Prof. Clemens Posten

Institute of Process Engineering in Life Sciences: Bioprocess Engineering
Karlsruhe Institute of Technology (KIT), Germany
Phone: +49 721 608 45200
Fax: +49 721 608 45202

Clemens Posten

About Clemens

Prof Posten’s area of expertise is in photobioreactor design for the optimal production of photosynthetic green algae, purple bacteria and mosses. In particular he is focused on the development of integrated bioprocesses, in which upstream photo bio-reactors are coupled with downstream processing such as the extraction of high value products (polysaccharides, pigments, unsaturated fatty acids), the production of biofuels (oil & methane and hydrogen) and recombinant proteins.

Prof Posten has extensively contributed to the optimisation of photobioreacters in terms of microalgal growth parameters such as light, CO2 and nutrient supply and low energy mixing through painstaking bioreactor design. In addition he has optimised innovative product recovery strategies (See B10.3).

Over the past few years he has increasingly specialised on the development of photobioreactors for the production of 2nd generation biofuels using microalgae. The importance of these biofuel systems is that they can use saline water and be located on non arable land eliminating the competition between 1st generation biofuel crops and food production.

Significant contributions to this project include the development of specialised photo-bioreactors, the cultivation of microalgae in different process strategies, and modelling of their growth kinetics. For this purpose he has custom built a unique set of highly sophisticated photobioreactors. The importance of these systems is that they enable the collection of the detailed kinetic data required for the successful scale-up of photo-bioprocesses. For scale-up this data is used to model photobioreactor operation parameters such as fluid-flow (via computational fluid dynamics), light adsorptions (via Monte-Carlo simulation), as well as the behaviour of the cells by physiological modelling. These calculations have already been used for the design of the world’s largest closed photo-bioreactor (700,000 L) in Klötze, Germany which is commercially producing high value products.

Over the past 10 years Prof Posten has designed and developed two study courses. The first one is the “International biotechnology study course” with 20 students from Germany and 20 from France completing their Masters degree together in locations in Germany and in France. The second course is entitled the “bioengineering study course” in Karlsruhe and is designed for 40 Master students. In both courses he is involved in teaching and therefore has direct access to students with an advanced level of training who will continue their bachelor and master thesis within the framework of this project.

He is also overseeing a program of research focused on engineering trials to construct a large scale photo-bioreactor specifically designed for microalgal bio-H2 production. Because of the gaseous nature of the product, the specific demands of the H2 producing cells and the requirement of a low bioreactor price this cannot be done using standard designs. However these same requirements have resulted in the development of new design concepts with major future market opportunities which are currently being patented for the production of 2nd generation microalgal biofuel systems. This fact is noted here, as it is not adequately reflected in his publication record.


Cultivation of phototrophic micro-organisms is a small, but nevertheless important and growing sector in biotechnology. Light is the only energy source they need, and CO2 is the sole, or at least major, carbon source. These features offer several advantages for processes:

  • Clean and environmentally friendly operation
  • Production of compounds with high degree of reduction of antimicrobial activity
  • In some cases, cheap outdoor production

Examples from the portfolio of "bio-ag" are process development for microalgae cultivation and production of recombinant proteins by moss cells. Special emphasis is on scale-up aspects.

Photobiotechnological Hydrogen Production with Microalgae

Certain unicellular green algae and cyanobacteria have evolved the ability to use solar energy to produce H2 from water. The solar conversion efficiency can be high, but only for transient period, owing to yet-incompletely understood mechanisms. These will need to be optimised to reach commercial viability. Further fundamental improvement will only be achieved through parallel interlocked biotechnology and engineering-driven approaches, in which algal bioengineering is closely connected to the construction of bioreactors optimised for the relevant physiological and technical parameters that are needed for the production process. The basis for the biological component of such a strategy is the availability of the high-H2 production Chlamydomonas reinhardtii mutant Stm6.