Biosynthesis and ultrasonic degradation of bacterial poly(gamma-glutamic acid)

A study of the production of poly(gamma-glutamic acid) (PGGA) by Bacillus l icheniformis NCIMB 11709 grown on medium E in shake flasks at 30 degrees C is reported. The enantiomeric composition of PGGA was found to be highly se nsitive to the concentration of Mn++, especially when the ion is present in small amounts (less than or equal to 20 mu M). Polymers with D-unit conten ts ranging from 10 to 90 % and Mw between 0.4 and 2.0 million g mol(-1) wer e obtained for [Mn++] ranging from 0 to 1230 mu M. Ultrasonic degradation w as proven to be an effective method to reduce both the molecular weight and the polydispersity of naturally produced PGGA without disturbing the chemi cal constitution of the polymer. (C) 1999 John Wiley & Sons, Inc.