The Sirius effect:

Sirius continues to push for a cleaner planet.  Creating products sustainably is one side of the change; making things biodegradable is the other. Some molecules (such as Ethoxybrite EFAs) lend themselves to eco-friendly formulations, but complex molecules such as chelates and optical brighteners do not.  Chelating agents, which are the focus of this newsletter, bind metal ions, and it has been difficult to find functional biodegradable substitutes for EDTA and phosphonic acids and salts. Two biodegradable chelating agents form the bulk of the products which are commercially available now, but Sirius is working to bring more to market. 

Biodegradable chelating agents are notoriously difficult to make. Chelators bind metals and ions and pull them out of the solution. They do this by donating electron pairs to a metal ion; in the correct geometry the bond is very stable and the metal “prefers” the chelating agent instead of floating freely in solution. Traditional chelating agents, such as EDTA, are very stable and long-lasting in solution, and while EDTA itself is not toxic, it does not biodegrade. This causes problems because the bioavailability of heavy metals (i.e., mercury, lead) is enhanced by the presence of EDTA, so organisms – including people – can more readily absorb them. Excess quantities of chelating agents can also complex with useful ions (such as copper) that are needed for photosynthesis, and remove them from the environment.  

The need for chelating functionality adds complexity to the structure of chelating agents. This complexity makes it difficult for bacteria to degrade the chelate. Long sugar chains and carbon chains are relatively easy for bacteria to break apart and use, but small, structurally tortuous molecules such as chelates do not break down into anything usable.  Briteframe GLDA and Briteframe MGDA are based on amino acids, which are the building blocks of protein and can thus be used by bacteria. However, GLDA and MGDA do not work well for all chelating needs, and there are some applications where EDTA and phosphonics remain the optimal compound. But that could change. 

Sirius is working to bring a line of new chelating agents to market, which are protein-based and 100% biodegradable. Proteins may seem a surprising choice, but many proteins incorporate metals and ions into their structure. Life would be impossible without the many, many different proteins controlling the quantities of free ions in our bodies. At this point in product development the release date is somewhere in 2022, so it is not quite ready yet, but it represents a major departure in how chelating agents are formulated and could indicate how we might formulate complex molecules to be more biodegradable.

Now, to tackle optical brighteners…

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