Optimization Of The Synthesis Pathway Of Acetone And Isopropanol From Acetate By Metabolically Engineered Escherichia Coli

Both acetone and isopropanol are widely applied in medicine,pesticide,chemical and other industries as important organic compound and excellent solvent.Acetone-butanol-ethanol(ABE)fermentation and isopropanol-butannol-ethanol(IBE)are traditional methods to produce acetone and isopropanol.The bioproduction from the traditional ABE and IBE fermentation are limited by the non-specificity of products and competitive utilization of food-based substrates.Products selectivity and cost-effective nonfood feedstocks are yet to be stuied.Acetic acid is a kind of cheap acid produced by both chemical and biological methods.Furthermore,we can get it from varies of industrial waste water.Eshecherichia coli can grow under aerobic condition with acetate,but there is no report to use acetate as the sole carbon source for the production of acetone and isopropanol by Escherichia coli.Using genetically modified Escherichia coli showed great potential to overcome these problems.A novel acetone biosynthetic pathway were constructed based on genes from Clostridium acetobutylicum(thlA encoding for thiolase,adc encoding for acetoacetate decarboxylase,ctfAB encoding for coenzyme A transferase)and Escherichia coli MG1655(atoB encoding acetyl-CoA acetyltransferase,atoDA encoding for acetyl-CoA:acetoacetyl-CoA transferase subunit ? and ?).Among these constructs,one recombinant MG 1655 derivative containing the hybrid pathway consisting of thlA,atoDA,and adc,produced the highest level of acetone from acetate.Enhancing the acetate uptake rate by overexpressing ack-pta pathway,reducing the gluconeogenesis pathway by knocking out the pckA and maeB genes,blocking the TCA cycle by knocking out the icdA gene enhanced the yield of acetone significantly.As a result,acetone concentration increased up to 113.18 mM in 24 h by the resting cell culture coupling with gas-stripping methods.On the basis of this pathway,adh gene was expressed from Clostridium beijerinckii to form isopropanol.It provides a potential method for industrial biomanufacturing of acetone and isopropanol by engineered E.coli strains from non-food based substrate.