Improvement of enzymatic xylooligosaccharides production by the co-utilization of xylans from different origins

Mathematical model for bale-density prediction in large steel roller-type round balers during bale rolling

To realize the intelligent production of straw bales and improve their economy, the density of straw bales in the working process of large-scale steel roller-type round balers must be measured in real time. Therefore, this study analyzes the forces acting on steel rollers and bales in the bale rolling process, constructs a mathematical model to predict the density of molded bales, and proposes a method for dynamically measuring the density of bales in a round bale machine. Sunflower straw was selected as the test material, and a bale density model validation test was conducted at a test stand. The results showed that the accuracy of the measured bale density of the data acquisition system ranged from 93% to 97%, verifying that the mathematical model for bale density prediction had good accuracy. This study provided an effective strategy for round baler design.

GalR, GalX and AraR co-regulate d-galactose and l-arabinose utilization in Aspergillus nidulans

Filamentous fungi produce a wide variety of enzymes in order to efficiently degrade plant cell wall polysaccharides. The production of these enzymes is controlled by transcriptional regulators, which also control the catabolic pathways that convert the released monosaccharides. Two transcriptional regulators, GalX and GalR, control d-galactose utilization in the model filamentous fungus Aspergillus nidulans, while the arabinanolytic regulator AraR regulates l-arabinose catabolism. d-Galactose and l-arabinose are commonly found together in polysaccharides, such as arabinogalactan, xylan and rhamnogalacturonan I. Therefore, the catabolic pathways that convert d-galactose and l-arabinose are often also likely to be active simultaneously. In this study, we investigated the interaction between GalX, GalR and AraR in d-galactose and l-arabinose catabolism. For this, we generated single, double and triple mutants of the three regulators, and analysed their growth and enzyme and gene expression profiles. Our results clearly demonstrated that GalX, GalR and AraR co-regulate d-galactose catabolism in A. nidulans. GalX has a prominent role on the regulation of genes of d-galactose oxido-reductive pathway, while AraR can compensate for the absence of GalR and/or GalX.

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.

Extraction of sugarcane bagasse arabinoxylan, integrated with enzymatic production of xylo-oligosaccharides and separation of cellulose

Sugarcane processing roughly generates 54 million tonnes sugarcane bagasse (SCB)/year, making SCB an important material for upgrading to value-added molecules. In this study, an integrated scheme was developed for separating xylan, lignin and cellulose, followed by production of xylo-oligosaccharides (XOS) from SCB. Xylan extraction conditions were screened in: (1) single extractions in NaOH (0.25, 0.5, or 1 M), 121 °C (1 bar), 30 and 60 min; (2) 3 × repeated extraction cycles in NaOH (1 or 2 M), 121 °C (1 bar), 30 and 60 min or (3) pressurized liquid extractions (PLE), 100 bar, at low alkalinity (0-0.1 M NaOH) in the time and temperature range 10-30 min and 50-150 °C. Higher concentration of alkali (2 M NaOH) increased the xylan yield and resulted in higher apparent molecular weight of the xylan polymer (212 kDa using 1 and 2 M NaOH, vs 47 kDa using 0.5 M NaOH), but decreased the substituent sugar content. Repeated extraction at 2 M NaOH, 121 °C, 60 min solubilized both xylan (85.6% of the SCB xylan), and lignin (84.1% of the lignin), and left cellulose of high purity (95.8%) in the residuals. Solubilized xylan was separated from lignin by precipitation, and a polymer with β-1,4-linked xylose backbone substituted by arabinose and glucuronic acids was confirmed by FT-IR and monosaccharide analysis. XOS yield in subsequent hydrolysis by endo-xylanases (from glycoside hydrolase family 10 or 11) was dependent on extraction conditions, and was highest using xylan extracted by 0.5 M NaOH, (42.3%, using Xyn10A from Bacillus halodurans), with xylobiose and xylotriose as main products. The present study shows successful separation of SCB xylan, lignin, and cellulose. High concentration of alkali, resulted in xylan with lower degree of substitution (especially reduced arabinosylation), while high pressure (using PLE), released more lignin than xylan. Enzymatic hydrolysis was more efficient using xylan extracted at lower alkaline strength and less efficient using xylan obtained by PLE and 2 M NaOH, which may be a consequence of polymer aggregation, via remaining lignin interactions.

Enzymatic production of xylooligosaccharide from date (Phoenix dactylifera L.) seed

Date palm (phonix dactylifera L.) is an important tropical fruit growing in central and southern regions of Iran. Date seed is composed of cellulose, hemicellulose, and lignin, that make it an excellent candidate for xylooligosaccharide (XOS) production. In this study, two different protocols are used for the extraction of hemicellulose from date seeds. In the first protocol, hemicellulose (xylan1) was extracted by 2.25 M alkaline solution at room temperature for 24 hr. In the second protocol, date seed was treated with LCHTA (low concentration, 0.1 M, high temperature, 80°C, alkaline solution) for 3 hr, and thereafter, hemicellulose (xylan2) was extracted by 2.25 M alkaline solution at room temperature for 24 hr. The carbohydrate units of xylan1 and xylan2 were qualified and quantified by HPAEC- PAD. Side groups of xylan1 and xylan2 were detected by FTIR. In the next step, xylan1 and xylan2 were exposed to two commercial endoxylanases namely veron 191 and pentopan mono BG. Temperature, pH, time, and enzyme dosage of hydrolyzation were optimized to maximize XOS and minimize xylose. The results showed that the enzymes successfully hydrolyzed xylan2 and produced XOS, but cannot hydrolyze xylan1. Pentopan mono BG and veron 191 produced the highest amount of XOS after 4 (1.17 mmol/g) and 6 hr (1.13 mmol/g) of incubation, respectively. Conversion factors of xylan2 to XOS for pentopan mono BG and veron were 0.41 and 0.36, respectively. This study presence the possible prebiotic properties of date seed XOS and its application in functional foods.

Simultaneous determination of cereal monosaccharides, xylo- and arabinoxylo-oligosaccharides and uronic acids using HPAEC-PAD

Xylo- and arabinoxylo-oligosaccharides (XOS and AXOS) are of interest for their prebiotic activity. The production of these oligomers might be accompanied with monosaccharides. The measurement of both oligosaccharides and monosaccharides usually requires two methods. The current work presents an HPAEC-PAD method based on gradient elution of aqueous solvents sodium hydroxide and sodium acetate, in contrast to conventional isocratic elution, for the simultaneous separation of 16 standards of monosaccharides, xylo-oligosaccharides, arabinoxylo-oligosaccharides and uronic acids using CarboPac PA 200 column. The presented method showed a stable baseline and high-resolution separation of the standards. The method showed acceptable accuracy and precision. Limits of Detection and Quantitation (LOD and LOQ) were estimated for all the standards. The method was applied to measure the activity of a commercial endoxylanase on wheat bran; a steady release of xylose monosaccharide was observed. Enzyme action on oligosaccharide standards showed a preference for the larger oligosaccharides.

Secondary Lactic Acid Bacteria Fermentation with Wood-Derived Xylooligosaccharides as a Tool To Expedite Sour Beer Production

Xylooligosaccharides (XOS) from woody biomass were evaluated as a substrate for secondary lactic acid bacteria (LAB) fermentation in sour beer production. XOS were extracted from birch (Betula pubescens) and added to beer to promote the growth of Lactobacillus brevis BSO 464. Growth, pH, XOS degradation, and metabolic products were monitored throughout fermentations, and the final beer was evaluated sensorically. XOS were utilized, metabolic compounds were produced (1800 mg/L lactic acid), and pH was reduced from 4.1 to 3.6. Secondary fermentation changed sensory properties significantly, and the resulting sour beer was assessed as similar to a commercial reference in multiple attributes, including acidic taste. Overall, secondary LAB fermentation induced by wood-derived XOS provided a new approach to successfully produce sour beer with reduced fermentation time (from 1-3 years to 4 weeks). The presented results demonstrate how hemicellulosic biomass can be valorized for beverage production and to obtain sour beer with improved process control.

Impact of in vitro gastrointestinal digestion on the chemical composition, bioactive properties, and cytotoxicity of Vitis vinifera L. cv. Syrah grape pomace extract

Grape pomace (GP) is a major byproduct worldwide, and it is well known for its bioactive compounds, such as fibers and phenolic compounds, that are popular for their impact upon human health, including gastrointestinal health. The objective of this work was to evaluate the chemical composition and biological activities of an enzymatic GP extract, as well as to investigate how gastrointestinal digestion (GID) modulates these properties. GP extract was previously produced using an enzymatic cocktail with xylanase activity and was then exposed to simulated conditions of GID, characterized for its chemical composition, and screened for antimicrobial, prebiotic, and antioxidant activities. The safety of this ingredient after GID was also assessed. GP extract presented high contents of dietary fiber and other carbohydrates, including xylooligosaccharides, in addition to minerals and phenolic compounds. In vitro simulated GID revealed that xylobiose was resistant to gastric conditions, unlike phenolic compounds. The use of 2% (w/v) of this ingredient proved to be a potential carbon source that could be fermented by Lactobacillus and Bifidobacterium spp, even after digestion. The extract also exhibited strong antioxidant and antimicrobial activities against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa; however, after GID, the antioxidant capacity decreased, and the antimicrobial capacity was strongly reduced or lost. Furthermore, the extract safety was also guaranteed on Caco-2 intestinal cells. This novel and green GP extract proved to be composed of relevant bioactive molecules, including xylooligosaccharides, polyphenols, organic acids, and minerals, which provided different biological properties; it has potential applications in the food industry such that it can be used as an ingredient in the development of new functional foods.

Enzymatic hydrolysis of brewer's spent grain to obtain fermentable sugars

Lignocellulosic biomass is a feedstock with the potential to be converted into value-added bioproducts. The use of enzymatic hydrolysis allows the cleavage of lignocellulose into their monomeric units, but there are some drawbacks that make its use in industrial biocatalysis unfeasible. In the present study, we describe the hydrolysis of brewer's spent grain (BSG) with an enzymatic cocktail produced by Aspergillus niger CECT 2700 and its comparison with commercial enzymes. In addition, it was determined whether pretreating the BSG (non-pressurized alkaline hydrolysis or treatment with cholinium glycinate ionic liquid) is necessary. Results show that both pretreatments enhanced xylose release (10.55 ± 0.07 g/L and 8.14 ± 0.13 g/L respectively), meanwhile the hydrolysis of raw BSG with the enzymatic cocktail produced solutions containing high levels of glucose (18.45 ± 1.66 g/L) and xylose (6.38 ± 0.26 g/L).

Enzymatic production of xylooligosaccharides from Brazilian Syrah grape pomace flour: a green alternative to conventional methods for adding value to agricultural by- products

BACKGROUND

The aim of this work was to determine the most favorable conditions for the production of xylooligosaccharides (XOS) from Brazilian Syrah grape pomace. Chemical processes were performed using a rotatable central composite design where the concentration of sulfuric acid or sodium hydroxide and the grape pomace flour/solvent mass ratio were the dependent variables. Enzymatic production was also evaluated using xylanase produced by Aspergillus niger 3T5B8 and Viscozyme^® enzymatic commercial cocktail.

RESULTS

Chemical extraction allowed to recover 21.8-74.6% and 5.2-96.3% of total XOS for acidic and alkaline processes respectively. Enzymatic production extracted up to 88.68 ± 0.12% of total XOS using xylanase and up to 84.09 ± 2.40% with Viscozyme^® .

CONCLUSION

The present study demonstrated different feasible methods to produce high-added-value molecules, i.e. XOS, from Syrah grape pomace flour, valorizing this major by-product. The use of enzymatic cocktails demonstrated to be an alternative to the conventional methods, allowing to obtain an eco-friendly and sustainable grape pomace extract. © 2018 Society of Chemical Industry.

An integrated process for xylooligosaccharide and bioethanol production from corncob

An integrated process for xylooligosaccharides (XOs) and bioethanol production from corncob was investigated. XOs were produced by a consecutive process of KOH treatment and hydrolysis by an in-house thermostable endo-xylanase from Streptomyces thermovulgaris. XO yields of 0.15 g/g_{KOH-treated corncob} (22.13 g/L) and 0.52 g/g_{raw corncob} of cellulose-rich corncob (CRC) were obtained. After 96 h of enzymatic hydrolysis, CRC hydrolysate contained 62.16, 51.21, 10.03 and 0.92 g/L of total sugar, glucose, xylose and arabinose, respectively. Bioethanol production by separate hydrolysis and fermentation (SHF) using CRC hydrolysate, and by simultaneous saccharification and fermentation (SSF) using CRC was studied at 40 °C for thermotolerant Candida glabrata. SHF showed an ethanol yield of 0.28 g/g_CRC (21.92 g/L) and ethanol productivity of 0.304 g/L/h with 93% theoretical yield. Surprisingly, by SSF, those parameters were 0.27 g/g_CRC (31.32 g/L), 0.33 g/L/h and 89%, respectively. This integrated process might be a new cost-effective approach for corncob valorization.

Screening of filamentous fungi to produce xylanase and xylooligosaccharides in submerged and solid-state cultivations on rice husk, soybean hull, and spent malt as substrates

We investigated the enzymatic complex produced by selected fungi strains isolated from the environment using the agro-industrial residues rice husk, soybean hull, and spent malt as substrates. Microbial growth was carried out in solid-state cultivation (SSC) and in submerged cultivations (SC) and the enzymatic activities of xylanase, cellulase, β-xylosidase, and β-glucosidase were determined. All substrates were effective in inducing enzymatic activities, with one strain of Aspergillus brasiliensis BLf1 showing maximum activities for all enzymes, except for cellulases. Using this fungus, the enzymatic activities of xylanase, cellulase, and β-glucosidase were generally higher in SSC compared to SC, producing maxima activities of 120.5, 25.3 and 47.4 U g-1 of dry substrate, respectively. β-xylosidase activity of 28.1 U g-1 of dry substrate was highest in SC. Experimental design was carried out to optimize xylanase activity by A. brasiliensis BLf1 in SSC using rice husk as substrate, producing maximum xylanase activity 183.5 U g-1 dry substrate, and xylooligosaccharides were produced and characterized. These results suggest A. brasiliensis BLf1 can be used to produce important lytic enzymes to be applied in the preparation of xylooligosaccharides.

Development, validation and application of a hydrophilic interaction liquid chromatography-evaporative light scattering detection based method for process control of hydrolysis of xylans obtained from different agricultural wastes

Purified standards of xylooligosaccharides (XOSs) (DP2-6) were first prepared from a mixture of XOSs using solid phase extraction (SPE), followed by semi-preparative liquid chromatography both under hydrophilic interaction liquid chromatography (HILIC) modes. Then, an accurate quantitative analysis method based on hydrophilic interaction liquid chromatography-evaporative light scattering detection (HILIC-ELSD) was developed and validated for simultaneous determination of xylose (X1), xylobiose (X2), xylotriose (X3), xylotetraose (X4), xylopentaose (X5), and xylohexaose (X6). This developed HILIC-ELSD method was applied to the comparison of different hydrolysis methods for xylans and assessment of XOSs contents from different agricultural wastes. The result indicated that enzymatic hydrolysis was preferable with fewer by-products and high XOSs yield. The XOSs yield (48.40%) from sugarcane bagasse xylan was the highest, showing conversions of 11.21g X2, 12.75g X3, 4.54g X4, 13.31g X5, and 6.78g X6 from 100g xylan.