New Material Made from Fish Protein

Hydrogel may boost value of by-catch

About five years ago, Srinivasan Damodaran learned that disposable diapers, made with synthetic polymers that do not readily decompose, are the third largest source of the solid waste rapidly filling up the country’s landfills.  That’s when he started thinking seriously about fish carcasses.

Damodaran, a food scientist at UW-Madison, suspected that proteins from discarded fish parts might be made into an inexpensive, biodegradable, and super-absorbent material that could be used in disposable diapers. Such a novel material, he thought, might also show potential for other interesting applications.

He was right.

With funding from UW Sea Grant, Damodaran developed a process for extracting protein from fish by-catch and processing waste and turning it into a hydrogel—a material that chemically binds water molecules to itself. As expected, the new material has intriguing qualities that may alleviate the diaper pile-up and other problems too.

Depending on how he formulates it, Damodaran’s protein-based hydrogel absorbs up to 600 times its weight in water. That’s about six times more absorbent than a common household sponge.  The gel is also biodegradable, so diapers using it won’t permanently take up space in land fills.

Additionally, the raw materials for the gel are abundant, renewable, and free.  He said commercial fishers in the Great Lakes are happy to give non-target fish away, since they often have to pay to dispose of them. 

“In commercial fishing, a very large portion of the catch is by-catch that is not economically useful.  We might be able to start a by-product industry, where these underutilized fish can be converted into industrial polymers like hydrogels,” Damodaran said.

Other attributes of the hydrogel sound equally promising. Damodaran has already demonstrated that it binds heavy metals, which may make it useful for removing contaminants like mercury, lead, and cadmium from industrial effluent. 

He said protein-based hydrogels might also make a much more efficient delivery mechanism than aerial spraying for applying pesticides or herbicides to crops.  Soaked in an herbicide solution and spread on crops, he said, the gel would release its solution more slowly than conventional spraying, reduce the enormous amount of water normally lost to evaporation, and release nitrogen into the soil when it decomposes.

A Canadian company is evaluating the gel for use as a moisturizing agent in cosmetics because it may cause fewer allergic reactions than plant-based hydrogels. The gel may also make a useful coating for paper because its absorbency would help ink dry quickly.

Making protein-based hydrogels is so easy and inexpensive that Damodaran was surprised to find no one developed the process before he did. Many proteins are not utilized for food, he said, and they’re highly versatile chemicals with tremendous potential for novel industrial applications. Anticipating these applications, Damodaran has applied for a patent on the process he developed for making protein-based hydrogels from waste fish.  The patent application was made by the Wisconsin Alumni Research Foundation.

- John Karl

Last updated 28 April 2000 by Karl
All contents copyright 2000 University of Wisconsin Sea Grant Institute

http://www.seagrant.wisc.edu/Communications/news/LDstories/2000/hydrogels.html