6-19: Characterization and Modeling of Ethanol Production from Gluconate

              Conversion of gluconate to ethanol was investigated with the objective of evaluating gluconate as an alternative carbon source for ethanol production via fermentation as compared to glucose. Escherichia coli KO11 was used as the ethanologen. The experimental data showed that gluconate can be fermented to ethanol at high efficiency comparable to glucose.  On per mole gluconate basis, about 1.5 moles of ethanol and 0.5 mole of acetate were produced as fermentation products as compared to 2 moles of ethanol produced from 1 mole of glucose. When the fermentation started with equal mole of glucose and gluconate, gluconate was utilized simultaneously with glucose, however at a faster speed. More than 40g/L of ethanol can be produced from a glucose and gluconate mixture in 4 days without any pH control in batch culture. Ethanol production is tightly related to cell growth. Cell growth and ethanol production were inhibited by both ethanol and acetate. A kinetic model including substrate and multiple product inhibition was developed to simulate the cell growth and ethanol production using sodium gluconate as substrate. 
Key words: gluconate, ethanol, kinetic model, Escherichia coli KO11