The filamentous fungus Ashbya gossypii as a competitive industrial inosine producer

Abstract

Inosine is a nucleoside with growing biotechnological interest due to its recently attributed beneficial health effects and as a convenient precursor of the umami flavor. At present, most of the industrial inosine production relies on bacterial fermentations. In this work, we have metabolically engineered the filamentous fungus Ashbya gossypii to obtain strains able to excrete high amounts of inosine to the culture medium. We report that the disruption of only two key genes of the purine biosynthetic pathway efficiently redirect the metabolic flux, increasing 200-fold the excretion of inosine with respect to the wild type, up to 2.2 g/L. These results allow us to propose A. gossypii as a convenient candidate for large-scale nucleoside production, especially in view of the several advantages that Ashbya has with respect to the bacterial systems used at present for the industrial production of this food additive. Biotechnol. Bioeng. 2016;113: 2060-2063. © 2016 Wiley Periodicals, Inc.

New biotechnological applications forAshbya gossypii: Challenges and perspectives

“…Of all the metabolic engineering strategies tested, this was the most efficient in redirecting the metabolic flux of A. gossypii toward the production of inosine, allowing the obtainment of up to 2.2 g/L inosine in rich medium containing 40 g/L glucose. 9,12,13 Guanosine excretion was also increased in this strain (Dade12/ Dpnp1), but only by up to 2-fold. 13 In view of these results, A. gossypii became the first eukaryotic microorganism presenting good potential for the industrial production of inosine, which traditionally has been accomplished with B. subtilis and Escherichia coli modified strains.…”

“…11 With the increasing number of genomic, transcriptomic, proteomic, fluxomic and bioinformatic data that became available for A. gossypii in the last years, 2,[4][5][6][7]15 several systems metabolic engineering strategies have been designed and implemented to improve its metabolic flux toward the production of these commercially valuable bioproducts. [10][11][12][13]…”

“…12 These nucleosides are very appreciated by the food industry, as they are the direct precursors of the umami flavour enhancers IMP and GMP, and have various beneficial effects associated to them, such as antioxidant and immunomodulatory properties. 12,13 Through rational metabolic engineering of key genes in the A. gossypii purine biosynthetic pathway, inosine excretion could be increased by up to 150fold. 13 This particular improvement was achieved by disrupting only 2 genes: AgADE12, which encodes the enzyme that catalyzes the conversion of IMP into adenylosuccinate, and AgPNP1, which encodes the enzyme that catalyzes the conversion of the nucleosides inosine and guanosine into the nucleobases hypoxanthine and guanine, respectively.…”

“…12,13 Through rational metabolic engineering of key genes in the A. gossypii purine biosynthetic pathway, inosine excretion could be increased by up to 150fold. 13 This particular improvement was achieved by disrupting only 2 genes: AgADE12, which encodes the enzyme that catalyzes the conversion of IMP into adenylosuccinate, and AgPNP1, which encodes the enzyme that catalyzes the conversion of the nucleosides inosine and guanosine into the nucleobases hypoxanthine and guanine, respectively. Of all the metabolic engineering strategies tested, this was the most efficient in redirecting the metabolic flux of A. gossypii toward the production of inosine, allowing the obtainment of up to 2.2 g/L inosine in rich medium containing 40 g/L glucose.…”

“…Although the industrial production of riboflavin has come a long way, the recent advances in the field of systems biology for A. gossypii 2,[4][5][6][7] have shown that the carbon flux of this fungus toward riboflavin production can be further improved. 8,9 Moreover, the in silico modeling tools that recently became available for A. gossypii are also boosting the emergence of other commercially valuable biotechnological applications for this fungus, such as SCO production, 10 flavour compounds production [11][12][13] and also recombinant protein production 14,15 (Fig. 1).…”