia coli. XynST7 belonged to the glycoside hydrolase family 10, with a molecular mass of approximately 47 kDa. The optimum pH and temperature of XynST7 were pH 6.0 and 60 °C, respectively, and it showed wide pH and temperature adaptability and stability, retaining more than half of its enzyme activity between pH 5.0 and 11.0 below 80 °C. XynST7 showed only endo-β-1,4-xylanase activity without cellulase- or β-xylosidase activity, and it showed maximal hydrolysis for corncob xylan in all the test substrates. Then, XynST7 was used for the production of xylo-oligosaccharides (XOSs) by hydrolyzing xylan extracted from raw corncobs. The maximum yield of the XOS was 8.61 ± 0.13 mg/mL using 15 U/mL of XynST7 and 1.5% corncob xylan after 10 h of incubation at 60 °C. The resulting hydrolysate products mainly consisted of xylobiose and xylotriose. These data indicated that XynST7 might by a promising tool for various industrial applications.

Xylooligosaccharide Production with Low Xylose Release Using Crude Xylanase from Aureobasidium pullulans: Effect of the Enzymatic Hydrolysis Parameters

Xylooligosaccharides (XOS) are non-digestible and fermentable oligomers that stand out for their efficient production by enzymatic hydrolysis and beneficial effects on human health. This study aimed to investigate the influence of the main reaction parameters of the beechwood xylan hydrolysis using crude xylanase from Aureobasidium pullulans CCT 1261, thus achieving the maximum XOS production. The effects of temperature (40 to 50 °C), reaction time (12 to 48 h), type of agitation, substrate concentration (1 to 6%, w/v), xylanase loading (100 to 300 U/g xylan), and pH (4.0 to 6.0) on the XOS production were fully evaluated. The most suitable conditions for XOS production included orbital shaking of 180 rpm, 40 °C, and 24 h of reaction. High contents of total XOS (10.1 mg/mL) and XOS with degree of polymerization (DP) of 2-3 (9.7 mg/mL), besides to a high percentage of XOS (99.1%), were obtained at 6% (w/v) of beechwood xylan, xylanase loading of 260 U/g xylan, and pH 6.0. The establishment of the best hydrolysis conditions allowed increasing both the content of total XOS 1.5-fold and the percentage of XOS by 9.4%, when compared to the initial production (6.7 mg/mL and 89.7%, respectively). Thus, this study established an efficient enzymatic hydrolysis process that results in a hydrolysate containing XOS with potential prebiotic character (i.e., rich in XOS with DP 2-3) and low xylose amounts.

Valorization of renewable resources to functional oligosaccharides: Recent trends and future prospective

Lignocellulosic wastes have the ability to be transformed into oligosaccharides and other value-added products. The synthesis of oligosaccharides from renewable sources bestow to growing bioeconomies. Oligosaccharides are synthesized chemically or biologically from agricultural residues. These oligosaccharides are functional food supplements that have a positive impact on humans and livestock. Non-digestible oligosaccharides, refered as prebiotics are beneficial for the colonic microbiota inhabiting the f the digestive system. These microbiota plays a crucial role in stimulating the host immune system and other physiological responses. The commonly known prebiotics, galactooligosaccharides (GOS), xylooligosaccharides (XOS), fructooligosaccharides (FOS), mannanooligosaccharides (MOS), and isomaltooligosaccharides (IOS) are synthesized either through enzymatic or whole cell-mediated approaches using natural or agricultural waste substrates. This review focusses on recent advancements in biological processes, for the synthesis of oligosaccharides using renewable resources (lignocellulosic substrates) for sustainable circular bioeconomy. The work also addresses the limitations associated with the processes and commercialization of the products.

A Fungal Versatile GH10 Endoxylanase and Its Glycosynthase Variant: Synthesis of Xylooligosaccharides and Glycosides of Bioactive Phenolic Compounds

The study of endoxylanases as catalysts to valorize hemicellulosic residues and to obtain glycosides with improved properties is a topic of great industrial interest. In this work, a GH10 β-1,4-endoxylanase (XynSOS), from the ascomycetous fungus Talaromyces amestolkiae, has been heterologously produced in Pichia pastoris, purified, and characterized. rXynSOS is a highly glycosylated monomeric enzyme of 53 kDa that contains a functional CBM1 domain and shows its optimal activity on azurine cross-linked (AZCL)-beechwood xylan at 70 °C and pH 5. Substrate specificity and kinetic studies confirmed its versatility and high affinity for beechwood xylan and wheat arabinoxylan. Moreover, rXynSOS was capable of transglycosylating phenolic compounds, although with low efficiencies. For expanding its synthetic capacity, a glycosynthase variant of rXynSOS was developed by directed mutagenesis, replacing its nucleophile catalytic residue E236 by a glycine (rXynSOS-E236G). This novel glycosynthase was able to synthesize β-1,4-xylooligosaccharides (XOS) of different lengths (four, six, eight, and ten xylose units), which are known to be emerging prebiotics. rXynSOS-E236G was also much more active than the native enzyme in the glycosylation of a broad range of phenolic compounds with antioxidant properties. The interesting capabilities of rXynSOS and its glycosynthase variant make them promising tools for biotechnological applications.

Recent advancements in prebiotic oligomers synthesis via enzymatic hydrolysis of lignocellulosic biomass

Interest in functional food, such as non-digestible prebiotic oligosaccharides is increasing day by day and their production is shifting toward sustainable manufacturing. Due to the presence of high carbohydrate content, lignocellulosic biomass (LCB) is the most-potential, cost-effective and sustainable substrate for production of many useful products, including lignocellulose-derived prebiotic oligosaccharides (LDOs). These have the same worthwhile properties as other common oligosaccharides, such as short chain carbohydrates digestible to the gut flora but not to humans mainly due to their resistance to the low pH and high temperature and their demand is constantly increasing mainly due to increased awareness about their potential health benefits. Despite several advantages over the thermo-chemical route of synthesis, comprehensive and updated information on the conversion of lignocellulosic biomass to prebiotic oligomers via controlled enzymatic saccharification is not available in the literature. Thus, the main objective of this review is to highlight recent advancements in enzymatic synthesis of LDOs, current challenges, and future prospects of sustainably producing prebiotic oligomers via enzymatic hydrolysis of LCB substrates. Enzyme reaction engineering practices, custom-made enzyme preparations, controlled enzymatic hydrolysis, and protein engineering approaches have been discussed with regard to their applications in sustainable synthesis of lignocellulose-derived oligosaccharide prebiotics. An overview of scale-up aspects and market potential of LDOs has also been provided.

Paludibacter propionicigenes GH10 xylanase as a tool for enzymatic xylooligosaccharides production from heteroxylans

Bioconversion of lignocellulosic biomass into value-added products relies on polysaccharides depolymerization by carbohydrate active enzymes. This work reports biochemical characterization of Paludibacter propionicigenes xylanase from GH10 (PpXyn10A) and its application for enzymatic xylooligosaccharides (XOS) production from commercial heteroxylans and liquor of hydrothermally pretreated corn cobs (PCC). PpXyn10A is tolerant to ethanol and NaCl, and releases xylobiose (X2) and xylotriose (X3) as the main hydrolytic products. The conversion rate of complex substrates into short XOS was approximately 30% for glucuronoxylan and 8.8% for rye arabinoxylan, after only 4 h; while for PCC, PpXyn10A greatly increased unbranched XOS yields. B. adolescentis fermentation with XOS from beechwood glucuronoxylan produced mainly acetic and lactic acids. Structural analysis shows that while the glycone region of PpXyn10A active site is well preserved, the aglycone region has aromatic interactions in the +2 subsite that may explain why PpXyn10A does not release xylose.

Hydrothermal pretreatment for the production of oligosaccharides: A review

Oligosaccharides are low-molecular-weight carbohydrates with crucial physical, chemical, and physiological properties, which are increasingly important in the fields of food, pharmaceuticals, cosmetics, and biomedicine. Pretreating biomass in a cost-effective way is a significant challenge for oligosaccharides research. Hydrothermal pretreatment is a potentially eco-friendly technology to obtain oligosaccharides by deconstructing biomass. In this work, we compared the differences between hydrothermal pretreatment and the traditional pretreatment method. The fundamentals and classification of hydrothermal pretreatment, as well as the latest studies on hydrothermal preparation of oligosaccharides, were further reviewed and evaluated to provide a theoretical basis for the production and application of oligosaccharides. Some challenges and future trends to develop green and large-scale hydrothermal pretreatment were proposed for the production of oligosaccharides.

Co-production of functional xylo-oligosaccharides and fermentable sugars from corn stover through fast and facile ball mill-assisted alkaline peroxide pretreatment

The aim of this work was to develop a feasible ball mill-assisted alkaline peroxide pretreatment followed by stepwise hydrolysis to improve the yield of xylo-oligosaccharides (XOS) and fermentable sugars. The hydrogen peroxide charge, ball-milling time, and solid-to-liquid ratio affected the compositions, particle sizes, morphology, and crystallinity of the corn stover, directly improving the following hydrolytic efficiency. The optimal pretreatment was with 0.45 g/g (H₂O₂: substrate) and 1:3 solid-to-liquid ratio (w/v) for 1.0 h ball-milling, resulting in 84.29% delignification. Physicochemical properties of the pretreated samples were characterized and their correlations to the enzymatic hydrolysis were revealed. Compared with one-step cellulase hydrolysis, the two-step xylanase-cellulase hydrolysis of the pretreated corn stover showed significant advance in preparing XOS, producing 69.65% (on the base of xylan content in pretreated sample) of XOS, along with 20.55% xylose, 68.94% glucose, and 21.15% gluco-oligosaccharides. The yield of XOS was 2-7 times higher than those in previous studies.