Browsing by Author "Mohammadi Nargesi, Behrouz"

Filter results by typing the first few letters
Now showing 1 - 1 of 1
  • Thumbnail Image
    ItemOpen Access
    Biotechnological production of aromatic amines and aromatic alcohols by recombinant Escherichia coli strains
    (2019) Mohammadi Nargesi, Behrouz; Sprenger, Georg A. (Prof. Dr.)
    Aromatic amine (AA) are an important group of industrial chemicals which are widely used for technical and pharmaceutical applications and described as the building block of drugs (Bedair et al. 2006; Jobdevairakkam and Velladurai 2009; Sacco and Bientinesi 2016), antibiotics, plastics and aromatic polymers (Arora 2015; Masuo et al. 2016; Tsuge et al. 2016; Kawasaki et al. 2018). In addition, aromatic alcohols, as other valuable compounds, are widely used in manufacturers of perfumes, cosmetics, and foods, and pharmaceutical industry (Etschmann et al. 2002; Miró-Casas et al. 2003; Bai et al. 2014). Most of the AAs and aromatic alcohols are chemically synthesized from petroleum sources and considered as “unnatural”, which are inappropriate to make cosmetic, drugs or food ingredient, thereby natural microbial biosynthesis of these valuable compounds in E.coli would be an alternative approach. In the first part of this study, a de-novo biosynthesis pathway was established for high titer production of three aromatic amines, para-amino-L-phenylalanine (L-PAPA), para-amino-phenylethanol (PAPE) and para-amino-phenylacetic acid (4-APA) from glucose/glycerol via genetic modification of the shikimate pathway in recombinant E. coli (Mohammadi et al. 2018 and 2019). To generate a platform strain for L-PAPA production from shikimate pathway, the genes pabAB from Corynebacterium glutamicum (Kozak 2006), papB and papC from Streptomyces venezuelae (Blanc et al. 1997; He et al. 2001; Mehl et al. 2003) were heterologously overexpressed from plasmid in E. coli FUS4.7R (Gottlieb et al. 2014). Then, the metabolic flux was directed to PAPE and 4-APA production via overexpression of aro10 from Saccharomyces cerevisiae (Kneen et al. 2011; Vuralhan et al. 2003 and 2005) and both aro10 and feaB in E. coli FUS4BCR, respectively. The engineered E. coli strains were cultured in the shake-flasks with fed batch condition and investigated for L-PAPA, PAPE and 4-APA production by HPLC and LC-MS. In the simple shake flask experiments, the plasmid based strain produced L-PAPA as high as 0.534 ± 0.024 g l-1 from 5 ± 0.24 g l-1 glycerol. Also, introduction of aro10 and yahK in L-PAPA producing strain resulted in 0.526 ± 0.025 g l-1 PAPE. Furthermore, by introducing feaB into the PAPE- producing strain, 4-APA was obtained with a titer of 0.458 ± 0.014 g l-1. Last but not least, by further strain improvement and optimizing growth condition via glucose/glycerol feed strategy, an increasing titer of L-PAPA, PAPE and 4-APA approximately 5.5 ± 0.4 g l-1, 2.5 ± 0.15 g l-1 and 3.4 ± 0.3 g l-1 were obtained, respectively. In subsequent fed-batch cultivation with a final volume of 12.2 l and the carbon sources glycerol, a final L-PAPA-titer of 16.8 g l-1 was obtained. This equals a yield of 0.13 L-PAPA / glycerol (g g-1) and a space-time-yield of 0.22 g l-1 h-1 L-PAPA formation over the whole process. Furthermore, a de-novo biosynthesis pathway for the production of 2-Phenylethanol (2-PE)/tyrosol from glucose with genetically engineered E. coli strains without additional L-phenylalanine/ L-tyrosine as supplement was demonstrated. Starting from chorismate, which is the direct precursor of phenylpyruvate (PP)/ 4-Hydroxyphenylpyruvate (4-HPP), an artificial Ehrlich biosynthesis pathway was created (Etschmann et al. 2002) toward 2-PE or tyrosol. To generate a platform strain for production of 2-PE and tyrosol from shikimate pathway, the genes pheA or tyrA encoding proteins chorismate mutase/prephenate dehydratase or prephenate dehydrogenase (feedback resistance variant, Rüffer et al. 2004; Gottlieb et al. 2014), respectively, were cloned and subsequently overexpressed from plasmid in E. coli. In the next step, the metabolic flux was directed to 2-PE and tyrosol production via overexpression of aro10 encoding phenylpyruvate decarboxylase from S. cerevisiae. Furthermore, in order to enhance the flux toward downstream 2-PE/tyrosol pathway, the relevant genes of three rate limiting steps including aroF, aroB and aroL were subcloned and overexpressed from plasmid. Upon simple batch cultivation, these strains separately yielded 369 ± 25 mg l-1 2-PE and 437 ± 33 mg l-1 tyrosol from 4.5 ± 0.21 g l-1 glucose. Final titer in the shake flask was further improved through glucose fed-batch fermentation to 1.75 ± 0.12 g l-1 2-PE and 1.68 ± 0.19 g l-1 tyrosol. The subsequent significant enhancement of 2-PE/tyrosol production occurred through employing in situ product removal (ISPR) techniques including two-phase extraction by different organic compounds (Etschmann et al. 2002; Rüffer et al. 2004; Schügerl and Hubbuch 2005; Hu and Xu 2011; Chreptowicz et al. 2018). In subsequent glucose-limited fed-batch cultivation with a benchtop bioreactor system (0.75 l), a final 2-PE and tyrosol-titer of 3.1 g l-1 and 3.6 g l-1 reached with a yield and a space-time-yield of 0.07 g g-1 and 0.03 g l-1 h-1 for 2-PE and 0.08 g g-1 and 0.04 g l-1 h-1 for tyrosol, respectively. These works have successfully demonstrated the possibility of synthesizing of several invaluable fine chemicals in whole-cell system using plasmid based-E.coli strains. In addition, the titter and yield previously reported in the biosynthesis of aromatic amines (L-PAPA, PAPE or 4-APA) or even aromatic alcohols (2-PE or tyrosol) have been significantly improved in this study.