Submitted to: Journal of American Leather Chemists Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/26/2010
Publication Date: 6/1/2010
Citation: Taylor, M.M., Lee, J., Bumanlag, L.P., Hernandez Balada, E., Brown, E.M. 2010. Effect of chrominium in blue hides on activity of microbial transglutaminase. Journal of American Leather Chemists Association. 105(6):175-180. Interpretive Summary: In recent years, we have produced and successfully applied products that fill leather to give a more uniform product, by enzymatically treating waste proteins, such as gelatin from the leather industry and casein and whey from the dairy industry. These treatments have resulted in leather products with improved properties. To insure that these products do not migrate out of the leather either during washing steps or when the leather is further processed, we have used an enzyme treatment which reacts with the hide and with the fillers and holds them in place. Many tanning agents are used in hide treatment, one of which is chromium, and in this study we investigated what part the chromium would play in the enzyme’s ability to react. In a model system study using gelatin to represent leather, the enzyme was reacted in the presence and absence of chromium. Finally to show that the enzyme helped to hold the fillers in place, we added a fluorescent label to the fillers before hide treatment; this label can be seen in the treated leather with an appropriately equipped microscope. It was shown that the amount of chromium in the reaction solutions was quite low, that its presence does not affect the enzyme assay, that in a model protein modification system in which the enzyme is reacting in a chromium environment, similar results to that reacted in water were found, and, finally, that these fillers were not removed during the washing steps. This study has further confirmed the important role that the enzyme plays in hide filler treatments.
Technical Abstract: Microbial transglutaminase (mTgase) has been used in the modification of proteins from sustainable resources to make products that have application in leather production. It has also been successfully used to treat blue stock, prior to addition of the products, for the purpose of stabilizing the fillers and lessening the chance that they will be washed out during further processing steps. There is always a concern that metals may have an effect (either positively or negatively) on the enzyme’s activity and literature has addressed many of these issues. However, one area that has not been addressed is whether chromium may affect activity of mTgase. Even though we have only seen positive results after hide treatment with enzyme, we designed an experiment to elucidate this matter. Using Atomic Absorption Spectroscopy (AAS), we first determined the concentration of chromium in the floats during the processing of the hides. When the hides were washed and then neutralized, the concentration of unbound chromium was found to be less than 5 ppm. Next, to test mTgase sensitivity, we carried out activity assays in absence and presence of chromium and found that activity results were similar. We prepared a model system in which gelatin, swollen and solubilized in solutions containing chromium, was reacted with mTgase using standard conditions. It was found, when compared to a control, that the reaction proceeded at the same rate (chemical gel formed in 2 h @ 50°C), and the physical properties and molecular weight distributions (SDS-PAGE) of the products were similar. Finally, epi-fluorescent microscopy studies showed that enzyme-pretreatment, when compared to a control in which no enzyme pretreatment was applied, prevented migration of the fillers during subsequent processing steps. Thus, under the conditions in which we treat wet blue hides, the chromium used to tan the hides does not affect enzyme activity.