African Journal of
Microbiology Research

  • Abbreviation: Afr. J. Microbiol. Res.
  • Language: English
  • ISSN: 1996-0808
  • DOI: 10.5897/AJMR
  • Start Year: 2007
  • Published Articles: 5211

Full Length Research Paper

Optimization of fermentative production of poly-(γ-glutamic acid) by a newly isolated Bacillus subtilis BABRC-11

Tianlei Qiu1, Xiang Yu1,2, Meilin Han1, Xuming Wang1* and Qunhui Wang2
1Beijing Agro-Biotechnology Research Center, Beijing Academy of Agriculture and Forestry Sciences, Banjing, Haidian District, Beijing 100097, People’s Republic of China. 2Department of Environmental Engineering, University of Science and Technology Beijing, Xueyuan Road, Haidian District, Beijing 10083, People’s Republic of China.
Email: [email protected]

  •  Accepted: 28 September 2012
  •  Published: 06 November 2012


A newly isolated poly-(γ-glutamic acid) (γ-PGA)-producing strain BABRC-11 was identified as Bacillus subtilis based on its morphological and physiological characteristics as well as 16S rDNA sequence. The fermentation medium for the production of γ-PGA by B. subtilisBABRC-11 was optimized statistically. The parameters significantly affecting γ-PGA production were found to be sodium glutamate, calcium chloride (CaCl2) and zinc chloride (ZnCl2) by Plackett–Burman design, but ZnCl2 was a negatively significant factor. A further advanced statistical approach, central composite design, found the optimum levels of the screened variables as follows: sodium glutamate 18.74 g/L; CaCl2 0.17 g/L. After 48-h fermentation, 13.67 g/L of γ-PGA was produced under the optimum condition with only 0.1% differences from the statistically predicted value (13.69 g/L).


Key words: Poly (γ-glutamic acid), Bacillus subtilis, Plackett–Burman design, central composite design.

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