Biotechnological production of gluconic acid: future implications

Improving glucose oxidase catalysis in Aspergillus niger via Vitreoscilla hemoglobin fusion protein

Oxygen is crucial for converting glucose to gluconic acid catalyzed by glucose oxidase (Gox). However, industrial gluconic acid production faces oxygen supply limitations. To enhance Gox efficiency, Vitreoscilla hemoglobin (VHb) has been considered as an efficient oxygen transfer carrier. This study identified GoxA, a specific isoform of Gox in the industrial gluconic acid-producing strain of Aspergillus niger. Various forms of VHb expression in A. niger were tested to improve GoxA's catalytic efficiency. Surprisingly, the expression of free VHb, both intracellularly and extracellularly, did not promote gluconic acid production during shake flask fermentation. Then, five fusion proteins were constructed by linking Gox and VHb using various methods. Among these, VHb-GS1-GoxA, where VHb's C-terminus connected to GoxA's N-terminus via the flexible linker GS1, demonstrated a significantly higher Kcat/Km value (96% higher) than GoxA. Unfortunately, the expression of VHb-GS1-GoxA in A. niger was limited, resulting in a low gluconic acid production of 3.0 g/L. To overcome the low expression problem, single- and dual-strain systems were designed with tools of SpyCatcher/SpyTag and SnoopCatcher/SnoopTag. In these systems, Gox and VHb were separately expressed and then self-assembled into complex proteins. Impressively, the single-strain system outperformed the GoxA overexpression strain S1971, resulting in 23% and 9% higher gluconic acid production under 0.6 vvm and 1.2 vvm aeration conditions in the bioreactor fermentation, respectively. The successful construction of Gox and VHb fusion or complex proteins, as proposed in this study, presents promising approaches to enhance Gox catalytic efficiency and lower aerodynamic costs in gluconic acid production. KEY POINTS: • Overexpressing free VHb in A. niger did not improve the catalytic efficiency of Gox • The VHb-GS1-GoxA showed an increased Kcat/Km value by 96% than GoxA • The single-strain system worked better in the gluconic acid bioreactor fermentation.

A comprehensive review of recent advances in the applications and biosynthesis of oxalic acid from bio-derived substrates

Organic acids are important compounds with numerous applications in different industries. This work presents a comprehensive review of the biological synthesis of oxalic acid, an important organic acid with many industrial applications. Due to its important applications in pharmaceuticals, textiles, metal recovery, and chemical and metallurgical industries, the global demand for oxalic acid has increased. As a result, there is an increasing need to develop more environmentally friendly and economically attractive alternatives to chemical synthesis methods, which has led to an increased focus on microbial fermentation processes. This review discusses the specific strategies for microbial production of oxalic acid, focusing on the benefits of using bio-derived substrates to improve the economics of the process and promote a circular economy in comparison with chemical synthesis. This review provides a comprehensive analysis of the various fermentation methods, fermenting microorganisms, and the biochemistry of oxalic acid production. It also highlights key sustainability challenges and considerations related to oxalic acid biosynthesis, providing important direction for further research. By providing and critically analyzing the most recent information in the literature, this review serves as a comprehensive resource for understanding the biosynthesis of oxalic acid, addressing critical research gaps, and future advances in the field.

Processing of Grape Bagasse and Potato Wastes for the Co-Production of Bacterial Cellulose and Gluconic Acid in an Airlift Bioreactor

The feasibility of using Garnacha Tintorera bagasse and potato wastes as substrate for the co-production of bacterial cellulose (BC) and gluconic acid by Komagataibacter xylinus fermentation was studied. Firstly, the sulfuric acid hydrolysis of bagasse was evaluated depending on the sulfuric acid concentration (2-4%), temperature (105-125 °C), and time (60-180 min). The bagasse hydrolysates showed a low monosaccharide concentration profile: glucose 3.24-5.40 g/L; cellobiose 0.00-0.48 g/L; arabinose 0.66-1.64 g/L and xylose 3.24-5.40 g/L. However, the hydrolysis treatment enhanced the total phenolic content of the bagasse extract (from 4.39 up to 12.72 mg GAE/g dried bagasse). The monosaccharide profile of the culture medium was improved by the addition of potato residues. From a medium containing bagasse-potato powder (50:50 w/w) and optimal hydrolysate conditions (125 °C for 60 min and 2% H2SO4), the composition of glucose increased up to 30.14 g/L. After 8 days of fermentation in an airlift bioreactor by Komagataibacter xylinus, 4 g dried BC/L and 26.41 g gluconic acid/L were obtained with a BC productivity of 0.021 g/L·h, an efficiency of 0.37 g/g and yield of 0.47 g/g. The productivity of gluconic acid was 0.14 g/L·h with an efficiency of 0.93 g/g and yield of 0.72 g/g. This research demonstrates the promising potential of utilizing waste materials, specifically Garnacha Tintorera bagasse and potato residues, as sustainable substrates for the co-production of valuable bioproducts, such as bacterial cellulose and gluconic acid.

Entrapment of Glucose Oxidase and Catalase in Silica-Calcium-Alginate Hydrogel Reduces the Release of Gluconic Acid in Must

Glucose oxidase (GOX) and catalase (CAT) were co-immobilized in silica-calcium-alginate hydrogels to degrade must glucose. The effect of the enzyme dose (1.2-2.4 U/mL), the initial must pH (3.6-4.0), and the incubation temperature (10-20 °C) on the glucose consumption, gluconic acid concentration, pH, and color intensity of Verdejo must was studied by using a Box-Behnken experimental design and comparing free and co-immobilized enzymes. A reduction of up to 37.3 g/L of glucose was observed in co-immobilized enzyme-treated must, corresponding to a decrease in its potential alcohol strength of 2.0% vol. (v/v), while achieving a slight decrease in its pH (between 0.28 and 0.60). This slight acidification was due to a significant reduction in the estimated gluconic acid found in the must (up to 73.7%), likely due to its accumulation inside the capsules. Regarding the operational stability of immobilized enzymes, a gradual reduction in glucose consumption was observed over eight consecutive cycles. Finally, co-immobilized enzymes showed enhanced efficiency over a reaction period of 48 h, with an 87.1% higher ratio of glucose consumed per enzyme dose in the second 24 h period compared with free enzymes. These findings provide valuable insights into the performance of GOX-CAT co-immobilized to produce reduced-alcohol wines, mitigating excessive must acidification.

Effective production of kojic acid in engineered Aspergillus niger

BACKGROUND

Kojic acid (KA) is a widely used compound in the cosmetic, medical, and food industries, and is typically produced by Aspergillus oryzae. To meet increasing market demand, it is important to optimize KA production through seeking alternatives that are more economic than current A. oryzae-based methods.

RESULTS

In this study, we achieved the first successful heterologous production of KA in Aspergillus niger, an industrially important fungus that does not naturally produce KA, through the expression of the kojA gene from A. oryzae. Using the resulting KA-producing A. niger strain as a platform, we identified four genes (nrkA, nrkB, nrkC, and nrkD) that negatively regulate KA production. Knocking down nrkA or deleting any of the other three genes resulted in a significant increase in KA production in shaking flask cultivation. The highest KA titer (25.71 g/L) was achieved in a pH controlled batch bioreactor using the kojA overexpression strain with a deletion of nrkC, which showed a 26.7% improvement compared to the KA titer (20.29 g/L) that was achieved in shaking flask cultivation.

CONCLUSION

Our study demonstrates the potential of using A. niger as a platform for studying KA biosynthesis and regulation, and for the cost-effective production of KA in industrial strain development.

Efficient aerobic fermentation of gluconic acid by high tension oxygen supply strategy with reusable Gluconobacter oxydans HG19 cells

Gluconic acid is a widely used food and beverage additive, but its production suffers from low efficiency and high cost. In this study, a preferable gluconic acid biosynthesis method without repeated seed culture was proposed and developed using the superior performance of Gluconobacter oxydans. A high oxygen atmosphere satisfying the demand of bio-oxidation increased the productivity of gluconic acid up to ~ 32 g/L/h and the accumulation up to ~ 420 g/L within 24 h of fed-batch fermentation. However, the productivity remarkably decreased when the gluconic acid content was over 350 g/L. Therefore, a continuous fermentation was designed, which in combination with 5 runs of fed-batch fermentation resulted in the final production of 1700 g gluconic acid from 1750 g glucose within 60 h in a 3 L bioreactor. The results suggest that the validity of this model and can enable cost-competitive gluconic acid production in the industry.

Recent progress in the microbial production of xylonic acid

Interest in the production of renewable chemicals from biomass has increased in the past years. Among these chemicals, carboxylic acids represent a significant part of the most desirable bio-based products. Xylonic acid is a five-carbon sugar-acid obtained from xylose oxidation that can be used in several industrial applications, including food, pharmaceutical, and construction industries. So far, the production of xylonic acid has not yet been available at an industrial scale; however, several microbial bio-based production processes are under development. This review summarizes the recent advances in pathway characterization, genetic engineering, and fermentative strategies to improve xylonic acid production by microorganisms from xylose or lignocellulosic hydrolysates. In addition, the strengths of the available microbial strains and processes and the major requirements for achieving biotechnological production of xylonic acid at a commercial scale are discussed. Efficient native and engineered microbial strains have been reported. Xylonic acid titers as high as 586 and 171 g L^-1 were obtained from bacterial and yeast strains, respectively, in a laboratory medium. Furthermore, relevant academic and industrial players associated with xylonic acid production will be presented.

Eliminating the need for anodic gas separation in CO2 electroreduction systems via liquid-to-liquid anodic upgrading

Electrochemical reduction of CO₂ to multi-carbon products (C₂₊), when powered using renewable electricity, offers a route to valuable chemicals and fuels. In conventional neutral-media CO₂-to-C₂₊ devices, as much as 70% of input CO₂ crosses the cell and mixes with oxygen produced at the anode. Recovering CO₂ from this stream adds a significant energy penalty. Here we demonstrate that using a liquid-to-liquid anodic process enables the recovery of crossed-over CO₂ via facile gas-liquid separation without additional energy input: the anode tail gas is directly fed into the cathodic input, along with fresh CO₂ feedstock. We report a system exhibiting a low full-cell voltage of 1.9 V and total carbon efficiency of 48%, enabling 262 GJ/ton ethylene, a 46% reduction in energy intensity compared to state-of-art single-stage CO₂-to-C₂₊ devices. The strategy is compatible with today’s highest-efficiency electrolyzers and CO₂ catalysts that function optimally in neutral and alkaline electrolytes.

In the electrified conversion of CO2 to multicarbon products, CO2 crossover to the O2-rich anodic stream adds a further, energy-intensive, chemical separation step. Here, the authors demonstrate a strategy that eliminates the separation requirement.

Production of Gluconic Acid and Its Derivatives by Microbial Fermentation: Process Improvement Based on Integrated Routes

Gluconic acid (GA) and its derivatives, as multifunctional biological chassis compounds, have been widely used in the food, medicine, textile, beverage and construction industries. For the past few decades, the favored production means of GA and its derivatives are microbial fermentation using various carbon sources containing glucose hydrolysates due to high-yield GA production and mature fermentation processes. Advancements in improving fermentation process are thriving which enable more efficient and economical industrial fermentation to produce GA and its derivatives, such as the replacement of carbon sources with agro-industrial byproducts and integrated routes involving genetically modified strains, cascade hydrolysis or micro- and nanofiltration in a membrane unit. These efforts pave the way for cheaper industrial fermentation process of GA and its derivatives, which would expand the application and widen the market of them. This review summarizes the recent advances, points out the existing challenges and provides an outlook on future development regarding the production of GA and its derivatives by microbial fermentation, aiming to promote the combination of innovative production of GA and its derivatives with industrial fermentation in practice.

Tellurium in carbohydrate synthesis

In this article, we discuss about the influence of tellurium in carbohydrate synthesis. Mainly the chapter focuses on the importance of the tellurium during the synthesis of glycosides and during the oxidation of glucose.

Features of Profiles of Biologically Active Compounds of Primary and Secondary Metabolism of Lines from VIR Flax Genetic Collection, Contrasting in Size and Color of Seeds

Flax is one of the oldest oil crops, but only since the end of the twentieth century nutritional use of its whole seeds and flour has been resumed. This crop has been evaluated for its oil fatty acid composition, content of sterols and tocopherols, carbohydrate composition of mucilage, but a comprehensive study has never been carried out, so the aim of the work was to identify differences in the metabolomic profiles of flax lines contrasting in color and size of seeds. The biochemical composition of seeds from 16 lines of the sixth generation of inbreeding was tested using gas chromatography coupled with mass spectrometry. In total, more than 90 compounds related to sugars (78% of the identified substances), free fatty acids (13%), polyatomic alcohols (5%), heterocyclic compounds, free amino acids, phytosterols and organic acids (no more than 2.5% in total) were identified. Statistical analyses revealed six main factors. The first is a factor of sugar content; the second one affects most of organic acids, as well as some free fatty acids, not related to reserve ones, the third factor is related to compounds that play a certain role in the formation of "storage" substances and resistance to stress, the fourth factor is influencing free polar amino acids, some organic and free fatty acids, the fifth one is a factor of phenolic compounds, the sixth factor combined substances not included in the first five groups. Factor analysis made it possible to differentiate all 16 lines, 10 of which occupied a separate position by one or two factors. Interestingly, the first two factors with the highest loads (20 and 15% of the total variability, respectively) showed a separate position of the gc-432 line, which differed from the others, not only by chemical composition, but also by the phenotype of the seeds, while gc-159 differed from the rest ones by the complex of organic acids and other substances taking about 1% of the extracted substances of the seed. Thus, the analysis of metabolomic profiles is promising for a comprehensive assessment of the VIR flax genetic collection, which has wide biochemical diversity.

Dehydrogenases of acetic acid bacteria

Acetic acid bacteria (AAB) are a group of bacteria that can oxidize many substrates such as alcohols and sugar alcohols and play important roles in industrial biotechnology. A majority of industrial processes that involve AAB are related to their dehydrogenases, including PQQ/FAD-dependent membrane-bound dehydrogenases and NAD(P)⁺-dependent cytoplasmic dehydrogenases. These cofactor-dependent dehydrogenases must effectively regenerate their cofactors in order to function continuously. For PQQ, FAD and NAD(P)⁺ alike, regeneration is directly or indirectly related to the electron transport chain (ETC) of AAB, which plays an important role in energy generation for aerobic cell growth. Furthermore, in changeable natural habitats, ETC components of AAB can be regulated so that the bacteria survive in different environments. Herein, the progressive cascade in an application of AAB, including key dehydrogenases involved in the application, regeneration of dehydrogenase cofactors, ETC coupling with cofactor regeneration and ETC regulation, is systematically reviewed and discussed. As they have great application value, a deep understanding of the mechanisms through which AAB function will not only promote their utilization and development but also provide a reference for engineering of other industrial strains.

Enzymes, In Vivo Biocatalysis, and Metabolic Engineering for Enabling a Circular Economy and Sustainability

Since the industrial revolution, the rapid growth and development of global industries have depended largely upon the utilization of coal-derived chemicals, and more recently, the utilization of petroleum-based chemicals. These developments have followed a linear economy model (produce, consume, and dispose). As the world is facing a serious threat from the climate change crisis, a more sustainable solution for manufacturing, i.e., circular economy in which waste from the same or different industries can be used as feedstocks or resources for production offers an attractive industrial/business model. In nature, biological systems, i.e., microorganisms routinely use their enzymes and metabolic pathways to convert organic and inorganic wastes to synthesize biochemicals and energy required for their growth. Therefore, an understanding of how selected enzymes convert biobased feedstocks into special (bio)chemicals serves as an important basis from which to build on for applications in biocatalysis, metabolic engineering, and synthetic biology to enable biobased processes that are greener and cleaner for the environment. This review article highlights the current state of knowledge regarding the enzymatic reactions used in converting biobased wastes (lignocellulosic biomass, sugar, phenolic acid, triglyceride, fatty acid, and glycerol) and greenhouse gases (CO₂ and CH₄) into value-added products and discusses the current progress made in their metabolic engineering. The commercial aspects and life cycle assessment of products from enzymatic and metabolic engineering are also discussed. Continued development in the field of metabolic engineering would offer diversified solutions which are sustainable and renewable for manufacturing valuable chemicals.

Influence of the Pd : Bi ratio on Pd-Bi/Al2O3 catalysts: structure, surface and activity in glucose oxidation

Pd-Bi nanoparticles show high efficiency in catalyzing gluconic acid production by the glucose oxidation reaction. Although this type of catalyst was studied for some time, the correlation between bismuth content and catalytic activity is still unclear. Moreover, there is little information on the principles of the formation of Pd-Bi nanoparticles. In this work, the relation between bismuth content and the activity and selectivity of the PdxBiy/Al2O3 catalyst in the glucose oxidation process was studied. The catalytic samples were prepared by co-impregnation of the alumina support utilizing the metal-organic precursors of Pd and Bi. The samples obtained were tested in the glucose oxidation reaction and were studied by transmission electron microscopy (TEM), X-ray fluorescence analysis, X-ray photoelectron spectroscopy (XPS), and BET adsorption. It has been found that the Pd3 : Bi1 atomic ratio grants the highest catalytic efficiency for the studied samples. To explain this, we predicted stable Pd-Bi nanoparticles using ab initio evolutionary algorithm USPEX. The calculations demonstrate that nanoparticles tend to form Pd(core)-Bi(shell) structures turning to a crown-jewel morphology at lower Bi concentration, thus exposing the active Pd centers while maintaining the promoting effect of Bi.

Brewing of glucuronic acid-enriched apple cider with enhanced antioxidant activities through the co-fermentation of yeast (Saccharomyces cerevisiae and Pichia kudriavzevii) and bacteria (Lactobacillus plantarum)

Co-fermentation using yeast (Saccharomyces cerevisiae and Pichia kudriavzevii) and the bacteria (Lactobacillus plantarum) as starters isolated from spontaneous sourdough was conducted for the brewing of glucuronic acid (GlcA)-enriched apple cider. The concentration of GlcA in the apple cider co-fermented for 14 d with commercial S. cerevisiae and L. plantarum was 37.7 ± 1.7 mg/mL while a concentration of 62.8 ± 3.1 mg/mL was recorded for fermentation with P. kudriavzevii and L. plantarum, which was higher than the corresponding single yeast fermentation. The co-fermented apple cider revealed higher 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity of 171.67 ± 0.79 µg trolox equivalents (TE)/mL using P. kudriavzevii and L. plantarum, compared to the control (143.89 ± 7.07 µg TE/mL) just using S. cerevisiae. Thus, the co-fermentation of S. cerevisiae and L. plantarum and P. kudriavzevii and L. plantarum provided a new strategy for the development of GlcA-enriched apple cider with enhanced antioxidant capacity.

Structure-Reactivity Effects of Biomass-based Hydroxyacids for Sustainable Electrochemical Hydrogen Production

Biomass electro-oxidation is a promising approach for the sustainable generation of H₂ by electrolysis with simultaneous synthesis of value-added chemicals. In this work, the electro-oxidation of two structurally different organic hydroxyacids, lactic acid and gluconic acid, was studied comparatively to understand how the chemical structure of the hydroxyacid affects the electrochemical reactivity under various conditions. It was concluded that hydroxyacids such as gluconic acid, with a considerable density of C-OH groups, are highly reactive and promising for the sustainable generation of H₂ by electrolysis at low potentials and high conversion rates (less than -0.15 V vs. Hg/HgO at 400 mA cm^-2 ) but with low selectivity to specific final products. In contrast, the lower reactivity of lactic acid did not enable H₂ generation at very high conversion rates (<100 mA cm^-2 ), but the reaction was significantly more selective (64 % to pyruvic acid). This work shows the potential of biomass-based organic hydroxyacids for sustainable generation of H₂ and highlights the importance of the chemical structure on the reactivity and selectivity of the electro-oxidation reactions.

A Model Procedure for Catalytic Conversion of Waste Cotton into Useful Chemicals

Cotton is grown in about 90 countries and accounts for 24% of the fibers used in the global production of textiles. In 2018/2019, 25.8 Mt of cotton were produced around the world. Since this natural product consists mainly of cellulose, it can be used as a raw material in the so-called “sugar economy”. This paper discusses a model procedure for thermally assisted acidic hydrolysis of cotton into glucose and subsequent oxidation of the glucose into calcium gluconate over Pd-Au/SiO₂ catalyst. In the first step, H₂SO₄ was used as a catalyst for hydrolysis. The cotton hydrolysates were neutralized using CaCO₃ and applied as a substrate in the second step, where glucose was oxidized over Pd-Au/SiO₂ prepared by ultrasound assisted co-impregnation. With the appropriate Au/Pd molar ratio, small crystallites of palladium and gold were created which were active and selective towards the formation of gluconate ions. This approach to the transformation of glucose represents as a viable alternative to biological processes using fungal and bacterial species, which are sensitive to the presence of inhibitors such as furfurals and levulinic acid in hydrolysates.

Optimization of carbon source efficiency for lipid production with the oleaginous yeast Saitozyma podzolica DSM 27192 applying automated continuous feeding

BACKGROUND

Biotechnologically produced microbial lipids are of interest as potential alternatives for crude and plant oils. Their lipid profile is similar to plant oils and can therefore be a substitute for the production of biofuels, additives for food and cosmetics industry as well as building blocks for oleochemicals. Commercial microbial lipids production, however, is still not profitable and research on process optimization and cost reduction is required. This study reports on the process optimization using glucose or xylose with the unconventional oleaginous yeast Saitozyma podzolica DSM 27192 aiming to reduce the applied carbon source amount without sacrificing lipid productivity.

RESULTS

By optimizing the process parameters temperature and pH, lipid productivity was enhanced by 40%. Thereupon, by establishing a two-phase strategy with an initial batch phase and a subsequent fed-batch phase for lipid production in which a constant sugar concentration of about 10 g/L was maintained, resulted in saving of ~ 41% of total glucose and ~ 26% of total xylose. By performing the automated continuous sugar feed the total sugar uptake was improved to ~ 91% for glucose and ~ 92% for xylose and thus, prevented waste of unused carbon source in the cultivation medium. In addition, reduced glucose cultivation resulted in to 28% higher cell growth and 19% increase of lipid titer. By using xylose, the by-product xylonic acid was identified for the first time as by-product of S. podzolica.

CONCLUSIONS

These findings provide a broad view of different cultivation process strategies with subsequent comparison and evaluation for lipid production with S. podzolica. Additionally, new biotechnological characteristics of this yeast were highlighted regarding the ability to produce valuable organic acids from sustainable and renewable sugars.

Gluconokinase IDNK Promotes Cell Proliferation and Inhibits Apoptosis in Hepatocellular Carcinoma

Purpose

Hepatocellular carcinoma (HCC) is one of the deadliest cancers globally with a poor prognosis. Breakthroughs in the treatment of HCC are urgently needed. This study explored the role of IDNK in the development and progression of HCC.

Methods

IDNK expression was suppressed using short hairpin (shRNA) in BEL-7404 and Huh-7 cells. The expression of IDNK in HCC cells after IDNK knockdown was evaluated by real-time quantitative RT-PCR analysis and Western blot. After IDNK silencing, the proliferation and apoptosis of HCC cells were evaluated by Celigo cell counting, flow cytometry analysis, MTT assay, and caspase3/7 assay. Gene expressions in BEL-7404 cells transfected with IDNK shRNA lentivirus plasmid and blank control plasmid were evaluated by microarray analysis. The differentially expressed genes induced by deregulation of IDNKwere identified, followed by pathway analysis.

Results

The expression of IDNK at the mRNA and protein levels was considerably reduced in shRNA IDNK transfected cells. Knockdown of IDNK significantly inhibited HCC cell proliferation and increased cell apoptosis. A total of 1196 genes (585 upregulated and 611 downregulated) were differentially expressed in IDNK knockdown BEL-7404 cells. The pathway of tRNA charging with Z-score = -3 was significantly inhibited in BEL-7404 cells with IDNK knockdown.

Conclusion

IDNK plays a key role in the proliferation and apoptosis of HCC cells. IDNK may be a candidate therapeutic target for HCC.

Influence of the Method of Preparation of the Pd-Bi/Al2O3 Catalyst on Catalytic Properties in the Reaction of Liquid-Phase Oxidation of Glucose into Gluconic Acid

Gluconic acid and its derivatives are extensively used in pharmaceutical, food, textile, and pulp and paper branches of industry during production of food additives, cleansers, medicinal drugs, stabilizers, etc. To obtain gluconic acid, the method of conversion of glucose into gluconic acid by molecular oxygen in the presence of solid catalysts is promising. The process of obtaining Pd and bimetallic nanoparticles Pd-Bi, coated on Al2O3, has been considered in the work. Samples were prepared by combined and successive impregnation of the Al2O3 support using metalloorganic precursors Pd(acac)2, Bi(ac)3, and dissolved in an organic solvent (acetic acid), followed by the removal of excess solvent. To achieve the formation of Pd and bimetallic nanoparticles Pd-Bi on the substrate surface, the synthesized samples were subjected to thermal decomposition sequentially in the atmosphere of Ar, O2, and H2. The surface of the obtained catalysts was studied by a combination of physicochemical methods of analysis. The catalysts were analyzed in the reaction of liquid phase oxidation of glucose. The best results are achieved in the presence of the catalyst obtained by combined impregnation.

Isolation and characterization of nutrient dependent pyocyanin from Pseudomonas aeruginosa and its dye and agrochemical properties

Pyocyanin is a blue green phenazine pigment produced in large quantities by active cultures of Pseudomonas aeruginosa, with advantageous applications in medicine, agriculture and for the environment. Hence, in the present study, a potent bacterium was isolated from agricultural soil and was identified morphologically and by 16S rRNA sequencing as P. aeruginosa (isolate KU_BIO2). When the influence of nutrient supplements in both King’s A and Nutrient media as amended was investigated, an enhanced pyocyanin production of 2.56 µg ml⁻¹ was achieved in King’s A medium amended with soya bean followed by 1.702 µg ml⁻¹ of pyocyanin from the nutrient medium amended with sweet potato. Purified pyocyanin was characterized by UV-Vis Spectrophotometer and Fourier-Transform Infrared spectroscopy (FTIR). Furthermore, Liquid Chromatography Mass Spectrum (LCMS) and Nuclear Magnetic Resonance (NMR) confirmed its mass value at 211 and as N-CH₃ protons resonating at 3.363 ppm as a singlet respectively. The isolated pyocyanin displayed remarkable dye property by inducing color change in cotton cloth from white to pink. Lastly, the antifungal activity of test pyocyanin showed inhibition of growth of rice blast fungus, Magnaporthe grisea and bacterial blight of rice, Xanthomonas oryzae at concentrations of 150 and 200 ppm, respectively. Thus, this investigation provides evidence for diverse actions of pyocyanin which are nutrient dependent and are capable of acting on a large scale, by utilizing microbes existing in agriculture wastes, and thus could be used as an alternative source in the making of natural textile dyes with strong durability and a broad spectrum of ecofriendly agrochemicals.

Microbiological Laboratory Testing in the Diagnosis of Fungal Infections in Pulmonary and Critical Care Practice. An Official American Thoracic Society Clinical Practice Guideline

Background: Fungal infections are of increasing incidence and importance in immunocompromised and immunocompetent patients. Timely diagnosis relies on appropriate use of laboratory testing in susceptible patients.Methods: The relevant literature related to diagnosis of invasive pulmonary aspergillosis, invasive candidiasis, and the common endemic mycoses was systematically reviewed. Meta-analysis was performed when appropriate. Recommendations were developed using the Grading of Recommendations Assessment, Development, and Evaluation approach.Results: This guideline includes specific recommendations on the use of galactomannan testing in serum and BAL and for the diagnosis of invasive pulmonary aspergillosis, the role of PCR in the diagnosis of invasive pulmonary aspergillosis, the role of β-d-glucan assays in the diagnosis of invasive candidiasis, and the application of serology and antigen testing in the diagnosis of the endemic mycoses.Conclusions: Rapid, accurate diagnosis of fungal infections relies on appropriate application of laboratory testing, including antigen testing, serological testing, and PCR-based assays.

Combi-CLEAs of Glucose Oxidase and Catalase for Conversion of Glucose to Gluconic Acid Eliminating the Hydrogen Peroxide to Maintain Enzyme Activity in a Bubble Column Reactor

In this study combined cross-linked aggregates of catalase from bovine liver and glucose-oxidase from Aspergillus niger were prepared, and the effects of the precipitant and crosslinking agents, as well as the use of bovine serum albumin (BSA) as a feeder protein, on enzyme immobilization yield and thermal stability of both enzymes, were evaluated. Combi- crosslinking of enzyme aggregates (CLEAs) prepared using dimethoxyethane as precipitant, 25 mM glutaraldehyde and BSA/enzymes mass ratio of 5.45 (w/w), exhibited the highest enzyme activities and stabilities at 40 °C, pH 6.0, and 250 rpm for 5 h. The stability of both immobilized enzymes was fairly similar, eliminating one of the problems of enzyme coimmobilization. Combi-CLEAs were used in gluconic acid (GA) production in a bubble column reactor operated at 40 °C, pH 6.0 and 10 vvm of aeration, using 26 g L−1 glucose as the substrate. Results showed conversion of around 96% and a reaction course very similar to the same process using free enzymes. The operational half-life was 34 h, determined from kinetic profiles and the first order inactivation model. Combi-CLEAs of glucose-oxidase and catalase were shown to be a robust biocatalyst for applications in the production of gluconic acid from glucose.

A hybrid composite of hydroxyapatite and Ca-Al layered double hydroxide supported Au nanoparticles for highly efficient base-free aerobic oxidation of glucose

In this work, a new hybrid composite of hydroxyapatite and Ca-Al layered double hydroxide (HAP-LDH) was successfully assembled via an in situ growth route, by which large quantities of small needle-like HAP crystals in situ grew over the lateral surface of large platelet-like CaAl-LDH particles, and applied to immobilize Au nanoparticles for base-free aerobic glucose oxidation in water to produce gluconic acid using molecular oxygen. A combination of characterization techniques and catalytic experiments revealed that the activity of supported Au catalysts was strongly associated with the composition of supports, and the hybrid HAP-LDH supported one with a Au loading amount of about 0.2 wt% delivered a high gluconic acid yield of >98% under optimal reaction conditions, along with a quite high turnover frequency value of ∼20 225 h-1. High efficiency of the as-formed Au/HAP-LDH was mainly ascribed to cooperation between favorable surface Au species (Au0/Auδ+) and abundant basic sites. Furthermore, the present catalyst also presented good structural stability, because of the novel hybrid three-dimensional nano/microstructure of the HAP-LDH composite support facilitating the stabilization of active Au species and components of the support. The present synthesis strategy of employing a hybrid composite support provides a new way to design stable and high-performance supported metal nanocatalysts for a variety of advanced heterogeneous catalytic processes.

Effect of Sequential Acclimation to Various Carbon Sources on the Proteome of Acetobacter senegalensis LMG 23690T and Its Tolerance to Downstream Process Stresses

Acetic acid bacteria are very vulnerable to environmental changes; hence, they should get acclimated to different kinds of stresses when they undergo downstream processing. In the present study, Acetobacter senegalensis LMG 23690^T, a thermo-tolerant strain, was acclimated sequentially to different carbon sources including glucose (condition Glc), a mixture of glucose and ethanol (condition EtOH) and a mixture of glucose and acetic acid (condition GlcAA). Then, the effects of acclimation on the cell proteome profiles and some phenotypic characteristics such as growth in culture medium containing ethanol, and tolerance to freeze-drying process were evaluated. Based on the obtained results, despite the cells acclimated to Glc or EtOH conditions, 86% of acclimated cells to GlcAA condition were culturable and resumed growth with a short lag phase in a culture medium containing ethanol and acetic acid. Interestingly, if A. senegalensis LMG 23690^T had been acclimated to condition GlcAA, 92% of cells exhibited active cellular dehydrogenases, and 59% of cells were culturable after freeze-drying process. Proteome profiles comparison by 2D-DiGE and MS analysis, revealed distinct physiological status between cells exposed to different acclimation treatments, possibly explaining the resulting diversity in phenotypic characteristics. Results of proteome analysis by 2D-DiGE also showed similarities between the differentially expressed proteins of acclimated cells to EtOH condition and the proteome of acclimated cells to GlcAA condition. Most of the differentially regulated proteins are involved in metabolism, folding, sorting, and degradation processes. In conclusion, acclimation under appropriate sub-lethal conditions can be used as a method to improve cell phenotypic characteristics such as viability, growth under certain conditions, and tolerance to downstream processes.

Draft Genome Sequence of the Oleaginous Yeast Apiotrichum porosum (syn. Trichosporon porosum) DSM 27194

Here, we present the draft genome sequence of Apiotrichum porosum DSM 27194 generated on PacBio platform. Characterization of this oleaginous yeast originally collected from the grassland in Karlsruhe Germany, revealed potential for its utilization as a source of single cell oil (SCO) and gluconic acid (GA). The availability of the genome sequence provides a valuable resource for the elucidation of the genetic processes determining SCO and GA biosynthesis.

Forward Genetics by Genome Sequencing Uncovers the Central Role of the Aspergillus niger goxB Locus in Hydrogen Peroxide Induced Glucose Oxidase Expression

Aspergillus niger is an industrially important source for gluconic acid and glucose oxidase (GOx), a secreted commercially important flavoprotein which catalyses the oxidation of β-D-glucose by molecular oxygen to D-glucolactone and hydrogen peroxide. Expression of goxC, the GOx encoding gene and the concomitant two step conversion of glucose to gluconic acid requires oxygen and the presence of significant amounts of glucose in the medium and is optimally induced at pH 5.5. The molecular mechanisms underlying regulation of goxC expression are, however, still enigmatic. Genetic studies aimed at understanding GOx induction have indicated the involvement of at least seven complementation groups, for none of which the molecular basis has been resolved. In this study, a mapping-by-sequencing forward genetics approach was used to uncover the molecular role of the goxB locus in goxC expression. Using the Illumina and PacBio sequencing platforms a hybrid high quality draft genome assembly of laboratory strain N402 was obtained and used as a reference for mapping of genomic reads obtained from the derivative NW103:goxB mutant strain. The goxB locus encodes a thioredoxin reductase. A deletion of the encoding gene in the N402 parent strain led to a high constitutive expression level of the GOx and the lactonase encoding genes required for the two-step conversion of glucose in gluconic acid and of the catR gene encoding catalase R. This high constitutive level of expression was observed to be irrespective of the carbon source and oxidative stress applied. A model clarifying the role of GoxB in the regulation of the expression of goxC involving hydrogen peroxide as second messenger is presented.

Kinetic analysis of sodium gluconate production by Aspergillus niger with different inlet oxygen concentrations

To further understand fermentation kinetics of sodium gluconate (SG) production by Aspergillus niger with different inlet oxygen concentrations, logistic model for cell growth and two-step models for SG production and glucose consumption were established. The results demonstrated that the maximum specific growth rate (µ_m) presented exponential relationship with inlet oxygen concentration and the maximum biomass (X_m) exhibited linear increase. In terms of SG production, two-step model with Luedeking-Piret equation during growth phase and oxygen-dependent equation during stationary phase could well fit the experimental data. Notably, high inlet oxygen concentration exponentially improved SG yield (Y_P/S), whereas biomass yield to glucose (Y_X/S) and cell maintenance coefficient (m) were almost independent on inlet oxygen concentration, indicating that high oxygen supply enhancing SG synthesis not only functioning as a substrate directly, but also regulating glucose metabolism towards SG formation. Finally, the applicability and predictability of the proposed models were further validated by additional experiments.

Consolidated bioprocessing for sodium gluconate production from cellulose using Penicillium oxalicum

The feasibility of consolidated bioprocessing for sodium gluconate production from cellulose was studied. A recombinant strain named z19 was constructed from Penicillium oxalicum wild-type strain 114-2 for simultaneous expression of glucose oxidase and catalase from Aspergillus niger. While keeping a cellulolytic ability similar with that of 114-2, z19 secreted certain amounts of glucose oxidase and catalase. Fed-batch and two-stage temperature control strategy (0-120 h, 30 °C; 120-192 h, 45 °C) was utilized for sodium gluconate production from cellulose (filter paper power), with 13.54 g/L of sodium gluconate obtained at the end of the fermentation. The results provide an alternative route for producing sodium gluconate from cellulose in a one-pot reaction.

Production of sodium gluconate from delignified corn cob residue by on-site produced cellulase and co-immobilized glucose oxidase and catalase

The production of sodium gluconate by enzymatic catalysis of delignified corn cob residue (DCCR) hydrolysate was studied. Penicillium oxalicum I1-13 was used for the production of cellulase with high β-glucosidase activity. A fed-batch saccharification process was developed to obtain high yields of glucose. At the end of hydrolysis, the concentration of glucose reached 145.80g/L. Glucose oxidase and catalase were co-immobilized to catalyze DCCR hydrolysate to produce sodium gluconate. Under the optimum conditions, 166.87g/L sodium gluconate was obtained after 56h of reaction, with a yield of 98.24%. The immobilized enzymes could still maintain more than 60% of the activity after repeated use for 6 times. This study provides a potential route for the production of valuable chemicals by enzymatic conversion of lignocellulosic materials.

A synthetic hybrid promoter for D-xylonate production at low pH in the tolerant yeast Candida glycerinogenes

The tolerant yeast Candida glycerinogenes, with high D-xylonate and low-pH tolerances, was used as the host for D-xylonate production at low pH in this study. A low-pH inducible promoter, pGUKd, was engineered using the core promoter of the glyceraldehyde-3-phosphate dehydrogenase gene (pGAP) combined with the upstream activating sequence of the promoter of the guanylate kinase gene (pGUK1) that had substituted pH-responsive TF binding sites. The recombinant cells that expressed GFP from the hybrid promoter pGUKd displayed dramatically increased fluorescence intensity at pH 2.5, thus verifying that pGUKd is a low-pH inducible promoter. The promoter pGUKd was then used to express the D-xylose dehydrogenase gene xylB, resulting in increased expression levels of xylB at low pH. The recombinant protein exhibited higher specific activities under lower pH conditions and produced 38 g/l D-xylonate at pH 2.5. This rate is much higher than that produced by fermentation at pH 5.5. These results suggest that the novel hybrid promoter pGUKd functions to direct the production of D-xylonate at low pH, and we provide a candidate genetic tool for the stress tolerant yeast C. glycerinogenes.

Influence of carbon sources on the viability and resuscitation of Acetobacter senegalensis during high-temperature gluconic acid fermentation

Much research has been conducted about different types of fermentation at high temperature, but only a few of them have studied cell viability changes during high-temperature fermentation. In this study, Acetobacter senegalensis, a thermo-tolerant strain, was used for gluconic acid production at 38 °C. The influences of different carbon sources and physicochemical conditions on cell viability and the resuscitation of viable but nonculturable (VBNC) cells formed during fermentation were studied. Based on the obtained results, A. senegalensis could oxidize 95 g l^- 1 glucose to gluconate at 38 °C (pH 5.5, yield 83%). However, despite the availability of carbon and nitrogen sources, the specific rates of glucose consumption (q_s) and gluconate production (q_p) reduced progressively. Interestingly, gradual q_s and q_p reduction coincided with gradual decrease in cellular dehydrogenase activity, cell envelope integrity, and cell culturability as well as with the formation of VBNC cells. Entry of cells into VBNC state during stationary phase partly stemmed from high fermentation temperature and long-term oxidation of glucose, because just about 48% of VBNC cells formed during stationary phase were resuscitated by supplementing the culture medium with an alternative favorite carbon source (low concentration of ethanol) and/or reducing incubation temperature to 30 °C. This indicates that ethanol, as a favorable carbon source, supports the repair of stressed cells. Since formation of VBNC cells is often inevitable during high-temperature fermentation, using an alternative carbon source together with changing physicochemical conditions may enable the resuscitation of VBNC cells and their use for several production cycles.

Metabolic pathways regulated by abscisic acid, salicylic acid and γ-aminobutyric acid in association with improved drought tolerance in creeping bentgrass (Agrostis stolonifera)

Abscisic acid (ABA), salicylic acid (SA) and γ-aminobutyric acid (GABA) are known to play roles in regulating plant stress responses. This study was conducted to determine metabolites and associated pathways regulated by ABA, SA and GABA that could contribute to drought tolerance in creeping bentgrass (Agrostis stolonifera). Plants were foliar sprayed with ABA (5 μM), GABA (0.5 mM) and SA (10 μM) or water (untreated control) prior to 25 days drought stress in controlled growth chambers. Application of ABA, GABA or SA had similar positive effects on alleviating drought damages, as manifested by the maintenance of lower electrolyte leakage and greater relative water content in leaves of treated plants relative to the untreated control. Metabolic profiling showed that ABA, GABA and SA induced differential metabolic changes under drought stress. ABA mainly promoted the accumulation of organic acids associated with tricarboxylic acid cycle (aconitic acid, succinic acid, lactic acid and malic acid). SA strongly stimulated the accumulation of amino acids (proline, serine, threonine and alanine) and carbohydrates (glucose, mannose, fructose and cellobiose). GABA enhanced the accumulation of amino acids (GABA, glycine, valine, proline, 5-oxoproline, serine, threonine, aspartic acid and glutamic acid) and organic acids (malic acid, lactic acid, gluconic acid, malonic acid and ribonic acid). The enhanced drought tolerance could be mainly due to the enhanced respiration metabolism by ABA, amino acids and carbohydrates involved in osmotic adjustment (OA) and energy metabolism by SA, and amino acid metabolism related to OA and stress-defense secondary metabolism by GABA.

Plant Food Residues as a Source of Nutraceuticals and Functional Foods

This chapter describes the use of different plant and vegetable food residues as nutraceuticals and functional foods. Different nutraceuticals are mentioned and explained. Their uses are well addressed along with their disease management and their action as nutraceutical delivery vehicles.

High efficiency cell-recycle continuous sodium gluconate production by Aspergillus niger using on-line physiological parameters association analysis to regulate feed rate rationally

In this paper, a system of cell-recycle continuous fermentation for sodium gluconate (SG) production by Aspergillus niger (A. niger) was established. Based on initial continuous fermentation result (100.0h) with constant feed rate, an automatic feedback strategy to regulate feed rate using on-line physiological parameters (OUR and DO) was proposed and applied successfully for the first time in the improved continuous fermentation (240.5h). Due to less auxiliary time, highest SG production rate (31.05±0.29gL(-1)h(-1)) and highest yield (0.984±0.067molmol(-1)), overall SG production capacity (975.8±5.8gh(-1)) in 50-L fermentor of improved continuous fermentation increased more than 300.0% compared to that of batch fermentation. Improvement of mass transfer and dispersed mycelia morphology were the two major reasons responsible for the high SG production rate. This system had been successfully applied to industrial fermentation and SG production was greatly improved.