Chemical and pharmaceutical industries make extensive use of nitrile compounds for the manufacture of commodity chemicals and drug intermediates.  The conversion of nitriles to their corresponding amides is usually achieved using strongly acidic or basic conditions, high temperatures, and copper salts as catalysts producing unwanted by-products and toxic wastes.  Alternatively, this conversion can be achieved using nitrile hydratase (NHase, E.C. 4.2.1.84), one of the enzymes in the nitrile-degradation pathway in microorganisms.  Nitrile hydratases convert nitriles to amides in a chemo-, regio-, and/or enantio-selective manner at neutral pH and ambient temperatures, thus reducing production of unwanted by-products and toxic wastes.  A biomaterial for the conversion of nitrile compounds to amides, was developed by encapsulating the cobalt-type NHase from Pseudonocardia thermophilia JCM3095 (PtNHase) in tetramethyl orthosilicate sol-gel matrices to produce a PtNHase:sol-gel biomaterial.  The PtNHase:sol-gel biomaterial catalyzed the conversion of 600 mM acrylonitrile to acrylamide in 60 min at 35 �C with a yields of >90%.  Treatment of the biomaterial with proteases confirmed that the catalytic activity was due to the encapsulated enzyme and not surface bound NHase.  The biomaterial retained ~50% of its activity after being used in 13 consecutive reactions.  The thermostability and long-term storage of PtNHase was substantially improved by encapsulation compared to soluble PtNHase.  Additionally, the biomaterial significantly stabilized PtNHase at high methanol concentrations (50 and 70% v/v).  The enhanced stability and robustness of this biomaterial allows for potential industrial applications for the large-scale production of amide compounds.

Hydration of nitriles by a nitrile hydratase biomaterial

246th National Meeting (2013)

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