A flask of the cyanobacterium Synechocystis sp. PCC 6803 that was used to produce shinorine. The green color comes from the chlorophyll, which is a natural part of the bacterium. Shinorine is clear. Photo: Dr. Guang Yang, CC BY-NC-N

Yousong Ding, Assistant Professor of Medicinal Chemistry, University of Florida, writes in The Conversation that, in his laboratory in the College of Pharmacy at the University of Florida, they are interested in combing the world for naturally occurring chemicals that have applications in health, agriculture and environment. Recently, his colleagues and he have discovered a more efficient way to harvest shinorine — a natural sunscreen produced by cyanobacteria.

Shinorine belongs to a family of natural products, called mycosporine-like amino acids, and is made up of two amino acids and one sugar. Many aquatic organisms exposed to strong sunlight, like cyanobacteria and macroalgae, produce shinorine and other related compounds to protect themselves from solar radiation. The cosmetics industry is already infusing products with shinorine as a key active ingredient. Commercial supplies of shinorine come from marine red algae that grows slowly in large tidal pools that experience frequent environmental changes. That means that conventional extraction methods are time-consuming and unpredictable.

To ramp up shinorine production, Dr. Ding’s lab group sought a fast-growing strain of cyanobacteria that would thrive under predictable conditions. They decoded the genetic blueprints — genomes — of more than 100 varieties of cyanobacteria from marine and terrestrial ecosystems and selected one, Fischerella sp. PCC9339, to cultivate in the laboratory.

Yousong Ding, Assistant Professor of Medicinal Chemistry at the University of Florida.

To their delight, after four weeks this strain produced shinorine, but unfortunately not enough. To produce more they then transferred a set of genes that encode the instructions to make shinorine, into one freshwater cyanobacterium (from Berkeley, California), Synechocystis sp. PCC 6803, which grows fast with just water, carbon dioxide and sunlight.

Using the engineered cyanobacterium, they produced a quantity of shinorine comparable to the conventional method — but they did it in just a few weeks, instead of the one year that’s needed to cultivate red algae.

By advancing the method to produce more shinorine and other UV-absorbing natural products, they hope to make green sunscreens more available.

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