Enhancing the supply of oxaloacetate for l-glutamate production by pyc overexpression in different Corynebacterium glutamicum

Abstract

During L-glutamate production, phosphoenolpyruvate carboxylase and pyruvate carboxylase (PCx) play important roles in supplying oxaloacetate to the tricarboxylic acid cycle. To explore the significance of PCx for L-glutamate overproduction, the pyc gene encoding PCx was amplified in Corynebacterium glutamicum GDK-9 triggered by biotin limitation and CN1021 triggered by a temperature shock, respectively. In the fed-batch cultures, GDK-9pXMJ19pyc exhibited 7.4% lower L-alanine excretion and no improved L-glutamate production. In contrast, CN1021pXMJ19pyc finally exhibited 13% lower L-alanine excretion and identical L-glutamate production, however, 8.5% higher L-glutamate production was detected during a short period of the fermentation. It was indicated that pyc overexpression in L-glutamate producer strains, especially CN1021, increased the supply of oxaloacetate for L-glutamate synthesis and decreased byproduct excretion at the pyruvate node.