Isolation of Halotolerant Bacillus licheniformis WX-02 and Regulatory Effects of Sodium Chloride on Yield and Molecular Sizes of Poly-γ-Glutamic Acid

Abstract

A poly-gamma-glutamic acid (gamma-PGA) productive strain, halotolerant bacterium WX-02 was isolated from the saline soil of China (Yingcheng). By physiological, biochemical, and 16S rDNA sequence analysis methods, the strain was identified as Bacillus licheniformis. The effect of NaCl concentration on gamma-PGA production by WX-02 was investigated in modified E (ME) medium. It was found that the gamma-PGA production was salt-inducible, and the highest volumetric yield of gamma-PGA (13.86 g/l) was attained with 8% of NaCl. It was also observed that the molecular size of gamma-PGA decreased when the NaCl concentration increased. This was the first report of isolation and identification of a gamma-PGA productive strain, halotolerant B. licheniformis. This study provided a simple strategy for controlling the yield and molecular size of gamma-PGA by WX-02.

Expression of glr gene encoding glutamate racemase in Bacillus licheniformis WX-02 and its regulatory effects on synthesis of poly-γ-glutamic acid

“…Escherichia coli DH5a was used for plasmid construction and B. licheniformis WX-02 (Wei et al 2009) was transformed for glutamate racemase expression. The plasmid of pHY300PLK is a shuttle vector, containing tetracycline resistance gene and ampicillin resistance gene.…”

“…The biomass (Dry cell weight, DCW) was determined by the method of Wei et al (2009). Residual of glucose and L-glutamic acid were measured using an SBA-40C biosensor (Institute of Biology, Shandong Province Academy of Sciences, P. R. China).…”

“…Residual of glucose and L-glutamic acid were measured using an SBA-40C biosensor (Institute of Biology, Shandong Province Academy of Sciences, P. R. China). The recovery and purification of c-PGA was carried out by the method reported by Wei et al (2009). c-PGA was analyzed by HPLC according to the method of Wei et al (2009).…”

“…It has been applied widely in the fields of cosmetics, food, agriculture, medicinal industries and many others (Sung et al 2000;Richard and Margaritis 2003;Wei et al 2009). However, c-PGA with different stereochemical composition has different applications; for example, c-PGA with a high content of L-glutamate is used for cosmetics due to its skin compatibility; in other fields, c-PGA with high content of D-glutamate is used because it degrades more slowly.…”

Genome Sequence of Bacillus licheniformis WX-02

“…It has been noted that this strain can produce larger amounts of ␥-PGA under stress conditions than under normal ones; the stresses refer to high salt, high temperature, caustic alkali, ultrasonic shock, and so on. The yield of ␥-PGA can be raised 5.28 times against that of the control group when the salt concentration reaches 8% (13). In order to explore the mechanism of high production of ␥-PGA under adverse circumstances, the genome of B. licheniformis WX-02 was sequenced and compared with that of the type strain ATCC 14580 (10,12).…”