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

• Modeling done for a continuous and direct acetic acid production process.
• Microbial reaction kinetics as well as membrane transport phenomena captured.
• Model successfully predicts performance as evident in high Willmott d-index.
• Modeling and simulation study will pave the way for scale up of a novel process.
• Economic analysis done for the new process.

Modeling and simulation of direct and continuous production of acetic acid in a two-stage membrane-integrated 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/(m2 h) with yield of 0.98 g/g and productivity of 4.1 g/(L h). 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 (R2 > 0.98).