Poly (γ) glutamic acid: a unique microbial biopolymer with diverse commercial applicability

Abstract

Microbial biopolymers have emerged as promising solutions for environmental pollution-related human health issues. Poly-γ-glutamic acid (γ-PGA), a natural anionic polymeric compound, is composed of highly viscous homo-polyamide of D and L-glutamic acid units. The extracellular water solubility of PGA biopolymer facilitates its complete biodegradation and makes it safe for humans. The unique properties have enabled its applications in healthcare, pharmaceuticals, water treatment, foods, and other domains. It is applied as a thickener, taste-masking agent, stabilizer, texture modifier, moisturizer, bitterness-reducing agent, probiotics cryoprotectant, and protein crystallization agent in food industries. γ-PGA is employed as a biological adhesive, drug carrier, and non-viral vector for safe gene delivery in tissue engineering, pharmaceuticals, and medicine. It is also used as a moisturizer to improve the quality of hair care and skincare cosmetic products. In agriculture, it serves as an ideal stabilizer, environment-friendly fertilizer synergist, plant-growth promoter, metal biosorbent in soil washing, and animal feed additive to reduce body fat and enhance egg-shell strength.

Metabolic Engineering of Bacillus subtilis for the Production of Poly-γ-Glutamic Acid from Glycerol Feedstock

“…This safe status of different natural γ-PGA producer strains facilitates their industrial use in terms of downstream processing for the purification of the polymer [11]. Although naturally occurring strains have been successfully adopted for high-level polymer production, the cost-effectiveness of the process is still a challenge, mainly due to the trade-off between productivity and the cost of fermentation medium substrates [12][13][14].…”

“…Despite impurities that may pose challenges in its cost-effective utilization, it has been considered a convenient carbon source for polymer production [14,22]. In fact, purified glycerol, a known substrate for the growth of microbes such as B. subtilis and B. amyloliquefaciens, has been previously adopted in γ-PGA fermentation processes as an additive to glucose-based media to enhance polymer production [23,24] or as the main carbon source [12,25,26]; however, glycerol utilization is less efficient than that of glucose and biopolymer production needs to be improved.…”