Modelling and simulation of continuous L (+) lactic acid production from sugarcane juice in membrane integrated hybrid-reactor system

• Modelling done for a continuous and direct (L+) lactic acid production process.
• Microbial reaction kinetics as well as membrane transport phenomena captured.
• Model successfully predicts performance as evident in high Willmott d-index.
• Modelling and simulation study will pave the way for scale up of a novel process.

Modelling and simulation was done for a two-stage membrane-integrated hybrid reactor system for continuous production of L (+) lactic acid under non-neutralizing conditions. The model captures microbial conversion of sugar cane juice to lactic acid under substrate–product inhibitions with downstream purification by nanofiltration. All the major phenomena and the governing parameters like fluid flow, feed dilution, substrate–product inhibitions, Donnan and steric effects during micro and nanofiltration for cell recycle, product separation and purification have been reflected in the modelling. The model describes a green, integrated continuous process of direct lactic acid production starting with a cheap, renewable carbon source. The highest lactic acid concentration achieved after the final stage of nanofiltration was 66.97 g/L at 13 kg/cm2 operating pressure when the overall productivity reached 12.40 g/(L h). The developed model could successfully predict production, purification and transport of lactic acid through two stage membrane modules. Performance of the model was very good as indicated in the high overall correlation coefficient (R2 > 0.980) and the low relative error (RE < 0.1).