Overexpression of a novel endogenous NADH kinase in Aspergillus nidulans enhances growth

Gianni Panagiotou, Thomas Grotkjær, Gerald Hofmann, Prashant Madhusudhan Bapat, Lisbeth Olsson

    Research output: Contribution to journalJournal articleResearchpeer-review

    Abstract

    The complete genome sequence of the filamentous fungi Aspergillus nidulans has paved the way for fundamental research on this industrially important species. To the best of our knowledge, this is the first time a gene encoding for ATP-dependent NADH kinase (ATP: NADH 2'-phosphotransferase, EC 2.7.1.86) has been identified. The enzyme has a predicted molecular weight of 49 kDa. We characterised the role of this NADH kinase by genomic integration of the putative gene AN8837.2 under a strong constitutive promoter. The physiological effects of overexpressed NADH kinase in combination with different aeration rates were studied in well-controlled glucose batch fermentations. Metabolite pro. ling and metabolic network analysis with [1-C-13] glucose were used for characterisation of the strains, and the results demonstrated that NADH kinase activity has paramount influence on growth physiology. Biomass yield on glucose and the maximum specific growth rate increased from 0.47 g/g and 0.22 h(-1) (wild type) to 0.54 g/g and 0.26 h(-1) (NADH kinase overexpressed), respectively. The results suggest that overexpression of NADH kinase improves the growth efficiency of the cell by increasing the access to NADPH. Our findings indicate that A. nidulans is not optimised for growth in nutrient-rich conditions typically found in laboratory and industrial fermentors. This conclusion may impact the design of new strains capable of generating reducing power in the form of NADPH, which is crucial for efficient production of many industrially important metabolites and enzymes.
    Original languageEnglish
    JournalMetabolic Engineering
    Volume11
    Issue number1
    Pages (from-to)31-39
    ISSN1096-7176
    DOIs
    Publication statusPublished - 2009

    Keywords

    • Metabolic network analysis
    • Aspergillus nidulans
    • NADH kinase
    • Maximum specific growth rate
    • Metabolic engineering

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