Fakultät Naturwissenschaften

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Biologie, Ernährungs-wissenschaften und Lebensmittelwissenschaften sind die Schwerpunkte der Fakultät. Die Forschung befasst sich mit Schlüsselthemen der Life Sciences.

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Browsing Fakultät Naturwissenschaften by Journal "Applied microbiology and biotechnology"

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    Bacillus subtilis high cell density fermentation using a sporulation-deficient strain for the production of surfactin
    (2021) Klausmann, Peter; Hennemann, Katja; Hoffmann, Mareen; Treinen, Chantal; Aschern, Moritz; Lilge, Lars; Morabbi Heravi, Kambiz; Henkel, Marius; Hausmann, Rudolf
    Bacillus subtilis 3NA is a strain capable of reaching high cell densities. A surfactin producing sfp+ variant of this strain, named JABs32, was utilized in fed-batch cultivation processes. Both a glucose and an ammonia solution were fed to set a steady growth rate μ of 0.1 h-1. In this process, a cell dry weight of up to 88 g L-1 was reached after 38 h of cultivation, and surfactin titers of up to 26.5 g L-1 were detected in this high cell density fermentation process, achieving a YP/X value of 0.23 g g-1 as well as a qP/X of 0.007 g g-1 h-1. In sum, a 21-fold increase in surfactin titer was obtained compared with cultivations in shake flasks. In contrast to fed-batch operations using Bacillus subtilis JABs24, an sfp+ variant derived from B. subtilis 168, JABs32, reached an up to fourfold increase in surfactin titers using the same fed-batch protocol. Additionally, a two-stage feed process was established utilizing strain JABs32. Using an optimized mineral salt medium in this high cell density fermentation approach, after 31 h of cultivation, surfactin titers of 23.7 g L-1 were reached with a biomass concentration of 41.3 g L-1, thus achieving an enhanced YP/X value of 0.57 g g-1 as well as a qP/X of 0.018 g g-1 h-1. The mutation of spo0A locus and an elongation of AbrB in the strain utilized in combination with a high cell density fed-batch process represents a promising new route for future enhancements on surfactin production.
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    The RNF/NQR redox pumps: a versatile system for energy transduction in bacteria and archaea
    (2025) Buckel, Wolfgang; Ermler, Ulrich; Vonck, Janet; Fritz, Günter; Steuber, Julia
    The Na + (or H + )-translocating ferredoxin:NAD + oxidoreductase (also called RNF, rhodobacter nitrogen fixation, complex) catalyzes the oxidation of reduced ferredoxin with NAD + , hereby generating an electrochemical gradient. In the reverse reaction driven by an electrochemical gradient, RNF provides reduced ferredoxin using NADH as electron donor. RNF plays a crucial role in the metabolism of many anaerobes, such as amino acid fermenters, acetogens, or aceticlastic methanogens. The Na + -translocating NADH:quinone oxidoreductase (NQR), which has evolved from an RNF, is found in selected bacterial groups including anaerobic, marine, or pathogenic organisms. Since NQR and RNF are not related to eukaryotic respiratory complex I (NADH:quinone oxidoreductase), members of this oxidoreductase family are promising targets for novel antibiotics. RNF and NQR share a membrane-bound core complex consisting of four subunits, which represent an essential functional module for redox-driven cation transport. Several recent 3D structures of RNF and NQR in different states put forward conformational coupling of electron transfer and Na + translocation reaction steps. Based on this common principle, putative reaction mechanisms of RNF and NQR redox pumps are compared. Key points: • Electrogenic ferredoxin:NAD + oxidoreductases (RNF complexes) are found in bacteria and archaea. • The Na + -translocating NADH:quinone oxidoreductase (NQR) is evolutionary related to RNF. • The mechanism of energy conversion by RNF/NQR complexes is based on conformational coupling of electron transfer and cation transport reactions.