Evaluation of scale-up parameters of bioethanol production from Escherichia coli KO11

Objective: In recent years, increased attention has been devoted to the conversion of biomass into fuel ethanol, as one of the cleanest liquid fuel alternatives to fossil fuels. However, industrial production of bioethanol is related with successful scaling-up studies. Methods: In this study, the experimental designs of scale-up procedures based on constant mixing time, impeller tip speed and oxygen mass transfer coefficient were performed in 8 L stirred tank reactor and were compared in terms of product yield and productivity with those obtained from 2 L stirred tank reactor using quince pomace as a substrate for bioethanol production by Escherichia coli KO11. Results: Scale-up based on constant mixing time yielded a maximum ethanol concentration of 23.42 g/L which corresponded to 0.4 g ethanol/ g reduced sugar in 8 L stirred tank reactor. Moreover, shear stress increased only 1.1 fold which resulted in low cell damage and high cell viability. Conclusion: Constant mixing time was identified as the most important key parameter especially for scaling-up of viscous fermentation broths of bioethanol production due to the significance of the homogeneity.