Abstract:

Researchers at Cuidad Universitaria-Pabellón 2 in Argentina investigated the effects of different mutations on producing poly 3-hydroxybutyrate (PHB) in recombinant Escherichia coli. The group focused on mutations in the arcA regulator in recombinant E. coli strains carrying PHA synthesis genes from Azotobacter sp. strain FA8. The wildtype E. coli strain did not produce PHB under low-oxygen conditions in shaken flask cultures. However, recombinant strains carrying the mutants accumulated up to 24% of their cell dry weight when grown under the same conditions. Cultured in a bioreactor under microaerobic conditions the arcA deletion mutant achieved a PHB content of 27%. The arcA2 allele produced 35% PHB under the same conditions. The arc2A strain grew at a good growth rate on a simple medium. However, the deletion mutant needed several nutritional additives and the growth rate was still not as high as that of the arcA2 strain.