Lignin is one largely untapped natural resource that can be exploited as a raw material for the bioproduction of value-added chemicals. Meanwhile, the current petroleum-based process for the production of adipic acid faces sustainability challenges. Here we report the successful engineering of Pseudomonas putida KT2440 strain for the direct biosynthesis of adipic acid from lignin-derived aromatics. The devised bio-adipic acid route features an artificial biosynthetic pathway that is connected to the endogenous aromatics degradation pathway of the host at the branching point, 3-ketoadipoyl-CoA, by taking advantage of the unique carbon skeleton of this key intermediate. Studies of the metabolism of 3-ketoadipoyl-CoA led to the discovery of crosstalk between two aromatics degradation pathways in KT2440. This knowledge facilitated the formulation and implementation of metabolic engineering strategies to optimize the carbon flux into the biosynthesis of adipic acid. By optimizing pathway expression and cultivation conditions, an engineered strain AA-1 produced adipic acid at 0.76 g/L and 18.4% molar yield under shake-flask conditions and 2.5 g/L and 17.4% molar yield under fermenter-controlled conditions from common aromatics that can be derived from lignin. This represents the first example of the direct adipic acid production from model compounds of lignin depolymerization.

木质素是一种尚未开发的自然资源，可以用作生物增值化学品生产的原料。同时，当前以石油为基础的己二酸生产工艺面临可持续性挑战。在这里，我们报告恶臭假单胞菌的成功工程KT2440菌株，用于从木质素衍生的芳族化合物中直接生物合成己二酸。通过利用该关键中间体独特的碳骨架，设计的生物己二酸途径具有人工生物合成途径，该途径在分支点3-酮己二酰基-CoA上与宿主的内源性芳族化合物降解途径相连。对3-酮二酰基-CoA代谢的研究导致发现了KT2440中两个芳烃降解途径之间的串扰。该知识促进了代谢工程策略的制定和实施，以优化进入己二酸生物合成的碳通量。通过优化途径表达和培养条件，工程菌株AA-1在摇瓶条件下以0.76 g / L和18.4％的摩尔产率产生了己二酸，而在2.5 g / L和17下产生了己二酸。在发酵罐控制的条件下，由木质素衍生的普通芳烃的摩尔产率为4％。这代表了从木质素解聚的模型化合物直接生产己二酸的第一个例子。