High external pH enables more efficient secretion of alkaline α-amylase AmyK38 by Bacillus subtilis

Microbial Cell Factories

Research

Masatoshi Tohata¹  Katsuya Ozaki¹  Katsutoshi Ara¹  Yasushi Kageyama¹  Kenji Manabe²  Naotake Ogasawara³ 

[1] Biological Science Laboratories, Kao Corporation, 2606 Akabane Ichikai, 321-3497, Haga, Tochigi, Japan;Biological Science Laboratories, Kao Corporation, 2606 Akabane Ichikai, 321-3497, Haga, Tochigi, Japan;Graduate School of Information Science, Nara Institute of Science and Technology, 8916-5 Takayama, 630-0101, Ikoma, Nara, Japan;Graduate School of Information Science, Nara Institute of Science and Technology, 8916-5 Takayama, 630-0101, Ikoma, Nara, Japan;

关键词: α-Amylase;    AmyK38;    Bacillus subtilis;    CssRS;    Genome reduction;    HtrA;    HtrB;    MGB874;    Secretion stress response;   

DOI  :  10.1186/1475-2859-11-74

 received in 2012-03-01, accepted in 2012-06-08,  发布年份 2012

来源: Springer

【 摘 要 】

BackgroundBacillus subtilis genome-reduced strain MGB874 exhibits enhanced production of exogenous extracellular alkaline cellulase Egl-237 and subtilisin-like alkaline protease M-protease. Here, we investigated the suitability of strain MGB874 for the production of α-amylase, which was anticipated to provoke secretion stress responses involving the CssRS (Control secretion stress Regulator and Sensor) system.ResultsCompared to wild-type strain 168, the production of a novel alkaline α-amylase, AmyK38, was severely decreased in strain MGB874 and higher secretion stress responses were also induced. Genetic analyses revealed that these phenomena were attributable to the decreased pH of growth medium as a result of the lowered expression of rocG, encoding glutamate dehydrogenase, whose activity leads to NH3 production. Notably, in both the genome-reduced and wild-type strains, an up-shift of the external pH by the addition of an alkaline solution improved AmyK38 production, which was associated with alleviation of the secretion stress response. These results suggest that the optimal external pH for the secretion of AmyK38 is higher than the typical external pH of growth medium used to culture B. subtilis. Under controlled pH conditions, the highest production level (1.08 g l-1) of AmyK38 was obtained using strain MGB874.ConclusionsWe demonstrated for the first time that RocG is an important factor for secretory enzyme production in B. subtilis through its role in preventing acidification of the growth medium. As expected, a higher external pH enabled a more efficient secretion of the alkaline α-amylase AmyK38 in B. subtilis. Under controlled pH conditions, the reduced-genome strain MGB874 was demonstrated to be a beneficial host for the production of AmyK38.

【 授权许可】

Unknown   
© Manabe et al.; licensee BioMed Central Ltd. 2012. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.