Fengqing Wang1 
,
Jinzhong Liang2,
Wei Wang2,
Dawei Fu2,
Wei Xiao2
For correspondence:- Fengqing Wang Email: wangfengqing_100@126.com
Received: 22 February 2017 Accepted: 24 May 2017 Published: 29 June 2017
Citation: Wang F, Liang J, Wang W, Fu D, Xiao W. A new and efficient method for purification of poly-^7;-glutamic acid from high-viscosity fermentation broth. Trop J Pharm Res 2017; 16(6):1267-1275 doi: 10.4314/tjpr.v16i6.9
© 2017 The authors.
This is an Open Access article that uses a funding model which does not charge readers or their institutions for access and distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0) and the Budapest Open Access Initiative (http://www.budapestopenaccessinitiative.org/read), which permit unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited..
Purpose: To devise an efficient strategy for the separation and recovery of high-quality γ-PGA by investigation of the physical properties, pigment properties and microfiltration mode of high-viscosity fermentation broth.
Methods: The bacterial strain, Bacillus subtilis 115, was used in this study. The viscosity of the fermentation broth was determined by digital viscometer with spindle SP-2 at 25 oC. The concentrations of glucose and L-glutamate were analyzed with a biosensor equipped with both glucose oxidase and L-glutamate oxidase electrodes. The pigment in the fermentation liquid was scanned with a UV spectrophotometer at wavelength range of 200 - 500 nm and was removed using activated carbon. Measurement of IR spectrum was performed using an IR spectrophotometer with KBr pellet. .
Results: The results showed that the γ-PGA yield was 35 g/L. The viscosity of the fermentation broth was 1600 mPa.s at the end of the batch fermentation. After 3-fold dilution, the viscosity was reduced to one-fortieth of the original value at 65 °C for 30 min., which allowed effective removal of Bacillus subtilis 115 from the broth. Maximum UV absorption of the pigment was occurred at 260 nm. The pigment was removed by shaking with 0.6 % activated carbon powder at 50 rpm for 20 min, resulting in 88 % de-colorization. Concentration with hollow-fiber membrane (MWCO 500,000) resulted in complete removal of residual glucose and glutamic acid from the aqueous solution of γ-PGA. The molecular weight of the γ-PGA was 1095 kDa, and its UV scanning spectrum showed an absorption peak at 216 nm. The decomposition temperature (Td) of the γ-PGA was 312.92 oC. Its IR spectrum was consistent with the presence of carboxyl, hydroxyl, carbonyl and amide groups.
Conclusion: An efficient method for the extraction and purification of high-quality γ-PGA from high-viscosity fermentation broth.
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