- A genetically modified yeast can be fed with novel nutrients like xylose
- Xylose can help produce new biological engineering applications
- Adapting native GAL regulons can lead toward designing new synthetic organisms for industrial applications
A genetically modified yeast has been created that can consume xylose, a novel nutrient more efficiently. Xylose enables the yeast to grow faster and also to higher cell densities, which can aid in the designing of new synthetic organisms that can be used for industrial applications.
The research team at Tufts University have published the study in†Nature Communications.
‘New synthetic GAL regulon enables the yeast cells to multiply and can increase the cell densities much higher.’
Feeding Nutrients to Bacteria or Yeast
In synthetic biology, when organisms like bacteria or yeast are fed with nutrients can be transformed into "mini-factories" and produce a wide range of products from pharmaceuticals to industrial chemicals and biofuels.
However, the primary challenge was to convert abundant feedstocks into the final product, as bacteria or yeast do not normally "eat" the feedstock.
In this study, the conventional approaches that help to modify organisms to consume novel nutrients constitutively (i.e., with no "off switch") can lead to inefficiencies, if the nutrient metabolic pathways are not associated with downstream pathways for cell growth, stress-responses, and other important functions related to the health of the organism.
Role of GAL regulon on Yeast
The research team took a different approach by taking a set of regulatory genes called as GAL regulon aid in the process of galactose, which is a favorite and is on the yeast menu of nutrients.
GAL regulon replaced some of the genes with those genes that become activated and direct the breakdown of xylose. All other genes remained unchanged in the GAL regulon.
By doing this, the research team was able to preserve a more natural interaction between the genes that govern feeding and survival.
The new synthetic GAL regulon was able to dub XYL and enabled the yeast cells to multiply and move up to higher cell densities.
"Instead of building a metabolic framework from the ground up, we can reverse engineer existing regulons to enable an organism to thrive on a novel nutrient," said Nikhil U. Nair, Ph.D., assistant professor of chemical and biological engineering at Tufts and corresponding author of this study.
By adapting native GAL regulons can lead to a faster path toward designing new synthetic organisms for industrial applications and one best example is the production of ethanol as a biofuel.
The research had concerns over converting major portions of crops like corn to biofuel production might have the negative impact on the food supply's availability and cost.
Improving Survival of Xylose-eating Yeast Organism
In this study, Nair and his team observed a little closer and investigated as to what exactly improved the survival of xylose-eating yeast organism.
Numerous genes were activated in the XYL regulon that controlled yeast and upregulated pathways involving growth, cell division, adenosine triphosphate (ATP) production and mitochondrial biogenesis.
"Our study applied this approach to xylose, but it suggests a broader principle - adapting native regulons for the efficient assimilation of other non-native sugars and nutrients," said Nair.
Yeast strains that had unregulated control over xylose metabolism triggered pathways related to cell stress, starvation, and DNA damage.
"Nature has already done the work of tuning genes and metabolic pathways to the environment of the organism. Let's make use of that when introducing something new on the menu", said Nair.
Gopinarayanan VE, and Nair NU. A semi-synthetic regulon enables rapid growth of yeast on xylose, Nature CommunicationsDOI: 10.1038/s41467-018-03645-7†