Improved production of poly-γ-glutamic acid with low molecular weight under high ferric ion concentration stress in Bacillus licheniformis ATCC 9945a

• Published in: Process biochemistry (1991) Vol. 56; pp. 30 - 36
• Main Authors: Feng, Jin, Shi, Qingshan, Zhou, Gang, Wang, Lingling, Chen, Aimei, Xie, Xiaobao, Huang, Xiaomo, Hu, Wenfeng
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.05.2017
• Subjects: Ferric ions; Molecular weight; Poly-γ-glutamic acid; Transcription analysis; Yield; Yield; Ferric ions; Poly-γ-glutamic acid; Molecular weight; Transcription analysis
• ISSN: 1359-5113; 1873-3298
• DOI: 10.1016/j.procbio.2017.02.017

[Display omitted] •High Fe3+ concentrations lead to high γ-PGA production and low molecular weight.•High Fe3+ concentrations increase carbon source utilization for γ-PGA production.•The genes ggt and cwlO lead to low molecular weight under high Fe3+ concentrations. This study found that high ferric ion (Fe3+) concentrations lead to high poly-γ-glutamic acid (γ-PGA) production and low-molecular-weight γ-PGA. In cultures containing 7.4mmol/L FeCl3, the average molecular weight of γ-PGA reached 3.18±0.3×105Da, which is a 76% decrease from that in the culture without FeCl3 (1.31±0.14×106Da). Cultures containing increasing concentrations of FeCl3 (0–7.4mmol/L) showed a corresponding increase in γ-PGA yield from 26.57±1.64 to 34.93±1.05g/L. Transcription level analysis indicated that high FeCl3 concentrations could enhance the expression of γ-PGA synthetase genes (pgsA, pgsB, and pgsC), which may contribute to the improved production of γ-PGA. In addition, γ-PGA degradation genes ggt (encoding γ-glutamyltransferase) and cwlO were found to contribute to a lower γ-PGA molecular weight in cultures containing 7.4mmol/L FeCl3. The result of γ-glutamyltransferase activity was in agreement with the results of the transcription level analysis. Overall, this study would provide a novel method for the regulation of synthesis of γ-PGA with low molecular weight.