Incorporation of enzymes in bioplastics to increase their biodegradability or even to engineer their programmed degradation requires that the enzyme activity can “survive” exposure to high temperature for a more or less long time. The reason is that the processing of plastics often involves their extrusion, which causes a high temperature peak.
The University of Granada group has been characterizing ancestral forms of enzymes with potential plastic-degrading activity. In particular, they have used differential scanning calorimetry, a methodology for studying protein stability in which overpressure is applied to increase the boiling point of the aqueous solution, and temperatures above 100 degrees can be reached. Using this experimental approach, the Grenada researchers have found an ancestral enzyme that maintains a significant level of activity upon cooling after reaching 120 degrees.
These results are preliminary and require clarification in several respects. For example, it is necessary to find out whether the retention of activity after exposure to high temperature is due to a high intrinsic stability of the ancestral protein or to an ability to refold at low temperature after denaturation at high temperature. Likewise, it is important to characterize the dependence of activity retention on enzyme concentration and on the chemical composition of the environment.
In any case, the results are promising and may provide the basis for the development of improved enzymes for bioplastic degradation.