Steroid biotransformations in biphasic systems with Yarrowia lipolytica expressing human liver cytochrome P450 genes

BACKGROUND: Yarrowia lipolytica efficiently metabolizes and assimilates hydrophobic compounds such as n-alkanes and fatty acids. Efficient substrate uptake is enabled by naturally secreted emulsifiers and a modified cell surface hydrophobicity and protrusions formed by this yeast. We were examining the potential of recombinant Y. lipolytica as a biocatalyst for the oxidation of hardly soluble hydrophobic steroids. Furthermore, two-liquid biphasic culture systems were evaluated to increase substrate availability. While cells, together with water soluble nutrients, are maintained in the aqueous phase, substrates and most of the products are contained in a second water-immiscible organic solvent phase. RESULTS: For the first time we have co-expressed the human cytochromes P450 2D6 and 3A4 genes in Y. lipolytica together with human cytochrome P450 reductase (hCPR) or Y. lipolytica cytochrome P450 reductase (YlCPR). These whole-cell biocatalysts were used for the conversion of poorly soluble steroids in biphasic systems. Employing a biphasic system with the organic solvent and Y. lipolytica carbon source ethyl oleate for the whole-cell bioconversion of progesterone, the initial specific hydroxylation rate in a 1.5 L stirred tank bioreactor was further increased 2-fold. Furthermore, the product formation was significantly prolonged as compared to the aqueous system. Co-expression of the human CPR gene led to a 4-10-fold higher specific activity, compared to the co-overexpression of the native Y. lipolytica CPR gene. Multicopy transformants showed a 50-70-fold increase of activity as compared to single copy strains. CONCLUSIONS: Alkane-assimilating yeast Y. lipolytica, coupled with the described expression strategies, demonstrated its high potential for biotransformations of hydrophobic substrates in two-liquid biphasic systems. Especially organic solvents which can be efficiently taken up and/or metabolized by the cell might enable more efficient bioconversion as compared to aqueous systems and even enable simple, continuous or at least high yield long time processes

Проект установки получения синтез-газа

ВКР 91 страницу, 6 рисунков, 40 таблиц, 24 литературных источника. Ключевые слова: синтез-газ, конверсия, применение синтез-газа, сырье, природный газ, технологическая схема, производство, метан, метанол. Объект разработки: производство синтез-газа методом паровой каталитической конверсии природного газа. Цель работы: изучение всех физико - химических свойств процесса и их влияния на протекание реакции, а также конструирование основного аппарата установки получения синтез - газа. В результате исследования выполнен расчет материального и теплового балансов, также конструктивный и механический расчеты, на основании которых был выполнен чертеж основного аппарата. ВКР выполнена на кафедре ТОВПМ ст. группы 2Д2А Якимовой В.А., под руководством к.х.н. Мананковой А.А.The final qualifying work contains 91 page, 6 figures, 40 tables and 24 literature sources. Content words are conversion, synthesis gas. The object of the development is the production of synthesis gas by catalytic steam reforming of natural gas. The mission is the study of physical - chemical properties of the process and their influence on the reaction, as well as the construction of the main unit installation producing synthesis - gas. The study was carried out payment of material and heat balances, the constructive and mechanical calculations, drawing on the basis of which the main unit was made. The final qualifying work carried out at the Department of TOVPM student group 2D2A Vera Yakimova, under the leadership of Candidate of Chemical Sciences Ann Manankova

Thermodynamic transitions and topology of spin-triplet superconductivity: Application to UTe2_2

The discovery of unconventional superconductivity in the heavy-fermion material UTe$_2$ has reinvigorated research of spin-triplet superconductivity. We perform a theoretical study of coupled two-component spin-triplet superconducting order parameters and their thermodynamic transitions into the superconducting state. With focus on the behavior of the temperature dependence of the specific heat capacity, we find that two-component time-reversal symmetry breaking superconducting order may feature vanishing or even negative secondary specific heat anomalies. The origin of this unusual specific heat behavior is tied to the non-unitarity of the composite order parameter. Additionally, we supply an analysis of the topological surface states associated with the different possible spin-triplet orders: single-component orders host Dirac Majorana surface states in addition to possible bulk nodes. A second component breaking time-reversal symmetry gaps these surfaces states producing chiral Majorana hinge modes. DFT+$U$ band-structure calculations support that these topological phases are realized in UTe$_2$ when introducing weak superconducting pairing. Our topological analysis suggests measurable signatures for surface-probe experiments to acquire further evidence of the superconducting pairing symmetry.Comment: 20 pages, 8 figure

Identification of rotor and stator flux linkage maps of squirrel cage induction motors based on identification of rotor time constant maps

Model-predictive, field-oriented control of squirrel cage induction motors (SCIM) depends on the accurate identification and orientation of rotor and stator flux maps. In this paper, a new method is presented that utilizes the measured rotor time constant maps to reduce the orientation error of the identified flux maps. This enables the identification and modelling of the nonlinear and transient machine behavior, due to the estimation of the stator- and rotor-flux maps in dependence of stator and rotor currents

The BG-Sentinel, a novel mosquito trap for research and surveillance

Um Informationen zur Verbreitung und Populationsdichte von Stechmücken zu gewinnen, werden verschiedene Methoden verwendet. Neben der Suche nach Larven oder Puppen in den Brutgewässern, dem Absuchen von Ruheplätzen nach Adulten und den Fang aktiver, wirtssuchender Mückenweibchen durch freiwillige Mückenfänger werden vor allem unterschiedliche Fallentypen verwendet. Abgesehen von zwar preiswerten, aber wenig effizienten Fallen für gravide (also nicht mehr wirtsuchende) Mückenweibchen werden bisher Fallen mit unspezifische Lockreizen betrieben (Farbkontraste, Licht, Kohlendioxid). Letzteres ist in seiner Verwendung zudem aufwendig und teuer, da es aus Trockeneis, aus Gasflaschen oder der Verbrennung von Propangas freigesetzt werden muß. Wir stellen einen neuartigen Fallentypus für Stechmücken vor, den BG-Sentinel (Abb. 1). Die Falle wurde ursprünglich für die Überwachung der Gelbfiebermücke Stegomyia aegypti (ehemals Aedes aegypti, REINERT et al. 2004) entwickelt, ist aber auch für eine Reihe anderer Mücken attraktiv. Der BG-Sentinel ist die erste Falle, die neben visuellen Reizen auch, wie ein natürlicher Wirt, eine aufwärtsgerichtete Luftströmung produziert. Diese Luftströmung kann durch Zugabe geeigneter Düfte mit Lockstoffen beladen werden. Wir stellen außerdem mit der sogenannten BG-Lure einen neuen Mückenlockstoff vor, der aus Substanzen besteht, die auch auf der menschlichen Haut vorkommt. Die Konstruktion des BG-Sentinel ermöglicht es, eine Vielzahl verschiedener Reize auf ihre Attraktivität im Feld zu testen. Im Folgenden werden Feldtests des BG-Sentinel mit Stegomyia aegypti in Brasilien und Culex pipiens in Deutschland beschrieben.We introduce a novel, patent pending type of mosquito trap, the BG-Sentinel®. The trap consists of an easy to transport, collapsible white bucket with white gauze covering its opening. In the middle of the gauze cover, there is a black tube through which a down flow is created by a fan that draws approaching mosquitoes into a catch bag. The air then exits the trap through the gauze; the design therefore generates ascending currents. These are similar to convection currents produced by a human host, both in its direction, its geometrical structure, and, due to the addition of attractants, also in its chemical composition. The attractants are given off by the so-called BG-Lure®, a dispenser which releases a defined, patent pending combination of lactic acid, ammonia, and caproic acid, all substances that are found on human skin. The dispenser emits the attractants for up to 5 month. The addition of CO2 is not necessary for species such as Stegomyia aegypti (syn. Aedes aegypti) or St. albopicta (syn Ae. albopictus). In field tests in Belo Horizonte, Brazil, the BGSentinel with the BG-Lure was much more efficient in catching the yellow fever mosquito St. aegypti than a propane-powered CO2-trap and a bidirectional Fay-Prince trap. The tests also indicate that the BG-Sentinel can be a sensitive and easy-to-use alternative to human landing/biting collections in the surveillance of adult host seeking Dengue vectors. Further field tests near Regensburg in Germany showed that the BG-Sentinel with the BG-Lure is also an efficient trap for Culex pipiens. The addition of CO2 or 2-Undecanone did not further improve the attractiveness of the BG-Lure. Due to its design, the BG-Sentinel can be used with a variety of other potential mosquito attractants, making it a versatile tool for mosquito research and surveillance