Effect of <i>hemX</i> gene deletion on heme synthesis in <i>Bacillus amyloliquefaciens</i>.

Jiameng Liu; Yexue Liu; Chenxu Zhao; Wenhang Wang; Qinggang LI; Fuping LU; Yu LI

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Effect of hemX gene deletion on heme synthesis in Bacillus amyloliquefaciens.

Author: Jiameng LIU ¹ ; Yexue LIU ¹ ; Chenxu ZHAO ¹ ; Wenhang WANG ² ; Qinggang LI ¹ ; Fuping LU ¹ ; Yu LI ¹
Author Information

1. Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, College of Bioengineering, Tianjin University of Science & Technology, Tianjin 300457, China.
2. School of Food Science and Engineering, Tianjin University of Science & Technology, Tianjin 300457, China.
Publication Type:Journal Article
Keywords: 5-aminolevulinic acid; Bacillus amyloliquefaciens; hemX gene; heme
MeSH: Gene Deletion; Bacillus amyloliquefaciens/metabolism*; Aminolevulinic Acid/metabolism*; Heme/metabolism*; Fermentation
From: Chinese Journal of Biotechnology 2023;39(3):1119-1130
CountryChina
Language:Chinese
Abstract: Heme, which exists widely in living organisms, is a porphyrin compound with a variety of physiological functions. Bacillus amyloliquefaciens is an important industrial strain with the characteristics of easy cultivation and strong ability for expression and secretion of proteins. In order to screen the optimal starting strain for heme synthesis, the laboratory preserved strains were screened with and without addition of 5-aminolevulinic acid (ALA). There was no significant difference in the heme production of strains BA, BAΔ6 and BAΔ6ΔsigF. However, upon addition of ALA, the heme titer and specific heme production of strain BAΔ6ΔsigF were the highest, reaching 200.77 μmol/L and 615.70 μmol/(L·g DCW), respectively. Subsequently, the hemX gene (encoding the cytochrome assembly protein HemX) of strain BAΔ6ΔsigF was knocked out to explore its role in heme synthesis. It was found that the fermentation broth of the knockout strain turned red, while the growth was not significantly affected. The highest ALA concentration in flask fermentation reached 82.13 mg/L at 12 h, which was slightly higher than that of the control 75.11 mg/L. When ALA was not added, the heme titer and specific heme production were 1.99 times and 1.45 times that of the control, respectively. After adding ALA, the heme titer and specific heme production were 2.08 times and 1.72 times higher than that of the control, respectively. Real-time quantitative fluorescent PCR showed that the expressions of hemA, hemL, hemB, hemC, hemD, and hemQ genes at transcription level were up-regulated. We demonstrated that deletion of hemX gene can improve the production of heme, which may facilitate future development of heme-producing strain.