Heterologous production of mycosporine-like amino acids in Escherichia coli

Continuous exposure to ultraviolet radiation can cause detrimental health effects in humans, including erythema, hyperpigmentation, photo-aging, and skin cancer. Sunscreens provide important protection of skin against the harmful effects of ultraviolet radiation. However, chemical and physical sunblock filters can be harmful for both human beings and the environment. There is a need for natural alternatives to commercial filters currently used in sunscreens. Mycosporine-like amino acids (MAAs) are natural microbial sunscreens produced mainly by marine organisms to protect themselves from ultraviolet radiation. There has been over three decades of interest in these natural compounds for applications in the cosmetic industry. However, low production levels in nature have hindered large-scale processes for industrial applications. Here, we demonstrates the successful expression of a MAA biosynthetic pathway from cyanobacteria in a metabolically engineered strain of Escherichia coli. Heterologous expression of the artificial codon-optimized MAA biosynthetic pathway resulted in high-level production of porphyra-334 and shinorine. These two MAAs have exceptional high molar extinction coefficients and are found in a number of commercial sunscreen formulations that rely on algal extracts. The expression of a gene encoding an ABC-transporter, which is associated with cryptic MAA biosynthetic gene clusters in cyanobacteria, in Escherichia coli resulted in the effective transport of both porphyra-334 and shinorine outside the cell. Together, these two advances improve the possibility of biotechnological production of these microbial sunscreens in industrial microbial hosts