γ-Polyglutamic acid (γ-PGA) is a biosynthetic outcome of glutamic acid polymerization by microbes. In the current study, we have isolated Bacillus methylotrophicus on solid differential media containing methylene blue. This is the first report mentioning the use of methylene blue to distinguish the monomeric and polymeric form of glutamic acid in the liquid medium using UV-Vis spectrophotometer. Our method can simplify the analytical process of γ-PGA confirmation using the aforementioned studies. This screening protocol is sensitive to the detection of γ-PGA quantities as low as 3 μg/mL; thus, the potent producers can be effectively screened. Furthermore, we have carried out process optimization of the present strain for γ-PGA production wherein we could obtain 1.4-fold improvement in the yield with respect to utilization of carbon source and 2.6-fold increase with respect to nitrogen source under submerged fermentation at a shake flask level. We have shown an increase in γ-PGA titer from 1.5 to 36 g/L using mannitol, monosodium glutamate, peptone, and tween 20.

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Popularity of Polyglutamate (PGA) in industrial applications has motivated an extensive research in the area of bioprocess engineering for its production, strain improvement, advancements in analytical methods and applications. Some facets of PGA still remain a challenge and offer the researchers with time consuming methods to seek deeper insights into the behaviour of molecules. A few simple analytical approaches have been explained which can be used to address those challenges. This review focuses on understanding each step involved in manufacturing, analysis and applications of PGA. An attempt is made towards understanding the chemistry of PGA and its interaction with various other compounds. Occurrence of PGA in various conformational states under the influence of different environmental conditions is discussed. The properties of the biopolymer largely depend on its chain length which in turn arises due to diverse conditions in which it is biosynthesized by the microorganisms. Applications of PGA in various fields of food, agriculture, medical, cosmetics etc. are also dependent on the molecular weight and conformations of PGA under the given set of conditions. A few major applications of PGA which make this biopolymer an industrially influential molecule have been described.