Abstract
BackgroundThe fungus Ashbya gossypii is an important industrial producer of the vitamin riboflavin. Using this microbe, riboflavin is manufactured in a two-stage process based on a rich medium with vegetable oil, yeast extract and different precursors: an initial growth and a subsequent riboflavin production phase. So far, our knowledge on the intracellular metabolic fluxes of the fungus in this complex process is limited, but appears highly relevant to better understand and rationally engineer the underlying metabolism. To quantify intracellular fluxes of growing and riboflavin producing A. gossypii, studies with different 13C tracers were embedded into a framework of experimental design, isotopic labeling analysis by MS and NMR techniques, and model-based data processing. The studies included the use 13C of yeast extract, a key component used in the process.ResultsDuring growth, the TCA cycle was found highly active, whereas the cells exhibited a low flux through gluconeogenesis as well as pentose phosphate pathway. Yeast extract was the main carbon donor for anabolism, while vegetable oil selectively contributed to the proteinogenic amino acids glutamate, aspartate, and alanine. During the subsequent riboflavin biosynthetic phase, the carbon flux through the TCA cycle remained high. Regarding riboflavin formation, most of the vitamin’s carbon originated from rapeseed oil (81 ± 1%), however extracellular glycine and yeast extract also contributed with 9 ± 0% and 8 ± 0%, respectively. In addition, advanced yeast extract-based building blocks such as guanine and GTP were directly incorporated into the vitamin.ConclusionIntracellular carbon fluxes for growth and riboflavin production on vegetable oil provide the first flux insight into a fungus on complex industrial medium. The knowledge gained therefrom is valuable for further strain and process improvement. Yeast extract, while being the main carbon source during growth, contributes valuable building blocks to the synthesis of vitamin B2. This highlights the importance of careful selection of the right yeast extract for a process based on its unique composition.
Highlights
The fungus Ashbya gossypii is an important industrial producer of the vitamin riboflavin
A. gossypii B2 accumulates elevated amounts of riboflavin in a two‐stage process Ashbya gossypii B2 was cultivated on a typical production medium containing yeast extract, glycine, glutamate as well as formate with rapeseed oil as main carbon source
Note that the conversion of citrate to isocitrate via aconitase most likely does not occur in the peroxisome [68]. 3PG, 3-phosphoplycerate; C H2-THF, 5,10-methylenetetrahydrofolate; AcCoA, acetyl-CoA; AKG, α-ketoglutarate; ALA, alanine; ARG, arginine; ASP, aspartate; 10-for‐ myltetrahydrofolate (CHO-THF), 10-formyltetrahydrofolate; CIT, citrate; DHAP, dihydroxyacetone phosphate; E4P, erythrose 4-phosphate; F6P, fructose 6-phosphate; FA, fatty acids; FOR, formate; G3P, glyceraldehyde 3-phosphate; glucose 6-phosphate (G6P), glucose
Summary
The fungus Ashbya gossypii is an important industrial producer of the vitamin riboflavin. Using this microbe, riboflavin is manufactured in a two-stage process based on a rich medium with vegetable oil, yeast extract and different precursors: an initial growth and a subsequent riboflavin production phase. The ability of microorganisms to synthesize the vitamin has enabled production on an industrial level: more than two decades ago, the initially chemical synthesis of riboflavin was partially replaced by fermentation using the filamentous hemiascomycete Ashyba gossypii [5], which efficiently forms the vitamin on vegetable oil as major carbon source [6, 7]. The vitamin is exclusively produced via biotechnological synthesis [8]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
