Glucosinolates are sulfur-rich plant specialized metabolites with applications in nutraceutical and agricultural biotechnology. Microbial production of complex glucosinolates derived from chain-elongated amino acids remains constrained by difficult-to-express key biosynthetic enzymes. Here, we report the first microbial biosynthesis of 2-phenylethyl glucosinolate (2PE) through a modular engineering strategy combining Escherichia coli and Saccharomyces cerevisiae. The bacterial module was critical to achieve functional expression of an iron-sulfur cluster enzyme that catalyzes amino acid side chain elongation of phenylalanine to homophenylalanine. The yeast module contained the core structure pathway converting homophenylalanine to 2PE. By optimizing the modules separately, we identified superior CYP79F, MAM, and BCAT variants among the tested brassicaceous enzymes. To address a metabolic bottleneck in the sulfation step catalyzed by a sulfotransferase, we optimized PAPS co-factor availability via sulfate feeding, resulting in a 10-fold increase in 2PE titers and partial alleviation of the desulfo-2-phenylethyl glucosinolate (ds-2PE) bottleneck. Further optimization of carbon source selection and autoinduction strategies enabled the first demonstration of 2PE biosynthesis from phenylalanine by combining the two modules. This work establishes a platform for microbial production of complex glucosinolates derived from chain-elongated amino acids via pathway modularization and co-culture engineering.
Wajn et al. (Mon,) studied this question.