No abstract

No abstract

A comparative study between natural and synthetic environments is carried out by realizing six fermentation experiments in batch culture. The objective of this study is to consider the effect of carbon sources on growth and the production of glutamic acid by Corynebacterium glutamicum 2262. The difference between the culture media lies in the carbon source. Two natural environments of date juice, one of which is treated with invertase to hydrolyse sucrose with a concentration of total sugars of 88 g/L. Four synthetic media with a concentration of 34 g/L sugars: medium containing mixed sugars (glucose + fructose + sucrose) with rates proportional to that of date juice, the other three media are composed of a single sugar (either glucose, fructose, or sucrose). The results showed that Corynebacterium glutamicum is able to use the three sugars whether they are single or mixed, although the best results of glutamate production (8.41 g/L) are obtained on the mixture of three sugars, which explains the interest and valorisation of date waste. On the other hand, the date juice-based media are shown to have a glutamate concentration of 7.98 g/L during the hydrolysis of sucrose of date juice.

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.