A novel PGA/TiO₂ nanocomposite prepared with poly(-glutamic acid) from the newly isolated Bacillus subtilis 17B strain

Poly(gamma-glutamic acid) (PGA), naturally produced by Bacillus species, is a biodegradable, non-toxic, biocompatible and non-immunogenic negatively charged polymer. Due to its properties, it has found various applications in the food, cosmetic and pharmaceutical industries. In this work, Bacillus subtilis 17B was selected as the best PGA producer among fifty wild-types Bacillus strains tested and characterized as a glutamate-independent producer. The pro-duction of PGA by the newly identified strain was optimized and increased tenfold using the Box-Behnken experimental design. The purity of PGA after recovery and purification from the fermentation broth was confirmed by SDS--PAGEfollowed by methylene blue staining. PGA was characterized by ESI MS and used for the preparation of a new nanocomposite with TiO2. The syn-thesis of PGA/TiO2 nanocomposite, its structural analysis, and cytotoxic effect on the cervical cancer cell line (HeLa cell) was investigated to determine the potential anti-cancer usage of this newly prepared material. It is encouraging that PGA/TiO2 nanocomposite showed an increased cytotoxic effect compared to TiO2 alone.