Modeling of continuous hydrogen fermentation integrated with continuous in-line liquid-liquid extraction

Abstract

Hydrogen, a promising source of green energy, can be produced via fermentation. However, its productivity is often limited due to accumulation and inhibition of organic acid byproducts (e.g., acetic, propionic, butyric, and lactic acids). To alleviate the inhibitory effect, acids must be continuously removed. Continuous liquid-liquid extraction (LLE) can be used as an in-line removal, which also allows for recycle of remaining substrates. In this work, an integrated process of fermentation and continuous LLE was evaluated for its feasibility. The methodology involved collection of empirical fermentation data, formulation of a kinetic model, and simulation of the integrated process design in SuperPro Designer®. A fermentation process integrated with continuous in-line LLE and recycle (RS-LLE) can increase a production yield by up to 4.5-fold from the single-pass (SP) fermentation while maintaining a comparable productivity. Back extraction is found to reduce the amount of extractants required considerably, eventually improving feasibility of the process.