Research profile

Bioprocesses have great potential for the sustainable production of numerous products, but are often not (yet) suitable for the application on an industrial scale due to their complexity and concomitantly low product yields.

Microorganisms have a large number of possible synthesis routes that are still far from being fully discovered, so are process-relevant regulation and cell-cell / cell-reactor interaction. Parallel syntheses of different microorganisms in so-called synthetic co- and mixed cultivations beside traditional mono-cultivations have a great potential for novel processes and products. In all those cultivations, the formation of subpopulations (population heterogeneities) can be decisive for any economically viable process performance during scale-up and industrial application.

Therefore, we aim to develop and optimize bioprocesses under the consideration of single-cell physiology and population aspects in mono-, co- and mixed cultivations up to a mini-plant environment. Target organisms include aerobic, micro-aerotolerant or anaerobic protagonists for food, feed and fine chemical production. The integration of image-based and other optical analytical technologies from the early-stage process development on to allow for a close to real-time monitoring and control of microbial performance is an important part of our work. Examples of application are:

• Oleaginous yeast
• Filamentous, pellet forming microorganisms
• Synthetic co-cultures of yeast and lactic acid bacteria

Microbial hydrolysis has a great potential to convert biogenic residues for value addition in non-sterile environments and with a considerably low energy input. The challenge of biotechnology to use cheap, non-competing substrate can be resolved. Process coupling of (undefined or synthetic) mixed and mono-cultivation to achieve a broad usability of residual, recalcitrant feedstock is optimized through knowledge-driven bioreactor and process design, direct bioaugmentation and other means coupled to suitable monitoring technology. This includes the quantification and optimization of the physiological status of cells to achieve substrate flexibility while controlling the product spectra. Examples of application are:

• Microbial hydrolysis for short-chain carboxylic acid production
• Dark fermentation as first stage in full anaerobic digestion
• Phosphor and nitrogen fixation in mixed microbial communities

Single-use bioreactors have been applied for a long time in the pharmaceutical industry. Various designs include reactor concepts that are especially suited for the application for processes, in which shear plays a role for the evolvement of populations. Therefore, the role of shear and the suitability of single-use rocking-motion bioreactors for the application in seed cultures and continuous processes with small reactor volumes is investigated. Examples of application are:

• Morphology development of filamentous microorganisms
• Environmental assessment of single-use bioprocess equipment

Life-cycle and techno-economic assessments of bioprocesses are also conducted beyond single-use equipment in order to decide for sustainable process routes and the overall potential of a bio-based economy. The goal is to define, create and realize smart bioproduction grids, which are optimized for the valorization of biogenic residues as drop-in solutions for existing logistic chains, while resolving hurdles for the combination of decentralized and centralized bioproduction.

Technical equipment

• parallel bioreactors for lab-scale bioprocess development up to the L-scale
• Mini-plant for fermentative and micro-aerated food processes
• various optical and chromatography-based analytical tools for metabolite and (trace-) element analysis
• lab equipment for microbial cultivation from the µL-scale in microwell plates upwards to the mL - scale in shake flasks.

Teaching profile

Teaching covers mainly, but not exclusively microbial growth, cultivation modes with mono-/ co-/ mixed cultures, mechanistic process description, scale up and scale down, bioprocess and single-cell analytics, bioreactor design - including single-use technology for bioproduction, food/ feed/ material bioproduction with aerobic and anaerobic cultures, process coupling and bioproduction networks. Teaching activities support the international bioengineering education for example in:

• Microbial biotechnology (B. Sc.)
• Fermentation technology (M. Sc.)
• Industrial bioprocesses (M. Sc.)
• Techno-economic and life-cycle assessment of bioprocesses (M. Sc.)

A special focus is put on the flipped classroom concept and challenge-based learning. Furthermore, group work in the fields of bioprocess development, monitoring and control in upstream processing and economic and environmental assessments are supported.