Acrylamide production using encapsulated nitrile hydratase from Pseudonocardia thermophila in a sol–gel matrix

• Cobalt-containing nitrile hydratase has been successfully encapsulated in a silica-derived sol–gel material.
• Encapsulated nitrile hydrate converts >90% of a 600 mM acrylonitrile solution to acrylamide in 60 min at 35 °C.
• The biomaterial retains 50% activity after 13 consecutive reaction cycles converting acrylonitrile to acrylamide.
• The encapsulated enzyme exhibits significantly greater thermal stability compared to the enzyme in solution.
• The encapsulated enzyme is stable and active in high concentrations of methanol for the hydration of acrylonitrile.

The cobalt-type nitrile hydratase from Pseudonocardia thermophila JCM 3095 (PtNHase) was successfully encapsulated 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 is due to the encapsulated enzyme and not surface bound NHase. The biomaterial retained 50% of its activity after being used for a total of 13 consecutive reactions for the conversion of acrylonitrile to acrylamide. The thermostability and long-term storage of the PtNHase:sol–gel are substantially improved compared to the soluble NHase. Additionally, the biomaterial is significantly more stable at high concentrations of methanol (50% and 70%, v/v) as a co-solvent for the hydration of acrylonitrile than native PtNHase. These data indicate that PtNHase:sol–gel biomaterials can be used to develop new synthetic avenues involving nitriles as starting materials given that the conversion of the nitrile moiety to the corresponding amide occurs under mild temperature and pH conditions.

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