Fructose Yield Research Articles

Facile Synthesis of Silanol Group Rich Sn‐Beta for Highly Efficient Isomerization of Glucose to Fructose

AbstractThe isomerization of glucose to fructose is an important process in the conversion of biomass into valuable fuels and chemicals. Development of efficient catalyst for this reaction has attracted much attention. In this study, Sn‐Beta zeolites with rich silanols were synthesized for glucose isomerization by solid‐state ion‐exchange method, where Si‐Beta zeolites with different amounts of silanols were applied as the precursors. It is confirmed that open Sn sites show much higher catalytic performance than closed Sn sites for glucose isomerization (about 2.1 times). The silanol amount in Si‐Beta not only affects the formation of framework Sn sites in Sn‐Beta but also influences the isomerization reaction. More silanols in the catalyst can promote the 1,2‐H shift in isomerization and reduce the side reactions of formation of mannose and C3 products. Over 3Sn‐Beta‐3h with rich silanols, 64 % of fructose yield was obtained. Furthermore, the prepared Sn‐Beta catalyst is stable and recyclable. High fructose yield and facile synthesis method of Sn‐Beta reported in this work will contribute to the development of biomass and sugar industry.

Ball billing induced highly dispersed nano-MgO in biochar for glucose isomerization at low temperatures

The isomerization of glucose is a crucial step for biomass valorization to downstream chemicals. Herein, highly dispersed MgO doped biochar (BM-0.5@450) was prepared from rice straw via a solvent-free ball milling pretreatment and pyrolysis under nitrogen conditions. The nano-MgO doped biochar demonstrated enhanced conversion of glucose in water at low temperatures. A 31 % yield of fructose was obtained from glucose over BM-0.5@450 at 50 °C with 80.0 % selectivity. At 60 °C for 140 min, BM-0.5@450 achieved a 32.5 % yield of fructose. Compared to catalyst synthesized from conventional impregnation method (IM@450), the BM-0.5@450 catalyst shows much higher fructose yields (32.5 % vs 25.9 %), which can be attributed to smaller crystallite size of MgO (11.32 nm vs 19.58 nm) and homogenous distribution. The mechanism study shows that the activated MgOH+·OH− group by water facilitated the deprotonation process leading to the formation of key intermediate enediol.

Glucose Isomerization to Fructose Catalyzed by MgZr Mixed Oxides in Aqueous Solution

The catalytic isomerization of glucose to fructose plays a pivotal role in the application of biomass as a feedstock for chemicals. Herein, we propose a facile solid-state-grinding strategy to construct ZrO2/MgO mixed oxides, which offered an excellent fructose yield of over 34.55% and a high selectivity of 80.52% (80 °C, 2 h). The co-mingling of amphiphilic ZrO2 with MgO improved the unfavorable moderate/strongly basic site distribution on MgO, which can prohibit the side reactions during the reaction and enhance the fructose selectivity. Based on the catalyst characterizations, MgO was deposited on the ZrO2 surface by plugging the pores, and the addition of ZrO2 lessened the quantity of strongly basic sites of MgO. Additionally, the presence of ZrO2 largely enhanced the catalyst stability in comparison with pure MgO by recycling experiments.

Efficient enzymatic saccharification of agricultural wastes for the production of bioethanol, D-allulose and lactic acid

The demand for renewable resources to replace fossil fuels has increased. Fruit and agricultural wastes can be fermented to yield biofuels and biochemicals. However, the high cost of the feedstock and limitations of the catalytic process hinder the application of such wastes. Therefore, we aimed to develop an efficient enzymatic saccharification process, without pretreatment, for fruit and agricultural wastes. The conversion rate of the mixed agricultural wastes (MAW) to fermentable sugars was approximately 91 % after 24 h. The ethanol yield increased by 4.5 % after limonene removal. The D-allulose yield in the hydrolysate was 4.6 mg/mL at 4 °C and 3.3 mg/mL at 50 °C, whereas the fructose yield in the sugar medium was 13.2 mg/mL at 4°C, demonstrating a high conversion yield of 73.2 %. Lactic acid was produced at a conversion rate of approximately 67.4 %. Therefore, this study presents a novel approach of the biosynthesis of functional sugars and chemicals from waste biomass, introducing a cost-effective enzymatic saccharification process that bypasses pretreatment, thereby enabling the production of biofuels, biochemicals, and functional sugars and opening up a promising economic opportunity in the field.

Efficient isomerization of glucose to fructose over Al-loaded functional lignin biopolymer

Al-loaded functional lignin biopolymer (Alx-Lbp) catalysts were synthesized using H2O2 oxidized alkali lignin and aluminum acetate via mechanochemical modification without post-calcination treatment. The Alx-Lbp catalysts exhibited higher hydrophilicity and lower surface energy than lignin-free Al-activated carbon catalysts. Unprecedented high yields (58.5 %) of fructose from glucose were obtained over Al1-Lbp in ethanol at 140 ºC in 30 min reaction time. Al1-Lbp catalyst had Lewis acid sites (47.2 μmol/g), Brønsted acid sites (6.9 μmol/g) and a surface energy of 39.1 mN/m that facilitated glucopyranose ring-opening and gave a glucose isomerization activation energy of 65.2 kJ/mol, which was lower than values reported for Lewis acid-catalyzed systems. Active sites of Al2O3 and Al(OH)3 formed on the Al1-Lbp catalyst in ethanol promoted the formation of an enediol intermediate as confirmed with isotope experiments to achieve efficient isomerization of glucose to fructose. The Al1-Lbp catalyst demonstrated recyclability and maintained its initial activity for eight times reuse.

Highly Selective Isomerization of Glucose to Fructose through a Biphasic and Recyclable Mimetic Enzyme Catalyst

AbstractDeveloping a biphasic catalyst is of great significance for improving reaction efficiency and its industrial application. Herein a novel biphasic catalyst containing three functional groups of chlorophenol, amino and carboxyl was synthesized and used as mimic glucose isomerase to catalyze the isomerization. The mimic enzyme exhibited excellent catalytic performance for isomerization of glucose to fructose under mild conditions. Temperature and pH of solution showed significant influence on the conversion of glucose and the selectivity of fructose. The yield and selectivity of fructose reached 32.4 % and 91.0 % after reacting 2 h, respectively, at pH 9.5 and 90 °C. The solubility of the catalyst exhibited dual sensitivity to both pH and temperature. The catalyst was in a soluble state during the reaction process and could be precipitated by reducing the pH and temperature of the reaction system. The catalyst could be reused and still maintained good catalytic activity after five consecutive cycles.

Environmental impact of 5-hydroxymethylfurfural production from cellulosic sugars using biochar-based acid catalyst

In this study, HMF was successfully synthesized from a range of cellulosic sugars, utilizing sustainable acidic biochar derived from cassava rhizome (CR). Various acid precursors such as sulfuric acid (H2SO4),p-toluenesulfonic acid (TsOH), and ferric chloride (FeCl3) were chosen. Acids grafted biochar were carried out through a facile hydrothermal method. HMF production was performed at 175 °C for 0.5 h using 10 % of the acidic biochar catalyst in water to isopropanol (i-PrOH) mixture ratio of 1:4. The maximum HMF yields of fructose (53.29 wt%), glucose (2.94 wt%), and cellulose (0.38 wt%) could be achieved over 600-H2SO4, 700-FeCl3, and 400-H2SO4catalysts, respectively. Moreover, the recyclability of the acidic biochar catalysts could distinguish more than five times without significant loss of activity. Remarkably, the life cycle assessment (LCA) and cost analysis of the HMF production process indicated that the future sustainable industrial production of HMF could be realizedinvolving the 600-TsOH catalyst.

Highly efficient isomerization of glucose to fructose over Sn-doped silica nanotube

Isomerization of glucose to fructose is a fundamental and key intermediate process commonly included in the production of valuable chemicals from carbohydrates in biorefinery. Enhancement of fructose yield is a challenge. In this work, Sn-doped silica nanotube (Sn-SNT) was developed as a highly efficient Lewis acid catalyst for the selective isomerization of glucose to fructose. Over Sn-SNT, 69.1 % fructose yield with 78.5 % selectivity was obtained after reaction at 110 °C for 6 h. The sole presence of a large amount of Lewis acid sites in Sn-SNT without Brønsted acid site is one of the reasons for the high fructose yield and selectivity. Otherwise, high density of Si−OH groups in Sn-SNT can ensure the presence of Si−OH groups near the Sn sites, which is important for the isomerization of glucose to fructose, leading to the high fructose yield and selectivity. Furthermore, the Sn-SNT is recyclable.

Insight into the alkaline earth metal salt promotion for alkali-catalyzed glucose isomerization

An approach to improving the efficiency of alkali-catalyzed glucose isomerization into fructose by adding alkaline earth metal salts was explored. 70.3% fructose yield with 99% fructose selectivity can be achieved in Ca(OH)2–CaCl2 solution at 50 °C for 25 min.

Graphene oxide enabled efficient multi-enzyme immobilization for thermodynamic-driven biomanufacturing of fructose

Thermodynamic-driven biomanufacturing of fructose catalyzed by phosphorylation and dephosphorylation cascade reactions is considered as the future of industrial fructose production due to its high theoretical yield of 100 %. Co-immobilizing all four cascade enzymes involved on solid materials is crucial for its successful industrial application, as it significantly reduces costs through enzyme reusage. Graphene oxide served as a multi-enzyme carrier in the thermodynamic-driven biosystem of fructose and displayed high loading capacities for the four cascade enzymes. The resulting co-immobilized biosystem based on graphene oxide exhibited superior biocatalytic performance than the other support materials. Additionally, it yielded 54.7 % fructose from maltodextrin. Utilizing two additional enzymes to improve the substrate utilization, an 85.2 % fructose yield was achieved, surpassing the current industrial-scale fructose production process employing monosaccharide isomerization. This study sheds light on the potential industrial applications of thermodynamic-driven biomanufacturing systems for fructose production.

Strategies for enhancing catalytic efficiency and stability of MgO-biochar catalysts in glucose isomerization to fructose

Glucose isomerization to fructose is crucial for its application in food industry and biorefinery. Herein, strategies for developing MgO-biochar catalysts to convert glucose to fructose were explored and optimized with an emphasis on the influence of synthesis method on the stability of the catalyst. Despite the favorable activity exhibited by all catalysts, the embedding of MgO on the surface, loading onto porous structures, or incorporating into a carbon framework significantly diminished the catalytic activity and stability of magnesium species. The one-step synthesis approach facilitates the uniform distribution of MgO nanoparticles on the biochar matrix, enhancing their interactions and preventing Mg leaching compared to MgO-biochar prepared through two-step methods. After optimization, fructose yield exceeding 26% and a selectivity of 91% were obtained under mild conditions of 80 ℃ for 2 h in water. In summary, the effective anchoring of MgO on the biochar exhibited dual effects for enhanced catalytic activity and stability.

Incorporation of MgO into nitrogen-doped carbon to regulate adsorption for near-equilibrium isomerization of glucose into fructose in water

Glucose isomerization to fructose is an essential step for biomass valorization, but implementing this reaction via chemocatalysis suffers from low reaction efficiency and inferior catalyst reusability. Herein, MgO was incorporated into nitrogen-doped carbon via pyrolysis of ZIF-8 with MgCl2 to synchronously enhance the catalytic performance and stability. The resultant MgO/NC-700 catalyst gave fructose yields of 42.9 % and 40.8 % at glucose loading of 10 and 20 wt%, respectively, approaching to the upper limit of reaction equilibrium. The average fructose productivity was 0.2267 mmol g−1 h−1, more than 2.29 times higher than the state-of-the-art heterogeneous catalysts. Moreover, the catalyst showed good stability and reusability without complicated regeneration steps. Isotope labelling study by NMR spectra revealed that the reaction is mainly proceeded via proton transfer mechanism. Both static adsorption experiment and DFT calculation indicated that the shift of reaction equilibrium towards fructose is due to the preferential adsorption of glucose.

Facile fabrication of magnesium-enriched porous carbon for highly active and stable isomerization of glucose in water

The endogenous MgO in-situ self-doped porous carbon (MgO@C) was fabricated from reliable magnesium citrate by a facile one-step pyrolysis process. Up to ∼60 wt% active magnesium oxide could be successfully embedded into the carbon skeleton with uniformly distributed MgO nanoparticles. The characterization analyses suggested that MgO@C had a “sand rose” structure with a large surface area, uniform pore-size distribution and small MgO crystal size. The MgO@C showed a high catalytic ability with a maximum fructose yield of 31.2% and selectivity of 86.2% from glucose isomerization in water at 85 °C within 60 min, which was better than that of the pure MgO and MgO supported on porous carbon (MgO/C). Moreover, the activation energy of glucose-fructose over MgO@C was calculated to be 54.20 kJ⋅mol−1, the value was less than that of MgO and MgO/C. The excellent catalytic activity was closely related to the moderate catalyst basicity, which was mainly caused by the smaller crystal size of magnesium oxide due to the confinement effect of porous carbon. More significantly, the as-prepared MgO@C exhibited good tolerability under high substrate concentrations (20 wt%), and could maintain good reusability without a serious decrease in activity during five cycles.

Engineering Cyanobacterial Cell Factories for Photosynthetic Production of Fructose.

Fructose is an important monosaccharide product widely applied in the food, medicine, and chemical industries. Currently, fructose is mainly manufactured with plant biomass-sourced polysaccharides through multiple steps of digestion, conversion, separation, and purification. The development of cyanobacterial metabolic engineering provides an attractive alternative route for the one-step direct production of fructose utilizing carbon dioxide and solar energy. In this work, we developed a paradigm for engineering cyanobacterial chassis cells into efficient cell factories for the photosynthetic production of fructose. In a representative cyanobacterial strain, Synechococcus elongatus PCC 7942, knockout of fructokinase effectively activated the synthesis and secretion of fructose in hypersaline conditions, independent of any heterologous transporters. The native sucrose synthesis pathway was identified as playing a primary role in fructose synthesis. Through combinatory optimizations on the levels of metabolism, physiology, and cultivation, the fructose yield of the Synechococcus cell factories was stepwise improved to 3.9 g/L. Such a paradigm was also adopted to engineer another Synechococcus strain, the marine species Synechococcus sp. PCC 7002, and facilitated an even higher fructose yield of over 6 g/L. Finally, the fructose synthesized and secreted by the cyanobacterial photosynthetic cell factories was successfully extracted and prepared from the culture broth in the form of products with 86% purity through multistep separation-purification operations. This work demonstrated a paradigm for systematically engineering cyanobacteria for photosynthetic production of desired metabolites, and it also confirmed the feasibility and potential of cyanobacterial photosynthetic biomanufacturing as a simple and efficient route for fructose production.

Isomerization of Hemicellulose Aldoses to Ketoses Catalyzed by Basic Anion Resins: Catalyst Screening and Stability Studies

Isomerization of aldoses to ketoses is an essential step in carbohydrate valorization routes in biorefineries to produce a wide variety of bioproducts. In this work, selective isomerization of aldoses into ketoses was investigated using different commercial Brønsted basic anion resins at low temperature conditions. Weak and strong basic resins were tested under different reaction conditions. Amberlite IRA-900 and Amberlyst A-26 (strong resins) and Amberlite IRA-67 and Amberlyst A-21 (weak resins) were tested to assess their catalytic properties. Strong basic resins provided high yields of fructose. IRA-900 was also tested in the isomerization of different sugar monosaccharides conventionally present in lignocellulosic biomass (xylose, arabinose, galactose, glucose and mannose) aiming to explore the performance of this material in hemicellulose-derived sugar mixtures. Very promising performance was observed for IRA-900, yielding fructose selectivity higher than 75% and fructose yield of 27% in the isomerization reaction. Notably, basic anionic resins were not suitable for reuse in different reaction cycles, although the use of organic cosolvents, specifically ethanol, improved the reusability of the tested resins.

Synthesis of Mg–K-biochar bimetallic catalyst and its evaluation of glucose isomerization

Highly efficient isomerization of glucose to fructose is essential for valorizing cellulose fraction of biomass to value-added chemicals. This work provided an innovative method for preparing Mg-biochar and Mg–K-biochar catalysts by impregnating either MgCl2 alone or in combination with different K compounds (Ding et al. in Bioresour Technol 341:125835, 2021, https://doi.org/10.1016/j.biortech.2021.125835 and KHCO3) on cellulose-derived biochar, followed by hydrothermal carbonization and pyrolysis. Single active substance MgO existing in the 10Mg–C could give better catalytic effect on glucose isomerization than the synergy of MgO and KCl crystalline material present in 10Mg–KCl–C. But the catalytic effect of 10Mg–C was decreased when the basic site of MgO was overloaded. Compared to other carbon-based metal catalysts, 10Mg–KHCO3–C with 10 wt% MgCl2 loading had excellent catalytic performance, which gave a higher fructose yield (36.7%) and selectivity (74.54%), and catalyzed excellent glucose conversion (53.99%) at 100 °C in 30 min. Scanning electron microscope–energy dispersive spectrometer and X-Ray diffraction revealed that the distribution of Mg2+ and K+ in 10Mg–KHCO3–C was uniform and the catalytic active substances (MgO, KCl and K2CO3) were more than 10Mg–C (only MgO). The synergy effects of MgO and K2CO3 active sites enhanced the pH of reaction system and induced H2O ionization to form considerable OH− ions, thus easily realizing a deprotonation of glucose and effectively catalyzing the isomerization of glucose. In this study, we developed a highly efficient Mg–K-biochar bimetallic catalyst for glucose isomerization and provided an efficient method for cellulose valorization.Graphical

Factors influencing the enzymatic hydrolysis of soy molasses into fermentation feedstock

Soybean processing generates huge amounts of soy molasses that can support biorefinery but require development of waste-to-value conversion technologies. Here, soy molasses processing by Aspergillus niger enzymes was studied to optimize the conversion of oligosaccharides to monomeric sugars as ready fermentation feedstock. The effects of pH and temperature were first investigated using fixed enzyme composition and loading. pH, in the tested 3.0–6.5 range, significantly affected hydrolysis particularly in galactose release. The hydrolysis was fastest at pH 4.8 and 60 °C although the 48-h sugar (glucose, fructose, and galactose) yields were similar at pH 4.8 and 5.7, and 50 and 60 °C. Study was next made at these favorable pH and temperatures using different enzyme compositions and loadings. Glucose and fructose were effectively released, reaching ∼100 % yields in 24–48 h by most of the enzymes and loadings evaluated. Galactose production was less effective and varied significantly with the pH-temperature condition and enzyme loading and composition. Mechanistic evaluation suggested formation and accumulation of galactose disaccharide, whose slow hydrolysis was rate-limiting in the systems with complete glucose and fructose releases but low galactose yields. Model equations were developed to describe the kinetic sugar-release profiles and make technoeconomic analysis, which showed that a process of lower enzyme loading, while requiring longer duration, is more economical within the analyzed range of 5–50 (U α-galactosidase/g molasses). With 5 (U/g) loading, the total cost is about 30 % lower at 60 °C-pH 5.7 than 50 °C-pH 4.8. The α-galactosidase-to-sucrase ratio plays a less significant role in affecting the overall process cost.

Li-promoted C3N4 catalyst for efficient isomerization of glucose into fructose at 50 °C in water

Efficient and selective glucose-to-fructose isomerization is a crucial step for production of oxygenated chemicals derived from sugars, which is usually catalyzed by base or Lewis acid heterogeneous catalyst. However, high yield and selectivity of fructose cannot be simultaneously obtained under mild conditions which hamper the scale of application compared with enzymatic catalysis. Herein, a Li-promoted C3N4 catalyst was exploited which afforded an excellent fructose yield (40.3 wt%) and selectivity (99.5%) from glucose in water at 50 °C, attributed to the formation of stable Li–N bond to strengthen the basic sites of catalysts. Furthermore, the so-formed N6–Li–H2O active site on Li–C3N4 catalyst in aqueous phase changes the local electronic structure and strengthens the deprotonation process during glucose isomerization into fructose. The superior catalytic performance which is comparable to biological pathway suggests promising applications of lithium containing heterogeneous catalyst in biomass refinery.

Isomerization and epimerization of glucose and galactose in arginine solution and phosphate buffer under subcritical fluid conditions.

Reaction of glucose or galactose was performed in arginine solution or phosphate buffer (pH 7.0) using a batch reactor at 110°C. The yields of products, pH, and absorbances at 280 and 420nm were measured during the reaction. Fructose, mannose, and allulose were formed from glucose; tagatose, talose, and sorbose were done from galactose. The reaction proceeded more rapidly in arginine solution than in phosphate buffer. In arginine solution, yields of fructose and tagatose were 20% and 16%, respectively, after 30-min reaction; in phosphate buffer, they were 14% and 10%, respectively. However, in both reaction media, the pH drop and increase in absorbances continued even after the yield became almost constant. The absorbance increased particularly in the latter half of the reaction due to formation of browning products. Therefore, to avoid browning, the reaction should be stopped as soon as possible after the yield approaches its maximum value.

Thermodynamic Insights into MgBr2-Mediated Glucose Interconversion to Fructose Undertaking Multiple Reaction Pathways by Applying the Macro- and Micro-Kinetic Principles

While many reports on the kinetics and mechanism of glucose isomerization to fructose via a chemical pathway have been published, thermodynamic insights into the interconversion reaction are rarely reported. Here, we report the temperature-dependent characteristics of the cation- and anion-mediated glucose conversion to fructose. The counter ions of MgBr2 enabled the reaction via different pathways in water; e.g., Mg2+ influenced the reaction by undertaking the 1,2-hydride shift mechanism and accounted for up to 50% of the conversion. However, the counter ion (Br–) promoted the conversion via the proton transfer mechanism, which contributed to the remaining 50%, based on the results of the isotopic labeling experiments. This selective transformation (32% wt fructose yield and 76% selectivity) aided by MgBr2 is attributed to the formation of a weak water shell around Mg2+ (due to a lower ratio of MgBr2 to water), which permitted the cation to expose its catalytic activity and affected the administering activity by Br–, which induces maximum side reactions. By applying the principles of transition-state Eyring and Marcus theories to the elementary steps involving a proton transfer and electron transfer, respectively, the temperature-dependent characteristics of the corresponding pathways were determined. The Eyring model exhibited a linear trend in the ln(k/T) vs 1/T plot with an activation energy barrier of 70.25 kJ/mol (comparable to the value of the collision-based Arrhenius model). The semi-classical Marcus model disclosed that the hydride shift is a normal electron transfer rate based on the localization of kET in the λ< -ΔGo >0 region.