The biosynthesis and characterization of poly(gamma-glutamic acid) produced by Bacillus licheniformis (ATCC 9945A)

The bacteria B. licheniformis (ATCC 9945A) produces the polymer {dollar}gamma{dollar}-Poly(Glutamic Acid), {dollar}gamma{dollar}-PGA, as a major component of its capsular material.; Fermentations investigated culture time and nutrient availability on polymer molecular weights and yields. An improved, one-step batch culture system for {dollar}gamma{dollar}-PGA production in Medium E by B. licheniformis (ATCC 9945A) was developed. Consistently high yields of polymer ({dollar}>{dollar}20 g/L crude wt.) were obtained.; Cell growth and polymer formation kinetics showed biomass reaching a maximum after 24h, whereas PGA production started later, peaking at 96h.; Experiments in which the L-glutamic acid was replaced by D-glutamic acid, or a 50:50 mixture of D + L isomers indicated the L-isomer is preferred monomer source for PGA production. Results from experiments in which {dollar}sp{lcub}13{rcub}{dollar}C enriched L-glutamic acid (1 and 2 position) was added to the broth indicated there was a substantial direct incorporation of the {dollar}sp{lcub}13{rcub}{dollar}C at the #2 carbon, but there was some scrambling of {dollar}sp{lcub}13{rcub}{dollar}C at the #1 position.