Optimization of fermentation conditions, purification and rheological properties of poly (γ-glutamic acid) produced by Bacillus subtilis 1006-3. Issue 3 (1st March 2022)

• Record Type: Journal Article
• Authors: Zhang, Ruoshi; Zhang, Shihao; Jiang, Guangyang; Gan, Longzhan; Xu, Zhe; Tian, Yongqiang
• Is Part Of: Preparative biochemistry & biotechnology. Volume 52:Issue 3(2022)
• Page Start: 302
• Page End: 310
• Publication Date: 2022-03-01
• Subjects: Poly-γ-glutamic acid -- purification -- response surface methodology -- rheological properties; Biochemistry -- Technique -- Periodicals; Biotechnology -- Technique -- Periodicals; Biochemistry -- methods -- Periodicals; Biotechnology -- methods -- Periodicals; 660.6
• DOI: 10.1080/10826068.2021.1941103
• Languages: English
• ISSNs: 1082-6068

Abstract

Abstract: This study aimed to investigate the optimal fermentation condition, purification and rheological properties of extracellular polymers produced by Bacillus subtilis 1006-3. An optimum temperature of 30.2 °C, inoculation amount of 6.1%, and pH of 8.2 were determined via Response Surface Methodology. The result of amino acid analysis and gel electrophoresis indicated that the obtained polymer contained only glutamic acid, with a wide molecular weight range. This polymer was finally determined as γ-PGA by infrared spectroscopy. The γ-PGA solution displayed a behavior of pseudoplastic non-Newtonian fluid with shear thinning properties, which can be described by the Ostward-de Waele power law model. The apparent viscosity of γ-PGA solution increased with the increase in its concentration from 1% to 10%. The deviation in pH from neutral value, and the addition of NaCl or MgCl2 can reduce the apparent viscosity of γ-PGA solution, and it was more sensitive to Mg 2+ than to Na + addition. At the concentration of 4, 6, and 8%, γ-PGA solution showed predominantly viscous response in the range of 0.1–100 rad/s angular frequency ( G ″> G′ ). These results indicated the potential application of the γ-PGA as a thickening agent.