Modeling and simulation of direct production of acetic acid from cheese whey in a multi-stage membrane-integrated bioreactor

Modeling and simulation of direct and continuous production of acetic acid in a two-stage membraneintegrated hybrid reactor system was done. The total production and purification scheme involved fermentation of a cheap, renewable carbon source (cheese whey) under non-neutralizing regime in a membrane-integrated new reactor with provisions of downstream separation and recycle of microbial cells and unconverted carbon source from product acetic acid by microfiltration and nano-filtration membranes. The model attempts to capture the major governing parameters like dilution rate, cross flow rate, recycling of materials, pH along with fermentation kinetics under substrate-product inhibitions and all the associated transport phenomena of the components through micro and nanofiltration membranes. The system produced 98.6% pure acetic acid at a flux of 75 L/(m(2)h) with yield of 0.98 g/g and productivity of 4.1 g/(Lh). Performance of the model is well reflected in low relative error (<0.05), high Willmott d-index (d > 0.97) and high overall correlation coefficient (R-2 >0.98). (C) 2014 Elsevier B.V. All rights reserved.