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- ItemEffects of proline substitutions on the thermostable LOV domain from Chloroflexus aggregans(Basel : MDPI AG, 2020) Remeeva, Alina; Nazarenko, Vera V.; Goncharov, Ivan M.; Yudenko, Anna; Smolentseva, Anastasia; Semenov, Oleg; Kovalev, Kirill; Gülbahar, Cansu; Schwaneberg, Ulrich; Davari, Mehdi D.; Gordeliy, Valentin; Gushchin, IvanLight-oxygen-voltage (LOV) domains are ubiquitous photosensory modules found in proteins from bacteria, archaea and eukaryotes. Engineered versions of LOV domains have found widespread use in fluorescence microscopy and optogenetics, with improved versions being continuously developed. Many of the engineering efforts focused on the thermal stabilization of LOV domains. Recently, we described a naturally thermostable LOV domain from Chloroflexus aggregans. Here we show that the discovered protein can be further stabilized using proline substitution. We tested the effects of three mutations, and found that the melting temperature of the A95P mutant is raised by approximately 2◦ C, whereas mutations A56P and A58P are neutral. To further evaluate the effects of mutations, we crystallized the variants A56P and A95P, while the variant A58P did not crystallize. The obtained crystal structures do not reveal any alterations in the proteins other than the introduced mutations. Molecular dynamics simulations showed that mutation A58P alters the structure of the respective loop (Aβ-Bβ), but does not change the general structure of the protein. We conclude that proline substitution is a viable strategy for the stabilization of the Chloroflexus aggregans LOV domain. Since the sequences and structures of the LOV domains are overall well-conserved, the effects of the reported mutations may be transferable to other proteins belonging to this family. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.
- ItemBulk and Single Crystal Growth Progress of Iron-Based Superconductors (FBS): 1111 and 1144(Basel : MDPI AG, 2022) Singh, Shiv J.; Sturza, Mihai I.The discovery of iron-based superconductors (FBS) and their superconducting properties has generated huge research interest and provided a very rich physics high Tc family for fundamental and experimental studies. The 1111 (REFeAsO, RE = Rare earth) and 1144 (AEAFe4As4, AE = Ca, Eu; A = K, Rb) families are the two most important families of FBS, which offer the high Tc of 58 K and 36 K with doping and without doping, respectively. Furthermore, the crystal growth of these families is not an easy process, and a lot of efforts have been reported in this direction. However, the preparation of high-quality and suitable-sized samples is still challenging. In this short review, we will summarize the growth of materials with their superconducting properties, especially polycrystals and single crystals, for the 1111 and 1144 families, and make a short comparison between them to understand the developmental issues.
- ItemSyntheses, crystal structure and magnetic properties of Tl9RETe6 (RE = Ce, Sm, Gd)(Basel : MDPI AG, 2020) Isaeva, A.; Schönemann, R.; Doert, T.The three compounds Tl9RETe6 with RE = Ce, Sm, Gd were synthesized from the elements at 1020 K. Their isostructural crystal structures are ordered derivatives of the Tl5Te3 type with rare-earth metal and thallium occupying different Wyckoff positions. The structures can be understood as charge-ordered in accordance with the Zintl-Klemm concept: 9 Tl+ + RE3+ + 6 Te2-. DFT calculations for Tl9GdTe6, however, result in a low, but finite density of states at the Fermi level. Magnetic data confirm trivalent Gd, but indicate a small amount of Ce4+ in Tl9CeTe6; no indications for long-range magnetic order was found down to T = 2 K.
- ItemInfluence of MoS2 on activity and stability of carbon nitride in photocatalytic hydrogen production(Basel : MDPI AG, 2019) Sivasankaran, R.P.; Rockstroh, N.; Kreyenschulte, C.R.; Bartling, S.; Lund, H.; Acharjya, A.; Junge, H.; Thomas, A.; Brückner, A.MoS2/C3N4 (MS-CN) composite photocatalysts have been synthesized by three different methods, i.e., in situ-photodeposition, sonochemical, and thermal decomposition. The crystal structure, optical properties, chemical composition, microstructure, and electron transfer properties were investigated by X-ray diffraction, UV-vis diffuse reflectance spectroyscopy, X-ray photoelectron spectroscopy, electron microscopy, photoluminescence, and in situ electron paramagnetic resonance spectroscopy. During photodeposition, the 2H MoS2 phase was formed upon reduction of [MoS4]2− by photogenerated conduction band electrons and then deposited on the surface of CN. A thin crystalline layer of 2H MoS2 formed an intimate interfacial contact with CN that favors charge separation and enhances the photocatalytic activity. The 2H MS-CN phase showed the highest photocatalytic H2 evolution rate (2342 µmol h−1 g−1, 25 mg catalyst/reaction) under UV-vis light irradiation in the presence of lactic acid as sacrificial reagent and Pt as cocatalyst.
- ItemExploitation of Ultrasound Technique for Enhancement of Microbial Metabolites Production(Basel : MDPI AG, 2020) Behzadnia, Asma; Moosavi-Nasab, Marzieh; Ojha, Shikha; Tiwari, Brijesh K.Microbial metabolites have significant impacts on our lives from providing valuable compounds for nutrition to agriculture and healthcare. Ever-growing demand for these natural compounds has led to the need for smart and efficient production techniques. Ultrasound is a multi-applicable technology widely exploited in a range of industries such as chemical, medical, biotechnological, pharmaceutical, and food processes. Depending on the type of ultrasound employed, it can be used to either monitor or drive fermentation processes. Ultrasonication can improve bioproduct productivity via intensifying the performance of living organisms. Controlled ultrasonication can influence the metabolites' biosynthesis efficiency and growth rates by improvement of cell permeability as well as mass transfer and nutrient uptake rates through cell membranes. This review contains a summarized description about suitable microbial metabolites and the applications of ultrasound technique for enhancement of the production of these metabolites as well as the associated downstream processing.
- ItemA simple biorefinery concept to produce 2g-lactic acid from Sugar Beet Pulp (SBP): A high-value target approach to valorize awaste stream(Basel : MDPI AG, 2020) De Oliveira, Regiane Alves; Schneider, Roland; Lunelli, Betânia Hoss; Rossell, Carlos Eduardo Vaz; Filho, Rubens Maciel; Venus, JoachimLactic acid is a high-value molecule with a vast number of applications. Its production in the biorefineries model is a possibility for this sector to aggregate value to its production chain. Thus, this investigation presents a biorefinery model based on the traditional sugar beet industry proposing an approach to produce lactic acid from a waste stream. Sugar beet is used to produce sugar and ethanol, and the remaining pulp is sent to animal feed. Using Bacillus coagulans in a continuous fermentation, 2781.01 g of lactic acid was produced from 3916.91 g of sugars from hydrolyzed sugar beet pulp, with a maximum productivity of 18.06 g L-1h-1. Without interfering in the sugar production, ethanol, or lactic acid, it is also possible to produce pectin and phenolic compounds in the biorefinery. The lactic acid produced was purified by a bipolar membrane electrodialysis and the recovery reached 788.80 g/L with 98% w/w purity. © 2020 by the authors.
- ItemFilled carbon nanotubes as anode materials for lithium-ion batteries(Basel : MDPI AG, 2020) Thauer, E.; Ottmann, A.; Schneider, P.; Möller, L.; Deeg, L.; Zeus, R.; Wilhelmi, F.; Schlestein, L.; Neef, C.; Ghunaim, R.; Gellesch, M.; Nowka, C.; Scholz, M.; Haft, M.; Wurmehl, S.; Wenelska, K.; Mijowska, E.; Kapoor, A.; Bajpai, A.; Hampel, S.; Klingeler, R.Downsizing well-established materials to the nanoscale is a key route to novel functionalities, in particular if different functionalities are merged in hybrid nanomaterials. Hybrid carbon-based hierarchical nanostructures are particularly promising for electrochemical energy storage since they combine benefits of nanosize effects, enhanced electrical conductivity and integrity of bulk materials. We show that endohedral multiwalled carbon nanotubes (CNT) encapsulating high-capacity (here: conversion and alloying) electrode materials have a high potential for use in anode materials for lithium-ion batteries (LIB). There are two essential characteristics of filled CNT relevant for application in electrochemical energy storage: (1) rigid hollow cavities of the CNT provide upper limits for nanoparticles in their inner cavities which are both separated from the fillings of other CNT and protected against degradation. In particular, the CNT shells resist strong volume changes of encapsulates in response to electrochemical cycling, which in conventional conversion and alloying materials hinders application in energy storage devices. (2) Carbon mantles ensure electrical contact to the active material as they are unaffected by potential cracks of the encapsulate and form a stable conductive network in the electrode compound. Our studies confirm that encapsulates are electrochemically active and can achieve full theoretical reversible capacity. The results imply that encapsulating nanostructures inside CNT can provide a route to new high-performance nanocomposite anode materials for LIB.
- ItemProduction of Lactic Acid from Carob, Banana and Sugarcane Lignocellulose Biomass(Basel : MDPI AG, 2020) Azaizeh, Hassan; Abu Tayeh, Hiba N.; Schneider, Roland; Klongklaew, Augchararat; Venus, JoachimLignocellulosic biomass from agricultural residues is a promising feedstock for lactic acid (LA) production. The aim of the current study was to investigate the production of LA from different lignocellulosic biomass. The LA production from banana peduncles using strain Bacillus coagulans with yeast extract resulted in 26.6 g LA·L-1, and yield of 0.90 g LA·g-1 sugars. The sugarcane fermentation with yeast extract resulted in 46.5 g LA·L-1, and yield of 0.88 g LA·g-1 sugars. Carob showed that addition of yeast extract resulted in higher productivity of 3.2 g LA·L-1·h-1 compared to without yeast extract where1.95 g LA·L-1·h-1 was obtained. Interestingly, similar LA production was obtained by the end where 54.8 and 51.4 g·L-1 were obtained with and without yeast extract, respectively. A pilot scale of 35 L using carob biomass fermentation without yeast extract resulted in yield of 0.84 g LA·g-1 sugars, and productivity of 2.30 g LA·L-1·h-1 which indicate a very promising process for future industrial production of LA.
- ItemEffects of Promoter on Structural and Surface Properties of Zirconium Oxide-Based Catalyst Materials(Basel : MDPI AG, 2020) Borovinskaya, E.S.; Oswald, S.; Reschetilowski, W.Ternary mixed oxide systems CuO/ZnO/ZrO2 and CuO/NiO/ZrO2 were synthesized by one-pot synthesis for a better understanding of the synthesis-property relationships of zirconium oxide-based catalyst materials. The prepared mixed oxide samples were analysed by a broad range of characterisation methods (XRD, N2-physisorption, Temperature-Programmed Ammonia Desorption (TPAD), and XPS) to examine the structural and surface properties, as well as to identify the location of the potential catalytically active sites. By XPS analysis, it could be shown that a progressive enrichment of the surface composition with copper takes place by changing from ZnO to NiO as a promoter. Thus, by addition of the second component, not only electronic but also the geometric properties of active sites, i.e., copper species distribution within the catalyst surface, can be affected in a desired way.
- ItemRelevance of interactions between starch-based coatings and plum fruit surfaces: A physical-chemical analysis(Basel : MDPI AG, 2019) Basiak, Ewelina; Geyer, Martin; Debeaufort, Frédéric; Lenart, Andrzej; Linke, ManfredIn order to extend the shelf life of the fruit, improve appearance, and to keep all nutrition properties of the plum from diminishing, edible coatings comprised of wheat starch and wheat starch–whey protein isolate (in ratio 80/20) were created. Stand-alone films were produced to assess properties which helped to understand the phenomena occurring on the surface level of coated plums. The properties of coatings based on starch are similar to starch coatings containing oil because the natural epicuticular wax layer of plums merges with coating materials. Adding oil doubled the contact angle value and the dispersive component of the surface tension. The workings of adhesion and cohesion, spreading coefficient, water absorption, water content, and solubility in water of the films decreased. Similar processes were observed on the fruits’ surface. In appearance, the coating process is similar to polishing the plum surface for removing crystalline wax. The color parameters of coated fruits did not significantly change. Newly formed bonds or interactions established between starch, whey proteins, water, glycerol, and oil are displayed by Fourier transform infrared (FTIR) analysis. This work revealed how the interactions between the epicuticular wax on the fruit’s surface and the hydrocolloid-based coatings affect the efficiency of the coatings. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.