Industrial production of chiral intermediate of cilastatin by nitrile hydratase and amidase catalyzed one-pot, two-step biotransformation

High-throughput screening for distinguishing nitrilases from nitrile hydratases in Aspergillus and application of a Box-Behnken design for the optimization of nitrilase

Nitrilases and nitrile hydratases/amidases hydrolyze nitriles into carboxylic acids and/or amides, which are used in industrial chemical processes. In the present study, 26 microorganisms, including yeasts and filamentous fungi, in a minimum solid mineral medium supplemented with glucose and phenylacetonitrile were screened to evaluate their biocatalytic potential. Of these microorganisms, five fungi of the genus Aspergillus were selected and subjected to colorimetry studies to evaluate the production and distinction of nitrilase and nitrile hydratase/amidase enzymes. Aspergillus parasiticus Speare 7967 and A. niger Tiegh. 8285 produced nitrilases and nitrile hydratase, respectively. Nitrilase optimization was performed using a Box-Behnken design (BBD) and fungus A. parasiticus Speare 7967 with phenylacetonitrile volume (μl), pH, and carbohydrate source (starch:glucose; g/g) as independent variables and nitrilase activity (U ml^-1 ) as dependent variable. Maximum activity (2.97 × 10^-3  U ml^-1 ) was obtained at pH 5.5, 80 μl of phenylacetonitrile, and 15 g of glucose. A. parasiticus Speare 7967 showed promise in the biotransformation of nitriles to carboxylic acids.

Amidase as a versatile tool in amide-bond cleavage: From molecular features to biotechnological applications

Amidases (EC 3. 5. 1. X) are versatile biocatalysts for synthesis of chiral carboxylic acids, α-amino acids and amides due to their hydrolytic and acyl transfer activity towards the C-N linkages. They have been extensively exploited and studied during the past years for their high specific activity and excellent enantioselectivity involved in various biotechnological applications in pharmaceutical and agrochemical industries. Additionally, they have attracted considerable attentions in biodegradation and bioremediation owing to environmental pressures. Motivated by industrial demands, crystallographic investigations and catalytic mechanisms of amidases based on structural biology have witnessed a dramatic promotion in the last two decades. The protein structures showed that different types of amidases have their typical stuctural elements, such as the conserved AS domains in signature amidases and the typical architecture of metal-associated active sites in acetamidase/formamidase family amidases. This review provides an overview of recent research advances in various amidases, with a focus on their structural basis of phylogenetics, substrate specificities and catalytic mechanisms as well as their biotechnological applications. As more crystal structures of amidases are determined, the structure/function relationships of these enzymes will also be further elucidated, which will facilitate molecular engineering and design of amidases to meet industrial requirements.

Immobilization of amidase into a magnetic hierarchically porous metal–organic framework for efficient biocatalysis

A novel core–shell magnetic hierarchically porous MOF has been designed and used for amidase immobilization, which demonstrated excellent catalytic performance.

Substrate channel evolution of an esterase for the synthesis of cilastatin

Error-prone PCR and site-directed mutagenesis around substrate channel were employed for improving an esterase (RhEst1) activity towards Cilastatin building block. RhEst1_{A147I/V148F/G254A} showed 20 times higher activity than the native enzyme in whole cell biotransformation.