Poly(γ-glutamic acid) (PGA) is a biopolymer produced by Bacillus spp. via the γ-amide linkages of d- and/or l-glutamate. Although high-molecular-weight (HMW) PGA possesses many attractive properties, such as flocculating, wound healing, and immune-stimulating effects, no studies have reported factors useful for increasing the molecular weight of PGA during microbial production. PgsB, PgsC, and PgsA are the minimum protein sets required for PGA production in B. subtilis, and PgsE improves PGA productivity. Analysis by size-exclusion chromatography combined with multiangle laser light scattering revealed that the molecular weight of PGA was Mw = 2,900,000 g mol−1 and predominantly Mw = 47,000 g mol−1 in preparations derived from B. subtilis cells with and without pgsE, respectively. PgsE may be required to increase the molecular weight of PGA.
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This study was supported in part by the Osaka City University (OCU) Strategic Research Grant 2014 for exploratory research. We are grateful to Kousuke Shinoda for performing the experiments involving E. coli at an early stage of the study; Shou Komaki, Akane Kurita, Ayaka Fujii, and Nanako Iwamoto for technical assistance; Mizuki Taniwa and Saya Yamano for performing the additional experiments against revision; and the Research Center for Bioscience and Technology, Tottori University for amino acid analysis.
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Fujita, KI., Tomiyama, T., Inoi, T. et al. Effect of pgsE expression on the molecular weight of poly(γ-glutamic acid) in fermentative production. Polym J 53, 409–414 (2021). https://doi.org/10.1038/s41428-020-00413-7