Effect of Precursor Feeding on Riboflavin Production of Ashbya gossypii and Influence of Threonine Aldolase Overexpressi
Study of • riboflavin production in shake flask culture after supplementation of the cultivation medium with glycine • threonine aldolase specific activity in a strain overexpressing the corresponding gene GLY1 and effect of threonine supplementation of t
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Effect of Precursor Feeding on Riboflavin Production of Ashbya gossypii and Influence of Threonine Aldolase Overexpression K.-Peter Stahmann and Ulrike Weber
Aim Study of 䊉 riboflavin production in shake flask culture after supplementation of the cultivation medium with glycine 䊉
threonine aldolase specific activity in a strain overexpressing the corresponding gene GLY1 and effect of threonine supplementation of this strain on riboflavin production
Introduction Ashbya gossypii is a phytopathogenic hemiascomycete originally isolated from cotton (Gossypium hirsutum). Although closely related to Saccharomyces cerevisiae, it exclusively produces a mycelial growth rather than one that is yeast-like. The most striking property of A. gossypii is riboflavin overproduction. Since riboflavin is a pigment, culture broths or even the colonies on agar plates are bright yellow. This makes it possible to see strain differences in productivity or effects of precursor feeding with the naked eye, which is very convincing for students. A further argument to choose A. gossypii for a teaching class is that riboflavin production is a successful example for a biotechnical process which became comK.-Peter Stahmann (✉), Technische Mikrobiologie; Bio-, Chemie- und Verfahrenstechnik, Fachhochschule Lausitz, Großenhainer Str., 01968 Senftenberg Tel.: +49-3573-85-809, Fax: +49-3573-85-867, email: [email protected] Ulrike Weber, Institut für Biotechnologie, Forschungszentrum Jülich GmbH, LeoBrand-Str., 52425 Jülich Tel.: +49-2461-61-2710, Fax: +49-2461-61-5584, email: [email protected] Springer Lab Manual K. Wolf, K. Breunig, G. Barth (Eds.) Non-Conventional Yeasts in Genetics, Biochemistry and Biotechnology © Springer-Verlag Berlin Heidelberg 2003
K.-Peter Stahmann and Ulrike Weber
petitive with chemical synthesis on an industrial scale (Stahmann et al. 2000). Riboflavin (vitamin B2) is the precursor of FMN and FAD which are important coenzymes for oxidoreductases.Since humans and domestic animals cannot synthesize riboflavin they have to take it up by their diet.Therefore, riboflavin is classified as a vitamin. Biosynthesis of riboflavin has two roots in the metabolism.One starts with GTP and the other with ribulose-5P (Bacher 1991). Interestingly, the riboflavin-specific reactions converting both of these metabolites by seven enzymatic steps into riboflavin do not limit the productivity of A. gossypii. A limiting precursor is the amino acid glycine which is needed in GTP synthesis (Hanson 1967; Fig. 1). The easiest way to overcome the glycine limitation of riboflavin production is supplementation of the cultivation medium. Glycine-supplemented cultures show the same growth but a significant increase in produced riboflavin.A goal of current research is an enhanced glycine biosynthesis of the cells to avoid supplementation. A proof of concept was given by overexNH2
Glycine
Acetaldehyde
Ribose-P
NH3+
䉴
16
Threonine
䉴 Threonine Aldolase
Glycine Amide Ribonucleotide Synthetase
CH 2
ATP
O C
䉴
OH
ADP+Pi
䉴 NH
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