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Journal of Biomedicine and Biotechnology
Volume 2011, Article ID 672369, 9 pages
Research Article

Manipulation of pH Shift to Enhance the Growth and Antibiotic Activity of Xenorhabdus nematophila

1Research and Development Center of Biorational Pesticides, College of Plant Protection, Northwest A & F University, Yangling, Shaanxi 712100, China
2School of Plant Biology, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia

Received 2 September 2010; Accepted 19 March 2011

Academic Editor: Ali Khraibi

Copyright © 2011 Yonghong Wang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


To evaluate the effects of pH control strategy on cell growth and the production of antibiotic (cyclo(2-Me-BABA-Gly)) by Xenorhabdus nematophila and enhance the antibiotic activity. The effects of uncontrolled- (different initial pH) and controlled-pH (different constant pH and pH-shift) operations on cell growth and antibiotic activity of X. nematophila YL00I were examined. Experiments showed that the optimal initial pH for cell growth and antibiotic production of X. nematophila YL001 occurred at 7.0. Under different constant pH, a pH level of 7.5 was found to be optimal for biomass and antibiotic activity at 23.71 g/L and 100.0 U/mL, respectively. Based on the kinetic information relating to the different constant pH effects on the fermentation of X. nematophila YL001, a two-stage pH control strategy in which pH 6.5 was maintained for the first 24 h, and then switched to 7.5 after 24 h, was established to improve biomass production and antibiotic activity. By applying this pH-shift strategy, the maximal antibiotic activity and productivity were significantly improved and reaching 185.0 U/mL and 4.41 U/mL/h, respectively, compared to values obtained from constant pH operation (100.0 U/mL and 1.39 U/mL/h).