Degradation Of Monosaccharides Research Articles

A reaction–diffusion coupled kinetic model for hydrothermal acid pretreatment of wheat straw

Hydrothermal acid pretreatment is a promising method to overcome the recalcitrance of lignocellulosic biomass for subsequent efficient enzymatic hydrolysis and biofuel production. However, little is known about heterogeneous catalysis reactions involving the proton diffusion in the pore of lignocellulosic biomass coupled with the hydrolysis of hemicellulose and cellulose catalyzed by proton. In this study, a reaction–diffusion coupled kinetic model for hydrothermal acid pretreatment of wheat straw was developed based on the visualization of particle geometry and pore features. The increase rate of average proton concentration in the pores is higher at a higher temperature or a smaller particle size. A mathematical model was successfully developed to describe the time courses of average proton concentration dictated by initial acid concentration and an unsteady diffusion fitting parameter. The kinetic parameters of each reaction step for hydrothermal acid pretreatment of wheat straw were obtained by fitting experimental data. The activation energies for the hydrolysis of slow-hydrolyzing cellulose, fast-hydrolyzing cellulose, and hemicellulose were determined of 937.8 kJ·mol−1, 90.7 kJ·mol−1, and 39.8 kJ·mol−1, respectively, indicating the temperature dependence of slow-hydrolyzing cellulose with a high crystalline index is strongest. The prediction accuracy of this model can be further improved at higher stirring speeds and initial acid concentrations. Additionally, the model demonstrates high prediction accuracy across three different particle sizes. Generally, this model can gratifyingly correlate data of formation and degradation of monosaccharides and furfural in the hydrothermal acid pretreatment of wheat straw with fair accuracy.

Influence of Hydrothermal Treatment of Brewer's Spent Grain on the Concentration and Molecular Weight Distribution of 1,3-1,4-β-D-Glucan and Arabinoxylan.

Brewer's spent grain (BSG) is the most abundant residual in the brewing process. Non-starch polysaccharides such as 1,3-1,4-β-D-glucan (β-glucan) and arabinoxylan (AX) with proven beneficial effects on human health remain in this by-product in high amounts. Incorporating the valuable dietary fiber into the food industry could contribute to a healthy diet. However, a major challenge is extracting these dietary fibers (i.e., β-glucan and AX) from the solid residue. In this study, hydrothermal treatment (HT) was applied to dissolve the remaining water-insoluble carbohydrates from BSG with the aim to extract high amounts of β-glucan and AX. Particular focus was placed on the molecular weight (MW) range above 50 kDa and 20 kDa, respectively, as these are considered to have health-promoting effects. Different treatment temperatures, reaction times, and internal reactor pressures were tested to determine the best process settings to achieve high yields of β-glucan and AX and to examine the influence on their molecular weight distribution (MWD). Overall, 85.1% β-glucan and 77.3% AX were extracted corresponding to 6.3 g per kg BSG at 160 °C and 178.3 g kg-1 at 170 °C, respectively. However, less than 20% of both fiber substances were in the desirable MW range above 50 kDa and 20 kDa, respectively. When lower temperatures of 140 and 150 °C were applied, yields of only 3.0 g kg-1 β-glucan and 128.8 g kg-1 AX were obtained, whereby the proportion of desirable fiber fractions increased up to 45%. Further investigations focused on the heat-induced degradation of monosaccharides and the formation of undesirable by-products (i.e., HMF and furfural) that might pose a health risk.

Cultivar differences in the hormonal crosstalk regulating apple fruit development and ripening: Relationship with flavour components and postharvest susceptibility to Penicillium expansum

The hormonal interplay during the on-tree development and ripening of three apple cultivars with known differences in their postharvest ripening patterns was studied, at the biochemical and targeted gene expression level, along with characterizing the changes in main sugars, acids, phenylpropanoids and volatile organic compounds (VOCs). Our findings suggest that in ‘Royal Gala’ and ‘Opal®’ apples, a peak in indole 3-acetic acid (IAA) seems necessary to activate ethylene metabolism, being its intensity proportional to the ethylene production. The interplay between IAA and ethylene appears to be mediated by MdARF5, responsible for activating the expression of MdACS3 and triggering ethylene metabolism. On the other hand, the lack of ethylene production observed in ‘Granny Smith’ apples was likely related to the absence of an IAA peak and possibly caused by the over activation of IAA conjugation mechanisms leading to a greater accumulation of IAA inactive conjugates such as indole-3-acetyl-aspartate (IAAsp). Abscisic acid (ABA) accumulation was only observed in cultivars with the ability to accumulate sucrose and produce ethylene, suggesting a possible crosstalk among those hormones and sucrose in orchestrating apple on-tree ripening. While differences in hormone levels among cultivars led to noticeable differences in some specific VOCs, no evident associations were found between hormone changes and the accumulation or degradation of monosaccharides, organic acids or phenolic compounds during fruit development and ripening. Likewise, no clear relationship was found between the fruit susceptibility to blue mould and hormonal levels yet certain specific biochemical compounds (i.e., procyanidins and sucrose) could be acting as a source of resistance or susceptibility, respectively, to blue mould development. Overall, understanding the cultivar specific hormonal regulation of apple on-tree ripening provides valuable insights to optimize fruit quality at the time of harvest as well as to develop strategies for improved postharvest management.

Subcritical Water Process for Reducing Sugar Production from Biomass: Optimization and Kinetics

The competitive reactions of lignocellulose hydrolysis and monosaccharide degradation in the subcritical water (SCW) hydrolysis of coconut husk were investigated to optimize the reducing sugar yield. Optimization analysis was performed by response surface methodology (RSM) and kinetics studies. Parameters of process optimization were varied at 130-170 °C for 15-45 min. The reducing sugars were measured using the Dinitro salicylic acid method. The sugar yield increased when the temperature increased from 130 °C to 170 °C. The highest reduction sugar yield of 4.946 g/L was obtained at 183.6 °C for 4.8 min and 23.4 liquid/solid ratio (LSR). Kinetics studies were carried out at temperature variations of 150, 170, and 190 °C and pressures of 60, 80, and 100 bar for 5 to 60 min. The yield of reducing sugar decreased with increasing temperature. The kinetic model 2B is the best method to explain the competitive reaction kinetics of coconut husk hydrolysis. This research is an innovation to increase the reducing sugar to make the process more commercially viable. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Impacts of Cold Plasma Technology on Sensory, Nutritional and Safety Quality of Food: A Review.

As an emerging non-thermal food processing technology, cold plasma (CP) technology has been widely applied in food preservation due to its high efficiency, greenness and lack of chemical residues. Recent studies have indicated that CP technology also has an impressing effect on improving food quality. This review summarized the impact of CP on the functional composition and quality characteristics of various food products. CP technology can prevent the growth of spoilage microorganisms while maintaining the physical and chemical properties of the food. It can maintain the color, flavor and texture of food. CP can cause changes in protein structure and function, lipid oxidation, vitamin and monosaccharide degradation, starch modification and the retention of phenolic substances. Additionally, it also degrades allergens and toxins in food. In this review, the effects of CP on organoleptic properties, nutrient content, safety performance for food and the factors that cause these changes were concluded. This review also highlights the current application limitations and future development directions of CP technology in the food industry. This review enables us to more comprehensively understand the impacts of CP technology on food quality and promotes the healthy application of CP technology in the food industry.

One flow through hydrolysis and hydrogenation of semi-industrial xylan from birch (betula pendula) in a continuous reactor—Kinetics and modelling

Xylan obtained from birch (betula pendula) by a novel semi-industrial scale aqueous based method was used for studying the hydrolysis and consecutive hydrolysis-hydrogenation processes in continuous reactors. Dowex 50WX2-100 was chosen as the hydrolysis catalyst based on the results of catalyst screening performed previously in batch reactor. It was also observed to perform well in continuous reactor converting xylan to xylose in high yield under the studied reaction conditions. The influence of several reaction parameters were investigated for optimization. Similar experimental conditions used in the hydrolysis were then applied for studying one flow through hydrolysis and hydrogenation of the semi-industrial xylan. A consecutive catalyst bed consisting of ruthenium on carbon was introduced into the continuous reactor downstream from the hydrolysis bed to hydrogenate monosaccharides to xylitol. Hydrogen was co-fed into the reactor with the xylan solution. Reaction parameters, including temperature, residence time and hydrogen pressure, were varied to maximize the xylitol yield. The developed continuous process was demonstrated to be highly selective and efficient for the valorization of the semi-industrial xylan by yielding over 90% xylitol under optimal experimental conditions. It was noticed, that co-feeding hydrogenation decreased the degradation of monosaccharides during hydrolysis, thus improving the selectivity towards the target product and enabling remarkable process intensification. Moreover, mathematical modelling was performed for the hydrolysis and one flow through hydrolysis and hydrogenation processes. The models take into account the consecutive reaction pathways and the influence of the experimental conditions. Good fits of the model to the experimental data were obtained. The conversion of this novel, well characterized wood-based xylan to produce xylose or xylitol in continuous reactors has not been studied previously. The current work contributes significantly to understanding the processing of real feedstock in one flow through employing consecutive reactions and provides necessary data for process intensification.

Degradation of Monosaccharides, Disaccharides, and Fructans in the Stomach of Horses Adapted to a Prebiotic Dose of Fructooligosaccharides and Inulin

For a period of 20 days, 12 horses either received a prebiotic supplementation with fructooligosaccharides and inulin via Jerusalem artichoke meal (JAM) or corncob meal without grains (CMG) as placebo. The horses were euthanized 1 hour postprandial, gastric digesta was sampled from pars nonglandularis (PNG) and pars glandularis (PG), and concentrations of starch, mono- and disaccharides, fructans, d- and l-lactic acid, and short chain fatty acids were analyzed. Concentrations of starch and simple sugars were widely the same in JAM supplemented and not supplemented meals. However, fructans were less than half as much without supplementation as with supplementation of JAM. Glucose, fructose, sucrose, and fructans disappeared to a larger extent with prebiotic supplementation than without (106.6% vs. 86.7% glucose, 73.1% vs. 66.8% fructose, 91.5% vs. 14.7% sucrose, and 68.3% vs. 35.4% fructans remained in PNG; 81.9% vs. 38.3% glucose, 52.2% vs. 53.4% fructose, 47.1% vs. 0% sucrose, and 48.5% vs. 31.7% fructans remained in PG with CMG vs. JAM feeding). Disappearance of simple sugars and fructans was primarily associated with appearance of n-butyric acid (r = -0.21 – r = -0.33).

Subcritical water hydrolysis for sugar recovery from bakery leftovers: kinetic and thermodynamic analysis

This study aims to perform kinetic and thermodynamic analysis of subcritical water hydrolysis (SWH) of bakery leftovers. Hydrolysis kinetics of leftover croissants (LC) and leftover doughnuts (LD) into monosaccharides and by-product (hydroxymethylfurfural, HMF), via subcritical water hydrolysis, were studied in temperature range of 100 to 240°C for 6 to 30 minutes and solid loading of 10% (w/v). The monosaccharides yield increased from 100 to 200°C, but it decreased when the temperature further increased from 220–240°C due to degradation of monosaccharides into its by-product (HMF). The activation energy (Ea) monosaccharides degradation was higher than its formation: 104.87 and 88.55 kJ/mol (LC) and 104.69 and 75.72 kJ/mol (LD). The positive values of ΔG# signified that the SWH for sugar recovery from LC and LD is an endergonic reaction.

Monosaccharide Degradation Analysis by Functional Density Theory at Level B3lyp/6-311 G (D, P)

Monosaccharide Degradation Analysis by Functional Density Theory at Level B3lyp/6-311 G (D, P)

RETRACTED: Enhancing delignification and subsequent enzymatic hydrolysis of corn stover by magnesium oxide-ethanol pretreatment

Corn stover pretreatment by MgO-ethanol was investigated to improve sugar recovery by reducing sugar degradation and enhance enzymatic hydrolysis by improving delignification and reducing inhibitor formation. Results showed MgO as an effective additive and Lewis base, functioned to neutralize the acids released from hemicellulose during pretreatment, reduce monosaccharide degradation and inhibitor formation, and enhance delignification. The optimal pretreatment conditions were 50% ethanol, 0.08 mol/L MgO, and 10% solid loading at 190 °C for 40 min. Under optimal conditions, 98% glucose and 92% xylose were recovered with 89% glucan and 71% xylan recoveries and 60% lignin removal. A total sugar yield of 63% on a received biomass basis after enzymatic hydrolysis was obtained with 78% glucose and 41% xylose yields. The resulting biomass slurry was near-neutral and free of furfural and 5-hydroxymethylfurfural. Thus, the process to isolate high-purity value-added lignin and recover sugars from biomass liquor can be largely simplified.

Using Polyurethane Foam-Based Passive Air Sampling Technique to Monitor Monosaccharides at a Regional Scale

Monosaccharides are important tracers of pollution aerosol from biomass burning. Air sampling of monosaccharides is often conducted using active samplers. However, applicability of sampling monosaccharides using polyurethane foam passive air samplers (PUF-PASs) has not been investigated, since passive air samplers are often applied to monitor semivolatile organic contaminants in large scale and remote area. Our study successfully collected atmospheric monosaccharides using PUF-PASs, providing a valuable tool for monosaccharides sampling. PUF-PAS sampling rates for individual monosaccharides were calibrated using an active sampler for 92 days, and were 1.1, 1.5, and 1.1 m3/d for levoglucosan, mannosan, and galactosan, respectively. Degradation of monosaccharides in PUF-PAS was demonstrated to be negligible by spike test of 13C-labeled levoglucosan. Furthermore, passive sampling was carried out at 11 sites in the Pearl River Delta of Southern China from January to April and July to September of 2015. Monosaccharide concentrations derived from PUF-PASs were comparable with the reported data obtained by active sampling, demonstrating that the PUF-PAS approach is valid for monosaccharides monitoring. On the basis of our approach, we found that there is a clear correlation between the monosaccharide concentrations and the MODIS fire activities during January-April.

Quantification of food polysaccharide mixtures by 1H NMR

Polysaccharides are food ingredients that critically determine rheological properties and shelf life. A qualitative and quantitative assessment on food-specific polysaccharide mixtures by 1H NMR is presented. The method is based on the identification of intact polysaccharides, combined with a quantitative analysis of their monosaccharide constituents. Identification of the polysaccharides is achieved by 1H NMR line shape fitting with pure compound spectra. The monomeric composition was determined using the Saeman hydrolysis procedure, followed by direct monosaccharide quantification by 1H NMR. In the quantification, both the monosaccharide degradation during hydrolysis, as well as a correction for the non-instantaneous polysaccharide dissolution were taken into account. These factors were particularly important for the quantification of pectins. The method showed overall good repeatability (RSDr=4.1±0.9%) and within-laboratory reproducibility (RSDR=6.1±1.4%) for various food polysaccharides. Polysaccharide mixtures were quantitatively resolved by a non-negative least squares estimation, using identified polysaccharides and their molar monosaccharide stoichiometry as prior knowledge. The accuracy and precision of the presented method make it applicable to a wide range of food polysaccharide mixtures with complex and overlapping 1H NMR spectra.

Improvement of Acid Hydrolysis Procedures for the Composition Analysis of Herbaceous Biomass

The accurate characterization of biomass is critical for development of bioenergy feedstocks and their utilization. Most analytical approaches involve acid hydrolysis of the polysaccharides in biomass, leaving most of the lignin as insoluble residue. A limitation of this approach is that the same conditions used to hydrolyze polysaccharides also degrade the liberated monosaccharides. The NREL-compiled procedures account for this effect with “Sugar Recovery Standards”, in which a solution of the expected monosaccharides is prepared and subjected to the dilute-hydrolysis portion of the procedure; however, this tends to overestimate monosaccharide degradation and introduce bias between polysaccharides of different lability. The following recommended method modifications are intended to reduce these errors: (1) quantification of immediate degradation products of monosaccharides and their stoichiometric addition to the monosaccharide yield; (2) the adjustment of this combined yield with sugar recovery standards; and (3) preautoclave analysis of hydrolyzates to improve the estimation of monosaccharide concentration profiles for adjustment calculations.

Comprehensive evaluation of the liquid fraction during the hydrothermal treatment of rapeseed straw.

BackgroundThe requirement for efficient and green conversion technologies has prompted hydrothermal processing as a promising treatment option for sustainable biorefinery industry. The treatment has been applied to process plenty of lignocellulose materials, yielding abundant high value-degraded products, especially the products in the liquid fraction. Therefore, it is essential to systematically evaluate the degraded products in aqueous fraction by comprehensive analysis and structural characterization during the treatment.ResultsRapeseed straw was hydrothermally treated at temperature ranging from 145 to 205 °C for various retention time (15, 30, 60 and 120 min), and the degraded polysaccharides and lignin products in aqueous phase were systematically evaluated by comprehensive analysis and structural characterization. Results showed that with an increase of severity, the polymers were gradually depolymerized resulting in a decrease of the molecular weight from 8430 (log R0 3.26) to 2130 g/mol (log R0 5.08), an increase of oligosaccharides from 19.44 (log R0 2.88) to 99.94 g/kg (log R0 4.32) and an increase of monosaccharides from 0.91 (log R0 2.88) to 30.43 g/kg (log R0 4.37). With the increase of monosaccharide degradation components (8.26 to 125.68 g/kg), the saccharides gradually decreased after its maximum value. The maximum yield of oligosaccharides (99.94 g/kg) accompanying a relatively low level of monosaccharides (17.77 g/kg) was obtained at a high temperature (190 °C) for a short reaction time (15 min). The degraded polysaccharides had a linear backbone of (1 → 4)-linked β-d-xylopyranosyl xylan decorated with branches based on 2D NMR spectra analysis. Lignin was strongly condensed with a decrease of S/G ratio as the severity increased. The yields of the degraded constitutions have a incomplete linear correlation with the treatment severity.ConclusionsThe liquid fractions obtained from hydrothermal treatment were subjected to comprehensive analysis and structural characterization. Results indicated that hydrothermal treatment had a significant influence on the composition and structure of the polysaccharides and lignin in the aqueous phase. The treatment could be adopted to obtain XOS-rich fraction with limited formation of by-products. In addition, the result was expected to further reveal the mechanisms of hydrothermal treatment on rapeseed straw and to facilitate the value-added applications of agricultural residues in the biorefinery industry.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0552-8) contains supplementary material, which is available to authorized users.

Effect of Microwave-Assisted Pretreatment Conditions on Hemicellulose Conversion and Enzymatic Hydrolysis of Norway Spruce

The present study investigated the ability of pressurized microwave pretreatment to convert softwood lignocellulose to fermentable monosaccharides. Norway spruce lignocellulose was subjected to microwave pretreatment (600 and 1200 W) under high pressure at different temperatures. Microwave pretreatment at mild acid concentrations (0.05–0.1 % H2SO4), temperatures of 170 and 200 °C, and a very short incubation time (5 min) released 84–100 % of hemicellulosic monosaccharides (mannose, galactose, and xylose). In addition, minimal amounts of degradation products (5-(hydroxymethyl)-2-furaldehyde, levulinic acid) were formed. The highest yield of fermentable sugars was 75 %, after both the pressurized microwave pretreatment with conditions 0.05 % H2SO4/600 W/200 °C/5 min and enzymatic hydrolysis with 20 FPU Celluclast 1.5 L, 400 nkat of Novozyme 188, and polyethyleneglycol (PEG) 4000 (0.3 g/g of pretreated material). Results showed that already 0.05 % H2SO4 used in microwave pretreatment could effectively liberate hemicellulose monosaccharides without serious monosaccharide degradation and form a basis for enzymatic hydrolysis.

Subcritical water hydrolysis of rice straw for reducing sugar production with focus on degradation by-products and kinetic analysis

The competitive reactions of reducing sugar production and degradation in the subcritical water hydrolysis of rice straw were investigated to optimise reducing sugar yield. The optimised conditions (280°C, 20MPa, rice straw concentration of 5wt.% and agitation speed of 200rpm) resulted in a reducing sugar yield of 0.346g/g rice straw because of the enhanced reducing sugar production and decreased sugar degradation. The sugar yield increased when the temperature increased from 250°C to 280°C, but it decreased when the temperature further increased to 300°C because of the degradation of monosaccharides (e.g. glucose and xylose) into by-products (e.g. 2-methyltetrahydrofuran and acetic acid). A first-order reaction model was developed to elucidate the competitive reaction kinetics of sugar production and degradation at various temperatures. The highest reducing sugar yield based on the model was achieved at 280°C with the highest production and lowest degradation rates.

NOTE: Hydrolysis Temperature Affects the Phloroglucinol Assay for Arabinoxylan Quantification in Wheat Flour

ABSTRACTPhloroglucinol has a long history of use for the determination of pentose monomer content. Its application to cereal chemistry has been developed over several decades; however, no studies on the potential influence of hydrolysis temperature have yet been reported. We demonstrate the effect of hydrolysis temperature on the phloroglucinol assay for the measurement of pentosans in both refined and wholemeal wheat flours. In refined flour, monosaccharide degradation and interfering reactions from starch appear to effectively reduce the absorbance difference used to determine pentosan content. The presence of glucose in the reaction is also shown to provide stability to the reaction products. The potential impact of these factors on the determination of pentosan content needs to be considered when interpreting the results obtained using phloroglucinol‐based methods.

Existence of the Sugar–Bisulfite Adducts and Its Inhibiting Effect on Degradation of Monosaccharide in Acid System

Degradation of fermentable monosaccharides is one of the primary concerns for acid prehydrolysis of lignocellulosic biomass. Recently, in our research on degradation of pure monosaccharides in aqueous SO₂ solution by gas chromatography (GC) analysis, we found that detected yield was not actual yield of each monosaccharide due to the existence of sugar-bisulfite adducts, and a new method was developed by ourselves which led to accurate detection of recovery yield of each monosaccharide in aqueous SO₂ solution by GC analysis. By the use of this method, degradation of each monosaccharide in aqueous SO₂ was investigated and results showed that sugar-bisulfite adducts have different inhibiting effect on degradation of each monosaccharide in aqueous SO₂ because of their different stability. In addition, NMR testing also demonstrated possible existence of reaction between conjugated based HSO₃(-) and aldehyde group of sugars in acid system.

Monomeric carbohydrates production from olive tree pruning biomass: Modeling of dilute acid hydrolysis

Statistical modeling and optimization of dilute sulfuric acid hydrolysis of olive tree pruning biomass has been performed using response surface methodology. Central composite rotatable design was applied to assess the effect of acid concentration, reaction time and temperature on efficiency and selectivity of hemicellulosic monomeric carbohydrates to d-xylose. Second-order polynomial model was fitted to experimental data to find the optimum reaction conditions by multiple regression analysis. The monomeric d-xylose recovery 85% (as predicted by the model) was achieved under optimized hydrolysis conditions (1.27% acid concentration, 96.5°C and 138 min), confirming the high validity of the developed model. The content of d-glucose (8.3%) and monosaccharide degradation products (0.1% furfural and 0.04% 5-hydroxymethylfurfural) provided a high quality subtract, ready for subsequent biochemical conversion to value-added products.

Pretreatment and Fractionation of Wheat Straw Using Various Ionic Liquids

Pretreatment of lignocellulosic biomass with ionic liquids (ILs) is a promising and challenging process for an alternative method of biomass processing. The present work emphasizes the examination of wheat straw pretreatment using ILs, namely, 1-butyl-3-methylimidazolium hydrogensulfate ([bmim][HSO4]), 1-butyl-3-methylimidazolium thiocyanate ([bmim][SCN]), and 1-butyl-3-methylimidazolium dicyanamide ([bmim][N(CN)2]). Only [bmim][HSO4] was found to achieve a macroscopic complete dissolution of wheat straw during pretreatment. The fractionation process demonstrated to be dependent on the IL used. Using [bmim][SCN], a high-purity lignin-rich material was obtained. In contrast, [bmim][N(CN)2] was a good solvent to produce high-purity carbohydrate-rich fractions. When [bmim][HSO4] was used, a different behavior was observed, exhibiting similarities to an acid hydrolysis pretreatment, and no hemicellulose-rich material was recovered during fractionation. A capillary electrophoresis (CE) technique allowed for a better understanding of this phenomenon. Hydrolysis of carbohydrates was confirmed, although an extended degradation of monosaccharides to furfural and hydroxymethylfurfural (HMF) was observed.