Hyperproduction of a Fungal Natural Product, Calcarisarbulide A, From a Synthetic Transcriptional Cascade

Effective hyperproduction of fungal natural products (NPs) is one of the challenges in their pharmaceutical development. Calcarisarbulide A (1) is a promising anti-liver-fibrosis NP from the endophyte Calcarisporium arbuscula. Here, based on a hybrid transcription factor used to awaken the cal gene cluster (GC) in C. arbuscula and genetic engineering to block the biotransformation of 1, a yield of 1.13 g/L was obtained. To produce 1 more safely and at higher yields, heterologous expression in Aspergillus was demonstrated. However, the yields of 1 were much lower in A. nidulans and A. terreus, likely due to the endogenous metabolism of 1. In A. oryzae, where 1 is not metabolized, a synthetic transcriptional cascade was developed from the A. nidulans afo GC to produce 1.31 g/L of 1. Further aspartic acid feeding led to a 2.62 g/L yield. Our work provides a new synthetic biology strategy for the efficient production of bioactive fungal NPs.