title: Construction of a Bacillus amyloliquefaciens strain for high purity levan production.
abstract: Bacillus amyloliquefaciens NK-1 has the potential to produce levan and poly-gamma-glutamic acid (γ-PGA) simultaneously. However, it is not possible to purify each single product from the same strain because the extraction process is identical. We deleted the pgs cluster (for γ-PGA synthesis) from the NK-1 strain and constructed a γ-PGA-deficient NK-ΔLP strain. Nuclear magnetic results showed that the NK-ΔLP strain could produce high purity levan product. However, its levan titer was only 1.96 g L(-1) in the basal medium. Single-factor experimental and response surface methodology was used to optimize the culture condition, leading to levan titer of 13.9 and 22.6 g L(-1) in flask culture and in a 5-L bioreactor, respectively. The levan purity can reach to 92.7% after 48 h cultivation. Furthermore, the relationship between levanase (LevB) and levan molecular weight was studied. The results showed that LevB resulted in the production of low molecular weight levan and its expression level determined the ratio of high and low molecular weight levan. We also deleted the sac cluster (for levan synthesis) from the NK-1 strain and constructed a levan-deficient NK-L strain. The NK-L strain exhibited increased purity of γ-PGA product from 79.5 to 91.2%.
authors.affiliation: Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin 300071, China State Key Laboratory of Medicinal Chemical Biology, Nankai University, 94 Weijin Road, Tianjin 300071, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Feng
authors.affiliation: Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin 300071, China.
authors.forename: Yanyan
authors.initials: Y
authors.lastname: Gu
authors.affiliation: Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin 300071, China.
authors.forename: Lifang
authors.initials: L
authors.lastname: Han
authors.affiliation: Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin 300071, China.
authors.forename: Kexin
authors.initials: K
authors.lastname: Bi
authors.affiliation: Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin 300071, China.
authors.forename: Yufeng
authors.initials: Y
authors.lastname: Quan
authors.affiliation: Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin 300071, China.
authors.forename: Chao
authors.initials: C
authors.lastname: Yang
authors.affiliation: Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin 300071, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Department of Chemical and Biological Engineering, Iowa State University, Ames, IA 50011, USA.
authors.forename: Mingfeng
authors.initials: M
authors.lastname: Cao
authors.affiliation: State Key Laboratory of Medicinal Chemical Biology, Nankai University, 94 Weijin Road, Tianjin 300071, China.
authors.forename: Shufang
authors.initials: S
authors.lastname: Wang
authors.affiliation: Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin 300071, China.
authors.forename: Weixia
authors.initials: W
authors.lastname: Gao
authors.affiliation: Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin 300071, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Sun
authors.affiliation: Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin 300071, China songcj@nankai.edu.cn.
authors.forename: Cunjiang
authors.initials: C
authors.lastname: Song
mesh_terms: D001407:Bacillus / Q000235:genetics* / Q000378:metabolism*; D019149:Bioreactors; D003470:Culture Media; D005630:Fructans / Q000096:biosynthesis* / Q000302:isolation & purification; D055786:Gene Knockout Techniques; D006026:Glycoside Hydrolases / Q000235:genetics; D008970:Molecular Weight; D011099:Polyglutamic Acid / Q000031:analogs & derivatives / Q000096:biosynthesis / Q000302:isolation & purification
chemical_list: D003470:Culture Media; D005630:Fructans; C511775:poly(gamma-glutamic acid); D011099:Polyglutamic Acid; C072599:levan; D006026:Glycoside Hydrolases; C021512:levanase
keywords: levan; levanase; poly-γ-glutamic acid; response surface methodology