The Droppy project !

Polyhydroxyalcanoates (PHAs) are universal prokaryotic storage compounds of carbon and energy. They are accumulated into the cell as spherical inclusion bodies in case of oversupply of carbon sources. We aim to control the production and the composition of granules in Escherichia Coli. Many industrial and biomedical applications for those granules had been evocated. However, we want to focus especially on two potential applications (see Uses):

  1. the granule as self-cleaving micro-beads in order to purify a recombinant protein of interest, see Proteins purification
  2. the granule as a storage system for overproduced lipids of interest, for example DHA or EPA which have medical applications, see Storage of lipids of interest.

We aim to regulate the granule production in E. coli thanks to two different strategies: thermoregulation and chemoregulation (arabinose). However, our favorite new part is a strong promoter sensitive to temperature of the water bath (and also to shaking speed and osmolarity).

In bacteria, three separate monofunctional enzymes are required for PHA synthesis. In order to improve this pathway, we intend to design a single multifunctional enzyme based on the study of natural evolution of fatty acid synthesis in animals.

Indeed, in plants and bacteria, the reactions involved in fatty acid synthesis also are catalyzed by separate monofunctional enzymes. But in animals, evolution has done synthetic biology and the different enzymes are integrated into a single multifunctional polypeptide in which substrates are handed from one functional domain to the next. We have begun to analyse the work of evolution in animals in order to design multifunctional bacterial enzymes that integrate discrete monofunctional enzymes. We hope that these enzymes could promote the synthesis of particular lipids, such as tri-acyl glycerols, and store these molecules into granules.

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