Patent ID: 7364875

Claim:
A method for producing poly-gamma-glutamic acid (PGA), comprising: fermenting a Bacillus in a fermentation broth to allow production by the Bacillus of PGA, wherein the fermentation increases the broth viscosity; terminating the fermentation when the broth viscosity ceases to substantially increase; buffer exchanging the fermentation broth via diafiltration using a filter having a molecular weight cutoff of at least 30 kDA and less than 100 kDa; lowering pH of the buffer exchanged solution to about 2 or less; removing-the Bacillus cells from the buffer exchanged fermented broth comprising filtering the Bacillus cells from the buffer exchanged fermented broth using a filter with a pore opening of about 0.22 microns or less; and neutralizing the pH of the resulting cell free, buffer exchanged fermentation broth.