Enzymes are proteins that catalyze all the chemical reactions that allow
Life on Earth. Additionally, they possess interesting properties that can
be exploited for the synthesis of chemical compounds of interest for the
pharmaceutical, agrochemical and food industries.
Till the early eighties it was generally accepted that enzymes could work
just in water - a solvent in which most of the organic compounds are not
soluble - and that the organic solvents were poisons for their catalytic
activity. In order to overcome this reaction medium miss-match between
reagents and catalysts, the first research groups involved in the so-called
"biocatalysis" - including the one that started in early seventies in our
Institute - performed the reactions in the presence of increasing amounts
of organic solvents. Water-miscible co-solvents (e.g., acetone) were used
first, then non-miscible co-solvents (e.g., toluene) forming biphasic
systems were investigated: substrates (and products) were dissolved in the
organic phase, while the enzymes were still present in the water phase.
(Figure). By reducing the amount of water the next step was the use of
enzymes in pure organic solvents: the biocatalyst, an insoluble lyophilized
or precipitated powder, was suspended in the solvent in the presence of a
minimal amount of water, just the amount needed to maintain the catalytic
activity. Under these conditions a discrete water phase is usually not
visible, as water concentration is lower of its maximum solubility in the
organic solvent. Surprisingly, it was found that not only the enzymes are
still active under these extreme conditions but that they also show
unexpected new properties: an increased thermostability, the ability to
catalyze reverse reactions, different substrate specificity.
Scientists of our Institute, after having been active in the very first
investigations on the performances of enzymes in bi-phasic systems, are
deeply involved with biocatalysis in pure organic solvents. Our goals are
the preparative-scale biotransformation of non-natural substrates and the
optimization of reaction conditions, specifically concerning enzyme
formulation.
By analyzing the reasons that might produce a decrease of enzyme activity
and by studying the biocatalysts performances once immobilized/adsorbed on
solid supports or in the presence of suitable additives, it has been
possible to prepare enzymatic formulations that show a catalytic activity
comparable or even higher than that the same biocatalysts possess in water.
The general outcome of this multi-annual research activity is a better
knowledge of enzymatic behavior (stability and activity) and the
development of new synthetic methodologies, easily transferable to academic
and industrial research labs for the large-scale production of molecules of
interest for the fine chemistry.
These studies have been granted by CNR, by the EEC and by Italian
pharmaceutical companies.
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