Enhancement of γ-aminobutyric acid production in recombinant Corynebacterium glutamicum by co-expressing two glutamate decarboxylase genes from Lactobacillus brevis.
γ-Aminobutyric acid (GABA), a non-protein amino acid, is a bioactive component in the food, feed and pharmaceutical fields. To establish an effective single-step production system for GABA, a recombinant Corynebacterium glutamicum strain co-expressing two glutamate decarboxylase (GAD) genes (gadB1 and gadB2) derived from Lactobacillus brevis Lb85 was constructed. Compared with the GABA production of the gadB1 or gadB2 single-expressing strains, GABA production by the gadB1-gadB2 co-expressing strain increased more than twofold. By optimising urea supplementation, the total production of L-glutamate and GABA increased from 22.57 ± 1.24 to 30.18 ± 1.33 g L⁻¹, and GABA production increased from 4.02 ± 0.95 to 18.66 ± 2.11 g L⁻¹ after 84-h cultivation. Under optimal urea supplementation, L-glutamate continued to be consumed, GABA continued to accumulate after 36 h of fermentation, and the pH level fluctuated. GABA production increased to a maximum level of 27.13 ± 0.54 g L⁻¹ after 120-h flask cultivation and 26.32 g L⁻¹ after 60-h fed-batch fermentation. The conversion ratio of L-glutamate to GABA reached 0.60-0.74 mol mol⁻¹. By co-expressing gadB1 and gadB2 and optimising the urea addition method, C. glutamicum was genetically improved for de novo biosynthesis of GABA from its own accumulated L-glutamate.
State Key Laboratory of Food Science and Technology, Jiangnan University, 1800 Lihu Avenue, Wuxi, 214122, China, shifeng@jiangnan.edu.cn.
Feng
F
Shi
Junjun
J
Jiang
Yongfu
Y
Li
Youxin
Y
Li
Yilong
Y
Xie
D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D061249:Batch Cell Culture Techniques; D019149:Bioreactors; D048230:Corynebacterium glutamicum / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D005285:Fermentation / Q000187:drug effects; D005968:Glutamate Decarboxylase / Q000096:biosynthesis / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D052196:Levilactobacillus brevis / Q000201:enzymology* / Q000235:genetics*; D013997:Time Factors; D014508:Urea / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000096:biosynthesis* / Q000378:metabolism
D001426:Bacterial Proteins; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D014508:Urea; D005968:Glutamate Decarboxylase