High production of L-glutamic acid from date juice extracts by Corynebacterium glutamicum using fed-batch cultures: pulsed and continuous feeding modes

Nancib Aicha,Nancib Nabil,Mouffok Abdenacer,Boudrant Joseph

doi:10.2478/asn-2021-0004

Abstract

Abstract In the present work, L-glutamic acid production by Corynebacterium glutamicum fermentation on date juice extracts applying two fed-batch feeding modes, pulsed and continuous, were investigated. According to the obtained results, the continuous feeding fed-batch mode was found to be the most efficient process. Moreover the continuous feeding rate mode with a feeding medium containing date juice sugars enriched with ammonium sulfate was found even more favorable as it enhances the L-glutamic acid production by approximately 2.35 fold more than the batch culture and by about 1.17 fold more than the pulsed feeding. In this respect, comparing the traditional batch culture to the continuously fed culture with a medium containing date juice sugars with ammonium sulfate showed increases of 135.47% in L-glutamic acid production, 104% in productivity, 39.09% in biomass, and 47.69% in the yield respectively allowing us to reach a final L-glutamic acid concentration of about 138 g/L, the highest ever published.

Highlights

L-glutamic acid is an important industrial amino acid for producing the flavoring agent monosodium glutamate
At 30 h of culture, the maximum concentration of L-glutamic acid observed was 58.57 g/L and the maximum biomass, yield and productivity of L-glutamic acid were 18.52 g/L, 0.65 g/g and 2.25 g/L.h, respectively. This might result from the substrate inhibition and limitation effects that occur in L-glutamic acid fermentation as reported by Khan et al [27]
The continuous feeding rate using a solution with date juice sugars and ammonium sulfate provided better results than pulsed feeding in fed-batch culture

Summary

Introduction

L-glutamic acid is an important industrial amino acid for producing the flavoring agent monosodium glutamate. It is widely used in the food industry, pharmaceuticals, medical sciences, cosmetics, and polymer precursors. The annual production of glutamic acid reaches around 2.2 million tons [1]. As for the substrate, glucose is one of the major carbon sources for the production of Lglutamic acid. It is produced using different kinds of raw materials including submerged fermentation of palm waste hydrolysate [7], cassava starch [8], sugar cane bagasse [8], and date waste [10]

Methods

Results

Conclusion