389874 Cold-Water Protease: Reducing the Environmental Footprint of Residential Laundry through Low Temperature Cleaning
Each day, Americans do 123 million loads of laundry. They have become accustomed to a certain level of cleaning and ease in performing this essential activity of modern living. And when it comes to stain removal, most choose to set their dials to warm or hot to ensure a quality clean. As of February 2014 consumers have a choice to actually do better for their clothes, do better for the environment and better for their bottom line. That is because the research teams at DuPont, in partnership with P&G, have invented a new enzyme that allows consumers to wash their clothes at significantly lower temperatures with improved performance. This enzyme technology, cold-water protease, is available now in Tide Coldwater Clean. Current laundry washing creates 40 million metric tons of emissions of carbon dioxide. If the loads were cleaned instead in cold water, the energy savings would reduce those emissions by 80% or the equivalent of taking 6.3 million cars from the road, based on annual U.S. emissions. And when the electricity bill rolls around at the end of each month, consumers will notice a savings there as well because they have reduced their energy use by 50% with each load. Joint commercialization of this breakthrough technology means it has the potential to become the number one selling engineered enzyme in the world – greening one of the most common household chores on a macro scale, one washing machine at a time.
DuPont’s Genencor scientists applied novel protein engineering methods to invent an optimal protease that at 60°F matches the cleaning performance of the previous incumbent generation product at 90°F, without loss of stability and thus enabling commercialization. The properties of enzymes functioning outside of their natural milieu are often suboptimal for industrial biotechnology applications. We systematically mapped all properties of interest across sequence space, in order to enable a productive search for a protease satisfying multiple, conflicting constraints. Historically, protein engineers have evolved enzymes through introduction of mutations at or near the active site that affect specific interactions with the substrate. They have failed to recognize the contribution of both short- and long-range non-specific interactions arising from intermolecular colloidal and surface forces that govern association and dissociation with the substrate. We modulate the electrostatic forces between enzyme and substrate through systematic variation of the enzyme net charge by accumulation of charged mutations on its surface, i.e. charge ladders. We have shown that working at a defined pH against a charged substrate, such as protein soils on cloth, there is an optimum surface charge for performance. We have discovered that this charge optimum effect is general, and applies to all enzymes we have studied. When viewed as charged colloids, the performance of enzymes from different families on a charged substrate reduces to a common scale described by their zeta potential. In fact, knowing the charge of the substrate and the reaction conditions allows us to calculate the optimal enzyme surface properties. Identification of physico-chemical and structural constraints allows for a productive search through an essentially infinite number of possible protein sequences in order to rapidly optimize enzymes for industrial needs.