Browsing by Person "Hermann, Alexander"

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Genetic code expansion for controlled surfactin production in a high cell-density Bacillus subtilis strain
(2025) Hermann, Alexander; Hiller, Eric; Hubel, Philipp; Biermann, Lennart; Benatto Perino, Elvio Henrique; Kuipers, Oscar Paul; Hausmann, Rudolf; Lilge, Lars; Hermann, Alexander; Department of Bioprocess Engineering, Institute of Food Science and Biotechnology, University of Hohenheim, 70599 Stuttgart, Germany; (A.H.); (E.H.); (L.B.); (E.H.B.P.); (R.H.); Hiller, Eric; Department of Bioprocess Engineering, Institute of Food Science and Biotechnology, University of Hohenheim, 70599 Stuttgart, Germany; (A.H.); (E.H.); (L.B.); (E.H.B.P.); (R.H.); Hubel, Philipp; Core Facility Hohenheim, Mass Spectrometry Core Facility, University of Hohenheim, 70599 Stuttgart, Germany;; Biermann, Lennart; Department of Bioprocess Engineering, Institute of Food Science and Biotechnology, University of Hohenheim, 70599 Stuttgart, Germany; (A.H.); (E.H.); (L.B.); (E.H.B.P.); (R.H.); Benatto Perino, Elvio Henrique; Department of Bioprocess Engineering, Institute of Food Science and Biotechnology, University of Hohenheim, 70599 Stuttgart, Germany; (A.H.); (E.H.); (L.B.); (E.H.B.P.); (R.H.); Kuipers, Oscar Paul; Department of Molecular Genetics, University of Groningen, 9747 AG Groningen, The Netherlands;; Hausmann, Rudolf; Department of Bioprocess Engineering, Institute of Food Science and Biotechnology, University of Hohenheim, 70599 Stuttgart, Germany; (A.H.); (E.H.); (L.B.); (E.H.B.P.); (R.H.); Lilge, Lars; Department of Bioprocess Engineering, Institute of Food Science and Biotechnology, University of Hohenheim, 70599 Stuttgart, Germany; (A.H.); (E.H.); (L.B.); (E.H.B.P.); (R.H.); Fouillaud, Mireille
Background: In biotechnology, B. subtilis is established for heterologous protein production. In addition, the species provides a variety of bioactive metabolites, including the non-ribosomally produced surfactin lipopeptide. However, to control the formation of the target product-forming enzyme, different expression systems could be introduced, including the principle of genetic code expansion by the incorporation of externally supplied non-canonical amino acids. Methods: Integration of an amber stop codon into the srfA operon and additional chromosomal integration of an aminoacyl-tRNA synthetase/tRNA mutant pair from Methanococcus jannaschii enabled site-directed incorporation of the non-canonical amino acid O-methyl-L-tyrosine (OMeY). In different fed-batch bioreactor approaches, OMeY-associated surfactin production was quantified by high-performance thin-layer chromatography (HPTLC). Physiological adaptations of the B. subtilis production strain were analyzed by mass spectrometric proteomics. Results: Using a surfactin-forming B. subtilis production strain, which enables high cell density fermentation processes, the principle of genetic code expansion was introduced. Accordingly, the biosynthesis of the surfactin-forming non-ribosomal peptide synthetase (NRPS) was linked to the addition of the non-canonical amino acid OMeY. In OMeY-associated fed-batch bioreactor fermentation processes, a maximum surfactin titre of 10.8 g/L was achieved. In addition, the effect of surfactin induction was investigated by mass spectrometric proteome analyses. Among other things, adaptations in the B. subtilis motility towards a more sessile state and increased abundances of surfactin precursor-producing enzymes were detected. Conclusions: The principle of genetic code expansion enabled a precise control of the surfactin bioproduction as a representative of bioactive secondary metabolites in B. subtilis . This allowed the establishment of inducer-associated regulation at the post-transcriptional level with simultaneous use of the native promoter system. In this way, inductor-dependent control of the production of the target metabolite-forming enzyme could be achieved.
The influence of growth rate-controlling feeding strategy on the surfactin production in Bacillus subtilis bioreactor processes
(2024) Hiller, Eric; Off, Manuel; Hermann, Alexander; Vahidinasab, Maliheh; Benatto Perino, Elvio Henrique; Lilge, Lars; Hausmann, Rudolf
Background The production of surfactin, an extracellular accumulating lipopeptide produced by various Bacillus species, is a well-known representative of microbial biosurfactant. However, only limited information is available on the correlation between the growth rate of the production strain, such as B. subtilis BMV9, and surfactin production. To understand the correlation between biomass formation over time and surfactin production, the availability of glucose as carbon source was considered as main point. In fed-batch bioreactor processes, the B. subtilis BMV9 was used, a strain well-suited for high cell density fermentation. By adjusting the exponential feeding rates, the growth rate of the surfactin-producing strain, was controlled. Results Using different growth rates in the range of 0.075 and 0.4 h-1, highest surfactin titres of 36 g/L were reached at 0.25 h-1 with production yields YP/S of 0.21 g/g and YP/X of 0.7 g/g, while growth rates lower than 0.2 h-1 resulted in insufficient and slowed biomass formation as well as surfactin production (YP/S of 0.11 g/g and YP/X of 0.47 g/g for 0.075 h-1). In contrast, feeding rates higher than 0.25 h-1 led to a stimulation of overflow metabolism, resulting in increased acetate formation of up to 3 g/L and an accumulation of glucose due to insufficient conversion, leading to production yields YP/S of 0.15 g/g and YP/X of 0.46 g/g for 0.4 h-1. Conclusions Overall, the parameter of adjusting exponential feeding rates have an important impact on the B. subtilis productivity in terms of surfactin production in fed-batch bioreactor processes. A growth rate of 0.25 h-1 allowed the highest surfactin production yield, while the total conversion of substrate to biomass remained constant at the different growth rates.