Acidic hydrolyzed xylo-oligosaccharides bioactivity on the antioxidant and immune activities of macrophage.

Xylo-oligosaccharides (XOS) prepared by the acetic acid hydrolysis of corncob were adulterated with many impurities including pigments, salts, and monosaccharides. Monosaccharides, acids, and most of the pigment were removed by a combination of decolorization, bipolar membrane electrodialysis and catalysis by Gluconobacter oxydans. These steps retain 90% of XOS in the acidolysis slurry. In this study, the effects of purified-XOS (PXOS) and crude XOS (CXOS) on the antioxidant and immune activities of macrophage were compared to verify the bioactivity of acidic hydrolyzed XOS, mainly focusing on the benefits of the purification process. PXOS was more effective in increasing superoxide dismutase activity and reducing malondialdehyde content, and thus had more potent antioxidant activity. In addition, PXOS could more efficiently promote the secretion of tumor necrosis factor-α, interleukin-6, nitric oxide, and interleukin-1ß by macrophage. All these data, suggest that the purification process contributed to improve the immunomodulatory activity of XOS from acidolysis slurry.

Aliphatic extractive effects on acetic acid catalysis of typical agricultural residues to xylo-oligosaccharide and enzymatic hydrolyzability of cellulose.

BACKGROUND: Xylo-oligosaccharide is the spotlight of functional sugar that improves the economic benefits of lignocellulose biorefinery. Acetic acid acidolysis technology provides a promising application for xylo-oligosaccharide commercial production, but it is restricted by the aliphatic (wax-like) compounds, which cover the outer and inner surfaces of plants. RESULTS: We removed aliphatic compounds by extraction with two organic solvents. The benzene-ethanol extraction increased the yield of acidolyzed xylo-oligosaccharides of corncob, sugarcane bagasse, wheat straw, and poplar sawdust by 14.79, 21.05, 16.68, and 7.26% while ethanol extraction increased it by 11.88, 17.43, 1.26, and 13.64%, respectively. CONCLUSION: The single ethanol extraction was safer, more environmentally friendly, and more cost-effective than benzene-ethanol solvent. In short, organic solvent extraction provided a promising auxiliary method for the selective acidolysis of herbaceous xylan to xylo-oligosaccharides, while it had minimal impact on woody poplar.

Comparison of various organic acids for xylo-oligosaccharide productions in terms of pKa values and combined severity.

BACKGROUND: Methods to produce XOS have been intensively investigated, including enzymatic hydrolysis, steam explosion, and acid hydrolysis. Acid hydrolysis is currently the most widely used method to produce XOS due to its advantages of fewer processing steps, stronger raw material adaptability, higher yield, and better reproducibility. Especially, organic acids such as acetic acid, formic acid and xylonic acid work better as compared with mineral acids. However, the catalytic mechanism of different organic acids has been little studied. In this paper, four different organic acids, including formic acid, glycolic acid, lactic acid, and acetic acid were selected to compare their hydrolytic effects. RESULTS: Using pKa values as the benchmark, the yield of xylo-oligosaccharide (XOS) increased with the increasing value of pKa. The yield of XOS was 37% when hydrolyzed by 5% acetic acid (pKa = 4.75) at 170 â„ƒ for 20 min. Combined severity (CS), a parameter associated with temperature and reaction time was proposed, was proposed to evaluate the hydrolysis effect. The results of CS were consistent with that of pKa values on both the yield of XOS and the inhibitor. CONCLUSION: The results based on pKa values and combined severity, a parameter associated with temperature and reaction time, concluded that acetic acid is a preferred catalyst. Combining the techno-economic analysis and environmental benefits, acetic acid hydrolysis process has lower factory production costs, and it is also an important metabolite and a carbon source for wastewater anaerobic biological treatment. In conclusion, production of xylo-oligosaccharides by acetic acid is an inexpensive, environment-friendly, and sustainable processing technique.

An integrated biorefinery process for adding values to corncob in co-production of xylooligosaccharides and glucose starting from pretreatment with gluconic acid.

Increasing attention has been paid to the production of high value-added products from lignocellulosic biomass. This study aims to valorize corncob, utilizing it as feedstock for a multi-biorefinery framework, using gluconic acid in the pretreatment. In attempts to maximize yield of xylooligosaccharides, corncob was first subjected to hydrolysis by gluconic acid using response surface methodology, from which the maximum xylooligosaccharides yield of 56.2% was achieved using 0.6 mol/L gluconic acid at 154 °C for 47 min. Results indicated that gluconic acid was an effective solvent for xylooligosaccharides production: a total of 180 g of xylooligosaccharides was obtained from 1 kg corncob as a result of hydrolysis. Moreover, 86.3% conversion of cellulose was achieved from enzymatic hydrolysis of gluconic acid-treated corncob at 10% solids loading. This study presents a strategy for valorizing corncob using it to produce xylooligosaccharides and glucose, which should pave the way for valorizing other agriculture wastes.

Comparison of selective acidolysis of xylan and enzymatic hydrolysability of cellulose in various lignocellulosic materials by a novel xylonic acid catalysis method.

An economically-prudent pretreatment is a crucial first step towards realization of the industrial lignocellulosic biorefinery. The aim of this study was to utilize lignocellulosic biomass to co-produce xylo-oligosaccharides (XOS) and glucose starting from a novel self-providing xylonic acid (XA) acidolysis method. Based on the optimization results of main acidolysis pretreatment parameters by uniform design experiments, we found that among various lignocellulosic materials, the highest yield of XOS from xylan was 54.16% with corncob, followed by 39.19% with wheat straw, 29.01% with corn straw and 30.23% with poplar sawdust. By effective degradation and removal of xylan constituents with XA acidolysis, enzymatic hydrolysabilities of inert cellulose constituents of corn cob, corn straw, wheat straw and poplar sawdust were achieved to 100%, 72.94%, 75.35% and 38.97%. Comparative mass balance diagrams of xylan and cellulose reveal that XA acidolysis pretreatment is environmental-friendly and effective for three agricultural residues, apart from woody poplar.

Investigation on decolorization kinetics and thermodynamics of lignocellulosic xylooligosaccharides by highly selective adsorption with Amberlite XAD-16N.

Xylooligosaccharides (XOS) are booming in food, pharmacy and feed industries that they have attracted great interest in the high-value utilization of lignocellulose. Selective acidolysis dominates the commercial production of XOS except for intractable color contaminations derivate from ligoncellulosic degradation. Based on a detailed kinetics and thermodynamics investigation, Amberlite XAD-16N was designated as preferred decolorant because of its high adsorption-selectivity for XOS and the colored contaminants. The adsorption of the main compositions in lignocellulosic acidolysis solution was well described by Langmuir models, the kinetics were clearly fitted by Pseudo-second-order model, showing that the adsorption was controlled by electron sharing/transfer between the resin cross-linking groups and colorant. The adsorption mechanism was also verified by the adsorption-simulation of three detected typical colorants. The thermodynamics clearly indicated a spontaneous endothermic reaction. This study provides an important approach for industrial technology development to not only xylooligosaccharides production and lignocellulosic acidolysis, but also Amberlite XAD-16N adsorbent.

One-step continuous/semi-continuous whole-cell catalysis production of glycolic acid by a combining bioprocess with in-situ cell recycling and electrodialysis.

Bioprocess for successive bio-production of glycolic acid (GA) from ethylene glycol (EG) using Gluconobacter oxydans is hindered by strong end-product inhibitory effect. Based on the model of compressed oxygen supplied-sealed stirred tank reactor (COS-SSTR), we developed a new system by attaching an ultrafiltration instrument and electrodialysis cell to in-situ separate GA, including conductivity meter to control automatic EG feeding. The combined bioprocess was therefore set up as compressed oxygen supplied cell catalysis-ultrafiltration-electrodialysis (COS-CUE). In comparison with the conventional resin and electrodialysis separation process, this device simplified the whole bioprocess. We realized the potential of combined bioprocess for producing GA without EG through continuous/semi-continuous 'one-step' process. Finally, 288.4 g GA was obtained at the yield of 96.5% and average productivity of 4.0 g/L/h in 72 h, with an increment of 148.8% and 20.9% in production compared with batch and cell-recycling fermentation.

Efficient Preparation of Xylonic Acid from Xylonate Fermentation Broth by Bipolar Membrane Electrodialysis.

Preparation of xylonic acid from xylonate fermentation broth was studied in a four-chamber bipolar membrane electrodialysis (BMED) setup. The effects of metal-ion size, current density, and xylonate concentration on BMED were evaluated principally with respect to acid yield and partially with respect to efficiency and energy consumption. Sodium xylonate was more successful than potassium xylonate because of its smaller size and easier membrane penetrability for BMDE. Efficient electrodialysis was achieved using 50 mA/cm2 current density for 14 min; thus, we obtained 92% xylonic acid from 100 g/L sodium xylonate fermentation broth. In conclusion, BMED can be used for producing xylonic acid from fermentation broth. Moreover, this study highlights ways of improving the efficiency of BMED.

Integrated process for scalable bioproduction of glycolic acid from cell catalysis of ethylene glycol.

Glycolic acid (GA) is presently booming as a versatile raw material in the fields of high-grade cosmetics, polymer degradable materials, and drug production. The biocatalysis of ethylene glycol (EG) to GA is promising, with environmentally friendly benefits, while the effective and straight bioproduction of GA qualified for polymer synthesis purity is a challenge. In this study, we combine whole cell catalysis step and acidification-purification step. A compressed oxygen supply in the sealed aerated stirred tank reaction (COS-SSTR) and a weak basic anion-exchange resins were integrated to develop an efficient process of GA bioproduction from EG. Finally, 110.5 g/L of GA was obtained at the yield of 94.4% and the volume productivity of 2.3 g/L/h in 48 h that presently is the greatest level for GA bioproduction. After 335 resins treatment of 5.0 L catalyzed broth containing 497.2 g EG, we obtained 575.4 g GA at the recovery rate of 98.9%.

Efficient coproduction of gluconic acid and xylonic acid from lignocellulosic hydrolysate by Zn(II)-selective inhibition on whole-cell catalysis by Gluconobacter oxydans.

With Zn(II)-selective inhibition on the whole-cell catalysis of Gluconobacter oxydans NL71, gluconic acid and xylonic acid were coproduced efficiently from the hydrolysate of corn stover. Further metabolism of gluconic acid to the by-product 2-ketogluconic acid was prevented by addition of 10g/L ZnCl2. Remarkably, yields of 93.91% of gluconic acid and 93.36% of xylonic acid were obtained with the supplement of ZnCl2 in the synthetic medium, without by-product production. After optimization of the concentrations of ZnCl2 and inocula of the strain, maximum amounts of gluconic acid and xylonic acid were coproduced at titers of 63.01g/L and 33.81g/L, with an overall utilization of 100% of the sugars in the enzymatic hydrolysate of corn stover. The results showed execution of our objective to prove this novel bioconversion method for simultaneously producing gluconic acid and xylonic acid, which would benefit subsequent studies on the comprehensive utilization of lignocellulosic materials.