Kinetic analysis of ethanol production by an acetate-resistant strain of recombinant Zymomonas mobilis

Abstract

Zymomonas mobilis ZM4/Ac^R (pZB5), a mutant recombinant strain with increased acetate resistance, has been isolated following electroporation of Z. mobilis ZM4/Ac^R. This mutant strain showed enhanced kinetic characteristics in the presence of 12 g sodium acetate l⁻¹ at pH 5 in batch culture on 40 g glucose, 40 g xylose l⁻¹ medium when compared to ZM4 (pZB5). In continuous culture, there was evidence of increased maintenance energy requirements/uncoupling of metabolism for ZM4/Ac^R (pZB5) in the presence of sodium acetate; a result confirmed by analysis of the effect of acetate on other strains of Z. mobilis.

Nomenclature m

Cell maintenance energy coefficient (g g⁻¹ h⁻¹)

Maximum overall specific growth rate (1 h⁻¹)

Maximum specific ethanol production rate (g g⁻¹ h⁻¹)

Maximum specific total sugar utilization rate (g g⁻¹ h⁻¹)

Biomass yield per mole of ATP (g mole⁻¹

Ethanol yield on total sugars (g g⁻¹)

Biomass yield on total sugars (g g⁻¹)

True biomass yield on total sugars (g g⁻¹)