Nele Buschke

Technische Universität Braunschweig, Brunswyck, Lower Saxony, Germany

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Publications (7)15.93 Total impact

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    ABSTRACT: The sustainable production of chemicals from renewable, non-food raw materials is one of the great challenges in industrial biotechnology. Corynebacterium glutamicum was metabolically engineered for the production of the bio-nylon precursor 1,5-diaminopentane from the hemicellulose sugar xylose. First, comparison of a basic diaminopentane producer on xylose and glucose revealed 30% reduced diaminopentane yield and productivity on the pentose sugar. The integration of in vivo and in silico metabolic flux analysis by 13 C and elementary modes identified bottlenecks in the pentose phosphate pathway and the tricarboxylic acid cycle that limited the performance on xylose. By the integration of global transcriptome profiling this could be specifically targeted to the tkt operon, the genes that encoded for fructose bisphosphatase (tfbp) and isocitrate dehydrogenase (icd), and to genes involved in formation of lysine (lysE) and N-acetyl diaminopentane (act). This was used to create the strain C. glutamicum strain DAP-Xyl1 icdGTG Peftu fbp Psod tkt Δact ΔlysE. The novel producer, designated DAP-Xyl2, exhibited a 54% increase in product yield to 233 mmol mol-1 and a 100% increase in productivity to 1 mmol g-1 h-1 on the carbon five substrate. In a fed-batch process, the strain achieved 103 g L-1 of diaminopentane from xylose with a product yield of 32%. As xylose utilization is one of the most relevant current metabolic engineering subjects. In this regard, the present work displays a milestone in industrial strain engineering of C. glutamicum.
    No preview · Article · May 2013 · Biotechnology Journal
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    ABSTRACT: Bio-based production promises a sustainable route to myriads of chemicals, materials and fuels. With regard to eco-efficiency, its future success strongly depends on a next level of bio-processes using raw materials beyond glucose. Such renewables, i.e., polymers, complex substrate mixtures and diluted waste streams, often cannot be metabolized naturally by the producing organisms. This particularly holds for well-known microorganisms from the traditional sugar-based biotechnology, including Escherichia coli, Corynebacterium glutamicum and Saccharomyces cerevisiae which have been engineered successfully to produce a broad range of products from glucose. In order to make full use of their production potential within the bio-refinery value chain, they have to be adapted to various feed-stocks of interest. This review focuses on the strategies to be applied for this purpose which combine rational and evolutive approaches. Hereby, the three industrial platform microorganisms, E. coli, C. glutamicum and S. cerevisiae are highlighted due to their particular importance.
    No preview · Article · Nov 2012 · Bioresource Technology
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    R. Schäfer · N. Buschke · J. Becker · C. Wittmann

    Preview · Article · Aug 2012 · Chemie Ingenieur Technik
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    Full-text · Article · Aug 2012 · Chemie Ingenieur Technik
  • R. Schäfer · N. Buschke · J. Becker · C. Wittmann

    No preview · Article · Jan 2012 · Chemie Ingenieur Technik
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    ABSTRACT: In the present work, the bio-based production of 1,5-diaminopentane (cadaverine), an important building block for bio-polyamides, was extended to hemicellulose a non-food raw material. For this purpose, the metabolism of 1,5-diaminopentane-producing Corynebacterium glutamicum was engineered to the use of the C(5) sugar xylose. This was realized by heterologous expression of the xylA and xylB genes from Escherichia coli, mediating the conversion of xylose into xylulose 5-phosphate (an intermediate of the pentose phosphate pathway), in a defined diaminopentane-producing C. glutamicum strain, recently obtained by systems metabolic engineering. The created mutant, C. glutamicum DAP-Xyl1, exhibited efficient production of the diamine from xylose and from mixtures of xylose and glucose. Subsequently, the novel strain was tested on industrially relevant hemicellulose fractions, mainly containing xylose and glucose as carbon source. A two-step process was developed, comprising (i) enzymatic hydrolysis of hemicellulose from dried oat spelts, and (ii) biotechnological 1,5-diaminopentane production from the obtained hydrolysates with the novel C. glutamicum strain. This now opens a future avenue towards bio-based 1,5-diaminopentane and bio-polyamides thereof from non-food raw materials.
    No preview · Article · Mar 2011 · Biotechnology Journal
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    ABSTRACT: In this study, we replaced the natural start codons of different enzymes in the central carbon metabolism of Corynebacterium glutamicum to influence their activity toward improved production of the feed amino acid lysine. It was found that the translational start codon directly affects the intracellular activity of the encoded enzyme, whereby the common ATG generally led to higher values as compared with the rare variant GTG. This could be exploited to specifically amplify or attenuate enzyme activities in order to redirect carbon flux from undesired, competing pathways toward reactions supporting lysine formation. Replacement of the natural ATG codon by GTG reduced the specific enzyme activity of pyruvate dehydrogenase (PDH) and phosphoglucoisomerase by 60 and 40%, respectively. Vice versa, the activity of glucose 6-phosphate dehydrogenase was increased by 40% by the substitution GTG->ATG. Implementation of the attenuated pyruvate dehydrogenase in the background of lysine producing C. glutamicum increased product yield by 17%. This was related to a redirection of the metabolic flux toward the supply of the lysine precursor oxaloacetate. The amplified expression of glucose 6-phosphate dehydrogenase by the start codon exchange increased lysine yield by 10%, linked to an increased flux toward NADPH supply in the pentose phosphate pathway.
    No preview · Article · Oct 2010 · Engineering in Life Sciences