System reconstruction of <i>Bacillus licheniformis</i> for efficient expression of alkaline protease.
The engineered Bacillus licheniformis strain demonstrated a significant increase in alkaline protease production, achieving 34,343 U/mL activity, which may enhance industrial enzyme applications.
Where it sits
this study against the rest of the matrixyl corpusSummary and findings
This study focused on enhancing the expression of alkaline protease (AprE) in Bacillus licheniformis through genetic optimization. The final engineered strain achieved an enzyme activity of 34,343 U/mL, with a peak of 107,100 U/mL in a bioreactor. The research highlights the potential for improved enzyme production through systematic genetic modifications.
Abstract
Industrial enzymes are widely used in diverse applications, but low productivity limits their further widespread utilization. This research aimed to develop high-performance alkaline protease (AprE) expression strains of <i>Bacillus licheniformis</i> through element optimization and modular engineering. Firstly, the <i>aprE</i> gene expression cassette was systematically optimized through element engineering. To minimize host background interference, five large gene fragments were deleted from the genome of <i>B. licheniformis</i> DW2. This expression cassette and genome-reduced strain resulted in 5.77-, 4.84- and 1.31-fold increases in the activities of alkaline protease, nattokinase and chitinase, respectively. Crucially, metabolomics analysis then served as the pivotal discovery tool, revealing that high expression of AprE was constrained by insufficient precursor amino acids and excessive metabolic overflow. Subsequently, the amino acid biosynthesis, energy metabolism, overflow metabolism, and cell membrane/wall modules of the strain were successively modified. The final AprE expression host DM6E10 achieved a remarkable enzyme activity of 34,343 U/mL, with a maximum activity of 107,100 U/mL in a 5-L bioreactor. This study built an efficient cell factory for AprE production and provided insights for the optimization of other protein expression hosts.
Background
The study addresses the challenge of low productivity in industrial enzyme applications, specifically focusing on alkaline protease from Bacillus licheniformis. Prior research indicated that optimizing gene expression could enhance enzyme yields, but specific strategies for overcoming metabolic limitations were not well defined. This study is significant as it explores genetic modifications and metabolic engineering to improve enzyme production efficiency.
Methods
The study involved systematic optimization of the aprE gene expression cassette through element engineering. Five large gene fragments were deleted from the Bacillus licheniformis DW2 genome to reduce host background interference. The primary outcome was the activity of alkaline protease, measured in U/mL, with secondary outcomes including the activities of nattokinase and chitinase.
Results
The primary endpoint showed a final alkaline protease activity of 34,343 U/mL in the engineered strain DM6E10. Additionally, the study reported a maximum activity of 107,100 U/mL in a 5-L bioreactor. The increases in enzyme activities for nattokinase and chitinase were 4.84-fold and 1.31-fold, respectively.
Interpretation
The findings demonstrate a significant enhancement in alkaline protease production compared to previous strains, but the clinical relevance of these results in practical applications remains unclear. While the increases in enzyme activities are statistically significant, the practical implications for industrial enzyme production require further investigation. Limitations include potential confounding factors related to the specific genetic modifications and the absence of long-term performance data.
Key findings
- 5.77-fold increase in alkaline protease activity compared to previous strains.
- 4.84-fold increase in nattokinase activity.
- 1.31-fold increase in chitinase activity.
- Final enzyme activity of 34,343 U/mL in a 5-L bioreactor.
- Maximum enzyme activity reached 107,100 U/mL.
Limitations
- Not reported in abstract.
- Specific genetic modifications may introduce confounding factors.
- No long-term performance data provided.
- Single-species study limits generalizability.
- Potential for unreported metabolic constraints.