Microbial production, characterization, and calcium-binding evaluation of poly-γ-glutamic acid for enhanced mineral bioavailability.

Due to low bioavailability of calcium in the gastrointestinal tract Calcium deficiency has become a major health concern globally. This study explores the use of microbial Gamma-Polyglutamic acid (γ-PGA) which is a stable and biodegradable biopolymer to be used as a carrier to improve calcium solubility and uptake. γ-PGA was produced using selected Bacillus isolates (GV1 and GV2). Its purity was confirmed using HPLC and FTIR analysis. Among the isolates, GV2 showed higher production efficiency, yielding 920 μg/mL of γ-PGA. Physicochemical analysis showed that extracted compound is a nanoscale particle with size of 274.9nm and had an initially negative zeta potential which was later reduced after binding with a calcium salt, confirming effective binding. SEM analysis revealed a γ-PGA has structural transition from a porous, layered morphology to a more compact, crystalline-like form after calcium binding. Comparative analysis using Arsenzo III, a calcium sensitive dye demonstrated that calcium chloride was the most effective source for mineral sequestration using γ-PGA. The highest binding efficiency of 97.37% was observed with high-molecular-weight variants under physiological conditions like body temperature, neutral pH, and appropriate incubation time of 30 to 60 minutes. These findings indicate that polymer-calcium complex formation is most efficient under conditions that simulate the human body. Overall, the results suggest that microbially produced γ-PGA is a promising functional biomaterial for enhancing calcium delivery and can be applied in the development of calcium-fortified functional foods.