Abstract:

The L-glutamate produced by the fermentation of Corynebacterium glutamicum is mainly released by the L-glutamate exporters’ opening the channel when the cell membrane is stretched. The biotin in medium can affect the components of cell membrane and thus affect the membrane tension,and the concentration of biotin can indirectly affect the capacity of L-glutamate exporter and the accumulation of extracellular L-glutamate in the fermentation broth. In this study,we investigated the effect of L-glutamate exporter MscCG on the L-glutamate production from the fermentation of C. glutamicum,and online monitored the changes of biomass,dissolved oxygen and pH in the fermentation process using the M2P BioLector micro-bioreactor. The results showed that biotin had a great influence on the efflux of L-glutamate by MscCG. 0.5 μg/L biotin was the suboptimal under the condition of this experiment,at which the amount of L-glutamate exported by MscCG reached the highest. When the concentration was lower than that,the growth rate of the bacteria was slow and the efflux of L-glutamate reduced. When the concentration was > 0.5 μg/L,the growth rate of bacteria was fast but the concentration of L-glutamate was low,and the lack of dissolved oxygen led to the accumulation of lactate. Therefore,the concentration of biotin,the dissolved oxygen and pH control should be adjusted in a combined way for maximum productivity of L-glutamate.

Key words: L-glutamate, biotin, MscCG, fermentation, Corynebacterium glutamicum