- Research Grants
|Support type:||Scholarships in Brazil - Master|
|Effective date (Start):||August 01, 2010|
|Effective date (End):||May 31, 2012|
|Field of knowledge:||Biological Sciences - Microbiology - Applied Microbiology|
|Principal Investigator:||Luiziana Ferreira da Silva|
|Home Institution:||Instituto de Ciências Biomédicas (ICB). Universidade de São Paulo (USP). São Paulo , SP, Brazil|
Polyhydroxyalkanoates (PHA) are natural polyesters of carbon and energy reserve accumulated intracellularly by many bacteria under conditions of nutrient stress. Poly[(R)-3-hydroxybutyrate] (PHB), the most widely studied member of PHAs is very promising as a biodegradable plastic because of its material properties which are comparable to those of the polypropylene. In Brazil the sugarcane bagasse is an important lignocellulosic waste associated with sugar and ethanol mills. In order to utilize bagasse as raw material to produce PHA, acid hydrolysis is usually performed to release sugars like glucose, xilose and arabinose. Escherichia coli cells have the capacity to select, from a mixture of carbon sources, the one that affords the highest growth rate. This response is called carbon catabolite repression (CCR). These phenomena are close related to the phosphoenolpyruvate: sugar phosphotransferase system (PTS). During glucose transport, the glucose specific enzyme IIAglc-P is dephosphorylated to IIAglc which inhibits several enzymes required for carbon metabolism, including certain non-PTS sugar transporters. Hernandez-Montalvo et al. (2003) studied a PTS- E. coli and overexpressed an alternative sugar transport system (GalP+) as a strategy to abolish carbon catabolite repression, resulting in an E. coli strain capable to consume sugar mixtures simultaneously. This strain, E. coli VH32 PTS- GalP+ will be studiedfor PHA production using sugar mixtures. Genes phaCAB from Ralstonia eutropha (involved on PHA production) and crp* from E. coli ET25 (encoding a modified cAMP-independent catabolite gene activator) will be inserted on E. coli VH32 PTS- GalP+. It is expected to improve the simultaneous consumption of sugar mixtures by reducing catabolite repression and also to improve PHA yields. Metabolic flux analysis will be applied to indicate a representative model for the phenomena observed from the results.