Engineering Corynebacterium glutamicum triggers glutamic acid accumulation in biotin-rich corn stover hydrolysate

Jingbai Wen,Jie Bao

doi:10.1186/s13068-019-1428-5

Jingbai Wen, Jie Bao

Open Access

https://doi.org/10.1186/s13068-019-1428-5

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Abstract

BackgroundLignocellulose biomass contains high amount of biotin and resulted in an excessive biotin condition for cellulosic glutamic acid accumulation by Corynebacterium glutamicum. Penicillin or ethambutol triggers cellulosic glutamic acid accumulation, but they are not suitable for practical use due to the fermentation instability and environmental concerns. Efficient glutamic acid production from lignocellulose feedstocks should be achieved without any chemical inductions.ResultsAn industrial strain C. glutamicum S9114 was metabolically engineered to achieve efficient glutamic acid accumulation in biotin-excessive corn stover hydrolysate. Among the multiple metabolic engineering efforts, two pathway regulations effectively triggered the glutamic acid accumulation in lignocellulose hydrolysate. The C-terminal truncation of glutamate secretion channel MscCG (ΔC110) led to the successful glutamic acid secretion in corn stover hydrolysate without inductions. Then the α-oxoglutarate dehydrogenase complex (ODHC) activity was attenuated by regulating odhA RBS sequence, and glutamic acid accumulation was further elevated for more than fivefolds. The obtained C. glutamicum XW6 strain reached a record-high titer of 65.2 g/L with the overall yield of 0.63 g/g glucose using corn stover as the starting feedstock without any chemical induction.ConclusionsMetabolic engineering method was successfully applied to achieve efficient glutamic acid in biotin-rich lignocellulose hydrolysate for the first time. This study demonstrated the high potential of glutamic acid production from lignocellulose feedstock.

Highlights

Lignocellulose biomass contains high amount of biotin and resulted in an excessive biotin condition for cellulosic glutamic acid accumulation by Corynebacterium glutamicum
We tried two metabolic modifications to facilitate glutamic acid secretion, either by restricting the biotin uptake to reduce the intracellular biotin content to a sub-optimal biotin level suitable for glutamate secretion [15], or by truncating the C-terminal amino acid residue to activate the activity of glutamate exporter mechanosensitive channel (MscCG) [13, 14]
The cell growth rate was decreased by about 50%, and the corresponding glucose consumption rate was reduced by about 36% compared to that of C. glutamicum S9114 (Fig. 1b)

Summary

Introduction

Lignocellulose biomass contains high amount of biotin and resulted in an excessive biotin condition for cellulosic glutamic acid accumulation by Corynebacterium glutamicum. Penicillin or ethambutol triggers cellulosic glutamic acid accumulation, but they are not suitable for practical use due to the fermentation instability and environmental concerns. Efficient glutamic acid production from lignocellulose feedstocks should be achieved without any chemical inductions. Lignocellulose biomass is the most promising alternative feedstock for the production of glutamic acid that can be used as building block chemical [1]. The rich biotin in lignocellulose biomass maintains stability during the biorefinery processing and creates an excessive condition for glutamic acid secretion [2]. Excessive biotin resulted in reduced carbon flux for glutamic acid. Metabolic engineering of C. glutamicum strain to achieve efficient glutamic acid production in lignocellulose hydrolysate is the best way for the production of cellulosic glutamic acid in industrial practice

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