Corncob Xylan Research Articles

Aspergillus labruscus ITAL 22.223 xylanase - immobilization and application for the obtainment of corncob xylan targeting xylitol production.

Corncob is an agro-residue rich in lignocellulosic material that can be used for the xylitol production, through its enzymatic conversion obtaining fermentable sugars and their subsequent fermentation. In light of the above, this study targeted the immobilization of Aspergillus labruscus xylanase and the use of the derivative to hydrolyze the corncob xylan for the obtainment of xylose, and its subsequent use for the production of xylitol. The extracellular xylanase was immobilized using different supports (sodium alginate, DEAE-Cellulose, DEAE-Sephadex and CM-Sephadex). Among all supports used, the best results were obtained with the DEAE-Cellulose derivative showing an efficiency of immobilization of 97-99%, yield of 93-95% and recovered activity of 81-100%. The sodium alginate derivative showed 3 cycles of reuse, with drop in activity of about 65% in the 3rd cycle using both CaCl2 and MnCl2 as crosslinkers. The best enzymatic activity for the DEAE-Cellulose derivative was observed at 55ºC and pH 5.0. This derivative presented reuse of 10 cycles using commercial xylan as substrate, and 4 cycles using corncob xylan. This derivative was used in an enzymatic reactor to hydrolyze corncob xylan, obtaining 2.7mg/mL of xylose after 48h of operation under optimal condition of temperature and pH. The xylose obtained from the corncob was fermented by Candida tropicalis for 96h with consumption of 60%. The HPLC analyses indicated a production of 1.02mg/mL of xylitol with 48h of fermentation. In conclusion, this is the first report on the immobilization of the A. labrucus xylanase as an alternative for the obtainment of xylose from corncob xylan, and the subsequent production of xylitol.

The Properties of Xylan Extracted from Corncob Using Deep Eutectic Solvent

Abstract Corncob is an abundant agricultural biomass that is generally underutilized and discarded. It has potential to be a resource for high-value products due to its cellulose and hemicellulose content. Xylan, which is the primary constituent of hemicellulose, can serve as a raw material or intermediary in both non-food and food industry. This research aims to study the extraction of xylan from corncob using deep eutectic solvent (DES) for clean processing and analyzes the characteristics of corncob xylan. DES comprises choline chloride and acetic acid with a molar ratio of 1:2. Xylan was extracted from corncobs by immersion in aqueous DES (70% and 90%) and heating using an autoclave at 105°C for 15 minutes. FT-IR and NMR characterized the chemical structures of xylan, while FE-SEM observed the surface. The FT-IR result showed that xylan had a peak range of 1041 cm−1, which is attributed to the glycosidic bond. A delignification process seems to have occurred as indicated by the absorption peak at 1475-1477 cm−1, indicating the presence of lignin in xylan and solid residue. Both types of extracted xylan had similar NMR spectra in the 3-4.3 ppm range, which indicates that they contained xylose. The solid residue structure obtained from extracting two DES concentrations shows the difference in the extraction process. However, the surface morphology of the two types of extracted xylan had a similar irregular shape and roughness. The use of the DES choline chloride-acetic acid could lead to the extraction and separation of xylan from lignocellulosic corncob.

The CBM91 module enhances the activity of β-xylosidase/α-L-arabinofuranosidase PphXyl43B from Paenibacillus physcomitrellae XB by adopting a unique loop conformation at the top of the active pocket

Carbohydrate-binding module (CBM) family 91 is a novel module primarily associated with glycoside hydrolase (GH) family 43 enzymes. However, our current understanding of its function remains limited. PphXyl43B is a β-xylosidase/α-L-arabinofuranosidase bifunctional enzyme from physcomitrellae patens XB belonging to the GH43_11 subfamily and containing CBM91 at its C terminus. To fully elucidate the contributions of the CBM91 module, the truncated proteins consisting only the GH43_11 catalytic module (rPphXyl43B-dCBM91) and only the CBM91 module (rCBM91) of PphXyl43B were constructed, respectively. The result showed that rPphXyl43B-dCBM91 completely lost hydrolysis activity against both p-nitrophenyl-β-D-xylopyranoside and p-nitrophenyl-α-L-arabinofuranoside; it also exhibited significantly reduced activity towards xylobiose, xylotriose, oat spelt xylan and corncob xylan compared to the control. Thus, the CBM91 module is crucial for the β-xylosidase/α-L-arabinofuranosidase activities in PphXyl43B. However, rCBM91 did not exhibit any binding capability towards corncob xylan. Structural analysis indicated that CBM91 of PphXyl43B might adopt a loop conformation (residues 496–511: ILSDDYVVQSYGGFFT) to actively contribute to the catalytic pocket formation rather than substrate binding capability. This study provides important insights into understanding the function of CBM91 and can be used as a reference for analyzing the action mechanism of GH43_11 enzymes and their application in biomass energy conversion.

Toward Enhanced Antioxidant and Protective Potential: Conjugation of Corn Cob Xylan with Gallic Acid as a Novel Approach.

Maize ranks as the second most widely produced crop globally, yielding approximately 1.2 billion tons, with corn cob being its primary byproduct, constituting 18 kg per 100 kg of corn. Agricultural corn production generates bioactive polysaccharide-rich byproducts, including xylan (Xyl). In this study, we used the redox method to modify corn cob xylan with gallic acid, aiming to enhance its antioxidant and protective capacity against oxidative stress. The conjugation process resulted in a new molecule termed conjugated xylan-gallic acid (Xyl-GA), exhibiting notable improvements in various antioxidant parameters, including total antioxidant capacity (1.4-fold increase), reducing power (1.2-fold increase), hydroxyl radical scavenging (1.6-fold increase), and cupric chelation (27.5-fold increase) when compared with unmodified Xyl. At a concentration of 1 mg/mL, Xyl-GA demonstrated no cytotoxicity, significantly increased fibroblast cell viability (approximately 80%), and effectively mitigated intracellular ROS levels (reduced by 100%) following oxidative damage induced by H2O2. Furthermore, Xyl-GA exhibited non-toxicity toward zebrafish embryos, offered protection against H2O2-induced stress, and reduced the rate of cells undergoing apoptosis resulting from H2O2 exposure. In conclusion, our findings suggest that Xyl-GA possesses potential therapeutic value in addressing oxidative stress-related disturbances. Further investigations are warranted to elucidate the molecular structure of this novel compound and establish correlations with its pharmacological activities.

Study on the green extraction of corncob xylan by deep eutectic solvent

Corn as one of the world's major food crops, its by-product corn cob is also rich in resources. However, the unreasonable utilization of corn cob often causes the environmental pollution, waste of resources and other problems. As one of the most abundant polymers in nature, xylan is widely used in food, medicine, materials and other fields. Corn cob is rich in xylan, which is an ideal raw material for extracting xylan. However, the intractable lignin is covalently linked to xylan, which increases the difficulty of xylan extraction. It has been reported that the deep eutectic solvent (DES) could preferentially dissolve lignin in biomass, thereby dissolving the xylan. Then, the xylan in the extract was separated by ethanol precipitation method. The xylan precipitate was obtained after centrifugation, while the supernatant was retained. The components of the supernatant after ethanol precipitation were separated by the rotary evaporator. The ethanol, water and DES were collected for the subsequent extraction of corn cob xylan. In this study, a novel way was provided for the green production of corn cob xylan. The DES was used to extract xylan from corn cob which was used as the raw material. The effects of solid-liquid ratio, reaction time, reaction temperature and water content of DES on the extraction rate of corn cob xylan were investigated by the single factor test. Furthermore, the orthogonal test was designed to optimize the xylan extraction process. The structure of corn cob xylan was analyzed and verified. The results showed that the optimum extraction conditions of corn cob xylan were as follows: the ratio of corn cob to DES was 1 : 15 (g : mL), the extraction time was 3 h, the extraction temperature was 60 °C, and the water content of DES was 70%. Under these conditions, the extraction rate of xylan was 16.46%. The extracted corn cob xylan was distinctive triple helix of polysaccharide, which was similar to the structure of commercially available xylan. Xylan was effectively and workably extracted from corn cob by the DES method. This study provided a new approach for high value conversion of corn cob and the clean production of xylan.

Reassigning the role of a mesophilic xylan hydrolysing family GH43 β-xylosidase from Bacteroides ovatus, BoExXyl43A as exo-β-1,4-xylosidase

The recombinant 40 kDa BoExXyl43A glycoside hydrolase family 43 (GH43) from bacterium Bacteroides ovatus exhibited highest specific activity (U/mg) against corn cob xylan (136.8), followed by Beechwood xylan (81.1), Carbosynth xylan (69.3), 4-O-D-methylglucuronoxylan (61.4) and Birchwood xylan (59.9). BoExXyl43A demonstrated optimal performance at 37 °C and pH 7.6 with Vmax and Km of 141.8 U/mg and 4.0 mg/mL as well as 64.1 U/mg and 6.0 mg/mL against corn cob and Birchwood xylan, respectively. The activity of BoExXyl43A increased by 48 % by addition of 10 mM Ca2+ ions, while 1 mM EDTA or 1 mM EGTA decreased its activity by 100 % or 42.5 %, respectively, highlighting its calcium-ion dependence. Thin-layer chromatography (TLC) analysis of BoExXyl43A hydrolysates of Birchwood and Beechwood xylan as well as that of various xylooligosaccharides (DP2-DP9) from corn cob xylan showed the release of D-xylose, identifying it as an exo-β-1,4-xylosidase/exo-β-1,4-xylanase (EC 3.2.1.-/3.2.1.37). Moreover, the time-dependent TLC analysis of xylobiose hydrolysis showed release of D-xylose units, confirming its β-xylosidase activity. BoExXyl43A also exhibited exo-1,4-β-xylosidase activity on Larchwood and Carbosynth xylans. Notably, it released D-xylose from α-L-Araf2-xylotriose demonstrating its activity against decorated xylooligosaccharides. BoExXyl43A's exo-1,4-β-xylosidase and residual β-xylosidase activity on xylan and xylobiose, respectively, could potentially enhance xylan saccharification efficiency in bioethanol-based refineries. The molecular modeling showed that BoExXyl43A has 5-bladed β-propeller structure with a very shallow active-site having −1, +1 and + 2 subsites, which could accommodate three D-xylose units of longer xylan like xylododecaose thus supporting its exoxylosidase activity.

A Glycosyl Hydrolase 30 Family Xylanase from the Rumen Metagenome and Its Effects on In Vitro Ruminal Fermentation of Wheat Straw.

The challenge of wheat straw as a ruminant feed is its low ruminal digestibility. This study investigated the impact of a xylanase called RuXyn, derived from the rumen metagenome of beef cattle, on the in vitro ruminal fermentation of wheat straw. RuXyn encoded 505 amino acids and was categorized within subfamily 8 of the glycosyl hydrolase 30 family. RuXyn was heterologously expressed in Escherichia coli and displayed its highest level of activity at pH 6.0 and 40 °C. RuXyn primarily hydrolyzed xylan, while it did not show any noticeable activity towards other substrates, including carboxymethylcellulose and Avicel. At concentrations of 5 mM, Mn2+ and dithiothreitol significantly enhanced RuXyn's activity by 73% and 20%, respectively. RuXyn's activity was almost or completely inactivated in the presence of Cu2+, even at low concentrations. The main hydrolysis products of corncob xylan by RuXyn were xylopentose, xylotriose, and xylotetraose. RuXyn hydrolyzed wheat straw and rice straw more effectively than it did other agricultural by-products. A remarkable synergistic effect was observed between RuXyn and a cellulase cocktail on wheat straw hydrolysis. Supplementation with RuXyn increased dry matter digestibility; acetate, propionate, valerate, and total volatile fatty acid yields; NH3-N concentration, and total bacterial number during in vitro fermentation of wheat straw relative to the control. RuXyn's inactivity at 60 °C and 70 °C was remedied by mutating proline 151 to phenylalanine and aspartic acid 204 to leucine, boosting activity to 20.3% and 21.8% of the maximum activity at the respective temperatures. As an exogenous enzyme preparation, RuXyn exhibits considerable potential to improve ruminal digestion and the utilization of wheat straw in ruminants. As far as we know, this is the first study on a GH30 xylanase promoting the ruminal fermentation of agricultural straws. The findings demonstrate that the utilization of RuXyn can significantly enhance the ruminal digestibility of wheat straw by approximately 10 percentage points. This outcome signifies the emergence of a novel and highly efficient enzyme preparation that holds promise for the effective utilization of wheat straw, a by-product of crop production, in ruminants.

Discovery of a Novel β-xylosidase with Xylanase Activity and Its Application in the Production of Xylitol from Corncob Xylan

Although β-xylosidases with xylanase activity are preferential for the hydrolysis of xylan and production of xylitol, reports on their use are scarce. In this study, a multifunctional β-xylosidase (XYL4) was identified. In addition to β-xylosidase activity, XYL4 also exhibited xylanase and low α-arabinosidase activity. The enzyme was able to hydrolyze bagasse xylan, oat spelt xylan, birchwood xylan, beechwood xylan, and corncob xylan, and showed the highest hydrolysis activity for corncob xylan. Structural modeling analysis indicated that XYL4 had an additional PA14 domain, which may play a key role in binding xylan substrates. Moreover, XYL4 was used to hydrolyze corncob xylan to produce xylose. When enzymatic hydrolysis and whole-cell catalysis were used to hydrolyze 100 g/L of corncob xylan, the xylose yields were 60.26% and 35.85%, respectively. Then, the Candida tropicalis was inoculated with the above hydrolysates for fermentation to produce xylitol. Using enzymatic hydrolysis and whole-cell catalysis, xylitol yields of 77.56% and 73.67% were obtained by C. tropicalis after the optimization of fermentation, respectively.

Co-immobilization of β-xylosidase and endoxylanase on zirconium based metal–organic frameworks for improving xylosidase activity at high temperature and in acetone

Improving the activity of β-xylosidase at high temperature and organic solvents is important for the conversion of xylan, phytochemicals and some hydroxyl-containing substances to produce xylose and bioactive substances. In this study, a β-xylosidase R333H and an endoxylanase were simultaneously co-immobilized on the metal–organic framework UiO-66-NH2. Compared with the single R333H immobilization system, the co-immobilization enhanced the activity of R333H at high temperature and high concentration of acetone, and the relative activities at 95 °C and 50% acetone solution were >95%. The Km value of co-immobilized R333H towards p-Nitrophenyl-β-D-xylopyranoside (pNPX) shifted from 2.04 to 0.94 mM, which indicated the enhanced affinity towards pNPX. After 5 cycles, the relative activities of the co-immobilized enzymes towards pNPX and corncob xylan were 52% and 70% respectively, and the accumulated amount of reducing sugars obtained by co-immobilized enzymes degrading corncob xylan in 30% (v/v) acetone solution was 1.7 times than that with no acetone.

Comprehensive Genome Analysis of Cellulose and Xylan-Active CAZymes from the Genus Paenibacillus: Special Emphasis on the Novel Xylanolytic Paenibacillus sp. LS1.

Xylan is the most abundant hemicellulose in hardwood and graminaceous plants. It is a heteropolysaccharide comprising different moieties appended to the xylose units. Complete degradation of xylan requires an arsenal of xylanolytic enzymes that can remove the substitutions and mediate internal hydrolysis of the xylan backbone. Here, we describe the xylan degradation potential and underlying enzyme machinery of the strain, Paenibacillus sp. LS1. The strain LS1 was able to utilize both beechwood and corncob xylan as the sole source of carbon, with the former being the preferred substrate. Genome analysis revealed an extensive xylan-active CAZyme repertoire capable of mediating efficient degradation of the complex polymer. In addition to this, a putative xylooligosaccharide ABC transporter and homologues of the enzymes involved in the xylose isomerase pathway were identified. Further, we have validated the expression of selected xylan-active CAZymes, transporters, and metabolic enzymes during growth of the LS1 on xylan substrates using qRT-PCR. The genome comparison and genomic index (average nucleotide identity [ANI] and digital DNA-DNA hybridization) values revealed that strain LS1 is a novel species of the genus Paenibacillus. Lastly, comparative genome analysis of 238 genomes revealed the prevalence of xylan-active CAZymes over cellulose across the Paenibacillus genus. Taken together, our results indicate that Paenibacillus sp. LS1 is an efficient degrader of xylan polymers, with potential implications in the production of biofuels and other beneficial by-products from lignocellulosic biomass. IMPORTANCE Xylan is the most abundant hemicellulose in the lignocellulosic (plant) biomass that requires cooperative deconstruction by an arsenal of different xylanolytic enzymes to produce xylose and xylooligosaccharides. Microbial (particularly, bacterial) candidates that encode such enzymes are an asset to the biorefineries to mediate efficient and eco-friendly deconstruction of xylan to generate products of value. Although xylan degradation by a few Paenibacillus spp. is reported, a complete genus-wide understanding of the said trait is unavailable till date. Through comparative genome analysis, we showed the prevalence of xylan-active CAZymes across Paenibacillus spp., therefore making them an attractive option towards efficient xylan degradation. Additionally, we deciphered the xylan degradation potential of the strain Paenibacillus sp. LS1 through genome analysis, expression profiling, and biochemical studies. The ability of Paenibacillus sp. LS1 to degrade different xylan types obtained from different plant species, emphasizes its potential implication in lignocellulosic biorefineries.

Fusion of Oligopeptide to the C Terminus of α-Glucuronidase from Thermotoga maritima Improves the Catalytic Efficiency for Hemicellulose Biotransformation.

Fusion protein combined the oligopeptide (HQAFFHA) with the C terminus of α-glucuronidase from Thermotoga maritima was produced in E. coli and purified for characterization and applications of glucuronic and glucaric acid production. The fusion protein with oligopeptide exhibited a 2.97-fold higher specific activity than individual protein. Their catalytic efficiency kcat/Km and kcat increased from 469.3 ± 2.6s-1 (g mL-1)-1 and 62.4 ± 0.9s-1 to 2209.5 ± 26.3s-1 (g mL-1)-1 and 293.9 ± 4.9s-1, respectively. Fusion protein had similar temperature and pH profiles to those without oligopeptide, but the thermal stability decreases and the pH stability shifts to alkaline. Using beech xylan hydrolysate as a substrate, the glucuronic acid yield of fusion enzyme increased by 9.94% compared with its parent at 65°C pH 8.5 for 10h, and can hydrolyze corn cob xylan with xylanase to obtain glucuronic acid, and can be combined with uronate dehydrogenase to obtain high-added value glucaric acid. Homologous modeling analysis revealed the factors contributing to the high catalytic efficiency of fusion enzyme. These results show that the peptide fusion strategy described here may be useful for improving the catalytic efficiency and stability of other industrial enzymes, and has great potential for producing high value-added products from agricultural waste.

A novel reducing-end xylose-releasing exo-oligoxylanase (PphRex8A) from Paenibacillus physcomitrellae XB

In order to better understand the function of a putative GH8 xylanase gene in the xylan-degrading bacterium Paenibacillus physcomitrellae XB, a novel reducing-end xylose-releasing exo-oligoxylanase (Rex) PphRex8A of GH8 family was characterized. Phylogenetic analysis showed that it was clustered tightly with other published GH8 Rexs and exhibited the highest amino acid sequence identity (77.4 %) with the Rex of PbRex8 from P. barengoltzii G22. The three-dimensional (3D) structure of PphRex8A was also built based on the template of PbRex8 (5YXT) and three conserved catalytic active sites (Glu71, Asp263, and Asp129) were predicted and further confirmed by the enzymatic inactivity of their mutants (E71A, D129A, and D263A). The hydrolysis assay of PphRex8A showed that it could hydrolyze xylo-oligosaccharides (XOSs) with a degree of polymerization (DP) ≥ 3, such as xylotriose (X3) through xylohexaose (X6), and some natural XOSs, such as corncob xylan (CCX) and oat spelt xylan (OSX) to release xylose. However, it could not hydrolyze p-nitrophenyl-β-D-xylopyranoside (pNPX), which suggested that it mainly released xylose from the reducing-end of XOSs and belonged to a Rex. In addition, PphRex8A also could deconstruct xylans with high DP, such as wheat arabinoxylan (AX) and beech wood xylan (BWX) to produce XOSs with DP3–6. Moreover, PphRex8A had synergistic effects with other xylanolytic enzymes of P. physcomitrellae XB, such as with PphXyn10 or PphXyn11 at a ratio of 1:3, or with PphXyl43B as a ratio of 3:1, significantly increasing the amounts of reducing sugars toward different xylan substrates. Thus, PphRex8A could be an exo-xylanase toward XOSs and could improve the deconstruction capability of high DP xylans, thereby complementing other xylanolytic enzymes to contribute to xylan degradation and improve the efficiency of converting hemicellulose biomass into energy by P. physcomitrellae XB.

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 Vmax 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.

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.

Improving catalytic efficiency of endoxylanase for degrading corncob xylan to produce xylooligosaccharides by fusing a β-xylosidase

A robust endoxylanase with high activity has great potential in biomass utilization. Here, the catalytic efficiency of the endoxylanase XynF derived from Herbinix hemicellulosilytica was improved by fusing a β-xylosidase xln-DT derived from Dictyoglomus thermophilum with linkers (L0 and L3) and the direction from xln-DT to XynF. The biochemical properties and application potential of chimeras towards corncob xylan were explored. The result showed that the chimeras Xln-L0-XynF and Xln-L3-XynF exhibited higher catalytic efficiency (31-fold and 20-fold enhancement, respectively), and maintained high stability in some harsh environments compared with parental enzymes. This might be attributed to the appropriate linkers and the direction which decrease the adverse interactions between the two modules. These two chimeras could hydrolyze corncob xylan to produce approximately 30% xylooligosaccharides with polymerization of 2–6. This work represents the promising xylanases for participating in XOS production from an abundant corncobs and promote us to modify glycoside hydrolase by fusion technology.

Insights about the effect of composition, branching and molecular weight on the slow pyrolysis of xylose-based polysaccharides

This work provides insights into the relationship between the pyrolysis products distribution and the structural features of xylose-based hemicelluloses. Three xylose-based hemicelluloses differing in composition, molecular weight, chain branching and origin were selected, structurally characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis and nuclear magnetic resonance and then used as feedstocks for slow pyrolysis tests up to 700 °C in nitrogen environment. Commercial beechwood xylan was selected as representative of the glucuronoxylan hemicellulose type, typical of hardwood species. Commercial corncob xylan was selected as it is composed by a mixture of low molecular weight xylo-oligosaccharides with a low acetylation degree. In the end, the xylan extracted from grape pruning, being an arabinoglucuronoxylan, was chosen as representative of hemicellulose structure common to most annual plants and agricultural wastes. Low-branched material (corncob xylan) produced the lowest yield of char and the highest yield of pyrolysis liquids, while highly-branched material (grape pruning xylan) exhibited an opposite trend. The liquid composition was qualitatively similar for all the considered xylans. However, the comparison of the quantifiable species showed different relative abundances. The pyrolysis products distribution indicated that the chain branching degree affected at a higher extent the feedstock pyrolytic behavior with respect to the ash content.

Contributions and characteristics of two bifunctional GH43 β-xylosidase /α-L-arabinofuranosidases with different structures on the xylan degradation of Paenibacillus physcomitrellae strain XB

Xylan is one of the major polymeric hemicellulosic constituents of lignocellulosic biomass, and its effective utilization by microorganisms is crucial for the economical production of biofuels. In this study, Paenibacillus physcomitrellae XB exhibited different xylan degradation ability on different substrates of corncob xylan (CCX), oat spelt xylan (OSX), wheat flour arabinoxylan (AX) and beech wood xylan (BWX). The RT-QPCR result showed that two genes (Pph_0602 and Pph_2344) belonging to the glycoside hydrolase family 43 were up-regulated more than 5-fold on CCX and xylose. Substrate-specific assays with purified proteins Ppxyl43A (Pph_0602) and Ppxyl43B (Pph_2344) revealed that both exhibited β-xylosidase activity toward the chromogenic substrate p-nitrophenyl-β-D-xylopyranoside, and α-L-arabinofuranosidase activity toward p-nitrophenyl-α-L-arabinofuranoside, indicating their bifunctionality. By testing their degradation characteristics on different natural substrates, it was found that both Ppxyl43A and Ppxyl43B showed similar degradation ability on CCX and OSX. Both enzymes could hydrolyze xylohexaose and xylobiose completely to xylose, but could not hydrolyze BWX and AX, suggesting they mainly hydrolyze xylo-oligosaccharides by β-xylosidase activity. Further analysis showed that both of them displayed very high pH stability and thermostability on the β-xylosidase activity, but Ppxy143B exhibited wider pH and temperature ranges, higher pH and temperature stability, was less influenced by metal ions, and had a slower start-up response than Ppxyl43A. Given their predicted structure, it is likely that the enzymatic differences between Ppxyl43A and Ppxyl43B might be related to the extra C-terminus domain (GH43_C2) in Ppxyl43B, which could enhance the enzymatic stability while restricting the substrates’ or metal ions’ access to the active sites of Ppxyl43B. In conclusion, both Ppxyl43A and Ppxyl43B were β-xylosidase/α-L-arabinofuranosidase bifunctional enzymes and might be useful in xylan biomass conversion, especially in the hydrolysis of xylo-oligosaccharides into xylose.

Multi-Objective Optimization Through Machine Learning Modeling for Production of Xylooligosaccharides from Alkali-Pretreated Corn-Cob Xylan Via Enzymatic Hydrolysis.

The hemicellulose content present in corn cobs can help in producing a high amount of xylooligosaccharides (XOS) in an eco-friendly manner. In this work, the XOS was produced from alkali pre-treated corn-cobs having a true yield of 38 ± 1.4% via enzymatic hydrolysis with the help of xylanase from T. lanuginosus VAPS-24. The production process was optimized to achieve a high concentration of XOS using innovative multi-objective optimization through machine learning modeling and finding out the most suitable parameters where xylobiose production is higher than xylose. The Multi-objective connected neural networks (MOCNN) model with tangent sigmoid activation function yielded a correlation coefficient of 96.51%; there were six optimal sets where xylobiose concentration was higher than xylose. The best-optimized conditions yielded 3.03mg/ml of xylobiose and 1.31mg/ml of xylose. Therefore, this novel approach of machine learning can target the increasing demand for xylooligosaccharides in the growing industrial market of prebiotics.

Produksi dan Pemurnian Xilooligosakarida dari Xilan Tongkol Jagung menggunakan Xilanase Streptomyces P26B4 dan Khamir IP4

Xylooligosaccharides (XOS) are sugar oligomers from xylan that can be used as prebiotics to improve digestive tract health. Xylan can be extracted from corncobs which are a by-product of agriculture. The purpose of this study was to produce XOS through hydrolysis of corn cobs xylan using Streptomyces P26B4 xylanase. The products of hydrolysis also consisted of monomer xylose; for that xilooligosaccharides were purified using yeast IP4. The xylan hydrolysis products are quantitatively analyzed based on the value of reducing sugars and degree of polymerization (DP), strengthened qualitatively with TLC. Sugar component was analyzed after the addition of yeast by HPLC. P26B4 xylanase isolates had the highest activity on the 7th day incubation, pH 5,5 buffer citrate and temperature of 50°C. The lowest DP value of xylan hydrolysis was 2.49 at a concentration of 6%, and the 24th hour of incubation. TLC chromatograms showed that xylose and XOS products were produced. Purification of XOS at 6%, showed a decreasing in the area of xylose before and after receiving yeast respectively 1.87% and 1.41%.Therefore, yeast IP4 has the potential to consume xylose amnd purify the XOS. 
 Keywords: corncobs xylan, IP4 yeast, purification, Streptomyces P26B4 xylanase, xylooligosaccharides

Isolation of Corncob Xylan-Degrading Fungi and Its Application in Xylobiose Production

In the present study, a potential corncob xylan degradation fungi was isolated and screened from soil to produce xylanase, and was identified as Fusarium oxysporum. The production of xylanase by F. oxysporum under solid state fermentation using corncob powder as the solid substrate reached the maximum xylanase activity when using particle size of substrate of 60 mesh, water content ratio of 2 mL/g substrate, incubation temperature of 30°C, initial pH of 6.0, size of inoculum of 5x107 spore/3 g substrate, and incubation time of 2 days. The xylanase activity increased about 4 times up to 7.92 U/mL after optimization. The potential application of xylanase of F. oxysporum in hydrolyzing alkali-treated corncob xylan to produce xylobiose was also demonstrated. Hydrolysis of 6% of corncob xylan using 100 U/g substrate of enzyme loading under optimum pH and temperature conditions (pH 5.5 and 50°C, respectively) achieved the yield of xylobiose up to 28.7 g/100 g pure xylan after 12 h incubation. The purification of hydrolysate could retain 91.1% of xylobiose. Further separation step using activated charcoal column chromatography was able to get a pure xylobiose, but could only recover 59.3% of xylobiose.