Institute of Chemical Engineering
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Bio-ABC: development of a two-step biological CO2-fixing process for the production of fuel chemicals

Problem statement and project goal: 

The need for bio-based plastics has significantly increased considering the drastic negative impacts of petroleum-based plastics on the environment. The best studied biodegradable polymers are polyhydroxyalkanoates (PHAs), polyesters, polysaccharides and various copolymers. PHAs, especially (PHB), are the most promising polymers to replace conventional plastics.

PHB is a natural energy and carbon storage product of prokaryotes and is accumulated under nitrogen and/or phosphorous limitations in presence of excess carbon. Until now, it has been produced by heterotrophic bacteria such as Alcaligenes eutrophus with the help of fermentation technology. Until now, high production costs have limited the use of PHB for biopolymer production. However, if these costs can be reduced, there would be widespread economic interest. In this context cyanobacteria are emerging as the best alternative host system due to their minimal nutrient requirements and photoautotrophic nature. PHB accumulation of < 10 % of dry cell weight (dcw) has been reported for a few cyanobacterial species under photoautotrophic conditions. Higher PHB yield in cyanobacteria has been detected under sugar supplementation or genetic modification. There are no general ways to increase the PHB productivity in cyanobacteria.

This project aims to use sustainable resources CO2 and sunlight for production of PHB from cyanobacteria. PHB productivity would be increased by means of mutations and process engineering. We have screened for various cyanobacterial strains for PHB accumulation out of which a Synechocystis sp. strain has been selected for detailed studies. The strain has been characterized and growth and PHB accumulation has been studied in a lab-scale photobioreactor. We have succeeded to establish cultivations of photosynthetic organisms and could increase specific growth rates and PHB accumulation. Further experiments will be done in order to increase PHB productivity using random mutagenesis. The scalability will be tested at the end using cultivations in 150 L pilot scale photobioreactor. 

 

 

Methodology:

Quantitative bioprocess development employed by our group for many different applications will be used to develop light integrated processes for cultivation of cyanobacteria.

Analytical methods such as NMR, HPLC and Scanning Electron Microscopy will be used to generate reliable data which allows for the generation of process knowledge.

Cyanobacterial strain improvement would be done by means of natural mutations.

 

Funding

This project is done in cooperation with “Lackner Ventures and Consulting”.

Contact:

Project assistant Donya Kamravamanesh

Dr. nat. techn. Stefan Pflügl