The synthesis of a commercial fragrance,
methyl cinnamate, via
Fischer esterification was evaluated for use as a second-year organic
chemistry course. The experiment utilizes trans-cinnamic
acid, a commercial flavoring that possesses a mild honey floral odor,
as an inexpensive starting material. Both the starting material and
the product are listed as GRAS (Generally Recognized as Safe) for
use in foods and fragrances. The high-yielding experiment enables
students to explore concepts of flavor and fragrances, transmutation
of scent, catalysis, green chemistry, NMR spectroscopy, thin layer
chromatography (TLC), and acid–base extractions. In addition
to the commonly employed sulfuric acid catalyst, alternative conditions
were developed using p-toluenesulfonic acid monohydrate
as an easier to handle catalyst, and conditions for performing both
reactions under microwave irradiation are also reported. The experiment
was analyzed in a second-year organic chemistry laboratory over six
semesters.
We report the first complete genome of Microcystis aeruginosa from North America. A harmful bloom that occurred in the Caloosahatchee River in 2018 led to a state of emergency declaration in Florida. Although strain FD4 was isolated from this toxic bloom, the genome did not have a microcystin biosynthetic gene cluster.
In aquatic environments, chemical
and biological processes represent
major sources of reactive oxygen species (ROS) such as hydrogen peroxide.
Diurnal patterns of hydrogen peroxide in surface water may suggest
photochemical processes affect ROS dynamics. We hypothesized that
thin surface hydrogen peroxide maxima could be detected through millimeter-scale
depth profiling. These maxima were previously overlooked because they
cannot be detected using standard surface water sampling techniques.
Combined field and laboratory experiments demonstrated that cyanobacterial
blooms could create extremely high concentrations of hydrogen peroxide
in a thin layer of surface water (5–60 mm). Hydrogen peroxide
concentrations were higher within surface scums of Microcystis
aeruginosa than in areas without scum. The cyanobacterial
scum increased the temperature of the ambient water, and hydrogen
peroxide concentrations were higher at locations exposed to sunlight
that at locations in the shade. We found that scum samples directly
collected from the field could release hydrogen peroxide to the surrounding
water when the biomass was exposed by the light, while 20 laboratory
cultures tested did not. The production of hydrogen peroxide from
cyanobacteria may depend on the physiological condition of cells.
Overall, we identified thin surface water layers during subtropical
freshwater cyanobacterial blooms as hydrogen peroxide hot spots.
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