Kinetics of molecular weight reduction of poly(glutamic acid) by in situ depolymerization in cell-free broth of Bacillus subtilis

Poly(glutamic acid) (PGA) is a water soluble, biodegradable biopolymer that is produced by microbial fermentation. Recent research has shown that poly(glutamic acid) can be used in drug delivery applications for the controlled release of paclitaxel (Taxol) in cancer treatment. The molecular weight of microbial poly(glutamic acid) is generally larger than what is required for drug delivery. As such, molecular weight reduction is a necessary step in producing poly(glutamic acid) for this application. Poly(glutamic acid) produced by Bacillus subtilis IFO 3335 was subjected to in situ depolymerization in the cell-free fermentation broth. Molecular weight reduction was measured, and an empirical kinetic model was used to correlate the experimental data. The kinetic rate constant, k, was found to be 6.92 × 10−6 h−1 at pH 7.0 and 37 °C, which were the optimum depolymerization conditions.