Recruiting a new strategy to improve levan production in Bacillus amyloliquefaciens.
Microbial levan is an important biopolymer with considerable potential in food and medical applications. Bacillus amyloliquefaciens NK-ΔLP strain can produce high-purity, low-molecular-weight levan, but production is relatively low. To enhance the production of levan, six extracellular protease genes (bpr, epr, mpr, vpr, nprE and aprE), together with the tasA gene (encoding the major biofilm matrix protein TasA) and the pgsBCA cluster (responsible for poly-γ-glutamic acid (γ-PGA) synthesis), were intentionally knocked out in the Bacillus amyloliquefaciens NK-1 strain. The highest levan production (31.1 g/L) was obtained from the NK-Q-7 strain (ΔtasA, Δbpr, Δepr, Δmpr, Δvpr, ΔnprE, ΔaprE and ΔpgsBCA), which was 103% higher than that of the NK-ΔLP strain (ΔpgsBCA) (15.3 g/L). Furthermore, the NK-Q-7 strain also showed a 94.1% increase in α-amylase production compared with NK-ΔLP strain, suggesting a positive effect of extracellular protease genes deficient on the production of endogenously secreted proteins. This is the first report of the improvement of levan production in microbes deficient in extracellular proteases and TasA, and the NK-Q-7 strain exhibits outstanding characteristics for extracellular protein production or extracellular protein related product synthesis.
Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Nankai University, Tianjin 300071, China.|Department of Microbiology, College of Life Science, Nankai University, Tianjin 300071 China.
Jun
J
Feng
Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Nankai University, Tianjin 300071, China.
Yanyan
Y
Gu
Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Nankai University, Tianjin 300071, China.
Yufen
Y
Quan
Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Nankai University, Tianjin 300071, China.
Wei
W
Zhang
Department of Chemical and Biological Engineering, Iowa State University, Ames, Iowa 50011, United States.
Mingfeng
M
Cao
Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Nankai University, Tianjin 300071, China.
Weixia
W
Gao
Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Nankai University, Tianjin 300071, China.
Cunjiang
C
Song
Department of Microbiology, College of Life Science, Nankai University, Tianjin 300071 China.
Chao
C
Yang
State Key Laboratory of Medicinal Chemical Biology, Nankai University, 94 Weijin Road, Tianjin 300071, China.
Shufang
S
Wang
D001407:Bacillus / Q000235:genetics* / Q000378:metabolism*; D018441:Biofilms; D005110:Extracellular Space / Q000378:metabolism; D005285:Fermentation; D005630:Fructans / Q000096:biosynthesis*; D017353:Gene Deletion; D005798:Genes, Bacterial; D060847:Metabolic Engineering / Q000379:methods; D010447:Peptide Hydrolases / Q000378:metabolism; D011099:Polyglutamic Acid / Q000031:analogs & derivatives / Q000096:biosynthesis; D000516:alpha-Amylases / Q000096:biosynthesis
D005630:Fructans; C511775:poly(gamma-glutamic acid); D011099:Polyglutamic Acid; C072599:levan; D000516:alpha-Amylases; D010447:Peptide Hydrolases