Transcriptional analysis of heterologous phosphoketolase expression in Saccharomyes cerevisiae

Phosphoketolases (Xfpk) are a to yeast non-native group of enzymes, which theoretically can be expressed in combination with other metabolic enzymes to positively influence the yield of acetyl-CoA derived products by reducing carbon losses in the form of CO2. In this study, a yeast strain expressing Xfpk from Bifidobacterium breve, which was previously found to have a growth defect and increased acetate production, was characterized.RNAseq analysis shows that Xfpk expression increases transcription of genes related to the glyoxylate cycle, the TCA cycle and respiration, while expression of genes related to ethanol and acetate formation is reduced in chemostat cultivations. The transcriptional changes indicate that a heterologous phosphoketolase flux in combination with endogenous hydrolysis of acetyl-phosphate to acetate increases the cellular demand for acetate degradation and respiratory ATP-generation, leading to carbon losses.