Corncob-induced endo-1,4-beta-d-xylanase of Aspergillus oryzae MTCC 5154: production and characterization of xylobiose from glucuronoxylan

Biochemical characterization of a novel acidophilic β-xylanase from Trichoderma asperellum ND-1 and its synergistic hydrolysis of beechwood xylan

Acidophilic β-xylanases have attracted considerable attention due to their excellent activity under extreme acidic environments and potential industrial utilizations. In this study, a novel β-xylanase gene (Xyl11) of glycoside hydrolase family 11, was cloned from Trichoderma asperellum ND-1 and efficiently expressed in Pichia pastoris (a 2.0-fold increase). Xyl11 displayed a maximum activity of 121.99 U/ml at pH 3.0 and 50°C, and exhibited strict substrate specificity toward beechwood xylan (K_m = 9.06 mg/ml, V_max = 608.65 μmol/min/mg). The Xyl11 retained over 80% activity at pH 2.0–5.0 after pretreatment at 4°C for 1 h. Analysis of the hydrolytic pattern revealed that Xyl11 could rapidly convert xylan to xylobiose via hydrolysis activity as well as transglycosylation. Moreover, the results of site-directed mutagenesis suggested that the Xyl11 residues, Glu¹²⁷, Glu¹⁶⁴, and Glu²¹⁶, are essential catalytic sites, with Asp¹³⁸ having an auxiliary function. Additionally, a high degree of synergy (15.02) was observed when Xyl11 was used in association with commercial β-xylosidase. This study provided a novel acidophilic β-xylanase that exhibits excellent characteristics and can, therefore, be considered a suitable candidate for extensive applications, especially in food and animal feed industries.

Prebiotics as a Tool for the Prevention and Treatment of Obesity and Diabetes: Classification and Ability to Modulate the Gut Microbiota

Diabetes and obesity are metabolic diseases that have become alarming conditions in recent decades. Their rate of increase is becoming a growing concern worldwide. Recent studies have established that the composition and dysfunction of the gut microbiota are associated with the development of diabetes. For this reason, strategies such as the use of prebiotics to improve intestinal microbial structure and function have become popular. Consumption of prebiotics for modulating the gut microbiota results in the production of microbial metabolites such as short-chain fatty acids that play essential roles in reducing blood glucose levels, mitigating insulin resistance, reducing inflammation, and promoting the secretion of glucagon-like peptide 1 in the host, and this accounts for the observed remission of metabolic diseases. Prebiotics can be either naturally extracted from non-digestible carbohydrate materials or synthetically produced. In this review, we discussed current findings on how the gut microbiota and microbial metabolites may influence host metabolism to promote health. We provided evidence from various studies that show the ability of prebiotic consumption to alter gut microbial profile, improve gut microbial metabolism and functions, and improve host physiology to alleviate diabetes and obesity. We conclude among other things that the application of systems biology coupled with bioinformatics could be essential in ascertaining the exact mechanisms behind the prebiotic–gut microbe–host interactions required for diabetes and obesity improvement.

Dietary supplemental xylooligosaccharide modulates nutrient digestibility, intestinal morphology, and gut microbiota in laying hens

This study was conducted to evaluate the prebiotic effects of dietary xylooligosaccharide (XOS) supplementation on performance, nutrient digestibility, intestinal morphology, and gut microbiota in laying hens. In a 12-wk experiment, a total of 288 Hy-Line Brown layers at 50 wk of age were randomly assigned into 3 dietary treatments supplemented with XOS at 0, 200 or 400 mg/kg. Each treatment had 8 replicates with 12 birds each. Hens fed XOS diets showed a lower feed-to-egg ratio during wk 7 to 12 and a higher egg yolk color value in wk 12 compared with those fed the control diet (P < 0.05). Dietary XOS supplementation improved the apparent total tract digestibility of gross energy and nitrogen at the end of the 12th wk (P < 0.05). In addition, a higher villus height-to-crypt depth ratio of the ileum was observed in XOS-added groups (P < 0.05). The high throughput sequencing analysis of bacterial 16S rRNA revealed that dietary XOS supplementation at 200 mg/kg altered cecal microbiota. Alpha diversity analysis illustrated a higher cecal bacterial richness in birds fed with XOS at 200 mg/kg. The composition of cecal microbiota modulated by the XOS addition was characterized by an increased abundance of Firmicutes along with a reduced abundance of Bacteroidetes. At the genus level, dietary XOS supplementation triggered decreases in Bacteroides and Campylobacter concurrent with increases in Lactobacillus and several short chain fatty acid producers including Desulfovibrio, Faecalitalea, Faecalicoccus, and 5 genera of family Lachnospiraceae. Collectively, dietary XOS addition improved the feed conversion ratio by modulating nutrient digestibility and ileal morphology in laying hens, which could be attributed to the enhancement of bacterial diversity and alteration of microbial composition.

Optimal Production of β-Galactosidase from Lactobacillus fermentum for the Synthesis of Prebiotic Galactooligosaccharides (Gos)

The enzyme β-galactosidase (β-gal) has extensively used for improvement of lactose intolerance condition. Present study, was designed to assess the potential of β-gal enzyme produced by Lactobacillus fermentum, a kefir isolate, as a biocatalyst for the manufacture of prebiotic galactooligosaccharides (GOS) from lactose. The efficiency of L. fermentum to produce β-gal of 4,254 u/ml was determined by permeabilizing the cells with solvents such as sodium dodecyl sulfate (SDS) and chloroform. Different parameters contributing β-gal production including reaction time, temperature, pH, carbohydrates, and substrate concentration on L. fermentum were studied and optimum β-gal activity was found to be 6,232.13 u/ml. It was observed that different experimental parameters for pH (7.0), temperature (35°C), and carbohydrates (galactose) were statistically significant (p<0.05). L. fermentum was found to produce GOS by transgalactosylation catalysed by β-gal during lactose hydrolysis which yielded di, tri, and tetra oligosaccharides, confirmed by TLC and HPLC. The culture showed β-gal activity, suggesting biotechnological applications and a promising organism for industrial β-gal production.

Metabolic Profiling of Xylooligosaccharides by Lactobacilli

Three lactic acid bacteria (LAB) strains identified as Lactobacillus plantarum, Lactobacillus brevis, and Lactobacillus sakei isolated from meat products were tested for their ability to utilize and grow on xylooligosaccharides (XOSs). The extent of carbohydrate utilization by the studied strains was analyzed by HPLC. All three strains showed preferences for the degree of polymerization (DP). The added oligosaccharides induced the LAB to form end-products of typical mixed-acid fermentation. The utilization of XOSs by the microorganisms requires the action of three important enzymes: β-xylosidase (EC 3.2.1.37) exo-oligoxylanase (EC 3.2.1.156) and α-L-arabinofuranosidase (EC 3.2.1.55). The presence of intracellular β-D-xylosidase in Lb. brevis, Lb. plantarum, and Lb. sakei suggest that XOSs might be the first imported into the cell by oligosaccharide transporters, followed by their degradation to xylose. The studies on the influence of XOS intake on the lipids of rat liver plasma membranes showed that oligosaccharides display various beneficial effects for the host organism, which are probably specific for each type of prebiotic used. The utilization of different types of oligosaccharides may help to explain the ability of Lactobacillus strains to compete with other bacteria in the ecosystem of the human gastrointestinal tract.

Hemicellulose from Plant Biomass in Medical and Pharmaceutical Application: A Critical Review

BACKGROUND

Due to the non-toxicity, abundance and biodegradability, recently more and more attention has been focused on the exploration of hemicellulose as the potential substrate for the production of liquid fuels and other value-added chemicals and materials in different fields. This review aims to summarize the current knowledge on the promising application of nature hemicellulose and its derivative products including its degradation products, its new derivatives and hemicellulosebased medical biodegradable materials in the medical and pharmaceutical field, especially for inmmune regulation, bacteria inhibition, drug release, anti-caries, scaffold materials and anti-tumor.

METHODS

We searched the related papers about the medical and pharmaceutical application of hemicellulose and its derivative products, and summarized their preparation methods, properties and use effects.

RESULTS

Two hundred and twenty-seven papers were included in this review. Forty-seven papers introduced the extraction and application in immune regulation of nature hemicellulose, such as xylan, mannan, xyloglucan (XG) and β-glucan. Seventy-seven papers mentioned the preparation and application of degradation products of hemicellulose for adjusting intestinal function, maintaining blood glucose levels, enhancing the immunity and alleviating human fatigue fields such as xylooligosaccharides, xylitol, xylose, arabinose, etc. The preparation of hemicellulose derivatives were described in thirty-two papers such as hemicellulose esters, hemicellulose ethers and their effects on anticoagulants, adsorption of creatinine, the addition of immune cells and the inhibition of harmful bacteria. Finally, the preparations of hemicellulose-based materials such as hydrogels and membrane for the field of drug release, cell immobilization, cancer therapy and wound dressings were presented using fifty-five papers.

CONCLUSION

The structure of hemicellulose-based products has the significant impact on properties and the use effect for the immunity, and treating various diseases of human. However, some efforts should be made to explore and improve the properties of hemicellulose-based products and design the new materials to broaden hemicellulose applications.

Evaluation of xylooligosaccharide production from residual hemicelluloses of dissolving pulp by acid and enzymatic hydrolysis

Xylooligosaccharides (XOS) are useful food and pharmaceutical additives, which can be produced from various xylans. However, the XOS prepared from lignocellulosic materials are difficult to purify due to the complexity of the degradation products. Thus, hemicelluloses with a high-purity will be the preferred feedstock for XOS production. In this work, acid hydrolysis and enzymatic hydrolysis were applied to prepare XOS from the residual hemicelluloses of the dissolving pulp. The results showed that the highest XOS yield (45.18%) obtained from the acid hydrolysis was achieved with 1% sulfuric acid at 120 °C for 60 min, and xylohexaose accounted for 47% of the XOS. For enzymatic hydrolysis, under optimal conditions, the highest XOS yield of 42.96% was observed, and xylobiose and xylotriose comprised 90.5% of the XOS. It is suggested that the distribution of the XOS could be controlled significantly according to the enzymatic or acid hydrolysis conditions used.

The hemicelluloses extracted from dissolving pulp were applied to produce xylooligosaccharides (XOS) by acid and enzymatic hydrolysis.

Xylooligosaccharides production by crude microbial enzymes from agricultural waste without prior treatment and their potential application as nutraceuticals

Aspergillus fumigatus R1, on submerged fermentation using agricultural residues as carbon source produced extracellular xylanase (152IU/ml after 96h of incubation at 37°C with constant shaking at 100rpm). A maximum yield of 1gm% Xylooligosaccharides (XOS) mixture was obtained after 12h by enzymatic hydrolysis of xylan rich wheat husk without any prior pretreatment using the crude enzyme without any purification. HP-TLC data confirmed the presence of an array of XOS for its prebiotic properties by carrying out studies on ten standard probiotic cultures. Six of ten probiotic cultures were able to utilize XOS produced from agricultural wastes and showed remarkable growth in the media containing XOS as the sole source of carbon. XOS mixture also exhibited concentration dependent anti-oxidant activity. Thus, the results showed that XOS produced from agricultural residues have great prebiotic potential and good antioxidant activity; therefore, it can be used in food-related applications.

Xylobiose, an Alternative Sweetener, Ameliorates Diabetes-Related Metabolic Changes by Regulating Hepatic Lipogenesis and miR-122a/33a in db/db Mice

Type 2 diabetes is a major public health concern worldwide. Xylobiose (XB) consists of two molecules of d-xylose and is a major disaccharide in xylooligosaccharides that are used as prebiotics. We hypothesized that XB could regulate diabetes-related metabolic and genetic changes via microRNA expression in db/db mice. For six weeks, C57BL/KsJ-db/db mice received 5% XB as part of the total sucrose content of their diet. XB supplementation improved glucose tolerance with reduced levels of OGTT AUC, fasting blood glucose, HbA1c, insulin, and HOMA-IR. Furthermore, XB supplementation decreased the levels of total triglycerides, total cholesterol, and LDL-C. The expression levels of miR-122a and miR-33a were higher and lower in the XB group, respectively. In the liver, expressions of the lipogenic genes, including, fatty acid synthase (FAS), peroxisome proliferator activated receptor γ (PPARγ), sterol regulatory element-binding protein-1C (SREBP-1C), sterol regulatory element-binding protein-2 (SREBP-2), acetyl-CoA carboxylase (ACC), HMG-CoA reductase (HMGCR), ATP-binding cassette transporter G5/G8 (ABCG5/8), cholesterol 7 alpha-hydroxylase (CYP7A1), and sterol 12-alpha-hydroxylase (CYP8B1), as well as oxidative stress markers, including superoxide dismutase 1 (SOD1), superoxide dismutase 2 (SOD2), glutathione peroxidase (GPX), and catalase, were also regulated by XB supplementation. XB supplementation inhibited the mRNA expressions levels of the pro-inflammatory cytokines, tumor necrosis factor (TNF)-α, interleukin (IL)-1β, interleukin (IL)-6, and monocyte chemoattractant protein (MCP)-1, as well as phosphorylation of c-Jun N-terminal kinase/stress activated protein kinase (JNK/SAPK), p38 mitogen-activated protein kinases (MAPK), and extracellular signal-regulated kinases 1/2 (ERK1/2). These data demonstrate that XB exhibits anti-diabetic, hypolipogenic, and anti-inflammatory effects via regulation of the miR-122a/33a axis in db/db mice.

Highly efficient recovery of xylobiose from xylooligosaccharides using a simulated moving bed method

Xylobiose (X2), which is currently available from xylooligosaccharides (XOS), has been reported to have outstanding prebiotic function and to be highly suitable for application in food industries. This has sparked an interest in the economical production of X2 of high purity (> 99%) in food and prebiotic industries. To address such issue, we developed a highly-efficient chromatographic method for the recovery of X2 from XOS with high purity and high recovery. As a first step for this work, an eligible adsorbent for a large-scale separation between X2 and other XOS components was selected. For the selected adsorbent, a single-column experiment was carried out to determine the intrinsic parameters of all the XOS components, which were then used in the optimal design of the continuous X2-recovery process based on a simulated moving bed (SMB) chromatographic method. Finally, the performance of the designed X2-recovery SMB process was verified by the relevant SMB experiments, which confirmed that the developed process in this study could recover X2 from XOS with the purity of 99.5% and the recovery of 92.3% on a continuous-separation mode. The results of this study will be useful in enabling the economical production of high-purity X2 on a large scale.

Development and validation of a HPLC method for determination of degree of polymerization of xylo-oligosaccharides

A reliable reversed-phase HPLC method was developed for high resolution separation and high sensitivity determination of xylo-oligosaccharides (XOS) with degree of polymerization from 2 to 8. The method was carried out on a Kromasil C18 column using pre-column derivatization with 1-phenyl-3-methyl-5-pyrazolone (PMP) and UV detection at 245nm. The effects of pH value of mobile phase, volume proportion of acetonitrile, concentration of ammonium acetate buffer and flow rate on the retention time and degree of separation of XOS derivatives were investigated. A satisfactory result was achieved in 25min with a mobile phase of 10mmol/L ammonium acetate buffer (pH5.5)-acetonitrile by a gradient elution at 0.8mL/min. In addition, this method was validated by liquid chromatography-tandem mass spectroscopy (LC-MS) analysis and several uncertain compounds were identified. The proposed HPLC method is suitable for the compositional analysis and quality control of XOS.

Effects of Xylo-Oligosaccharides on Broiler Chicken Performance and Microbiota

In broiler chickens, feed additives, including prebiotics, are widely used to improve gut health and to stimulate performance. Xylo-oligosaccharides (XOS) are hydrolytic degradation products of arabinoxylans that can be fermented by the gut microbiota. In the current study, we aimed to analyze the prebiotic properties of XOS when added to the broiler diet. Administration of XOS to chickens, in addition to a wheat-rye-based diet, significantly improved the feed conversion ratio. XOS significantly increased villus length in the ileum. It also significantly increased numbers of lactobacilli in the colon and Clostridium cluster XIVa in the ceca. Moreover, the number of gene copies encoding the key bacterial enzyme for butyrate production, butyryl-coenzyme A (butyryl-CoA):acetate CoA transferase, was significantly increased in the ceca of chickens administered XOS. In this group of chickens, at the species level, Lactobacillus crispatus and Anaerostipes butyraticus were significantly increased in abundance in the colon and cecum, respectively. In vitro fermentation of XOS revealed cross-feeding between L. crispatus and A. butyraticus. Lactate, produced by L. crispatus during XOS fermentation, was utilized by the butyrate-producing Anaerostipes species. These data show the beneficial effects of XOS on broiler performance when added to the feed, which potentially can be explained by stimulation of butyrate-producing bacteria through cross-feeding of lactate and subsequent effects of butyrate on gastrointestinal function.

Permeabilized probiotic Lactobacillus plantarum as a source of β-galactosidase for the synthesis of prebiotic galactooligosaccharides

Permeabilized probiotic Lactobacillus plantarum was used as a source of β-galactosidase for the synthesis of galactooligosaccharides (GOS) from lactose. β-galactosidase activity was highest when galactose (1,724 Miller Units) was used as a carbon source compared to lactose, sucrose or glucose at 37 °C, 18 h. Permeabilized cells had the highest transgalactosylation activity resulting in 34 % (w/w) GOS synthesis from 40 % (w/v) lactose at 50 °C over 12 h. HPLC revealed that the GOS were composed of 13 % disaccharides (non-lactose), 17 % trisaccharides and 4 % tetrasaccharides that were further confirmed by ESI–MS.

Structural features and antioxidant activity of xylooligosaccharides enzymatically produced from sugarcane bagasse

Xylooligosaccharides (XOS) were prepared from xylan-rich hemicelluloses isolated by potassium hydroxide from sugarcane bagasse by hydrolysis with crude xylanase secreted by Pichia stipitis. Hydrolysis for 12h produced XOS with a maximum yield of 31.8%, equivalent to 5.29 mg mL(-1) in the hydrolyzate. XOS with degrees of polymerization (DP) from 2 to 4 (xylobiose, xylotriose, and xylotetraose) were the major components in the hydrolysates, whereas the oligosaccharides with higher DP of 5-6 (xylopentaose and xylohexose) showed a constant low level. FT-IR and NMR ((1)H, (13)C, HSQC) demonstrated that XOS contained Araf and 4-O-Me-α-D-GlcpA residues. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay showed that the XOS exhibited concentration-dependent antioxidant activity. The results obtained indicate that the XOS produced from sugarcane bagasse can be employed in food-related applications.

Production of xylooligosaccharides by xylanase from Pichia stipitis based on xylan preparation from triploid Populas tomentosa

Xylooligosaccharides (XOS) with DP 2-4 are important synbiotics used as food ingredients based on its prebiotic characteristics. In this work, the production of XOS from lignocellulosic material was performed by combined chemical-enzymatic methods. Xylan was prepared from triploid Populas tomentosa, and bioconverted into XOS by crude xylanase solution obtained from Pichia stipitis. The effects of reaction time, temperature, enzyme dosage, and pH value on the production of XOS were fully evaluated. Under the optimal condition (25U g(-1) substrate, pH 5.4 and 50°C), 36.8% of the xylan preparation was converted to XOS, equivalent to 3.95 mg/mL of the hydrolyzate. Xylobiose, xylotriose and xylotetrose were analyzed to be the main products of the enzymatic hydrolyzate, which together accounted for over 95% of the released oligosaccharides. Meanwhile, the effect of sonication pretreatment on the conversion efficiency of the xylan preparation was also investigated.

Beneficial effect of xylo-oligosaccharides and fructo-oligosaccharides in streptozotocin-induced diabetic rats

The beneficial influences of xylo-oligosaccharides (XOS) obtained from alkali-pretreated corncob and fructo-oligosaccharides (FOS) obtained from cane sugar were evaluated in experimental diabetes. These oligosaccharides were supplemented at 10 % (w/w) in the basal diet of streptozotocin-induced diabetic Wistar rats, while the control rats were fed with a basal diet for a period of 6 weeks. Both the oligosaccharides exerted favourable influences in diabetic rats by significantly improving body weight and reducing hyperglycaemia and cholesterol. The characteristic diabetic complications such as severe glucosuria, proteinuria and advanced glycation end products in renal tissue, diabetic nephropathy, and blood creatinine and urea concentrations were notably reduced. Besides, these oligosaccharide supplementations significantly increased the activity of antioxidant enzymes – catalase and glutathione reductase – in the blood of diabetic rats. Supplementation of XOS and FOS resulted in a significant increase in the bifidobacteria and lactobacilli population in the caecum. The present study indicates that XOS and FOS have an ameliorating influence on metabolic abnormalities associated with diabetes, besides conferring an optimal milieu of lactobacilli and bifidobacteria, thus suggesting their potential health benefit in diabetics.

Value addition to corncob: production and characterization of xylooligosaccharides from alkali pretreated lignin-saccharide complex using Aspergillus oryzae MTCC 5154

Comparison of various pretreatments such as mild alkali/acid treatments and pressure cooking of corncob to expose its lignin-saccharide complex has been carried out to enhance enzymatic hydrolysis of xylan to xylooligosaccharides (XOS). Scanning electron micrographs of lignin-saccharide complex of native and pretreated corncob powder showed that the complex was greatly altered during alkali pretreatment. Hydrolysis of alkali pretreated corncob powder using a commercial endoxylanase produced 81+/-1.5% of XOS in the hydrolyzate equivalent to 5.8+/-0.14 mg ml(-1) of XOS. Reaction parameters for the production of XOS from corncob using endoxylanase from Aspergillus oryzae MTCC 5154 were optimized and an XOS yield of 10.2+/-0.14 mg ml(-1) corresponding to 81+/-3.9% with 73.5% xylobiose was obtained. HPLC/RID and ESI/MS analysis of XOS mixture and purified fractions showed that XOS was a mixture of neutral oligosaccharides of DP, 2-7.

Production of xylanase by Aspergilli using alternative carbon sources: application of the crude extract on cellulose pulp biobleaching

The ability of xylanolytic enzymes produced by Aspergillus fumigatus RP04 and Aspergillus niveus RP05 to promote the biobleaching of cellulose pulp was investigated. Both fungi grew for 4-5 days in liquid medium at 40 degrees C, under static conditions. Xylanase production was tested using different carbon sources, including some types of xylans. A. fumigatus produced high levels of xylanase on agricultural residues (corncob or wheat bran), whereas A. niveus produced more xylanase on birchwood xylan. The optimum temperature of the xylanases from A. fumigatus and A. niveus was around 60-70 degrees C. The enzymes were stable for 30 min at 60 degrees C, maintaining 95-98% of the initial activity. After 1 h at this temperature, the xylanase from A. niveus still retained 85% of initial activity, while the xylanase from A. fumigatus was only 40% active. The pH optimum of the xylanases was acidic (4.5-5.5). The pH stability for the xylanase from A. fumigatus was higher at pH 6.0-8.0, while the enzyme from A. niveus was more stable at pH 4.5-6.5. Crude enzymatic extracts were used to clarify cellulose pulp and the best result was obtained with the A. niveus preparation, showing kappa efficiency around 39.6% as compared to only 11.7% for that of A. fumigatus.