Regulatory phosphorylation of poly-γ-glutamic acid with phosphate salts in the culture of Bacillus subtilis (natto)
Poly-γ-glutamic acid (PGA) was easily phosphorylated by direct addition of phosphorylating agents into the culture medium of Bacillus subtilis (natto). Tetrapolyphosphate salt was the most incorporated into PGA molecules of all used reagents. Phosphorylation occurred at the α-carboxyl side chains of PGA molecule. The amounts of bound phosphate to PGA were dependent on the amounts of added phosphorylating agent. In low molecular weight regions of less than 100 kDa, a cross-linked peak was observed in the phosphorylated PGAs, whereas their peaks at approximately 1000 kDa shifted to a higher molecular weight due to the bound phosphate. The PGA derivatives had a wide range in viscosity up to 15/1000 to 15 times when compared to the native PGA, depending on the degree of phosphorylation (DP) in the PGA derivatives. The PGA with low DP had a high viscosity due to the unfolding conformation whereas highly phosphorylated PGA had aggregation with low viscosity. Heat treatment at 80 °C after the addition of phosphate salt elicited a novel collagen-like helix structure. These observations show that phosphorylation is an effective way to diversify the physicochemical properties of PGA.
KeywordsBacillus subtilis Poly-γ-glutamic acid Phosphorylation Viscosity
We are thankful to Shaun O’Brien for comments on the manuscript.
- Cejas MA, Kinney WA, Chen C, Vinter JG, Almond JHR, Balss KM, Maryanoff CA, Schmidt U, Breslav M, Mahan A, Lacy E, Maryanoff BE (2008) Thrombogenic collagen-mimetic peptides: self-assembly of triple helix-based fibrils driven by hydrophobic interactions. Proc Natl Acad Sci USA 105:8513–8518CrossRefPubMedPubMedCentralGoogle Scholar
- Joseph MH, Davies P (1983) Electrochemical activity of o-phthalaldehyde -mercaptoethanol derivatives of amino acids: application to high-performance liquid chromatographic determination of amino acids in plasma and other biological materials. J Chromatogr B Biomed Sci Appl 277:125–136CrossRefGoogle Scholar
- Kongklom N, Chuensangjun C, Pechyen C, Sirisansaneeyakul S (2012) Production of poly-γ-glutamic acid by Bacillus licheniformis: synthesis and characterization. J Metal Mater Miner 22:7–11Google Scholar
- Moraes LP, Brito PN, Alergre RM (2013) The exsisting studies on biosynthesis of poly (γ-glutamic acid) by fermentation. Food Pub Health 3:28–36Google Scholar