Production of L (+) Glutamic Acid in a Fully Membrane-Integrated Hybrid Reactor System: Direct and Continuous Production under Non-Neutralizing Conditions

Abstract

Experimental investigations were carried out on continuous and direct production of l-glutamic acid in a hybrid reactor system that integrated a conventional fermentative production step with downstream membrane-based separation and purification in flat sheet cross-flow membrane modules. To ensure constant fermentor capacity, the system was operated at steady state at different set flux values ranging from 76 L m–2 h–1 to 90 L m–2 h–1 at a dilution rate of 0.15 h–1. Overcoming the substrate–product inhibitions of traditional batch production system, this new, compact, flexible, and largely fouling-free design ensured steady and continuous production of l-glutamic acid directly from a renewable carbon source at the rate of about 8.4 g L–1 h–1. Provisions of continuous product withdrawal, separation, and recycling of unconverted sugar and microbial cells ensured almost inhibition-free production under high cell concentration. Well-screened nanofiltration membranes with high selectivity helped achieve over 97% product purity while ensuring recovery and recycle of more than 95% unconverted carbon source resulting in a high yield of 0.95 g g–1. The direct production scheme involves no phase change and use of harsh chemicals. The study presents development of a green process of glutamic acid production for sustainable business.