Efficient production of extracellular alkaline protease in Bacillus amyloliquefaciens by host strain construction
Weijie Chen, Lu Li, Changwen Ye, Ziyue Zhao, Kuo Huang, Dian Zou, Xuetuan Wei
Abstract
Bacillus amyloliquefaciens is an important industrial microorganism, which can be applied as a protein expression host. However, the extracellular protein expression ability of B. amyloliquefaciens is still low. Hence, it is necessary to develop a B. amyloliquefaciens host with a high extracellular protein expression capacity. In this study, B. amyloliquefaciens HZ-12 was the original strain, then seven important extracellular protease genes (epr, nprE, aprE-a, mpr, pbpF, vpr, ykct1), one important intracellular protease gene (aprX) and two redundant proteins genes (htrB, hag) were deleted in HZ-12, resulting in B. amyloliquefaciens BAX-10. In order to evaluate the extracellular protein expression ability of BAX-10, the alkaline protease gene aprE from Bacillus subtilis D7 was expressed in BAX-10. After fermentation, the alkaline protease activity of BAX-10/aprE reached 666.82 U/mL, which was 57% higher than that of the control strain HZ/aprE. Moreover, the deletion of the ten genes had no negative effect on the growth of B. amyloliquefaciens. In summary, B. amyloliquefaciens BAX-10 could be used as a potential platform host for expression of target extracellular proteins.