A poly-gamma-glutamate synthetic system of Bacillus subtilis IFO 3336: gene cloning and biochemical analysis of poly-gamma-glutamate produced by Escherichia coli clone cells

Abstract

Three genes encoding a poly-gamma-glutamate synthetic system of Bacillus subtilis IFO 3336 (Bacillus natto) were cloned and expressed in Escherichia coli. The E. coli clone produced poly-gamma-glutamate extracellularly. The genes, newly designated as pgsBCA, were homologous with capBCA genes of Bacillus anthracis. All of pgsB, pgsC, and pgsA genes were essential for the polymer production. Addition of Mn(2+), instead of Mg(2+), to the polymer-synthesis medium resulted in an increase in the polymer yield. Co-expression of glutamate racemase gene in E. coli cells harboring pgsBCA genes increased both the polymer production and D-glutamate content in the polymer. The polymer produced by the E. coli clone was higher in average molecular size than that produced by B. subtilis IFO 3336.