Improving poly-γ-glutamic acid production by Bacillus licheniformis ATCC 9945a strain under citrate and glutamate pulsed feedings and biopolymer characteristic evaluation

Poly-gamma-glutamic acid (gamma-PGA) is a biopolymer composed of glutamate monomers. This polypeptide is used in the food, biomedical, and biopharmaceutical industries. It is used for wound healing and surgical suturing and applied as a drug carrier and drug delivery agent. Fermentative production of this polyamide is a usual method accomplished by microbial cultures. The E culture medium is common for the biopolymers synthesis by Bacillus licheniformis ATCC 9945(a) strain because of the high attained production amounts. Nevertheless, in this study, the culture medium E compounds were modified to attain a novel medium for more production of gamma-PGA. The next purpose of the research was more production increasing of gamma-PGA by using a novel simultaneous pulsed feeding strategy of citrate and glutamate in the modified E medium. Two pulsed feeding times of 24th and 48th hours with proper amounts of citrate and glutamate resulted in enhanced production of gamma-PGA to 119.31 g/l, which is the highest amount among previous researches. This polyamide's physical and chemical structures were investigated by SEM and FTIR, respectively. These analyses revealed a uniform nanostructured polyamide with chemical specifications similar to standard samples.