Construction and L-valine Accumulation of a Genetic Engineering Brevibacterium flavum Strain

XU Da-qing1,2, TAN Yan-zhen1, MIAO Ming1, WANG Xiao-yuan1,* (1. State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China; 2. College of Life Sciences, Agricultural University of Hebei, Baoding 071001, China)

acetyl-carboxylic acid synthase;anti-feedback inhibition;Brevibacterium flavum;fermentation;L-valine

As a rate-limiting enzyme for L-valine biosynthesis, the ilvBN gene encoding acetyl-carboxylic acid synthase (AHAS) from Corynebacterium glutamicum ATCC13032 was amplified by PCR, followed by site-direct mutagenesis to obtain an ilvBNr gene, the anti-feedback inhibition gene of ilvBN. The ilvBNr gene inserted into E. coli-Brevibacterium flavum shuttle expression vector pDXW-10 to construct a recombinant plasmid pDXW-10-ilvBNr, which was subsequently transformed into B. flavum ATCC14067, producing a genetic engineering strain ATCC14067/pDXW-10-ilvBNr. The fermentation experiments conducted in a 3 L fermentor showed that no L-valine accumulation was detected in the fermentation broth of the original strain, while an L-valine accumulation of 5.0 g/L was observed in the fermentation broth of the constructed engineering strain.