Surface modification of polyacrylonitrile fibre by NHase

Surface Modification of Polyacrylonitrile Fibre by Nitrile Hydratase from Corynebacterium nitrilophilus

S Chen, H Gao, J Chen, J Wu - Applied biochemistry and biotechnology, 2014

Previously, nitrile hydratase (NHase) from Corynebacterium nitrilophilus was obtained and showed potential in polyacrylonitrile (PAN) fibre modification. In the present study, the modification conditions of C. nitrilophilus NHase on PAN were investigated. In the optimal conditions, the wettability and dyeability (anionic and reactive dyes) of PAN treated by C. nitrilophilus NHase reached a similar level of those treated by alkali. In addition, the chemical composition and microscopically observable were changed in the PAN surface after NHase treatment. Meanwhile, it revealed that cutinase combined with NHase facilitates the PAN hydrolysis slightly because of the ester existed in PAN as co-monomer was hydrolyzed. All these results demonstrated that C. nitrilophilus NHase can modify PAN efficiently without textile structure damage, and this study provides a foundation for the further application of C. nitrilophilus NHase in PAN modification industry.

Polymers and nitrile hydratase activity

There have been a few papers over the years looking at the possibility that nitrile-active enzymes might be able to attack nitrile groups on the surface of nitrile-containing polymers such as polyacrylonitrile.  An early example of this is the paper by Gübitz and co-workers [Nitrile Hydratase and Amidase from Rhodococcus rhodochrous Hydrolyze Acrylic Fibers and Granular Polyacrylonitriles, from Appl Environ Microbiol (2000)] which uses a cell free extract from Rhodococcus rhodochrous NCIMB 11216 to create pendant carboxylate groups on the fibres.

More recently there has been another paper looking at this topic using a different cell-free extract

Vikash Babu, Bijan Choudhury, Competitive adsorptions of nitrile hydratase and amidase on polyacrylonitrile and its effect on surface modification, Colloids and Surfaces B: Biointerfaces, Volume 89, 1 January 2012, Pages 277-282, 10.1016/j.colsurfb.2011.08.025.

This uses an extract from Amycolatopsis, and they do show conversion of the surface to carboxylate, by functionally tracking a NHase activity and an amidase activity. I am not sure how they know there isnt a nitrilase in there helping along too (NCBI records currently an Amycolatopsis species nitrilase).

In the light of the congested active site entrance which is generally found with NHase, it is quite interesting this works.