cleaning requirements and the environmental liability of
large scale use of industrial cleaners.
STEP TWO: IDENTIFY POTENTIAL BIOACTIVE ADDITIVES
At Reactive Surfaces, we develop natural additives such that
the biocompounds and reactants are dispersed, embedded
and maintained in an active state within a continuous polymer phase, either as solid films or aqueous dispersions. To
create a single macroscopic phase without affecting biomolecule activity, the selection and/or modification of the biocatalyst is the first step forward in harnessing biomaterials in
functional coatings (Figure 1). Selection of the most appropriate bioactive (enzyme or peptide) from the diverse options
that nature has to offer is critical.
Fortunately, there are classification systems that help
narrow down the choices once a desired functionality has
been identified. The Enzyme Classification (EC) system
places enzymes into different categories (EC 1-6) based on
the general type of chemical reaction they mediate (Table
2). Enzymes are classified differently depending upon
whether they catalyze oxidations, cause the transfer of a
functional group from one molecule to another, add or
remove water from a molecule, break or create carbon-car-bon bonds or change the arrangement of bond connections
within a molecule. Sublevels within each of these categories provide increasingly specific information. Lipases,
for example, are a subclass in the group of enzymes known
as hydrolases (category EC 3), and each different lipase has
been assigned a specific classification number along with a
description of its specific characteristics (selected examples
of which are shown in Table 3). In the case of the self-degreasing additive DeGreez, the lipases were our first
choice, although whether these enzymes could withstand
the rigors of existence in a dry-film environment and exhibit a degreasing function was entirely unknown. Selecting
from the vast number of lipases (over 100 have been identified) presented another significant challenge.
This information is helpful in narrowing the selection of
appropriate enzyme candidates for use in a specific
biobased additive. There are, in fact, some defining charac-
teristics that should guide the selection of an appropriate
biocatalyst. In addition to identifying an enzyme that
meets the application parameters such as temperature, pH
and type of substrate (the term “substrates” is used here in
the biochemical sense as the molecule that the enzyme acts
upon), characteristics such as stability, catalytic rate and
substrate specificity must also be considered. In searching
for appropriate lipase enzymes for our DeGreez additive,
for example, we were looking for lipases that had broad
specificity for different substitution patterns and chain
lengths within the triglycerides in order to develop the
most effective product possible. A clear understanding of
both the characteristics of the different lipase enzymes and
the desired performance profile of the final additive were
required before this step could be completed. It cannot be
stressed enough that proper assessment of application
requirements and a detailed understanding of the func-
tionalities that are available within a set of related bioac-
tives (enzymes, peptides, etc.) is an essential step in
enabling the development of a reactive coating.
STEP THREE: ESTABLISH ASSAY METHOD
Once the biocompounds of interest have been selected, it
is necessary to establish a method or methods for detection and measurement of bioactivity under various conditions during the development process. In some cases,
there will be widely known techniques that can be adopt-
Figure 3
Visual indicator developed at USM for detecting real-time
lipase enzyme activity in applied coatings containing DeGreez
additive. The indicator material when applied is green and
changes to yellow when enzyme activity is detected.
Figure 4
Specific activity of lipase after extended exposure
in selected resin systems. (*denotes dry addition)
