Optimization and interaction of media components in ethanol production using Zymomonas mobilis by response surface methodology.

Ethanol production using Zymomonas mobilis strains with medium optimized by response surface methodology (RSM) was studied. A significant improvement in the ethanol yield (0.50 g/g ethanol) was demonstrated, resulting in very low residual sugar and fewer by-products. The five-factor and five-response full factorial design have shown that glucose and yeast extract are the key media components that influence ethanol production, followed by the inoculum concentration and ammonium sulfate, with phosphate showing little or no effect. The composition (all in g/l) of the optimized medium was glucose 120.4, ammonium sulfate 0.96, potassium dihydrogen phosphate 0.02, yeast extract 6.5, and magnesium sulfate 0.5. The optimum inoculum concentration was log10 8.4 cells.