Enhancement of ethanol production from potato-processing wastewater by engineering Escherichia coli using Vitreoscilla haemoglobin

Ethanologenic Escherichia coli strain FBR5 was transformed with the Vitreoscilla haemoglobin (VHb) gene (vgb) in two constructs (resulting in strains TS3 and TS4). Strains FBR5, TS3 and TS4 were grown at two scales in LB medium supplemented with potato-processing wastewater hydrolysate. Aeration was varied by changes in the medium volume to flask volume ratio. Parameters measured included culture pH, cell growth, VHb levels and ethanol production. VHb expression in strains TS3 and TS4 was consistently correlated with increases in ethanol production (5-18%) under conditions of low aeration, but rarely did this occur with normal aeration. The increase in ethanol yields under low aeration conditions was the result of enhancement of ethanol produced per unit of biomass rather than enhancement of growth. 'VHb technology' may be a useful adjunct in the production of biofuels from food-processing wastewater.