Biotechnology Research Centre and Biomedicine Centre, School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, People's Republic of China.
BMC Biotechnol. 2013 Jun 1;13:47. doi: 10.1186/1472-6750-13-47.
L-ornithine is effective in the treatment of liver diseases and helps strengthen the heart. The commercial applications mean that efficient biotechnological production of L-ornithine has become increasingly necessary. Adaptive evolution strategies have been proven a feasible and efficient technique to achieve improved cellular properties without requiring metabolic or regulatory details of the strain. The evolved strains can be further optimised by metabolic engineering. Thus, metabolic evolution strategy was used for engineering Corynebacterium glutamicum to enhance L-ornithine production.
A C. glutamicum strain was engineered by using a combination of gene deletions and adaptive evolution with 70 passages of growth-based selection. The metabolically evolved C. glutamicum strain, named ΔAPE6937R42, produced 24.1 g/L of L-ornithine in a 5-L bioreactor. The mechanism used by C. glutamicum ΔAPE6937R42 to produce L-ornithine was investigated by analysing transcriptional levels of select genes and NADPH contents. The upregulation of the transcription levels of genes involved in the upstream pathway of glutamate biosynthesis and the elevated NADPH concentration caused by the upregulation of the transcriptional level of the ppnK gene promoted L-ornithine production in C. glutamicum ΔAPE6937R42.
The availability of NADPH plays an important role in L-ornithine production in C. glutamicum. Our results demonstrated that the combination of growth-coupled evolution with analysis of transcript abundances provides a strategy to engineer microbial strains for improving production of target compounds.
L-鸟氨酸在治疗肝脏疾病和增强心脏方面有效。商业应用意味着高效的生物技术生产 L-鸟氨酸变得越来越必要。适应性进化策略已被证明是一种可行且有效的技术，可以在不要求菌株的代谢或调节细节的情况下，改善细胞特性。进化后的菌株可以通过代谢工程进一步优化。因此，代谢进化策略被用于工程化谷氨酸棒杆菌以提高 L-鸟氨酸的产量。
通过基因缺失和基于生长的选择进行 70 代适应性进化，对谷氨酸棒杆菌进行了工程改造。该代谢进化的谷氨酸棒杆菌菌株命名为ΔAPE6937R42，在 5 升生物反应器中生产 24.1 g/L 的 L-鸟氨酸。通过分析选择基因的转录水平和 NADPH 含量，研究了谷氨酸棒杆菌ΔAPE6937R42生产 L-鸟氨酸的机制。谷氨酸生物合成上游途径相关基因转录水平的上调以及 ppnK 基因转录水平上调导致 NADPH 浓度的升高，促进了谷氨酸棒杆菌ΔAPE6937R42中 L-鸟氨酸的生产。
NADPH 的可用性在谷氨酸棒杆菌中 L-鸟氨酸的生产中起着重要作用。我们的结果表明，将生长偶联进化与转录丰度分析相结合，为工程化微生物菌株以提高目标化合物的生产提供了一种策略。
