5-Aminolevulinic acid (5-ALA) is a promising biostimulant, feed nutrient, and photodynamic drug with wide applications in modern agriculture and therapy. Considering the complexity and low yield of chemical synthesis methods, bioproduction of 5-ALA has drawn intensive attention recently. However, the present bioproduction processes use refined glucose as the main carbon source and the production level still needs further enhancement. To lay a solid technological foundation for large-scale commercialized bioproduction of 5-ALA, an industrial workhorse Corynebacterium glutamicum was metabolically engineered for high-level 5-ALA biosynthesis from cheap renewable bioresources. After evaluation of 5-ALA synthetases from different sources, the 5-ALA biosynthetic pathway and anaplerotic pathway were rebalanced by regulating intracellular activities of 5-ALA synthetase and phosphoenolpyruvate carboxylase. The engineered biocatalyst produced 5.5 g/L 5-ALA in shake flasks and 16.3 g/L in 5-L bioreactors with a one-step fermentation process from glucose. To lower the cost of feedstock, cheap raw materials were used to replace glucose. Enzymatically hydrolyzed cassava bagasse was proven to be a perfect alternative to refined sugars since the final 5-ALA titer further increased to 18.5 g/L. Use of corn starch hydrolysate resulted in a similar 5-ALA production level (16.0 g/L) with glucose, whereas use of beet molasses caused seriously inhibition. The results obtained here represent a new record of 5-ALA bioproduction. It is estimated that replacing glucose with cassava bagasse will reduce the carbon source cost by 90.1%. The high-level biosynthesis of 5-ALA from cheap bioresources will brighten the prospects for industrialization of this sustainable and environment-friendly process. The strategy for balancing metabolic flux developed in this study can also be used for improving the bioproduction of other value-added chemicals.

中文翻译：

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工程谷氨酸棒杆菌从可再生生物资源中高效生物生产 5-氨基乙酰丙酸，这是一种有前途的生物刺激剂和营养物

5-氨基乙酰丙酸（5-ALA）是一种很有前途的生物刺激剂、饲料营养剂和光动力药物，在现代农业和治疗中有着广泛的应用。考虑到化学合成方法的复杂性和低产率，5-ALA的生物生产最近引起了广泛关注。然而，目前的生物生产工艺以精制葡萄糖为主要碳源，生产水平仍需进一步提高。为了为 5-ALA 的大规模商业化生物生产奠定坚实的技术基础，对工业主力谷氨酸棒杆菌进行代谢工程改造，用于从廉价的可再生生物资源中进行高水平的 5-ALA 生物合成。在评估了不同来源的 5-ALA 合成酶后，通过调节 5-ALA 合成酶和磷酸烯醇丙酮酸羧化酶的细胞内活性来重新平衡 5-ALA 生物合成途径和回补途径。工程生物催化剂在摇瓶中产生 5.5 g/L 5-ALA，在 5-L 生物反应器中产生 16.3 g/L，采用葡萄糖的一步发酵过程。为了降低原料成本，使用廉价原料代替葡萄糖。酶水解木薯甘蔗渣被证明是精制糖的完美替代品，因为最终的 5-ALA 滴度进一步增加到 18.5 g/L。玉米淀粉水解物的使用导致与葡萄糖相似的 5-ALA 生产水平 (16.0 g/L)，而甜菜糖蜜的使用导致严重的抑制。这里获得的结果代表了 5-ALA 生物生产的新记录。估计用木薯甘蔗渣代替葡萄糖可降低90.1%的碳源成本。从廉价的生物资源中高水平地生物合成 5-ALA 将照亮这种可持续和环境友好工艺的工业化前景。本研究中开发的平衡代谢通量的策略也可用于改善其他增值化学品的生物生产。