Authors: Marta Papini Intawat Nookaew Verena Siewers Jens Nielsen
Publish Date: 2012/02/26
Volume: 95, Issue: 4, Pages: 1001-1010
Abstract
Several bacterial species and filamentous fungi utilize the phosphoketolase pathway PHK for glucose dissimilation as an alternative to the Embden–Meyerhof–Parnas pathway In Aspergillus nidulans the utilization of this metabolic pathway leads to increased carbon flow towards acetate and acetyl CoA In the first step of the PHK the pentose phosphate pathway intermediate xylulose5phosphate is converted into acetylphosphate and glyceraldehyde3phosphate through the action of xylulose5phosphate phosphoketolase and successively acetylphosphate is converted into acetate by the action of acetate kinase In the present work we describe a metabolic engineering strategy used to express the fungal genes of the phosphoketolase pathway in Saccharomyces cerevisiae and the effects of the expression of this recombinant route in yeast The phenotype of the engineered yeast strain MP003 was studied during batch and chemostat cultivations showing a reduced biomass yield and an increased acetate yield during batch cultures To establish whether the observed effects in the recombinant strain MP003 were due directly or indirectly to the expression of the phosphoketolase pathway we resolved the intracellular flux distribution based on 13C labeling during chemostat cultivations From flux analysis it is possible to conclude that yeast is able to use the recombinant pathway Our work indicates that the utilization of the phosphoketolase pathway does not interfere with glucose assimilation through the Embden–Meyerhof–Parnas pathway and that the expression of this route can contribute to increase the acetyl CoA supply therefore holding potential for future metabolic engineering strategies having acetyl CoA as precursor for the biosynthesis of industrially relevant compounds
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