scholarly journals Efficient Optimization of Gluconobacter oxydans Based on Protein Scaffold-Trimeric CutA to Enhance the Chemical Structure Stability of Enzymes for the Direct Production of 2-Keto-L-gulonic Acid

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Lili Gao ◽  
Yuefeng Liu ◽  
Xiaoyu Zhang ◽  
Hongsheng Zhang
Keyword(s):  
Vitamin C ◽  
Chemical Structure ◽  
Gluconobacter Oxydans ◽  
Structure Stability ◽  
Scale Production ◽  
Direct Production ◽  
One Step ◽  
The One ◽  
Industrial Scale Production ◽  
Step Strain

2-Keto-L-gulonic acid (2-KLG), the direct precursor of vitamin C, is produced by a two-step fermentation route from D-sorbitol in industry. However, this route is a complicated mix-culture system which involves three bacteria. Thus, replacement of the conventional two-step fermentation process with a one-step process could be revolutionary in vitamin C industry. The one-step fermentation of 2-keto-L-gulonic acid (2-KLG) has been achieved in our previous study; 32.4 g/L of 2-KLG production was obtained by the one-step strain G. oxydans/pGUC-tufB-sdh-GGGGS-sndh after 168 h. In this study, L-sorbose dehydrogenase (SDH) and L-sorbosone dehydrogenase (SNDH) were expressed in G. oxydans after the codon optimization. Furthermore, the trimeric protein CutA was used to improve the chemical structure stability of SDH and SNDH. The recombinant strain G. oxydans/pGUC-tufB-SH3-sdh-GGGGS-sndh-tufB-SH3lig-(GGGGS)2-cutA produced 40.3 g/L of 2-KLG after 168 h. In addition, the expression levels of the cofactor PQQ were enhanced to further improve 2-KLG production. With the stepwise metabolic engineering of G. oxydans, the final 2-KLG production was improved to 42.6 g/L. The efficient one-step production of 2-KLG was achieved, and the final one-step industrial-scale production of 2-KLG is drawing near.

scholarly journals Identification of NAD-dependent xylitol dehydrogenase fromGluconobacter oxydansWSH-003

2019 ◽  
Author(s):  
Li Liu ◽  
Weizhu Zeng ◽  
Guocheng Du ◽  
Jian Chen ◽  
Jingwen Zhou
Keyword(s):  
Vitamin C ◽  
Gluconobacter Oxydans ◽  
Conversion Ratio ◽  
Xylitol Dehydrogenase ◽  
Industrial Scale ◽  
Scale Production ◽  
Optimum Temperature ◽  
Nadh Regeneration ◽  
High Preference ◽  
Industrial Scale Production

AbstractGluconobacter oxydansplays important role in conversion of D-sorbitol to L-sorbose, which is an essential intermediate for industrial-scale production of vitamin C. In the fermentation process, some D-sorbitol could be converted to D-fructose and other byproducts by uncertain dehydrogenases. Genome sequencing has revealed the presence of diverse genes encoding dehydrogenases inG. oxydans. However, the characteristics of most of these dehydrogenases remain unclear. Therefore, analyses of these unknown dehydrogenases could be useful for identifying those related to the production of D-fructose and other byproducts. Accordingly, dehydrogenases inG. oxydansWSH-003, an industrial strain used for vitamin C production, were examined. An NAD-dependent dehydrogenase, which was annotated as xylitol dehydrogenase 2, was identified, codon-optimized, and expressed inEscherichia coliBL21 (DE3) cells. The enzyme exhibited high preference for NAD+as the cofactor, while no activity with NADP+, FAD, or PQQ was noted. Although this enzyme presented high similarity with NAD-dependent xylitol dehydrogenase, it showed high activity to catalyze D-sorbitol to D-fructose. Unlike the optimum temperature and pH for most of the known NAD-dependent xylitol dehydrogenases (30°C–40°C and about 6–8, respectively), those for the identified enzyme were 57°C and 12, respectively. TheKmandVmaxof the identified dehydrogenase towards L-sorbitol were 4.92 μM and 196.08 μM/min, respectively. Thus, xylitol dehydrogenase 2 can be useful for cofactor NADH regeneration under alkaline conditions or its knockout can improve the conversion ratio of D-sorbitol to L-sorbose.ImportanceProduction of L-sorbose from D-sorbitol byGluconobacter oxydansis the first step for industrial scale production of L-ascorbic acid.G. oxydanscontains a lot of different dehydrogenases, among which only several are responsible for the conversion of D-sorbitol to L-sorbose, while others may responsible for the accumulation of byproducts, thus decreased the yield of L-sorbose on D-sorbitol. Therefore, a new xylitol dehydrogenase has been identified from 44 dehydrogenases ofG.oxydans. Optimum temperature and pH of the xylitol dehydrogenase are different to most of the known ones. Knock-out of the dehydrogenase may improve the conversion ratio of D-sorbitol to L-sorbose. Besides, the enzyme exhibits high preference for NAD+and have potential to be used for cofactor regeneration.

A Simple and Effective Method for the Preparation of Porous Graphene Nanosheets

2015 ◽  
Vol 719-720 ◽  
pp. 123-126
Author(s):  
Jin Sun ◽  
Qing Zhong Xue ◽  
Yong Gang Du ◽  
Fu Jun Xia ◽  
Qi Kai Guo
Keyword(s):  
Large Scale ◽  
Graphene Nanosheets ◽  
Scale Production ◽  
Green Method ◽  
Porous Graphene ◽  
Large Scale Production ◽  
Potential Applications ◽  
One Step ◽  
Autogenous Pressure ◽  
The One

Porous graphene is a collection of graphene-related materials which exhibits properties distinct from those of graphene, and it has widespread potential applications in various fields. Several approaches have been developed to produce porous graphene. However, the large-scale production of porous graphene nanosheets still remains a great challenge. Moreover, the costs of some methods are prohibitive for its commercial production and the processes are too complicated and time-consuming. In this work, we propose a simple and green method by which graphene nanosheets can be etched by sodium hydroxide under autogenous pressure at 180 °C. The morphologies and surface elements of the porous graphene nanosheets and sizes of pores were characterized. It is demonstrated that the one-step etching of graphene nanosheets is an effective method to obtain large-scale porous graphene nanosheets with high and uniform porosity. The pores in the porous graphene nanosheets were 6 nm depth (the same as the thickness of the graphene nanosheets) and 30-50 nm width.

scholarly journals Lactoferrin Production from Bovine Milk or Cheese Whey

2020 ◽  
pp. 1-9
Author(s):  
Jean-Paul Perraudin ◽  
◽  
Léo De Valck ◽  
Keyword(s):  
Bacterial Contamination ◽  
Cheese Whey ◽  
Biological Activities ◽  
Bovine Milk ◽  
Second Step ◽  
Scale Production ◽  
One Step ◽  
High Level ◽  
Industrial Scale Production

Today, the industrial scale production of lactoferrin is carried out in one step by extraction from bovine milk or whey. As the role of lactoferrin in the milk is to protect the liquid against the bacterial contamination binding the lipopolysaccharides (LPS) of those bacteria, it is not surprising that the lactoferrin extracted from milk is covered by bacterial LPS, losing the most part of its biological activities. It is absolutely crucial that the production of Lactoferrin consists to a two steps process. The first step consists to extract from milk or from whey a solution that we called lactenin which contains different molecules including lactoferrin, lactoperoxidase, angiogenin and some other minor components. The second step consists to purify the lactoferrin from the other components including the LPS. Only under such conditions, we could recuperate a high level pure molecule with all its biological activities as it is not done actually

scholarly journals Rapid Enabling of Gluconobacter oxydans Resistance to High D-Sorbitol Concentration and High Temperature by Microdroplet-Aided Adaptive Evolution

2021 ◽  
Vol 9 ◽  
Author(s):  
Li Liu ◽  
Weizhu Zeng ◽  
Shiqin Yu ◽  
Jianghua Li ◽  
Jingwen Zhou
Keyword(s):  
High Temperature ◽  
Adaptive Evolution ◽  
Genomic Analysis ◽  
Gluconobacter Oxydans ◽  
Protein Translation ◽  
Comparative Genomic ◽  
Scale Production ◽  
Genetic Changes ◽  
Short Time ◽  
Industrial Scale Production

Gluconobacter oxydans is important in the conversion of D-sorbitol into l-sorbose, which is an essential intermediate for industrial-scale production of vitamin C. In a previous study, the strain G. oxydans WSH-004 could directly produce 2-keto-l-gulonic acid (2-KLG). However, its D-sorbitol tolerance was poor compared with that of other common industrial G. oxydans strains, which grew well in the presence of more than 200 g/L of D-sorbitol. This study aimed to use the microbial microdroplet culture (MMC) system for the adaptive evolution of G. oxydans WSH-004 so as to improve its tolerance to high substrate concentration and high temperature. A series of adaptively evolved strains, G. oxydans MMC1-MMC10, were obtained within 90 days. The results showed that the best strain MMC10 grew in a 300 g/L of D-sorbitol medium at 40°C. The comparative genomic analysis revealed that genetic changes related to increased tolerance were mainly in protein translation genes. Compared with the traditional adaptive evolution method, the application of microdroplet-aided adaptive evolution could improve the efficiency in terms of reducing time and simplifying the procedure for strain evolution. This research indicated that the microdroplet-aided adaptive evolution was an effective tool for improving the phenotypes with undemonstrated genotypes in a short time.

scholarly journals Effects of Sheet Resistance on mc-Si Selective Emitter Solar Cells Using Laser Opening and One-Step Diffusion

2015 ◽  
Vol 2015 ◽  
pp. 1-9
Author(s):  
Sheng-Shih Wang ◽  
Jyh-Jier Ho ◽  
Jia-Jhe Liou ◽  
Jia-Show Ho ◽  
Song-Yeu Tsai ◽  
...  
Keyword(s):  
Solar Cells ◽  
Sheet Resistance ◽  
Open Circuit ◽  
Scale Production ◽  
Selective Emitter ◽  
Group A ◽  
Cell Sample ◽  
One Step ◽  
The One ◽  
Group B

In order to simplify process procedure and improve conversion efficiency (η), we present new steps of laser opening and one-step POCl3diffusion to fabricate selective emitter (SE) solar cells, in which heavily doped regions (HDR) and lightly doped regions (LDR) were formed simultaneously. For HDR, we divided six cells into two groups for POCl3diffusion with sheet resistance (RS) of 40 Ω/sq (for group A) and 50 Ω/sq (for group B). The dry oxidation duration at a temperature of 850°C was 18, 25, and 35 min for the 3 different cells in each group. This created six SE samples with differentRSpairings for the HDR and LDR. The optimal cell (sample SE2) withRSvalues of 40/81 Ω/Sq in HDR/LDR showed the bestηof 16.20%, open circuit voltage (VOC) of 612.52 mV, and fill factor (FF) of 75.83%. The improvement ratios are 1.57% forηand 14.32% for external quantum efficiency (EQE) as compared with those of the two-step diffusion process of our previous study. Moreover, the one-step laser opening process and omitting the step of removing the damage caused by laser ablation especially reduce chemistry pollution, thus showing ecofriendly process for use in industrial-scale production.

scholarly journals Solvent-Driven Selectivity on the One-Step Catalytic Synthesis of Manoyl Oxide Based on a Novel and Sustainable “Zeolite Catalyst–Solvent” System

2021 ◽  
Author(s):  
Dimitra Makarouni ◽  
Christos Kordulis ◽  
Vassilis Dourtoglou
Keyword(s):  
Large Scale ◽  
Zeolite Catalyst ◽  
Solvent System ◽  
High Yield ◽  
Scale Production ◽  
Large Scale Production ◽  
One Step ◽  
Catalyst Acidity ◽  
The One ◽  
Potential Precursor

AbstractApplication of a novel “zeolite catalyst–solvent” system for the sustainable one-step synthesis of the terpenoid manoyl oxide, the potential precursor of forskolin and ambrox. Manoyl oxide high-yield and large-scale production over a zeolite catalyst has been infeasible so far, while this system results in 90% yields at 135 °C and atmospheric pressure. Substrate-controlled methodology is used to achieve selectivity. Solvent-driven catalysis is shown, as the activation energy barrier decreases in the presence of appropriate solvents, being 62.7 and 93.46 kJmol−1 for a glyme-type solvent and dodecane, respectively. Finally, catalyst acidity is key parameter for the process. Graphic Abstract

Structure, Stability and Water Adsorption on Ultra-Thin TiO2 Supported on TiN

2019 ◽  
Author(s):  
Jose Julio Gutierrez Moreno ◽  
Marco Fronzi ◽  
Pierre Lovera ◽  
alan O'Riordan ◽  
Mike J Ford ◽  
...  
Keyword(s):  
Density Functional ◽  
Water Adsorption ◽  
Chemical Potential ◽  
Energy Gap ◽  
Molecular Water ◽  
Structure Stability ◽  
Ambient Conditions ◽  
Rutile Structure ◽  
The Stability ◽  
The One

<p></p><p>Interfacial metal-oxide systems with ultrathin oxide layers are of high interest for their use in catalysis. In this study, we present a density functional theory (DFT) investigation of the structure of ultrathin rutile layers (one and two TiO<sub>2</sub> layers) supported on TiN and the stability of water on these interfacial structures. The rutile layers are stabilized on the TiN surface through the formation of interfacial Ti–O bonds. Charge transfer from the TiN substrate leads to the formation of reduced Ti<sup>3+</sup> cations in TiO<sub>2.</sub> The structure of the one-layer oxide slab is strongly distorted at the interface, while the thicker TiO<sub>2</sub> layer preserves the rutile structure. The energy cost for the formation of a single O vacancy in the one-layer oxide slab is only 0.5 eV with respect to the ideal interface. For the two-layer oxide slab, the introduction of several vacancies in an already non-stoichiometric system becomes progressively more favourable, which indicates the stability of the highly non-stoichiometric interfaces. Isolated water molecules dissociate when adsorbed at the TiO<sub>2</sub> layers. At higher coverages the preference is for molecular water adsorption. Our ab initio thermodynamics calculations show the fully water covered stoichiometric models as the most stable structure at typical ambient conditions. Interfacial models with multiple vacancies are most stable at low (reducing) oxygen chemical potential values. A water monolayer adsorbs dissociatively on the highly distorted 2-layer TiO<sub>1.75</sub>-TiN interface, where the Ti<sup>3+</sup> states lying above the top of the valence band contribute to a significant reduction of the energy gap compared to the stoichiometric TiO<sub>2</sub>-TiN model. Our results provide a guide for the design of novel interfacial systems containing ultrathin TiO<sub>2</sub> with potential application as photocatalytic water splitting devices.</p><p></p>

A Study on the Rearrangement of Dialkyl 1-Aryl-1-hydroxymethylphosphonates to Benzyl Phosphates

2020 ◽  
Vol 24 (4) ◽  
pp. 465-471 ◽  
Author(s):  
Zita Rádai ◽  
Réka Szabó ◽  
Áron Szigetvári ◽  
Nóra Zsuzsa Kiss ◽  
Zoltán Mucsi ◽  
...  
Keyword(s):  
Quantum Chemical ◽  
Room Temperature ◽  
Phase Transfer ◽  
One Pot ◽  
Substrate Dependence ◽  
Triethylbenzylammonium Chloride ◽  
One Step ◽  
The Pudovik Reaction ◽  
The One ◽  
Solid Liquid

The phospha-Brook rearrangement of dialkyl 1-aryl-1-hydroxymethylphosphonates (HPs) to the corresponding benzyl phosphates (BPs) has been elaborated under solid-liquid phase transfer catalytic conditions. The best procedure involved the use of triethylbenzylammonium chloride as the catalyst and Cs2CO3 as the base in acetonitrile as the solvent at room temperature. The substrate dependence of the rearrangement has been studied, and the mechanism of the transformation under discussion was explored by quantum chemical calculations. The key intermediate is an oxaphosphirane. The one-pot version starting with the Pudovik reaction has also been developed. The conditions of this tandem transformation were the same, as those for the one-step HP→BP conversion.

scholarly journals A Review on Additive Manufacturing Possibilities for Electrical Machines

Energies ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1940
Author(s):  
Muhammad Usman Naseer ◽  
Ants Kallaste ◽  
Bilal Asad ◽  
Toomas Vaimann ◽  
Anton Rassõlkin
Keyword(s):  
Additive Manufacturing ◽  
Large Scale ◽  
Three Dimensional ◽  
Electrical Machines ◽  
Electromagnetic Properties ◽  
Scale Production ◽  
Performance Parameters ◽  
Large Scale Production ◽  
One Step ◽  
Manufacturing Techniques

This paper presents current research trends and prospects of utilizing additive manufacturing (AM) techniques to manufacture electrical machines. Modern-day machine applications require extraordinary performance parameters such as high power-density, integrated functionalities, improved thermal, mechanical & electromagnetic properties. AM offers a higher degree of design flexibility to achieve these performance parameters, which is impossible to realize through conventional manufacturing techniques. AM has a lot to offer in every aspect of machine fabrication, such that from size/weight reduction to the realization of complex geometric designs. However, some practical limitations of existing AM techniques restrict their utilization in large scale production industry. The introduction of three-dimensional asymmetry in machine design is an aspect that can be exploited most with the prevalent level of research in AM. In order to take one step further towards the enablement of large-scale production of AM-built electrical machines, this paper also discusses some machine types which can best utilize existing developments in the field of AM.

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