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

A study of the production of poly(γ-glutamic acid) (PGGA) by Bacillus licheniformis NCIMB 11709 grown on medium E in shake flasks at 30°C is reported. The enantiomeric composition of PGGA was found to be highly sensitive to the concentration of Mn++, especially when the ion is present in small amounts (⩽ 20 μM). Polymers with D-unit contents ranging from 10 to 90 % and Mw between 0.4 and 2.0 million g mol−1 were obtained for [Mn++] ranging from 0 to 1230 μM. Ultrasonic degradation was proven to be an effective method to reduce both the molecular weight and the polydispersity of naturally produced PGGA without disturbing the chemical constitution of the polymer. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 63: 110–115, 1999.