66 Chemische Verfahrenstechnik
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- Fermentation (5)
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- fermentation (2)
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Terrestrial cyanobacteria grow as phototrophic biofilms and offer a wide spectrum of interesting products. For cultivation of phototrophic biofilms different reactor concepts have been developed in the last years. One of the main influencing factors is the surface material and the adhesion strength of the chosen production strain. In this work a flow chamber was developed, in which, in combination with optical coherence tomography and computational fluid dynamics simulation, an easy analysis of adhesion forces between different biofilms and varied surface materials is possible. Hereby, differences between two cyanobacteria strains and two surface materials were shown. With longer cultivation time of biofilms adhesion increased in all experiments. Additionally, the content of extracellular polymeric substances was analyzed and its role in surface adhesion was evaluated. To test the comparability of obtained results from the flow chamber with other methods, analogous experiments were conducted with a rotational rheometer, which proved to be successful. Thus, with the presented flow chamber an easy to implement method for analysis of biofilm adhesion was developed, which can be used in future research for determination of suitable combinations of microorganisms with cultivation surfaces on lab scale in advance of larger processes.
The current work investigates the capability of a tailored multivariate curve resolution–alternating least squares (MCR-ALS) algorithm to analyse glucose, phosphate, ammonium and acetate dynamics simultaneously in an E. coli BL21 fed-batch fermentation. The high-cell-density (HCDC) process is monitored by ex situ online attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy and several in situ online process sensors. This approach efficiently utilises automatically generated process data to reduce the time and cost consuming reference measurement effort for multivariate calibration. To determine metabolite concentrations with accuracies between ±0.19 and ±0.96·gL−l, the presented utilisation needs primarily — besides online sensor measurements — single FTIR measurements for each of the components of interest. The ambiguities in alternating least squares solutions for concentration estimation are reduced by the insertion of analytical process knowledge primarily in the form of elementary carbon mass balances. Thus, in this way, the established idea of mass balance constraints in MCR combines with the consistency check of measured data by carbon balances, as commonly applied in bioprocess engineering. The constraints are calculated based on online process data and theoretical assumptions. This increased calculation effort is able to replace, to a large extent, the need for manually conducted quantitative chemical analysis, leads to good estimations of concentration profiles and a better process understanding.
Cryotropic gelation is one of the most common approaches to design novel hydrogels with multifaceted technological and biological functionalities. In the present paper, we studied the ability of highly galactosyl-substituted galactomannans, i.e. fenugreek and alfalfa gum, to form physically crosslinked hydrogels via cryogenic processing. Cycling of the galactomannan solutions (0.25 to 4% wt) from 25 to −20 to 25 °C induced the physical crosslinking of the galactomannan chains leading to the formation of different cryogel structures, i.e. filamentous aggregates (c* < c < 1%), cellular-like gel networks (1 ≤ c < 4%) or a homogeneously swollen gel (c ≥ 4%), depending on the total biopolymer content. Alfalfa gum-based cryogels exhibited higher elasticity and stiffness, better uniformity of the structure and a lower macropore size than their fenugreek counterparts. The physical blending of alfalfa or fenugreek gum with locust bean gum (2% total biopolymer) led to the reinforcement of the mechanical properties of the cryogels without significantly altering their microstructural aspects.
Innovative biogas multi-stage biogas plant and novel analytical system: First project experiences
(2012)
The here presented applied research and development project is targeted to the development and application of new and improved techniques in plant design, performance analysis and process control. Hereto following the required steps are illustrated and the goals are outlined. The project covers the development of a previously patented anaerobic digestion process, adaption of flow cytometry as an analytical instrument and investigation of innovative ways of disposal of solid fermentation wastes. The preliminary experiences with a newly built research plant employing a novel anaerobic biogas digestion technique are discussed. In this paper the first outcomes concerning the construction and operation are discussed. A novel method of disposal of the fermentation wastes is also discussed and first results are shown.
The present work aimed at investigating an extraction protocol based on consecutive steps of isoelectric point (pH ~ 4.25) mediated gum swelling and deproteinisation as an alternative method to produce flaxseed gum extracts of enhanced techno-functional characteristics. The osidic and proximate composition, structure conformation, flow behaviour, dynamic rheological and thermal properties of gums isolated from brown and golden flaxseeds were assessed. Gum extraction under near-to-isoelectric point conditions did not impair the extraction yield, residual protein and ash content, whilst it resulted in minor changes in the sugar composition of the flaxseed gum extracts. The deconvolution of the GPC/SEC chromatographs revealed the presence of four major polysaccharidic populations corresponding to arabinoxylans, rhamnogalacturonan–I and two AX-RG-I composite fractions. The latter appeared to minimise the intra- and interchain polymer non-covalent interactions (hydrogen bonding) leading to a better solvation affinity in water and lyotropic solvents. Golden flaxseed gums exerted higher molecular weight (Mw = 1.34–1.15 × 106 Da) and intrinsic viscosities (6.63–5.13 dL g−1) as well as better thickening and viscoelastic performance than the brown flaxseed gum exemplars. Golden flaxseed gums exhibited a better thermal stability compared to the brown flaxseed counterparts and therefore, they are suitable for product applications involving severe heat treatments.
This study introduced an automated long-term fermentation process for fungals grown in pellet form. The goal was to reduce the overgrowth of bioreactor internals and sensors while better rheological properties in the fermentation broth, such as oxygen transfer and mixing time, can be achieved. Because this could not be accomplished with continuous culture and fed-batch fermentation, repeated-batch fermentation was implemented with the help of additional bioreactor internals (“sporulation supports”). This should capture some biomass during fermentation. After harvesting the suspended biomass, intermediate cleaning was performed using a cleaning device. The biomass retained on the sporulation support went through the sporulation phase. The spores were subsequently used as inocula for the next batch. The reason for this approach was that the retained pellets could otherwise cause problems (e.g., overgrowth on sensors) in subsequent batches because the fungus would then show undesirable hyphal growth. Various sporulation supports were tested for sufficient biomass fixation to start the next batch. A reproducible spore concentration within the range of the requirements could be achieved by adjusting the sporulation support (design and construction material), and an intermediate cleaning adapted to this.
Automated evaluation of contact angles in a three-phase system of selective agglomeration in liquids
(2020)
This study aims to an automated evaluation of contact angles in a three-phase system of selective agglomeration in liquids. Wetting properties, quantified by contact angles, are essential in many industries and their processes. Selective agglomeration as a three-phase system consists of a suspension liquid, a heterogeneous solid phase and an immiscible binding liquid. It offers the chance of establishing more efficient separation processes because of the shape-dependent wetting properties of fine particles (size ≤ 10 µm). In the present paper, an experimental setup for contact angle measurements of fine particles based on the Sessile Drop Method is described. Moreover, a new algorithm is discussed, which can be used to automatically compute contact angles from image data captured by a high-speed camera. The algorithm uses a marker-based watershed transform to segment the image data into regions representing the droplet, the carrier plate coated by fine particles, and the background. The main idea is a parametric modelling approach forthe time-dependent droplet’s contour by an ellipse.
The results show that the development of the dynamic contact angles towards a static contact angle can be efficiently determined based on this novel technique. These findings are useful for a detailed discrimination of wetting properties of spherical and irregularly shaped particles as well as their wetting kinetics. Also, a better understanding of selective agglomeration processes will be promoted by this user-friendly method.
Zur Optimierung von Zulaufsatzkultur-Fermentationen von methylotrophen Organismen wird eine Online-Messmethode vorgestellt, mit der die Methanol-Konzentration im Medium während einer Fermentation durch ein Spülgaspervaporations-Prinzip bestimmt werden kann. Im Gegensatz zu anderen Analysemethoden bietet die Messmethode die Möglichkeit, die Substratkonzentration bei Prozessen mit Methanol als zentralem Substrat über eine Regelung auf einem definierten Wert zu halten. Es werden Schwierigkeiten, aber auch deren Überwindung bei der Adaption der Messmethode auf Fermentationsprozesse dargestellt.
The implementation of single-use technologies offers several major advantages, e.g. prevention of cross-contamination, especially when spore-forming microorganisms are present. This study investigated the application of a single-use bioreactor in batch fermentation of filamentous fungus Penicillium sp. (IBWF 040-09) from the Institute of Biotechnology and Drug Research (IBWF), which is capable of intracellular production of a protease inhibitor against parasitic proteases as a secondary metabolite. Several modifications to the SU bioreactor were suggested in this study to allow the fermentation in which the fungus forms pellets. Simultaneously, fermentations in conventional glass bioreactor were also conducted as reference. Although there are significant differences in the construction material and gassing system, the similarity of the two types of bioreactors in terms of fungal metabolic activity and the reproducibility of fermentations could be demonstrated using statistic methods. Under the selected cultivation conditions, growth rate, yield coefficient, substrate uptake rate, and formation of intracellular protease-inhibiting substance in the single-use bioreactor were similar to those in the glass bioreactor.
Purification of mRNA with oligo(dT)-functionalized magnetic particles involves a series of magnetic separations for buffer exchange and washing. Magnetic particles interact and agglomerate with each other when a magnetic field is applied, which can result in a decreased total surface area and thus a decreased yield of mRNA. In addition, agglomeration may also be caused by mRNA loading on the magnetic particles. Therefore, it is of interest how the individual steps of magnetic separation and subsequent redispersion in the buffers used affect the particle size distribution. The lysis/binding buffer is the most important buffer for the separation of mRNA from the multicomponent suspension of cell lysate. Therefore, monodisperse magnetic particles loaded with mRNA were dispersed in the lysis/binding buffer and in the reference system deionized water, and the particle size distributions were measured. A concentration-dependent agglomeration tendency was observed in deionized water. In contrast, no significant agglomeration was detected in the lysis/binding buffer. With regard to magnetic particle recycling, the influence of different storage and drying processes on particle size distribution was investigated. Agglomeration occurred in all process alternatives. For de-agglomeration, ultrasonic treatment was examined. It represents a suitable method for reproducible restoration of the original particle size distribution.
