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2027279 
Journal Article 
A Novel Method for the Selective Recovery and Purification of gamma-Polyglutamic Acid from Bacillus licheniformis Fermentation Broth 
Manocha, B; Margaritis, A 
2010 
Yes 
Biotechnology Progress
ISSN: 8756-7938
EISSN: 1520-6033 
26 
3 
734-742 
English 
20063385 
WOS:000279124800016 
Microbially produced gamma-polyglutamic acid (gamma-PGA) is a commercially important biopolymer with many applications in biopharmaceutical, food, cosmetic and waste-water treatment industries. Owing to its increasing demand in various industries, production of gamma-PGA is well documented in the literature, however very few methods have been reported for its recovery. In this paper, we report a novel method for the selective recovery and purification of gamma-PGA from cell-free fermentation broth of Bacillus licheniformis. The cell-free fermentation broth was treated with divalent copper ions, resulting in the precipitation of gamma-PGA, which was collected as a pellet by centrifugation. The pellet was resolubilized and dialyzed against de-ionized water to obtain the purified gamma-PGA biopolymer. The efficiency and selectivity of gamma-PGA recovery was compared with ethanol precipitation method. We found that 85% of the original gamma-PGA content in the broth was recovered by copper sulfate-induced precipitation, compared to 82% recovery by ethanol precipitation method. Since ethanol is a commonly used solvent for protein precipitation, the purity of gamma-PGA precipitate was analyzed by measuring proteins that co-precipitated with gamma-PGA. Of the total proteins present in the broth, 48% proteins were found to be co-precipitated with gamma-PGA by ethanol precipitation, whereas in copper sulfate-induced precipitation, only 3% of proteins were detected in the final purified gamma-PGA, suggesting that copper sulfate-induced precipitation offers better selectivity than ethanol precipitation method. Total metal content analysis of the purified gamma-PGA revealed the undetectable amount of copper ions, whereas other metal ions detected were in low concentration range. The purified gamma-PGA was characterized using infrared spectroscopy. 
gamma-polyglutamic acid recovery; biopolymer purification; metal cation-induced precipitation; Bacillus licheniformis; fermentation broth; Cu2+gamma-PGA complex