Towards hybrid production of fine chemicals and high-value compounds

  • Wege zur hybriden Produktion von Feinchemikalien und hochwertigen Substanzen

Labib, Mohamed Mamdouh Ali Abdelmoteleb; Wiechert, Wolfgang (Thesis advisor); Büchs, Jochen (Thesis advisor)

Aachen : RWTH Aachen University (2021, 2022)
Dissertation / PhD Thesis

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2021

Abstract

At present, industrial bioprocesses are predominantly based on a "one substrate - one product" concept. However, the implementation of a sustainable bioeconomy that is competitive with respect to ecologic and economic demands will critically depend on novel highly interwoven value networks based on "multi substrate - multi product" processes. The establishment of such "hybrid" production processes requires an efficient coupling of microbial biotransformations and enzymatic cascade reactions with tailored product separation methods. In the first part of this thesis, a sustainable bioprocess was established for the microbial production and subsequent downstream processing of protocatechuate (PCA). Combining in silico strain design and targeted metabolic engineering enabled Corynebacterium glutamicum to utilize D xylose efficiently, yielding 14-fold higher PCA production compared to the parental producer strain. Following this, a one-pot fermentation process was developed using D-glucose and D xylose as complementary substrates for cellular growth and product synthesis, respectively. Downstream processing of PCA from the fermentation supernatant was realized via electrochemically induced crystallization by taking advantage of the pH-dependent properties of PCA. In the second part of the work, microbial and enzymatic processes were developed to supply the sustainable formation of metaraminol with biosynthesized 3-hydroxybenzoate (3HB), pyruvate, L-alanine, and 3-hydroxybenzaldeyhde (3HBald). In this context, C. glutamicum underwent rational metabolic engineering to enable the production of 3HB from D xylose as the sole carbon source as well as the co-production of pyruvate and L-alanine under microaerobic conditions. Subsequently, the supernatants from cultivations of the respective strains were further investigated as substrates for downstream enzymatic cascade reactions. Hereby, the reduction of 3HB utilizing highly selective carboxylate reductases resulted in the efficient enzymatic synthesis of 3HBald without the formation of by-products. Similarly, the complete enzymatic conversion of pyruvate into (R)-phenylacetylcarbinol (3-OH-PAC) - a precursor for metaraminol - demonstrated the atom efficiency of the respective enzymatic reaction. The established production routes for PCA and metaraminol provide an exemplary demonstration of hybrid production processes. This demonstrator can be regarded as a blueprint for the development of highly interwoven networks and their use in the sustainable production of fine chemicals and high-value compounds.

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