γ‐Polyglutamic Acid Produced by Bacillus Subtilis (Natto): Structural Characteristics, Chemical Properties and Biological Functionalities

Abstract

γ‐(D,L)‐Polyglutamic acid [γ‐(D,L)‐PGA, or γ‐PGA] produced by Bacillus subtilis (natto) both on laboratory and pilot scale fermenter systems has been characterized. γ‐PGA in its free acid form (H+) is insoluble in water. The salt forms of K+, Na+, NH4+, Ca2+, and Mg2+ of γ‐polyglutamates are fully soluble in water. The structural characteristics of the salts of γ‐Polyglutamates (Na+, K+, NH4+, Ca2+, and Mg2+) were determined with 1H‐ and 13C‐NMR spectroscopy and FT‐IR spectroscopy. The thermal properties were determined with thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The typical physical and chemical properties including pH‐titration curve, concentration‐dependent viscosity temperature‐dependent viscosity, and heavy metal binding properties with Pb2+, Cd2+, and Cu2+ were also determined. The biological functionalities were partially characterized with in vivo feeding studies with broilers and egg‐layers, and activation of GTF (Glucose tolerance factor) activity with rat 3T3‐L1 cell culture studies. γ‐(D,L)‐Polyglutamic acid [γ‐(D,L)‐PGA] appears to have five different conformations depending on the environmental conditions. They are the α‐helix, β‐sheet, helix‐to‐random coil transition, random‐coil and enveloped aggregate. The conformational states, hydrogen bonding and polyanionic nature make γ‐PGA a versatile multi‐functional biopolymer possessing many useful biological functionalities.

Synthesis of Gelatin-γ-Polyglutamic Acid-Based Hydrogel for the In Vitro Controlled Release of Epigallocatechin Gallate (EGCG) from Camellia sinensis

“…The thermal properties of hydrogel are affected by water content, and since hydrogel is hygroscopic, preparation upon DSC analysis can alter its water content and change its thermal property in comparison to what is usually reported in the literature [35]. In the gelatin thermogram, a broad peak at 82 °C and a relatively small peak at 225 °C correspond to its glass transition temperature, Tg, and Tm, respectively [36].…”

Poly-γ-glutamic acid: production, properties and applications

“…The method produces IR spectra of c-PGA with peaks corresponding to specific bonds in the compound. According to Ho et al (2006), the IR spectra of c-PGA (free acid form) and c-polyglutamate salts in KBr pellets indicate distinctive strong amide absorption at 1620-1655 cm 21 , a weaker carbonyl C5O absorption at~1394-1454 cm 21 , a strong hydroxyl OH absorption at 3400-3450 cm 21 and a characteristic strong C-N groups absorption in the range from 1085 to 1165 cm 21 . The absorption peaks between 2900 and 2800 cm 21 are characteristic of aliphatic N-H stretching, whilst those around 1600-1660 and 1390-1450 cm 21 exhibit characteristics of amide groups and C5O groups, respectively.…”

In vitro removal of toxic heavy metals by poly(γ-glutamic acid)-coated superparamagnetic nanoparticles

“…The PGA is an edible and biodegradable natural biopolymer composed of numerous repetitive glutamic acid units connected by γ-peptide linkage, leaving the α-carboxyl groups free for conjugation to a variety of compounds (−[−NH−CH(COOH)−(CH 2 ) 2 −CO−] n −). 20,21 It is extracellularly synthesized by Bacillus species, by either the de nova method through solid state fermentation, or by the salvage bioconversion method in submerged fermentation. 20,21 Because of its unique γ-amide linkage, multifunctionality, and flexibility to be synthesized in different ionic forms (H, Ca, Na, Mg, etc) with varying molecular weights (10,000 to 2 million Daltons), PGA finds wide application in many different fields such as food, medicine, agriculture, hygiene, cosmetics, and the environment.…”

“…20,21 It is extracellularly synthesized by Bacillus species, by either the de nova method through solid state fermentation, or by the salvage bioconversion method in submerged fermentation. 20,21 Because of its unique γ-amide linkage, multifunctionality, and flexibility to be synthesized in different ionic forms (H, Ca, Na, Mg, etc) with varying molecular weights (10,000 to 2 million Daltons), PGA finds wide application in many different fields such as food, medicine, agriculture, hygiene, cosmetics, and the environment. 20,21 Our previous studies have demonstrated the efficiency of PGA as an adsorbent for the removal of heavy metals, organic dyes, and heterocyclic amines; [22][23][24][25] however, the application of PGA-functionalized SPIONs for removal of heavy metals remains unknown.…”

“…20,21 Because of its unique γ-amide linkage, multifunctionality, and flexibility to be synthesized in different ionic forms (H, Ca, Na, Mg, etc) with varying molecular weights (10,000 to 2 million Daltons), PGA finds wide application in many different fields such as food, medicine, agriculture, hygiene, cosmetics, and the environment. 20,21 Our previous studies have demonstrated the efficiency of PGA as an adsorbent for the removal of heavy metals, organic dyes, and heterocyclic amines; [22][23][24][25] however, the application of PGA-functionalized SPIONs for removal of heavy metals remains unknown. The objectives of this study were to synthesize, characterize, and evaluate the efficiency of PGASPIONs in removing heavy metals like lead and cadmium from both a metal solution and simulated gastrointestinal fluid.…”