Construction of A Recombinant Bacillus subtilis and Food-Grade Expression of Glutamate Decarboxylase

Abstract:

Glutamate decarboxylase（GAD）is a key enzyme that can be used to biosynthesize γ-aminobutyric acid（GABA）. In our study，four antibiotic-free marker recombinant Bacillus subtilis strains were constructed and glutamate decarboxylase derived from Lactococcus lactis ssp. lactis IL 1403 was expressed in those strains. By comparing growth curves and GAD production curves of the four recombinant strains，the recombinant strain B.subtilis WB600/ pUB-P43-gadB（opt）-dal with highest enzyme activity was selected. After fermentation of the B.subtilis WB600/ pUB-P43-gadB（opt）-dal for 42 h in primary fermentation medium，the volumetric activity of the fermented broth reached 4.1 U/mL. By modifying of the composition of fermentation medium，volumetric activity of the fermented broth was increased by 79% and reached 7.4 U/mL，which was the highest activity of GAD for the reported recombinant Bacillus subtilis strains.