How do cells generate and use energy? This question might seem simple, but the answer is far from simple. Furthermore, they know how microbial cell factories consume energy and how proteins are so important when they are used in industrial fermentation.
e. coli and baker's yeast by optimizing fermentation conditions.
"This information can be used to design new improved cell factors," corresponding author professor at Chalmers University of Technology, Sweden, and Scientific Director Jens Nielsen says
Together with first author postdoc Yu Chen from Department of Biology and Biological Engineering at Chalmers, Jens Nielsen has studied the metabolism of E. coli and baker's yeast through the use of mathematical models and biological experiments. ( PNAS ).
Cells constantly generating high-energy molecules called ATP from the sugar glucose. ATP is the cellular "food" consumed by the workers ̵
Using a computational approach, the ATP can be generated by either of two pathways: a high-yielding respiratory pathway resulting in 23.5 ATP's per glucose molecule or a low-yielding fermentative pathway, which only generates 11 ATP's per glucose molecule.
The two pathways supplement each other, but the researchers were able to shift the natural balance between the two by changing the conditions of the fermentation and the amount of sugar and protein available. Furthermore, they have shown that the high-yielding pathway needs more protein mass than the low-yielding pathway for consuming glucose at the same rate
This shift both results in more intracellular ATP, but also avoids the build-up of fermentative byproducts; acetate in E. coli and ethanol in baker's yeast.
"These byproducts are unwanted and decrease the yield of the sought-after molecules you want to produce in your cell factory," says Jens Nielsen.
Furthermore, the investigators showed
Thus, the solution to better performing cells in fermentations is not to switch off the fermentative pathway, but rather to allocate more protein to the high-yielding pathway.
The researchers report that the microbes to different fermentation conditions and do not genome engineering to evoke these changes.
Materials provided by Technical University of Denmark . Originally written by Anne Heat Lykke, Anders Østerby Mønsted. Note: Content may be edited for style and length.