苏氨酸是重要的饲料氨基酸,需求量持续增加,提高苏氨酸发酵产率和糖酸转化率,降低生产成本已成为一个重要课题。该实验以苏氨酸工程菌Escherichia coli THRD为出发菌,利用CRISPRi(clustered regularly interspaced short palindromic repeats interference)技术研究中心代谢9个基因转录水平的改变对苏氨酸合成的影响。发酵结果显示,干扰zwf、pfkA和gltA基因的转录水平提高了苏氨酸的合成效率,对应菌株苏氨酸产量分别为60.3、64.6和65.8 g/L,与出发菌(50.9 g/L)相比,分别提高了18.5%、26.9%和29.3%。糖酸转化率分别为40%、38%和39%,与出发菌(34%)相比,分别提高了17.7%、11.8%和14.7%。结果表明,通过CRISPRi干扰中心代谢基因的转录水平,可以调节合成代谢网络,使更多碳源流向苏氨酸,提高苏氨酸的合成效率。同时,该研究也为其他生物制品工程菌的构建提供了参考。
Threonine is an important feed amino acid with increasing demand. Improving threonine productivity and glucose conversion rate and reducing the production costs have become an important subject. In this study, Escherichia coli THRD, a threonine-producing strain, was used to study the effects of different transcription levels of nine genes involved in central metabolic pathway on threonine synthesis by using clustered regularly interspaced short palindromic repeats interference (CRISPRi). The results showed that the transcriptional interference of genes zwf, pfkA, and gltA improved the synthesis efficiency of threonine. The threonine titers of corresponding strains were 60.3, 64.6, and 65.8 g/L, respectively, which were increased by 18.5%, 26.9%, and 29.3%, respectively, compared with the original strain (50.9 g/L). The glucose conversion rates were 40%, 38%, and 39%, respectively, which were 17.7%, 11.8%, and 14.7% higher than that of the original strain (34%). The results showed that by modifying transcriptional levels of genes that involved in central metabolism by CRISPRi could regulate the cellular metabolic network and redirect more carbon flux to threonine, resulted improved synthesis efficiency of threonine. Overall, this study provides a reference for constructing other bioengineered bacteria.
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