Is there a value in chemical modification of lake whitefish scales?

Lake whitefish scales are an abundant biowaste that are at present unused.

Researchers are exploring the possibility of expanding the use of lake whitefish fish scales as a waste resource, by exploring the potential to modify the scale surface. Photo: Andrew Muir, Great Lakes Fishery Commission

Researchers are exploring the possibility of expanding the use of lake whitefish fish scales as a waste resource, by exploring the potential to modify the scale surface. Photo: Andrew Muir, Great Lakes Fishery Commission

In recent years the Michigan Great Lakes lake whitefish commercial harvest has averaged around five million pounds per year. Some Michigan commercial fish processors have sold their fish waste for use into other products such as fertilizers or have made fish waste compost. It is estimated that about two percent of the lake whitefish waste is composed of scales and with the current harvest rates about one hundred thousand pounds of scales are generated annually.

The inherent design of lake whitefish fish scales, with a biomineral upper surface and alternating arrays of collagen layers at their lower surface, imparts both high elasticity and high toughness, yet this abundant and growing waste resource is little used. Michigan Sea Grant working with Michigan Technological University scientists from the Departments of Chemistry, Mechanical Engineering and Engineering Mechanics, and Biomedical Engineering sought to explore the possibility of expanding the use of lake whitefish fish scales as a waste resource, by exploring the potential to modify the scale surface. This was the first research to investigate chemical modifications of fish scales, and their effects on functionality and nanomechanical properties of modified fish scales, and their relative effects on the biomineral and the collagen layer of the scale.

The research showed that modifications can be targeted to the biomineral or the collagen layer of the scale, but while some modifications were “preferential,” none were truly selective, so all the modifications had some effect on both layers. The types of chemical modifications ranged from a targeted partial removal of one or the other layer, and “supplementation” of one or the other layer by inorganic or organic polymers. The range of surface modification possible was explored because the most likely use for “intact” fish scales seems likely to be as an additive for biodegradable packaging or composite materials, and these potential applications benefit from good interfacial adhesion.

The study concluded there was a significant benefit from even simple surface modifications of scales as reinforcement. The overall significance of these results is that a wide range of modifications is possible to adjust the scale interface for a wide range of polymer matrices. However, before “intact” scales, be the modified or unmodified, can find wide use, a suitable mechanical cutting tool must be devised, as grinding the scales to a powder sacrifices the hierarchical design, and hand cutting is both unrealistic and leaves the scale pieces too large for truly effective distribution within a matrix. If the modified scale pieces were more effectively distributed within a matrix, possibly even greater mechanical benefit would be achieved.

The results of this research were recently published in the  Journal of Applied Polymer Science.

Michigan Sea Grant helps to foster economic growth and protect Michigan’s coastal, Great Lakes resources through education, research and outreach. A collaborative effort of the University of Michigan and Michigan State University and its MSU Extension, Michigan Sea Grant is part of the NOAA-National Sea Grant network of 33 university-based programs.