Stefan Junne

Verified

Stefan verified their affiliation via an institutional email.

Learn more

Verified

Stefan verified their affiliation via an institutional email.

Learn more

• Ph.D.
• assoc. Professor at Aalborg University

Lycium schweinfurthii, a wild shrub of the Solanaceae family, has received increasing attention in the last decade for its therapeutic potential in traditional medicine due to its diverse array of secondary metabolites, including phenolic substances and terpenoids. The aim of this study was to investigate the accumulation of phenolics, flavonoids,...

Lycium schweinfurthii , a wild shrub of the Solanaceae family, has received increasing attention in the last decade for its therapeutic potential in traditional medicine due to its diverse array of secondary metabolites, including phenolic substances and terpenoids. The aim of this study was to investigate the accumulation of phenolics, flavonoids,...

Background Short-chain carboxylic acids are interesting building blocks that can be synthesized from biogenic residues with the so-called dark fermentation. One challenge though is the hydrolysis of lignocellulosic residues to make them accessible for whole cell biotransformation. Accessibility can be achieved through conversion of lignocellulose t...

Hydrolysis at changing hydraulic retention time, recirculation, bedding straw content in the feed, bioaugmentation and the impact of those changes on gradient formation in the liquid phase in plug-flow reactors (PFRs) was examined. The pH-value, conductivity and oxidation–reduction potential (ORP) were monitored at three spots along the PFRs to stu...

Dissolved hydrogen (dH2) is an important parameter in anaerobic digestion (AD) processes, in particular in a two-stage operation mode encompassing separate hydrolytic/acidogenic and methanogenic stages. Then, monitoring of dH2 as a substrate of hydrogenotrophic methanogenesis is essential to avoid feast and famine conditions. Despite its significan...

Hydrolysis at changing hydraulic retention time (HRT), recirculation, bedding straw content in the feed, bioaugmentation and the impact of those changes on gradient formation in the liquid phase in plug-flow reactors (PFRs) was examined. The pH, conductivity and oxidation-reduction-potential (ORP) were monitored at three spots along the PFRs to stu...

Background Two parallel plug-flow reactors were successfully applied as a hydrolysis stage for the anaerobic pre-digestion of maize silage and recalcitrant bedding straw (30% and 66% w/w) under variations of the hydraulic retention time (HRT) and thin-sludge recirculation. Results The study proved that the hydrolysis rate profits from shorter HRTs...

Since natural resources for the bioproduction of commodity chemicals are scarce, waste animal fats (WAF) are an interesting alternative biogenic residual feedstock. They appear as by-product from meat production, but several challenges are related to their application: first, the high melting points (up to 60 °C); and second, the insolubility in th...

In the present study, a tailor-made plug-flow reactor with 3D-printed parts and a multi-position monitoring of the pH-value, conductivity and ORP at the inlet, center and outlet part is introduced and applied in anaerobic digestion in order to investigate whether i) the formation of gradients can be detected, ii) ideal single or multiple spots for...

Two parallel plug-flow reactors were successfully applied as a hydrolysis stage for the anaerobic pre-digestion of maize silage and recalcitrant bedding straw (30 % and 66 % w/w) under variations of the hydraulic retention time (HRT) and thin-sludge recirculation. The study proved that the hydrolysis rate profits from shorter HRTs while the hydroly...

In this work, the effect of bioaugmentation on the hydrolysis and acidogenesis efficiency of bedding straw mixed with maize silage is examined. A plug-flow bioreactor was operated for 70 weeks with maize silage as a reference feedstock and subsequently with an increasing straw content of 30% and 66% (w/w). Bioaugmentation with two Paenibacillus spe...

Hydrogen is a cofactor in many microbial transformation processes and therefore important to achieve a high product yield. The measurement of dissolved hydrogen in biogas processes is complex, because it is conducted at conditions, which may disturb stability and precision of the measured value. A new approach for the measurement of dissolved hydro...

A group of the DECHEMA working group “Single‐Use Technology in Biopharmaceutical Manufacture” is investigating the potential use of single‐use systems for cellular agricultural applications. The preliminary results are summarized in this article. In the biopharmaceutical industry, single‐use systems are well established alongside their reusable cou...

Single‐use technology has become important in biopharma processes since many years. Despite all the benefits, the generally rising concerns about single‐use material are hitting industrial bioproduction. The subgroup “Sustainability” of the DECHEMA workgroup “Single‐Use Technologies” aims to investigate any potential to quantify sustainability and...

Fat‐containing animal by‐product streams are locally available in large quantities. Depending on their quality, they can be inexpensive substrates for biotechnological processes. To accelerate industrial polyhydroxyalkanoate (PHA) bioplastic production, the development of efficient bioprocesses that are based on animal by‐product streams is a promi...

Energy from biomass has the potential to partially compensate for the temporarily fluctuating energy generation from wind and solar power. One way to dynamically produce methane is to separate the digestion process into an acidogenic and in a methanogenic stage. For this purpose, it is necessary that the processes of anaerobic digestion can be moni...

Streptomyces clavuligerus (S. clavuligerus) is a filamentous Gram-positive bacterial producer of the β-lactamase inhibitor clavulanic acid (CA). Antibiotics biosynthesis and secretion in the Streptomyces genus are closely related with nutritional and environmental perturbations. In this study, the low productivity of CA in wild-type S. clavuligerus...

The process of anaerobic digestion is a widely applied bioprocess to make use of all kinds of biogenic resources. In Germany, a large share of residual biomass waste comprises of straw and other cellulolytic compounds, which pose a challenge for their use as feedstock due to the lignocellulosic structure [1]. The application of microbial hydrolysis...

Background Due to their huge biodiversity and the capability to produce a wide range of secondary metabolites, lichens have a great potential in biotechnological applications. They have, however, hardly been used as cell factories to date, as it is considered to be difficult and laborious to cultivate lichen partners in pure or co-culture in the la...

Traditional kefir, which is claimed for health-promoting properties, is made from natural grain-based kefir, while commercial kefirs are made of defined mixtures of microorganisms. Here, approaches are described how to discriminate commercial and traditional kefirs. These two groups of kefirs were characterized by in-depth analysis on the taxonomic...

Fermented foods, such as yogurt and kefir, contain a versatile spectrum of volatile organic compounds (VOCs), including ethanol, acetic acid, ethyl acetate, and diacetyl. To overcome the challenge of overlapping peaks regarding these key compounds, the drift tube temperature was raised in a prototypic high-temperature ion mobility spectrometer (HTI...

Energy from biomass has the potential to partially compensate for the temporarily fluctuating energy generation from wind and solar power. For this purpose, it is necessary that the processes of anaerobic digestion can be monitored and controlled properly to enable flexible methane production – at the same time a combination of material and energy...

Shrimp farming in South‐East Asian and Latin American coastal regions generates economic benefits for the producer countries and contributes to a healthy nutrition of consumers. However, shrimp farming uses great amounts of fish meal and fish oil in the feed for the provision of essential proteins and polyunsaturated fatty acids during growth. This...

This work investigated the effects of enzyme applications on anaerobic digestion in batch experiments and continuously fed biogas reactors at laboratory-scale. Commercially available enzyme preparations were analyzed alongside several novel enzyme preparations in terms of lignocellulolytic enzyme activity, stability, and protein composition.

Dark fermentation (DF), a key biohydrogen-producing process, is generally operated as a black-box, by monitoring different operative macroscopic process parameters without evaluating or tracking the physiology of the biotic phase. The biotic phase in DF is constituted by a large variety of microorganisms, mainly fermentative bacteria. The present s...

The flexibilization of bioenergy production has the potential to counteract partly other fluctuating renewable energy sources (such as wind and solar power). As a weather-independent energy source, anaerobic digestion (AD) can offer on-demand energy supply through biogas production. Separation of the stages in anaerobic digestion represents a promi...

Kefir ist ein Milchgetränk, das durch natürliche Fermentation eines Konsortiums aus Mikroorganismen, den sogenannten Kefirknollen, hergestellt wird. Aufgrund seiner probiotischen Eigenschaften hat Milchkefir neuerdings das Interesse von Milchproduzenten und gesundheitsbewussten Verbrauchern geweckt. In dieser Arbeit haben wir die flüchtigen organis...

Streptomyces clavuligerus (S. clavuligerus) has been widely studied for its ability to produce clavulanic acid (CA), a potent inhibitor of β-lactamase enzymes. In this study, S. clavuligerus cultivated in 2D rocking bioreactor in fed-batch operation produced CA at comparable rates to those observed in stirred tank bioreactors. A reduced model of S....

Fish oil has been used in conventional aquaculture for decades, despite the known links between increasing global demand for fish and depletion of natural resources and vital ecosystems (FAO, 2020, 2019). Alternative feed ingredients, including algae oil rich in docosahexaenoic acid (DHA), has therefore been increasingly used to substitute traditio...

Therapeutic monoclonal antibodies (mAbs) are the fastest-growing class of biotherapeutics. They are mainly used to treat cancer, inflammatory, metabolic and autoimmune diseases. Their commercial production processes are mainly based on Chinese hamster ovary (CHO) suspension cells, which are currently cultivated in fed-batch mode at cubic meter scal...

Typically, bioprocesses on an industrial scale are dynamic systems with a certain degree of variability, system inhomogeneities, and even population heterogeneities. Therefore, the scaling of such processes from laboratory to industrial scale and vice versa is not a trivial task. Traditional scale-down methodologies consider several technical param...

Anaerobe Gärverfahren mit anschließenden Reinkulturprozessen erzeugen Chemikalien aus biogenen Rohstoffen. Beispiel für ein Kreislaufwirtschaftskonzept ist biologisch abbaubares Plastik aus Abfallfetten. Das Verfahren lässt sich modifizieren, um bestimmte Eigenschaften zu erzielen. Die Nutzung von Reststoffen erzeugt regionale Stoffkreisläufe.

There is a growing need of substrate flexibility for biobased production of energy and value-added products that allows the application of variable biodegradable residues within a circular economy. It can be used to balance fluctuating energy provision of other renewable sources. Hydrolysis presents one of the biggest limitations during anaerobic d...

In this paper, an approach for the monitoring of biotechnological process kinetics is proposed. The kinetics of each process state variable is presented as a function of two time-varying unknown parameters. For their estimation, a general software sensor is derived with on-line measurements as inputs that are accessible in practice. The stability a...

Streptomyces clavuligerus is a filamentous Gram-positive bacterial producer of the β-lactamase inhibitor clavulanic acid. Antibiotics biosynthesis in the Streptomyces genus is usually triggered by nutritional and environmental perturbations. In this work, a new genome scale metabolic network of Streptomyces clavuligerus was reconstructed and used t...

Kefir grains are complex microbial systems of several groups of microorganisms. The identification and quantification of the microbial composition of milk kefirs was described in several studies, which provided an insight into the microbial consortia in this complex ecosystem. Nevertheless, the current methods for identification and quantification...

There is a profound need in bioprocess manufacturing for low-cost single-use sensors that allow timely monitoring of critical product and production attributes. One such opportunity is screen-printed enzyme-based electrochemical sensors, which have the potential to enable low-cost online and/or off-line monitoring of specific parameters in bioproce...

Milk kefir is a traditional fermented milk product whose consumption is becoming increasingly popular. The natural starter for kefir production is kefir grain, which consists of various bacterial and yeast species. At the industrial scale, however, kefir grains are rarely used due to their slow growth, complex application, bad reproducibility and h...

Streptomyces clavuligerus is a gram-positive filamentous bacterium notable for producing clavulanic acid (CA), an inhibitor of β-lactamase enzymes, which confers resistance to bacteria against several antibiotics. Here we present a comparative analysis of the morphological and metabolic response of S. clavuligerus linked to the CA production under...

• High resolution inline microscopy • Monitoring fatty acid production by microalgae • Correlation of Budding Index with growth dynamics in yeast fermentations • Multidimensional and real-time image analysis

Corynebacterium glutamicum is well‐known as an industrial workhorse, most notably for its use in the bulk production of amino acids in the feed and food sector. Previous studies of the effect of gradients in scale‐down reactors with complex media disclosed an accumulation of several carboxylic acids and a parallel decrease of growth and product acc...

Clavulanic acid (CA) is a β-lactam antibiotic with a strong inhibitory effect on β-lactamase enzymes. CA is produced in submerged cultures by the filamentous Gram-positive bacterium Streptomyces clavuligerus (S. clavuligerus). CA is an unstable molecule in aqueous solution and its stability depends strongly on temperature and concentration. In this...

Clavulanic acid (CA) is a β-lactam antibiotic inhibitor of β-lactamase enzymes, which confers resistance to bacteria against several antibiotics. CA is produced in submerged cultures by the filamentous Gram-positive bacterium Streptomyces clavuligerus; yield and downstream process are compromised by a degradation phenomenon, which is not yet comple...

The formation of pH gradients in a 700 L batch fermentation of Streptococcus thermophilus was studied using multi‐position pH measurements and computational fluid dynamics (CFD) modeling. To this end, a dynamic, kinetic model of S. thermophilus and a pH correlation were integrated into a validated one‐phase CFD model, and a dynamic CFD simulation w...

The rapid assessment of cell viability is crucial for process optimization, e.g., during media selection, determination of optimal environmental growth conditions and for quality control. In the present study, the cells' electric anisotropy of polarizability (AP) as well as the mean cell length in Lactobacillus plantarum batch and fed-batch ferment...

Background Filamentous fungi including Aspergillus niger are cell factories for the production of organic acids, proteins and bioactive compounds. Traditionally, stirred-tank reactors (STRs) are used to cultivate them under highly reproducible conditions ensuring optimum oxygen uptake and high growth rates. However, agitation via mechanical stirrin...

Particles occur in almost all processes in chemical and life sciences. The particle size and shape influence the process performance and product quality. In many processes particles have certain attributes with respect to their size and shape distribution. The grain and drop size as well as shape during production is influenced by the flow behavior...

Dark fermentation is a widely used technique for bioenergy recovery under the form of biohydrogen. However, due to the versatility of the technique and the low environmental impact, it is a suitable process to convert a wide range of organic substrates into H2 and shorter molecules. This is carried out by microbiomes, which include a large variety...

Recent advances in sensor development and miniaturization offer new possibilities to monitor and control bioprocesses. Specific requirements for anaerobic processes in terms of low costs and high robustness against insoluble fractions and impurities in media led to a decelerated penetration of new technology in this field. Since no regulatory frame...

Bioprocess deviations are likely to occur at different operating scales, leading in most of the case to substrate deviation from main metabolic routes and impact product synthesis. Correlating qS and qP is of outmost importance for bioprocess observability and control and can be modeled actually by advanced metabolic flux models. However, if most o...

Abstract Oscillatory conditions, which usually appear in large scale bioreactors due to limitations in the power input and extended mixing times, can lead to cell stress and increased occurrence of population heterogeneity. Such heterogeneities are regularly observed in industrial production; however, the underlying mechanisms are seldom perceived...

Large-scale bioreactors are inhomogeneous systems in which the fluid phase expresses concentration gradients. They depend on the mass transfer and fluid dynamics in the reactor, the feeding strategy, the cell-specific substrate uptake parameters, and the cell density. As high cell densities are only obtained at low specific growth rates, it is nece...

Oscillatory conditions, which usually appear in large scale production due to extended mixing times, lead to cell stress and increased occurrence of population heterogeneity. Such heterogeneities are regularly observed in industrial production; however, the underlying mechanisms are seldom perceived or considered in bioprocess development. Since in...

The application of Raman spectroscopy as a monitoring technique for bioprocesses is severely limited by a large background signal originating from fluorescing compounds in the culture media. Here we compare time‐gated Raman (TG‐Raman)‐, continuous wave NIR‐process Raman (NIR‐Raman) and continuous wave micro‐Raman (micro‐Raman) approaches in combina...

Background: The morphology of yeast cells changes during budding, depending on the growth rate and cultivation conditions. A photo-optical microscope was adapted and used to observe such morphological changes of individual cells directly in the cell suspension. In order to obtain statistically representative samples of the population without the in...

Although the scalability of stainless steel bioreactors has been investigated for more than 50 years, and many methods for the characterization of these bioreactors have been evolved, the investigation of scalability of single-use bioreactors (SUBs) contains several new challenges. SUBs permit a versatile design that is not necessarily oriented tow...

In large-scale lactic acid bacteria production, the main issue is the uneven distribution of the pH value, mainly due to the external addition of base to compensate the acid production. This industrial process is important for the food industry, since these bacteria are used as starter cultures for manufacturing probiotics and dairy products (mainl...

Clavulanic acid (CA) is produced by Streptomyces clavuligerus (S. clavuligerus) as a secondary metabolite. Knowledge about the carbon flux distribution along the various routes that supply CA precursors would certainly provide insights about metabolic performance. In order to evaluate metabolic patterns and the possible accumulation of tricarboxyli...

Limitations in the power input together with increased mixing times cause the appearance of heterogeneities in production scale bioreactors. In lactic acid fermentation, an uneven distribution of the pH value occurs due to cellular acid production and external base addition. In order to study the impact of these gradients, pulse feeding experiments...

Abstract Oscillatory conditions, which usually appear in large scale production due to extended mixing times, lead to cell stress and increased occurrence of population heterogeneity. Such heterogeneities are regularly observed in industrial production; however, the underlying mechanisms are seldom perceived or considered in bioprocess development....

Physiologic responses of yeast to oscillatory environments as they appear in the liquid phase in large-scale bioreactors were studied in the past. So far, however, the impact on the sterol household and intracellular regulation remains to be investigated. Since oxygen is a co-factor in several reaction steps within the sterol metabolism, changes in...

Abstract The degree of polarizability of cells depends particularly on the cells’ composition and structure [1] and is related to their viability: cells with high metabolic activity have a larger polarizability [2]. The anisotropy of polarizability (AP) can be monitored atline applying electrooptical methods [2] coupled to automated sample preparat...

An affinity-viscometry-based micro-sensor probe for continuous glucose monitoring was investigated with respect to its suitability for bioprocesses. The sensor operates with glucose and dextran competing as binding partner for concanavalin A, while the viscosity of the assay scales with glucose concentration. Changes in viscosity are determined wit...

The era of Quality by Design (QbD) in industrial process monitoring requires new approaches for data analysis, i.e. on‐line data collection and analysis. Raman spectroscopy has a great potential for on‐line bioprocess monitoring that has not yet been realized due to limitations including (i) high threshold value for most analytes due to the high fl...

Abstract Insufficient mixing causes the appearance of inhomogeneities in production scale bioreactors. In lactic acid fermentation, an uneven distribution of the pH-value occurs due to cellular acid production and external base addition. In order to study the impact of these gradients, a two-compartment scale-down bioreactor was applied. In this co...

Abstract The degree of polarizability of cells depends particularly on the cells’ composition and structure [1] and is related to their viability: cells with high metabolic activity have a larger polarizability [2]. The anisotropy of polarizability (AP) can be monitored atline applying electrooptical methods [2] coupled to automated sample preparat...

Population heterogeneity among a microbial culture can occur in various stages of a bioprocess. When a nutrient-limited fed-batch process is applied in the large scale, gradient formation (e.g. at the substrate concentration or the pH-value) can have a tremendous impact on the process performance. It might also have an impact on population heteroge...

The anaerobic digestion of biomass is a complex, dynamic, and highly nonlinear process. Hence, a mathematical model that is capable of describing the complete operability region with sufficient accuracy cannot be identifiable even with the most advanced process monitoring technology. The complexity of the anaerobic digestion model no. 1 (ADM1) lead...

This work describes the development and application of different lance-based monitoring systems coupled to an integrated multiparameter sensor probe for the spatial investigation of the liquid phase in biotechnological processes. Miniaturized electrochemical sensors are integrated into a housing, which is fixed at the head of a lance, both made of...

Biotechnology and biopharmaceutical production have an increasing demand of monitoring in the era of quality by design approaches in industrial scale, requiring manufacturing capabilities of a previously unknown sophistication. This sophistication comes at a great cost – and new approaches are required to gain data rapidly and of sufficient quality...

To date, on line monitoring in bioprocesses is restricted to conventional parameters. Presently, advances in microscopy allow the monitoring of single-cell size distributions in a bypass or in situ. These data provide information regarding population heterogeneity, substrate conversion, or product synthesis as these parameters are related to the si...