Abstract
BackgroundInosine and guanosine monophosphate nucleotides are convenient sources of the umami flavor, with attributed beneficial health effects that have renewed commercial interest in nucleotide fermentations. Accordingly, several bacterial strains that excrete high levels of inosine and guanosine nucleosides are currently used in the food industry for this purpose.ResultsIn the present study, we show that the filamentous fungus Ashbya gossypii, a natural riboflavin overproducer, excretes high amounts of inosine and guanosine nucleosides to the culture medium. Following a rational metabolic engineering approach of the de novo purine nucleotide biosynthetic pathway, we increased the excreted levels of inosine up to 27-fold.ConclusionsWe generated Ashbya gossypii strains with improved production titers of inosine and guanosine. Our results point to Ashbya gossypii as the first eukaryotic microorganism representing a promising candidate, susceptible to further manipulation, for industrial nucleoside fermentation.Electronic supplementary materialThe online version of this article (doi:10.1186/s12934-015-0234-4) contains supplementary material, which is available to authorized users.
Highlights
Inosine and guanosine monophosphate nucleotides are convenient sources of the umami flavor, with attributed beneficial health effects that have renewed commercial interest in nucleotide fermentations
We demonstrate that the wild-type A. gossypii excretes high levels of the nucleosides guanosine and inosine to the culture medium, while their respective intracellular concentrations remain much lower
Inosine and guanosine nucleosides are excreted to the growth medium of A. gossypii
Summary
Inosine and guanosine monophosphate nucleotides are convenient sources of the umami flavor, with attributed beneficial health effects that have renewed commercial interest in nucleotide fermentations. Inosine monophosphate (IMP) and guanosine monophosphate (GMP) have flavour enhancer capabilities that, in combination with monosodium glutamate, increase the umami flavour synergistically [2]. Both inosine and guanosine have beneficial health effects, related to their antioxidant, neuroprotective, cardiotonic and immunomodulatory properties [3,4,5]. Most microorganisms synthesize purine nucleotides in two distinct pathways. Purine bases, either released by the hydrolytic degradation of nucleic acids and nucleotides or taken from the culture medium, can be recycled following the salvage pathway [8]
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