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Electromicrobial engineering is an emerging, highly interdisciplinary research area linking bioprocesses with electrochemistry. In this work, microbial electrosynthesis (MES) of biobutanol is carried out during acetone-butanol-ethanol (ABE) fermentations with Clostridium acetobutylicum. A constant electric potential of −600mV (vs. Ag/AgCl) with simultaneous addition of the soluble redox mediator neutral red is used in order to study the electron transfer between the working electrode and the bacterial cells. The results show an earlier initiation of solvent production for all fermentations with applied potential compared to the conventional ABE fermentation. The f inal butanol concentration can be more than doubled by the application of a negative potential combined with addition of neutral red. Moreover a higher biofilm formation on the working electrode compared to control cultivations has been observed. In contrast to previous studies, our results also indicate that direct electron transfer (DET) might be possible with C. acetobutylicum. The presented results make microbial butanol production economically attractive and therefore support the development of sustainable production processes in the chemical industry aspired by the “Centre for resource-efficient chemistry and raw material change” as well as the the project “NanoKat” working on nanostructured catalysts in Kaiserslautern.
Glucose ist ein primäres Zwischenprodukt der Verarbeitung nachwachsender Rohstoffe, wie z. B. Cellulose. Die wertsteigernde Weiterverarbeitung des Monosaccharids erfolgt häufig in Form vonFermentationsprozessen, jedoch kann der Rohstoff auch für zahlreiche chemische Verarbeitungsstufen genutzt werden. Ein großtechnisch relevanter Prozess ist die Herstellung von Gluconsäure (GS), die u. a. als Nahrungsmittelzusatz (E 574) eingesetzt wird. Die Darstellung der Säure erfolgt durch Oxidation von Glucose mit magnetisierbarem Gold-Nano-Katalysator. Die Rückgewinnung des Katalysators aus der Reaktionslösung wurde unter Einwirkung eines Magnetfeldgradienten verwirklicht. Die Synthese der magnetischen Goldkatalysatoren (sowohl Trägerpartikel als auch Gold-Nanopartikel) wurde durch nass-chemische Fällungsreaktionen durchgeführt. Die Charakteristiken der neuen Materialen konnte durch Messungen des PCD-Potenzials, Laserbeugung und REM/EDX untersucht werden. So wurden u. a. Partikeldurchmesser von 25 lm und ein Goldgehaltvon 1,03 % ermittelt. Weiterhin wurden für die Goldkatalysatoren optimale Reaktionsbedingungen für die Glucoseoxidation im geregelten Rührkesselreaktor etabliert. Hierdurch konnten eine Produktselektivität von 100 % und eine Wiederverwendbarkeit der Partikel über mindestens zehn Zyklen erreicht werden.
Gras hat ein hohes Potenzial als nachwachsender Rohstoff. Bei ungeeigneter Lagerung verderben Gräser allerdings innerhalb weniger Tage. Dieser Nachteil kann durch die Silierung des Grasschnittes behoben werden. Eines der wichtigsten in der Silage enthaltenen Produkte ist die Milchsäure. Um diese für weitere Aufarbeitungsschritte zugänglich zu machen, wird aus der Silage ein Presssaft hergestellt. Die Milchsäure wird aus einem Silagepresssaft mittels Extraktion durch ionische Flüssigkeiten isoliert. Dabei wird zum einen eine reine Milchsäure hergestellt, die z. B. für die Herstellung von Polymilchsäure genutzt werden kann. Zum anderen wird ein weniger aufgereinigter Extrakt gewonnen, der für die fermentative Produktion von L-Lysin und 1,2-Propandiol genutzt werden soll. Im Rahmen des Projekts erfolgt die gentechnische Optimierung von Corynebacterium glutamicum für die Umsetzung von Milchsäurezu L-Lysin. Die im nach der Pressung verbleibenden Presskuchen enthaltenen Grasfasern bestehen zu einem großen Teil aus Polysacchariden. Diese werden hydrolysiert und die dabei freigesetzten Zucker zu Grundchemikalien wie Ethanol oder Itakonsäure fermentiert. Im Rahmen einer vollständigen Nutzung der Silage wird das Raffinat aus der Milchsäureextraktion als Mediumsupplement in der Fermentation eingesetzt, was die Zugabe weiterer Medienbestandteile überflüssig macht. Die Rückstände der Hydrolysen und Fermentationen sollen darüberhinaus für die Herstellung von Biogas genutzt werden.
Magnetisierbare Partikel als Träger von Katalysatoren können durch Anlegen eines magnetisches Feldes einfach und schnell abgetrennt werden. Die Wiedergewinnung von wertvollen Enzymen unter geringem Energie- und Materialeinsatz der magnetischen Abtrennung eröffnet einen Wettbewerbsvorteil für Produktionsprozesse. Die Abtrennung von magnetisierbaren Partikeln vom Überstand wird üblicherweise entweder durch Anlegen eines äußeren Magnetfelds und der resultierenden Ablagerung der Partikel an den Reaktorwänden oder durch Hochgradientenmagnetseparation (HGMS)durchgeführt. Beide Verfahren resultieren meist in der Bildung eines Filterkuchens aus Magnetpartikeln und den Feststoffen des Reaktionsmediums. Das magnetische horizontale Wirbelbett ermöglicht simultan eine kontinuierliche Reaktionsführung und die Rückhaltung der Partikel im Durchfluss. Die Partikelsuspension fließt durch einen Rohrreaktor, der in einem Magnetfeld mit wechselnden Feldgradienten eingebracht ist. Die Änderung des Magnetfeldgradienten erfolgt entgegen der Strömungsrichtung der Reaktionslösung. Durch alternierende Feldmaxima an den beiden Seiten des Reaktors werden die magnetisierbaren Partikel zu dessen Wänden gezogen. Bei Umkehrung des Feldes wandern die Partikel an die gegenüberliegende Reaktorwand. Durch Wahl einer geeigneten Wechselfrequenz kann eine kontinuierliche Durchmischung und Rückhaltung der Mikropartikel im durchströmten Rohr erreicht werden. Somit können Immobilisierungsreaktionen und Biotransformationen mit den Partikelsystemen im Durchfluss durchgeführt werden.
Technische Cellulose wurde als möglicher Rohstoff zur fermentativen Produktbildung untersucht. Hierfür wird Cellulose in der Lignocellulose-Bioraffinerie hergestellt und daraus Hydrolysat gewonnen. Die Prüfung der technischen Hydrolysate als Substrate erfolgte anhand eines breiten Spektrums an Bioprodukten, von Kraftstoffen wie Ethanolund Butanol, bis zu den Dicarbonsäuren Itacon- und Bernsteinsäure. Dabei werden Bakterien, Hefen und Pilze als Produktionsorganismen eingesetzt. Die einzelnen Herstellverfahren stellen unterschiedliche Anforderungen an die Substrathandhabung. Im Fall der Ethanol- und Butanol-Gewinnung kann eine simultane Saccharifizierung und Fermentierung (SSF) durchgeführt werden. Aufgrund der Produkttoxizität erfordert die Butanol-Herstellung dabei eine In-situ-Produktabtrennung durch Lösemittelimprägnierte Partikel. Die Herstellung der beiden Dicarbonsäuren unterscheidet sich in der Sensitivität der verwendeten Mikroorganismen gegenüber Inhibitoren, die in Spuren im Hydrolysat enthalten sind. Die Bernteinsäurebildung mit Actinobacillussuccinogenes kann mit unbehandeltem Hydrolysat erfolgen. Dagegen erfordert die Gewinnung von Itaconsäure mit A. terreus eine Detoxifizierung des Hydrolysats. Insgesamt konnte gezeigt werden, dass sämtliche Bioraffinerie-Hydrolysate als Substrate für unterschiedliche Fermentationen geeignet sind.
Die Lösungsmittelherstellung durch Clostridien konnte wirtschaftlich nicht mit der chemischen Synthese von Lösungsmitteln auf Erdölbasis konkurrieren und wurde in den frühen 1960er Jahren nahezu vollständig eingestellt. Das Interesse an nachwachsenden Rohstoffen hat in den letzten Jahren zu einem Wiederaufleben der ABE-Fermentation geführt. Aufgrund seiner höheren Energiedichte im Vergleich zu Ethanol ist Biobutanol als Energieträgerbesonders interessant und bietet sich z. B. als Produkt einer Bioraffinerie der 2. Generation an. Für die beschriebenen Experimente wird durch das Organosolv-Verfahren aufgeschlossenes Buchenholz verwendet. Der Faserstoff wird mithilfe von CTec2-Enzymen hydrolysiert, wobei der erhaltene Überstand eine Glucosekonzentration von 66 g L⁻¹ aufweist. Auf der Basis dieses Materials können mit Clostridium acetobutylicum Butanol-Ausbeuten erzielt werden, die mit denen unter Verwendung von reinen Zuckern vergleichbar sind. Dem Problem der hohen Produktinhibierung wird mit einer In-situ-Produktaufarbeitung begegnet. Mithilfe von Lösungsmittelimprägnierten Partikeln (SIPs) kann die Produktausbeute drastisch gesteigert werden, indem die gebildeten Lösungsmittel durch das auf dem Partikel imprägnierte Lösungsmittel während der Fermentation extrahiert werden. Zudem wird hierdurch die weitere Produktaufarbeitungstark vereinfacht.
Hydrogen is playing an increasingly important role in research and politics as an energy carrier of the future. Since hydrogen has commonly been produced from methane by steam reforming, the need for climate-friendly, alternative production routes is emerging. In addition to electrolysis, fermentative routes for the production of so-called biohydrogen are "green" alternatives. The application of microorganisms offers the advantage of sustainable production from renewable resources using easily manageable technologies. In this project, the hyperthermophilic, anaerobic microorganism Thermotoga neapolitana is used for the productio nof biohydrogen from renewable resources. The enzymatically hydrolyzed resources were used in fermentation leading to yield coefficients of 1.8 mole H₂ per mole glucose when using hydrolyzed straw and ryegrass supplemented with medium, respectively. These results are similar to the hydrogen yields when using Thermotoga basal medium with glucose (TBGY) as control group. In order to minimize the supplementation of the hydrolysate and thus increase the economic efficiency of the process, the essential media components were identified. The experiments revealed NaCl, KCl, and glucose as essential components for cell growth as well as biohydrogen production. When excluding NaCl, a decrease of 96% in hydrogen production occured.
The emerging environmental issues due to the use of fossil resources are encouraging the exploration of new renewable resources. Biomasses are attracting more interest due to the low environmental impacts, low costs, and high availability on earth. In this scenario, green biorefineries are a promising platform in which green biomasses are used as feedstock. Grasses are mainly composed of cellulose and hemicellulose, and lignin is available in a small amount. In this work, a perennial ryegrass was used as feedstock to develop a green bio-refinery platform. Firstly, the grass was mechanically pretreated, thus obtaining a press juice and a press cake fraction. The press juice has high nutritional values and can be employed as part of fermentation media. The press cake can be employed as a substrate either in enzymatic hydrolysis or in solid-state fermentation. The overall aim of this work was to demonstrate different applications of both the liquid and the solid fractions. For this purpose, the filamentous fungus A. niger and the yeast Y. lipolythica were selected for their ability to produce citric acid. Finally, the possibility was assessed to use the press juice as part of fermentation media to cultivate S. cerevisiae and lactic acid bacteria for ethanol and lactic acid fermentation.
Lolium perenne (perennial ryegrass) is aproductive and high-quality forage grass indigenous to Southern Europe, temperate Asia, and North Africa. Nowadays it is widespread and the dominant grass species on green areas in temperate climates. This abundant source of biomass is suitable for the development of bioeconomic processes because of its high cellulose and water-soluble carbohydrate content. In this work, novel breeds of the perennial ryegrass are being examined with regards to their quality parameters and biotechnological utilization options within the context of bioeconomy. Three processing operations are presented. In the first process, the perennial ryegrass is pretreated by pressing or hydrothermal extraction to derive glucosevia subsequent enzymatic hydrolysis of cellulose. A yield of up to 82 % glucose was achieved when using the hydrothermal ex-traction as pretreatment. In a second process, the ryegrass is used to produce lactic acid in high concentrations. The influence of the growth conditions and the cutting time on the carboxylic acid yield is investigated. A yield of lactic acid of above 150 g kg⁻¹ dry matter was achieved. The third process is to use Lolium perenne as a substrate in the fermentation of K. marxianus for the microbial production of single-cell proteins. The perennial ryegrass is screw-pressed and the press juice is used as medium. When supplementing the press juice with yeast media components, a biomass concentration of up to 16 g L⁻¹ could be achieved.
A method for the integrated extraction and separation of fatty acids from algae using supercritical CO2 is presented. Desmodesmus obliquus and Chlorella sorokiniana were used as algae. First, a method for chromatographic separation of fatty acids of different degrees of saturation was established and optimized. Then, an integrated method for supercritical extraction was developed for both algal species. It was also verified whether prior cell disruption was beneficial for extraction. In developing the method for chromatographic separation, statistical experimental design was used to determine the optimal parameter settings. The methanol content in the mobile phase proved to be the most important parameter for successful separation of the three unsaturated fatty acids oleic acid, linoleic acid, and linolenic acid. Supercritical extraction with dried algae showed that about four times more fatty acids can be extracted from C. sorokiniana relative to the dry mass used.
The concept of energy conversion into platform chemicals using bioelectrochemical systems (BES) has gained increasing attention in recent years, as the technology simultaneously provides an opportunity for sustainable chemical production and tackles the challenge of Power-to-X technologies. There are many approaches to realize the industrial scale of BES. One concept is to equip standard bioreactors with static electrodes. However, large installations resulted in a negative influence on various reactor parameters. In this study, we present a new single-chamber BES based on a stirred tank reactor in which the stirrer was replaced by a carbon fiber brush, performing the functions of the working electrode and the stirrer. The reactor is characterized in abiotic studies and electro-fermentations with Clostridium acetobutylicum. Compared to standard reactors an increase in butanol production of 20.14±3.66 % shows that the new BES can be efficiently used for bioelectrochemical processes.
New insights into the influence of pre-culture on robust solvent production of C. acetobutylicum
(2024)
Clostridia are known for their solvent production, especially the production of butanol. Concerning the projected depletion of fossil fuels, this is of great interest. The cultivation of clostridia is known to be challenging, and it is difficult to achieve reproducible results and robust processes. However, existing publications usually concentrate on the cultivation conditions of the main culture. In this paper, the influence of cryo-conservation and pre-culture on growth and solvent production in the resulting main cultivation are examined. A protocol was developed that leads to reproducible cultivations of Clostridium acetobutylicum. Detailed investigation of the cell conservation in cryo-cultures ensured reliable cell growth in the pre-culture. Moreover, a reason for the acid crash in the main culture was found, based on the cultivation conditions of the pre-culture. The critical parameter to avoid the acid crash and accomplish the shift to the solventogenesis of clostridia is the metabolic phase in which the cells of the pre-culture were at the time of inoculation of the main culture; this depends on the cultivation time of the pre-culture. Using cells from the exponential growth phase to inoculate the main culture leads to an acid crash. To achieve the solventogenic phase with butanol production, the inoculum should consist of older cells which are in the stationary growth phase. Considering these parameters, which affect the entire cultivation process, reproducible results and reliable solvent production are ensured.
Drought and water shortage are serious problems in many arid and semi-arid regions. This problem is getting worse and even continues in temperate climatic regions due to climate change. To address this problem, the use of biodegradable hydrogels is increasingly important for the application as water-retaining additives in soil. Furthermore, efficient (micro-)nutrient supply can be provided by the use of tailored hydrogels. Biodegradable polyaspartic acid (PASP) hydrogels with different available (1,6-hexamethylene diamine (HMD) and L-lysine (LYS)) and newly developed crosslinkers based on diesters of glycine (GLY) and (di-)ethylene glycol (DEG and EG, respectively) were synthesized and characterized using Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) and regarding their swelling properties (kinetic, absorbency under load (AUL)) as well as biodegradability of PASP hydrogel. Copper (II) and zinc (II), respectively, were loaded as micronutrients in two different approaches: in situ with crosslinking and subsequent loading of prepared hydrogels. The results showed successful syntheses of di-glycine-ester-based crosslinkers. Hydrogels with good water-absorbing properties were formed. Moreover, the developed crosslinking agents in combination with the specific reaction conditions resulted in higher water absorbency with increased crosslinker content used in synthesis (10% vs. 20%). The prepared hydrogels are candidates for water-storing soil additives due to the biodegradability of PASP, which is shown in an exemple. The incorporation of Cu(II) and Zn(II) ions can provide these micronutrients for plant growth.
Throughout the last decade, and particularly in 2022, water scarcity has become a critical concern in Morocco and other Mediterranean countries. The lack of rainfall during spring was worsened by a succession of heat waves during the summer. To address this drought, innovative solutions, including the use of new technologies such as hydrogels, will be essential to transform agriculture. This paper presents the findings of a study that evaluated the impact of hydrogel application on onion (Allium cepa) cultivation in Meknes, Morocco. The treatments investigated in this study comprised two different types of hydrogel-based soil additives (Arbovit® polyacrylate and Huminsorb® polyacrylate), applied at two rates (30 and 20 kg/ha), and irrigated at two levels of water supply (100% and 50% of daily crop evapotranspiration; ETc). Two control treatments were included, without hydrogel application and with both water amounts. The experiment was conducted in an open field using a completely randomized design. The results indicated a significant impact of both hydrogel-type dose and water dose on onion plant growth, as evidenced by various vegetation parameters. Among the hydrogels tested, Huminsorb® Polyacrylate produced the most favorable outcomes, with treatment T9 (100%, HP, 30 kg/ha) yielding 70.55 t/ha; this represented an increase of 11 t/ha as compared to the 100% ETc treatment without hydrogel application. Moreover, the combination of hydrogel application with 50% ETc water stress showed promising results, with treatment T4 (HP, 30 kg, 50%) producing almost the same yield as the 100% ETc treatment without hydrogel while saving 208 mm of water.
This book is based on a multimedia course for biological and chemical engineers, which is designed to trigger students' curiosity and initiative. A solid basic knowledge of thermodynamics and kinetics is necessary for understanding many technical, chemical, and biological processes.
The one-semester basic lecture course was divided into 12 workshops (chapters). Each chapter covers a practically relevant area of physical chemistry and contains the following didactic elements that make this book particularly exciting and understandable:
- Links to Videos at the start of each chapter as preparation for the workshop
- Key terms (in bold) for further research of your own
- Comprehension questions and calculation exercises with solutions as learning checks
- Key illustrations as simple, easy-to-replicate blackboard pictures
Humorous cartoons for each workshop (by Faelis) additionally lighten up the text and facilitate the learning process as a mnemonic. To round out the book, the appendix includes a summary of the most popular experiments in basic physical chemistry courses, as well as suggestions for designing workshops with exhibits, experiments, and "questions of the day."
Suitable for students minoring in chemistry; chemistry majors are sure to find this slimmed-down, didactically valuable book helpful as well. The book is excellent for self-study.
Experimental determination of the cross sections of proton capture on radioactive nuclei is extremely difficult. Therefore, it is of substantial interest for the understanding of the production of the p-nuclei. For the first time, a direct measurement of proton-capture cross sections on stored, radioactive ions became possible in an energy range of interest for nuclear astrophysics. The experiment was performed at the Experimental Storage Ring (ESR) at GSI by making use of a sensitive method to measure (p,γ) and (p,n) reactions in inverse kinematics. These reaction channels are of high relevance for the nucleosyn-thesis processes in supernovae, which are among the most violent explosions in the universe and are not yet well understood. The cross section of the ¹¹⁸Te(p,γ) reaction has been measured at energies of 6 MeV/u and 7 MeV/u. The heavy ions interacted with a hydrogen gas jet target. The radiative recombination process of the fully stripped ¹¹⁸Te ions and electrons from the hydrogen target was used as a luminosity monitor. An overview of the experimental method and preliminary results from the ongoing analysis will be presented.
Preprint: Studies on the enzymatic reduction of levulinic acid using Chiralidon-R and Chiralidon-S
(2023)
The enzymatic reduction of levulinic acid by the chiral catalysts Chiralidon-R and Chiralidon-S which are commercially available superabsorbed alcohol dehydrogenases is described. The Chiralidon®-R/S reduces the levulinic acid to the (R,S)-4-hydroxy valeric acid and the (R)- or (S)- gamma-valerolactone.