Functions of poly-gamma-glutamic acid (γ-PGA) degradation genes in γ-PGA synthesis and cell morphology maintenance
- 1.1k Downloads
Poly-γ-glutamic acid (γ-PGA) is an important biopolymer with greatly potential in industrial and medical applications. In the present study, we constructed a metabolically engineered glutamate-independent Bacillus amyloliquefaciens LL3 strain with considerable γ-PGA production, which was carried out by single, double, and triple markerless deletions of three degradation genes pgdS, ggt, and cwlO. The highest γ-PGA production (7.12 g/L) was obtained from the pgdS and cwlO double-deletion strain NK-pc, which was 93 % higher than that of wild-type LL3 strain (3.69 g/L). The triple-gene-deletion strain NK-pgc showed a 28 % decrease in γ-PGA production, leading to a yield of 2.69 g/L. Furthermore, the cell morphologies of the mutant strains were also characterized. The cell length of cwlO deletion strains NK-c and NK-pc was shorter than that of the wild-type strain, while the ggt deletion strains NK-g, NK-pg, NK-gc, and NK-pgc showed longer cell lengths. This is the first report concerning the markerless deletion of γ-PGA degradation genes to improve γ-PGA production in a glutamate-independent strain and the first observation that γ-glutamyltranspeptidase (encoded by ggt) could be involved in the inhibition of cell elongation.
KeywordsPoly-γ-glutamic acid γ-PGA-degrading enzymes Glutamate-independent synthesis Gene markerless deletion
This work was supported by the National key Basic Research Program of China (“973”-Program) 2012CB725204, National High Technology Research and Development Program of China (“863”-Program) 2012AA021505, Natural Science Foundation of China Grant Nos. 31070039, 31170030, 31300032, and 51073081, Project of Tianjin, China (13JCZDJC27800, 13JCYBJC24900). The Project of Tianjin, China (13JCQNJC09700).
- Yeh CM, Wang JP, Lo SC, Chan WC, Lin MY (2010) Chromosomal integration of a synthetic expression control sequence achieves poly-γ-glutamate production in a Bacillus subtilis strain. Biotechnol Prog 24:1001–1007Google Scholar