METABOLICALLY ENHANCED CYANOBACTERIAL CELL FOR THE PRODUCTION OF ETHANOL

摘要

A metabolically enhanced cyanobacterial cell for the production of ethanol is provided. The metabolically enhanced cyanobacterial cell for the production of ethanol comprises at least one recombinant gene encoding a pyruvate decarboxylase enzyme (Pdc) converting pyruvate to acetaldehyde, and at least one recombinant gene encoding a first Zn2+ dependent alcohol dehydrogenase enzyme (Adh) converting acetaldehyde to ethanol. The alcohol dehydrogenase enzyme has (i) a Michaelis constant Km for NADPH which is lower than the Michaelis constant Km for NADH of the alcohol dehydrogenase enzyme, and (ii) a Michaelis constant Km for acetaldehyde which is lower than 0.08 ⋅10-3 M. Alternatively, the alcohol dehydrogenase enzyme has a Michaelis constant Km for acetaldehyde which is higher than 0.65 ⋅10-3 M but lower than 10 ⋅10-3 M in combination with a Michaelis constant Km for ethanol which is higher than 20 ⋅10-3 M. The invention also provides a method for producing the metabolically enhanced cyanobacterium, a method for producing ethanol with the metabolically enhanced cyanobacterium, and a method for screening of alcohol dehydrogenase enzyme expressing cyanobacterial strains for the presence of NADPH-dependent native alcohol dehydrogenase enzymes.