Fed-batch cultures of Bacillus licheniformis produced poly-gamma-glutamic acid (PGA), a water-soluble biodegradable polymer. PGA reached 35 g l(-1) with a productivity of 1 g l(-1) h(-1) by pulsed-feeding of citric acid (1.44 g h(-1)) and L-glutamic acid (2.4 g h(-1)) when citric acid was depleted from the culture medium.