Stem cell therapy for the treatment of severe tissue damage after radiation exposure

Abstract

I recent years, the application of attenuated strains of Salmonella spp. has been widely investigated for the development of various biotechnological products, especially vaccines. However, the industrial production of these compounds is hampered by metabolic constraints presented by Salmonella cells, which naturally produce high amounts of growth inhibitor metabolites, mainly acetate. To deal with this problem, two different approaches were evaluated in the present work: Changing culture conditions (carbon source evaluation) and implementing genetic modifications (enhancement of cell’s acetate scavenging capabilities by overexpression of acetyl-CoA synthetase (ACS)). Wild type and recombinant cells were cultured in minimal medium with glucose or glycerol as carbon source in Erlenmeyer flasks agitated at 200 rpm and 37 oC. Samples were collected during cultivation and analyzed by HPLC to quantify organic acids production and the carbon source consumption. Cellular growth was assessed by optical density readings (OD 600 nm) of the culture broth. The results showed that the carbon source plays an important role on byproducts excretion by S. typhimurium cells, indicating that for both strains acetate production is greatly reduced using glycerol. The overexpression of ACS also reduced the acetate accumulation as this enzyme acted assimilating the excreted acetate. From all the conditions studied, the best results were obtained by the recombinant cells cultured in glycerol. An increase of 40% of biomass production was achieved, while the acetate accumulation was reduced by more than 50% in comparison to the average values registered in the other experiments.