Effects of NCgl1221 Knockout and pyc Overexpression on Glutamine Fermentation
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Abstract:
Glutamine has important effects in biological systems and has been widely used in many areas, including in the food and medicine industries. Glutamic acid is the precursor for glutamine biosynthesis, and is the most common by-product in glutamine fermentation. Previous studies have shown that the protein encoded by NCgl1221 is an important glutamic acid exporter and that pyruvate carboxylase is a key enzyme in the feedback pathway of Corynebacterium glutamicum. In order to reduce glutamic acid accumulation during glutamine fermentation and to improve the yield of glutamine, in this study, NCgl1221 of the glutamine-producing strain GM34 was knocked out using homologous recombination technology, resulting in the construction of the mutant strain GM34ΔNCgl1221. Pyc encoding pyruvate carboxylase was also overexpressed in the constructed strain GM34-pXMJ19pyc. Fermentation carried out in 5-L bottles showed that NCgl1221 knockout reduced glutamic acid accumulation by 19.05%. Overexpression of pyc resulted in a promotion of glutamine production and conversion rate by 5.54% and 2.37%, respectively. Taken together, these results demonstrate that NCgl1221 knockout and pyc overexpression can effectively reduce glutamic acid accumulation and improve glutamine production.
