Advances in microbial biosynthesis of indirubin

Indirubin (IND), a bisindole alkaloid with remarkable pharmacological activities, has attracted significant attention in the pharmaceutical field due to its antileukemic, anti-inflammatory, and immunomodulatory properties. Currently, indirubin primarily relies on plant extraction and chemical synthesis, which are hindered by complex processes, low yields, and poor environmental compatibility. These challenges pose serious obstacles to clinical supply and sustainable industrial development. In recent years, microbial synthesis technology, which is based on synthetic biology and metabolic engineering, has provided a novel approach for the efficient production of indirubin. This method offers several advantages, including high efficiency, environmental sustainability, and eco-friendliness. Hence, this manuscript systematically summarizes the biosynthesis mechanisms of indirubin, the catalytic characteristics of key enzymes, the construction strategies of engineered bacteria, and the progress in fermentation condition. To address challenges such as the difficult separation of indirubin isomers, by-product inhibition, and industrialization bottlenecks, potential solutions are proposed, aiming to promote the green biomanufacturing of indirubin.