Engineering Corynebacterium glutamicum as a designer-bug for the bio-based production of chemical building blocks and biofuel

Abstract

The restriction of fossil raw materials, as well as the impact of their use on the environment heads to a global social and economic crisis. Therefore, a strong political and technical interest arises for the replacement of petroleum-derived chemicals and fuels by such derived from biomass. The well-known amino acid producer Corynebacterium glutamicum was used in the last decade for the bio-based production of building block chemicals, as well as for biofuels. In this work, C. glutamicum was engineered for efficient aerobic production of pyruvate from glucose leading to both significantly decreased by-product formation, and extensively increased pyruvate accumulation. Since pyruvate is a central precursor for the 1,4-dicarboxylic acids malate, fumarate and succinate, C. glutamicum ELB P was further used as a basis for the production of these compounds. At first, a fermentation system was established leading to succinate formation as major product of C. glutamicum ELB P under oxygen deprivation conditions. To investigate long-term succinate production, a tri-phasic fed-batch fermentation system was established, including an aerobic growth phase on acetate for biomass formation. This was followed by a self-induced microaerobic phase at the end of growth, using minimal aeration. At last an anaerobic production phase on glucose was established in the same bioreactor by gassing with CO2. Inactivation of succinate dehydrogenase (SDH) or fumarase (Fum) in C. glutamicum ELB P should interrupt the reductive branch of tricarboxylic acid cycle for the anaerobic production of fumarate and malate, respectively. However, deletion of the corresponding genes did not lead to satisfying production of fumarate or malate. Last, based on an aerobic 2-ketoisovalerate producing strain, a C. glutamicum mutant was successfully engineered for the production of isobutanol from glucose under oxygen deprivation conditions. Weitere Artikel, die für diese Dissertation verwendet wurden, sind erschienen in: Applied microbiology and biotechnology, 2012, Vol. 94, Heft 2, S. 449-459 (DOI 10.1007/s00253-011-3843-9) URL: http://link.springer.com/article/10.1007%2Fs00253-011-3843-9; Microbial Biotechnology, 2012, (DOI: 10.1111/1751-7915.12013) URL: http://onlinelibrary.wiley.com/doi/10.1111/1751-7915.12013/abstract