Bacterial Fermentation Platform for Producing Artificial Aromatic Amines and Its Utilization for High-Performance Aromatic Polyamide Synthesis

Aromatic amines containing an aminobenzene or an aniline moiety comprise versatile natural and artificial compounds including bioactive molecules and resources for advanced materials. However, a bio-production platform has not been implemented. Here we constructed a bacterial platform for para-substituted aminobenzene relatives of aromatic amines. We found 4-aminophenylalanine synthesis gene cluster in a Pseudomonad bacterium. Recombinant Escherichia coli expressing the corresponding genes produced 4-aminophenylalanine from glucose. Optimization of the metabolic pathway in the recombinant E. coli cells converted biomass glucose to 4-aminophenylalanine with high efficiency (4.4 g L^-1 in fed-batch cultivation). We designed and produced artificial pathways that mimicked the fungal Ehrlich pathway in E. coli and converted 4-aminophenylalanine into 4-aminophenylethanol and 4-aminophenylacetate at 90% molar yields. We also succeeded to produce 4-aminophenylethylamine and 4-aminocinnamic acid from 4-aminophenylalanine by taking advantage of phenylalanine decarboxylase and phenylalanine ammonia-lyase, respectively. Combining these conversion systems, the 4-aminophenylalanine-producing platform fermented glucose to 4-aminophenylethanol, 4-aminophenylacetate, and 4-phenylethylamine. Furthermore, we obtained 200 g of 4-aminophenylalanine by a large-scale fermentation, and converted them into 4-aminocinnamic acid by using phenylalanine ammonia-lyase from Rhodotorula glutinis. From the resulting 4-aminocinnamic acid, we synthesized high–performance bioplastics of aromatic polyamide by means of photodimerization and polycondensation reactions. These results denotes that the platform for synthesizing bio-derived aromatic amines constructed in the present study increases the potential for producing a range of bio-based aromatic amine materials for bio-polymers and other applications.