Gluconic Acid Yield Research Articles

Gold nanoparticles deposited on Amberlyst-15: Metal–acid bifunctional catalyst for cellobiose conversion to gluconic acid

Gold nanoparticles were deposited on two kinds of solid acids, i.e., amorphous SiO2–Al2O3 and cation-exchange resin Amberlyst-15; the resultant materials exhibited high activity as metal–acid bifunctional catalysts. SiO2–Al2O3 was impregnated with a chloride-free alkaline Au(III) solution containing Na+ and then dried. After calcination at 623K, gold nanoparticles with diameters of 4.2nm (measured by X-ray diffraction) were deposited at a Au loading of 1.0wt%. By replacing the Na+ ions with H+ ions through ammonium ion-exchange and heating, an acidic Au/SiO2–Al2O3 catalyst was obtained. In Amberlyst-15, gold nanoparticles with diameters of 7.3nm were deposited after impregnation and drying. Subsequent ion-exchange with dilute sulfuric acid generated the acidic form of the Au/Amberlyst-15 catalyst, which showed an esterification activity equivalent to that of the original Amberlyst-15. The catalyst exhibited high activity for the direct conversion of cellobiose to gluconic acid, which requires both acid hydrolysis and oxidation. A 45% yield of gluconic acid was obtained after 24h of reaction under ambient air at 373K, with an apparent synergistic effect between the gold nanoparticles and acidic resin surface.

Preparation, Characterization and Catalytic Activity of Highly Dispersed Gold Catalyst

Highly dispersed supported gold catalysts have been prepared by solution reduction method using L-lysine as protection agents, and their catalytic activity was evaluated by the liquid phase catalytic oxidation reaction of glucose to gluconic acid. The results suggested that the Au/ZrO2 catalyst, exhibited high activity for the selective oxidation of glucose. At the reaction temperature of 323K, reaction time of 1h, with the NaCO3-NaHCO3 as buffer solution, the yield of gluconic acid was 100%.

Co-immobilization of multi-enzyme on control-reduced graphene oxide by non-covalent bonds: an artificial biocatalytic system for the one-pot production of gluconic acid from starch

Here we report a simple and efficient approach to fabricate a new biocatalytic system by co-immobilizing multi-enzyme on chemically reduced graphene oxide (CRGO) via non-covalent bonds. The obtained artificial biocatalyst was characterized by UV/Vis, FTIR, AFM, TEM and SEM. Compared with native and graphene oxide (GO) bounded enzymes, it was found that the glucose oxidase (GOD) or glucoamylase (GA) immobilized on CRGO exhibited significantly higher enzymatic activity, due to the positive effect of the CRGO carrier. This multi-enzyme microsystem was employed as a biocatalyst to accomplish the starch-to-gluconic acid reaction in one pot, and the yield of gluconic acid could reach 82% within 2 hours. It was also proved that the stability of the multi-enzyme biocatalyst immobilized on CRGO was dramatically enhanced compared with the GO microsystem. About 85% of the activity of the artificial biocatalyst could be preserved after four cycles. These results demonstrated the feasibility of the novel strategy to construct bio-microsystems with multi-enzyme on 2D CRGO via non-covalent bonds to accomplish some complex conversions.

Carbon nanotube-supported gold nanoparticles as efficient catalysts for selective oxidation of cellobiose into gluconic acid in aqueous medium

Gold nanoparticles loaded on nitric acid-pretreated carbon nanotubes are efficient for the selective oxidation of cellobiose by molecular oxygen to gluconic acid in aqueous medium without pH control; a gluconic acid yield of 80% has been obtained at 145 degrees C.

SIMS study of the processes in buffer solutions of bioorganic systems

Enzymatic glucose oxidation in a system modeling a glucose biosensor have been investigated by SIMS with the use of a liquid matrix. The effect of some solution parameters on the reaction product (gluconic acid) yield has been analyzed. It is shown by an example of gluconolactone hydrolysis that SIMS makes it possible to study not only final but also intermediate stage of the glucose oxidation reaction.

Bioconversion of grape must into modulated gluconic acid production by Aspergillus niger ORS-4.410

Analysis of regulators for modulated gluconic acid production under surface fermentation (SF) condition using grape must as the cheap carbohydrate source, by mutant Aspergillus niger ORS-4.410. Replacement of conventional fermentation condition by solid-state surface fermentation (SSF) for semi-continuous production of gluconic acid by pseudo-immobilization of A. niger ORS-4.410. Grape must after rectification was utilized for gluconic acid production in batch fermentation in SF and SSF processes using mutant strain of A. niger ORS-4.410. Use of rectified grape must led to the improved levels of gluconic acid production (80-85 g l(-1)) in the fermentation medium containing 0.075% (NH4)2HPO4; 0.1% KH2PO4 and 0.015% MgSO4.7H2O at an initial pH 6.6 (+/-0.1) under surface fermentation. Gluconic acid production was modulated by incorporating the 2% soybean oil, 2% starch and 1% H2O2 in fermentation medium at continuously high aeration rate (2.0 l min(-1)). Interestingly, 95.8% yield of gluconic acid was obtained when A. niger ORS-4.410 was pseudo-immobilized on cellulose fibres (bagasse) under SSF. Four consecutive fermentation cycles were achieved with a conversion rate of 0.752-0.804 g g(-1) of substrate into gluconic acid under SSF. Use of additives modulated the gluconic acid production under SF condition. Semi-continuous production of gluconic acid was achieved with pseudo-immobilized mycelia of A. niger ORS-4.410 having a promising yield (95.8%) under SSF condition. The bioconversion of grape must into modulated gluconic acid production under SSF conditions can further be employed in fermentation industries by replacing the conventional carbohydrate sources and expensive, energy consuming fermentation processes.

Evaluation of agro-food byproducts for gluconic acid production by Aspergillus niger ORS-4.410

Certain cost-effective carbohydrate sources in crude as well as after purification were utilized as the sole sources of carbon for gluconic acid production using Aspergillus niger ORS-4.410 under submerged fermentation. Crude grape must (GM) and banana-must (BM) resulted into significant levels of gluconic acid production i.e. 62.6 and 54.6 g/l, respectively. The purification of grape and banana-must led to a 20–21% increase in gluconic acid yield. Molasses as such did not favour gluconate production (12.0 g/l) but a significant increase in production (60.3 g/l) was observed following hexacyanoferrate (HCF) treatment of the molasses. Rectified grape must (RGM) appeared to be best suitable substrate which after 144 h resulted in 73.2 g of gluconic acid/l with 80.6% yield followed by the yield obtained from the rectified banana must (RBM) (72.4%) and treated cane molasses (TM) (61.3%). Abundant growth of mould A. niger ORS-4.410 was observed with crude grape (0.131 g/l/h) and banana must (0.132 g/l/h).

OPTIMIZATION STUDY FOR THE PRODUCTION OF CITRIC AND GLUCONIC ACID FROM FIG WATER EXTRACT BY ASPERGILLUS NIGER IN SURFACE FERMENTATION

ABSTRACT The production of citric and gluconic acid from fig extract by Aspergillus niger ATCC 10577 and A. niger B60 in surface fermentation was investigated. The strain 10577 gave higher concentration of citric and gluconic acid than strain B60. A maximum citric and gluconic acid concentration (20.5 and 97.0 g/L, respectively), citric acid yield (12%), biomass dry weight (18.5 g/L), and sugar utilization (85%) was achieved at an initial sugar concentration of 200 g/L and a pH of 7.0. On the other hand, the highest gluconic acid yield (79.7%) was obtained in culture grown at initial sugar concentration 100 g/L. The addition of 4% (v/v) methanol in the fig extract increased the concentration of citric and gluconic acid from 20.5 and 97.0 g/L to 30.7 and 145.5 g/L, respectively. Citric acid was separated from the gluconic acid by extraction with diethyl ether or ethyl acetate.

Genetic programming assisted stochastic optimization strategies for optimization of glucose to gluconic acid fermentation.

This article presents two hybrid strategies for the modeling and optimization of the glucose to gluconic acid batch bioprocess. In the hybrid approaches, first a novel artificial intelligence formalism, namely, genetic programming (GP), is used to develop a process model solely from the historic process input-output data. In the next step, the input space of the GP-based model, representing process operating conditions, is optimized using two stochastic optimization (SO) formalisms, viz., genetic algorithms (GAs) and simultaneous perturbation stochastic approximation (SPSA). These SO formalisms possess certain unique advantages over the commonly used gradient-based optimization techniques. The principal advantage of the GP-GA and GP-SPSA hybrid techniques is that process modeling and optimization can be performed exclusively from the process input-output data without invoking the detailed knowledge of the process phenomenology. The GP-GA and GP-SPSA techniques have been employed for modeling and optimization of the glucose to gluconic acid bioprocess, and the optimized process operating conditions obtained thereby have been compared with those obtained using two other hybrid modeling-optimization paradigms integrating artificial neural networks (ANNs) and GA/SPSA formalisms. Finally, the overall optimized operating conditions given by the GP-GA method, when verified experimentally resulted in a significant improvement in the gluconic acid yield. The hybrid strategies presented here are generic in nature and can be employed for modeling and optimization of a wide variety of batch and continuous bioprocesses.

Citric and gluconic acid production from fig by Aspergillus niger using solid-state fermentation.

The production of citric and gluconic acids from fig by Aspergillus niger ATCC 10577 in solid-state fermentation was investigated. The maximal citric and gluconic acids concentration (64 and 490 g/kg dry figs, respectively), citric acid yield (8%), and gluconic acid yield (63%) were obtained at a moisture level of 75%, initial pH 7.0, temperature 30 degrees C, and fermentation time in 15 days. However, the highest biomass dry weight (40 g/kg wet substrate) and sugar utilization (90%) were obtained in cultures grown at 35 degrees C. The addition of 6% (w/w) methanol into substrate increased the concentration of citric and gluconic acid from 64 and 490 to 96 and 685 g/kg dry fig, respectively.

Degradation of Cellulose Models During an Ozone Treatment. Ozonation of Glucose and Cellobiose With Oxygen or Nitrogen as Carrier Gas at Different pH

Many parameters can influence the kinetics of cellulose models ozonation. In this work the effect of pH and oxygen as gas carrier on the evolution of the reaction was studied. The involvement of free radical species seemed to be unimportant in high ozone concentration available in water, even at high pH with regard to the reaction rate and by-product formation. Conversely, in basic pH conditions better reaction selectivity with formation in a higher yield of gluconic acid and cellobionic acid was found during the glucose and the cellobiose ozonation. The participation of the solvent and the partial ionization of the hydroxyl group at the Cl position explain this enhanced selectivity. Furthermore, the formation of compounds with a low molecular weight has been proved to be due to a hydrotrioxide fragmentation mechanism involving oxygen.

Critical analysis of the effect of metal ions on gluconic acid production by Aspergillus niger using a treated Indian cane molasses

Gluconic acid fermentation by Aspergillus niger has been investigated using untreated and treated Indian cane molasses. The yield of gluconic acid was found to be reduced using an untreated molasses medium compared to a defined medium. Hence, molasses was subjected to various pretreatment techniques. Pretreatment reduced the levels of various cations and anions. As the synthesis of gluconic acid has been observed to be influenced more by cations than anions, the effect of various metal ions, viz., copper, iron, zinc, manganese, calcium, and magnesium on the yield of gluconic acid has been critically examined in both untreated and treated cane molasses. These results have been compared with a defined medium. The yield of gluconic acid was influenced more by a combination of metal ions rather than individual ions. Potassium ferrocyanide treatment gave the most promising results compared to other treatment techniques.

Characterization of production of free gluconic acid by Gluconobacter suboxydans adsorbed on ceramic honeycomb monolith

Gluconobacter suboxydans IFO 3290 was immobilized by adsorption on ceramic honeycomb monolith and continuous production of free gluconic acid from glucose was performed in an aerated reactor. The effects of reactor residence time, aeration rate, and glucose concentration were investigated on the gluconic acid yield. Observation of SEM photographs revealed that the cells were adsorbed with a high density not only on the outer surface of the support but also on the inner surface of large pores. From measurement of the number of the adsorbed cells, it was elucidated that the biofilm comprised a monolayer or bilayer of the cells. Maximum specific rate of growth was estimated for the free and adsorbed cells, and the adsorbed cells were found to grow at a fast rate compared with the free cells. In the continuous fermentation performed for one month at the glucose concentration of 100 kg/m(3), reactor residence time of 3.5 h and aeration rate of 900 cm(3)/min, the activity of the adsorbed cells was appreciably stable. The high productivity of 26.3 kg/(m(3)-reactor . h) was attained with the gluconic acid yield of 84.6% and glucose conversion of 94%.

Studies on some Nutritional Factors Influencing the Production of Gluconic Acid

Investigations were carried out to formulate an economical medium that can give maximum yield of gluconic acid by the submerged culture technique, using Aspergillus niger NRRL3. It was found that the highest yield of acid could be secured when a medium of the following ingredients was used: 13.0% glucose syrup, 0.1% NaNO3, 0.025% calcium superphosphate, 0.007% KCl, 0.025% MgSO4-7H20, and 0.5% CaCO3. It was also found that glucose syrup, which represents an available and cheap carbohydrate source for gluconic acid production by fermentation, can replace glucose powder which is more expensive.

BEHAVIOR OF GLYCOSIDIC LINKAGES TO OXYGEN-ALKALI

The behavior of glycosidic linkages to the oxygen-alkali treatment has been studied, using low molecular compounds. This treatment of cellobiitol yielded many kinds of acids (Fig.1) together with glucitol which was only one neutral product. These acids, except 3-deoxy-pentonic acid (VII) and 3, 4-dihydroxybutyric acid (VIII), were also formed from glucose by the same treatment. This result suggests that glucose may be a precursor of the acids other than the acids (VII) and (VIII), although it was not detected among the degradation products owing to its low stability under the severe alkaline conditions adopted. The formation of the acids (VII) and (VIII), and glucose from cellobiitol may be explained by the scheme shown in Fig.2. A scheme in which hydroxyl radical is involved in the cleavage of glycosidic linkages (Fig.3) was expected, but found not to be important, if any, because the yield of gluconic acid was lower than that of mannonic acid. The formation of glucitol from cellobiitol can be explained by the scheme in Fig.4, but the cyclic acid (XII) which should be formed according to this scheme could not be detected.The oxygen-alkali treatment of methyl 4-O-methyl-β-_??_-glucopyranoside yielded only three kinds of acids. They were separated gas-liquid chromatographically as TMS derivatives (Fig.5) and identified as glyceric acid, methyl 2-carboxy-3-deoxy-β-D-pentofuranoside (XIV) and methyl 2-carboxy-3-O-methyl-β-D-pentofuranoside (XVII) by the use of a mass spectrometer (Fig.6).Methyl β-D-glucopyranoside has the same stability to oxygen-alkali as methyl β-D-xylopyranoside, though the former contains an extra primary hydroxyl group (Table 1).