Mild hydrolysis of nitriles byFusarium solani strain O1

Efficient total nitrogen removal from wastewater by Paracoccus denitrificans DYTN-1

Bioaugmentation is an effective treatment method to reduce nitrogenous pollutants from wastewater. A strain of DYTN-1, which could effectively remove TN from sewage, was isolated from the sludge of a wastewater treatment plant and was identified as Paracoccus denitrificans. The TN in wastewater reduced to <20 mg l^-1 within 12 h under optimal conditions by free cells of P. denitrificans DYTN-1. To enhance the removal of TN, P. denitrificans DYTN-1 cells were immobilized in sodium alginate (SA) using different divalent metal ions as cross-linking agents. It was found that the immobilized P. denitrificans DYTN-1 cells could reduce the TN concentration from 100 to below 20 mg l^-1 within 8 h. After the optimization of an orthogonal experiment, the immobilized P. denitrificans DYTN-1 cells could reduce the TN concentration from 100 mg l^-1 to below 20 mg l^-1 within 1 h and significantly reduce the fermentation cycle. These findings would provide an economical and effective method for the removal of total nitrogen in wastewater by immobilized cells of P. denitrificans DYTN-1. SIGNIFICANCE AND IMPACT OF THE STUDY: We identified a new Paracoccus denitrificans strain (DYTN-1) for removal of the total nitrogen in wastewater. The total nitrogen could be removed effectively by P. denitrificans DYTN-1 within 12 h in wastewater. Using sodium alginate as the carrier and Ba²⁺ as cross-linking agent, the immobilized P. denitrificans DYTN-1 cells could improve the removal efficiency of total nitrogen in wastewater and significantly reduce the fermentation cycle. The assay has provided an economical and effective method for the removal of total nitrogen in wastewater by immobilized cell.

Marine Microorganisms for Biocatalysis: Selective Hydrolysis of Nitriles with a Salt-Resistant Strain of Meyerozyma guilliermondii

A screening among marine yeasts was carried out for nitrile hydrolyzing activity. Meyerozyma guilliermondii LM2 (UBOCC-A-214008) was able to efficiently grow on benzonitrile and cyclohexanecarbonitrile (CECN) as sole nitrogen sources. A two-step one-pot method for obtaining cells of M. guilliermondii LM2 (UBOCC-A-214008) endowed with high nitrilase activity was established; the resulting whole cells converted different nitriles with high molar conversions and showed interesting enantioselectivity toward racemic substrates. Nitrilase from M. guilliermondii LM2 (UBOCC-A-214008) displayed high activity on aromatic substrates, but also arylaliphatic and aliphatic substrates were accepted. Salt-resistant M. guilliermondii LM2 (UBOCC-A-214008) was used in media with different salinity, being highly active up to 1.5 M NaCl concentration. Finally, hydrolysis of nitriles was efficiently performed using a bioprocess (yeast growth and biotransformation with resting cells) entirely carried out in seawater.

Effect of physicochemical parameters on nitrile-hydrolyzing potentials of newly isolated nitrilase of Fusarium oxysporum f. sp. lycopercisi ED-3

In recent years, nitrilases from fungus have received increasing attention, and most of the studies are performed on nitrilases of bacterial origin. Frequently used methods are based on analytical methods such as high-performance liquid chromatography, liquid chromatography-mass spectrometry, and gas chromatography; therefore, an efficient, user friendly, and rapid method has been developed to screen nitrilase enzyme based on the principle of color change of a pH indicator. Phenol red amended with the minimal medium appears light yellow at neutral pH, which changes into pink with the formation of ammonia, indicating nitrilase activity in the reaction medium. A highly potent strain ED-3 identified as Fusarium oxysporum f. sp. lycopercisi (specific activity 17.5 µmol/Min/mg dcw) was isolated using this method. The nitrilase activity of F. oxysporum f. sp. lycopercisi ED-3 strain showed wide substrate specificity toward aliphatic nitriles, aromatic nitriles, and orthosubstituted heterocyclic nitriles. 4-Aminobenzonitrile was found to be a superior substrate among all the nitriles used in this study. This nitrilase was active within pH 5-10 and temperature ranging from 25 to 60 °C with optimal at pH 7.0 and temperature at 50 °C. The nitrilase activity was enhanced to several folds through optimization of culture and biotransformation conditions from 1,121 to 1,941 µmol/Min.

Nitrilases in nitrile biocatalysis: recent progress and forthcoming research

Over the past decades, nitrilases have drawn considerable attention because of their application in nitrile degradation as prominent biocatalysts. Nitrilases are derived from bacteria, filamentous fungi, yeasts, and plants. In-depth investigations on their natural sources function mechanisms, enzyme structure, screening pathways, and biocatalytic properties have been conducted. Moreover, the immobilization, purification, gene cloning and modifications of nitrilase have been dwelt upon. Some nitrilases are used commercially as biofactories for carboxylic acids production, waste treatment, and surface modification. This critical review summarizes the current status of nitrilase research, and discusses a number of challenges and significant attempts in its further development. Nitrilase is a significant and promising biocatalyst for catalytic applications.

Stereo-selective conversion of mandelonitrile to (R)-(−)-mandelic acid using immobilized cells of recombinant Escherichia coli

Immobilized cells of a recombinant Escherichia coli expressing nitrilase from Pseudomonas putida were used to catalyze the hydrolysis of mandelonitrile (2-hydroxy-2-phenylacetonitrile) to (R)-(−)-mandelic acid. The cells had been immobilized by entrapment in an alginate matrix. Conditions for the hydrolysis reaction were optimized in shake flasks and in a packed bed reactor. In shake flasks the best conditions for the reaction were a temperature of 40 °C, pH 8, biocatalyst bead diameter of 4.3 mm, sodium alginate concentration in the gel matrix of 2 % (w/v, g/100 mL), a cell dry mass concentration in the bead matrix of 20 mg/mL, an initial substrate concentration of 50 mM and a reaction time of 60 min. Under these conditions, the conversion of mandelonitrile was nearly 95 %. In the packed bed reactor, a feed flow rate of 20 mL/h at a substrate concentration of 200 mM proved to be the best at 40 °C, pH 8, using 4.3 mm beads (2 % w/v sodium alginate in the gel matrix, 20 mg dry cell concentration per mL of gel matrix). This feed flow rate corresponded to a residence time of 0.975 h in the packed bed.

Fungal nitrilases as biocatalysts: Recent developments

Of the numerous putative fungal nitrilases available from protein databases only a few enzymes were purified and characterized. The purified nitrilases from Fusarium solani, Fusarium oxysporum f. sp. melonis and Aspergillus niger share a preference for (hetero)aromatic nitriles, temperature optima between 40 and 50 degrees C and pH optima in the slightly alkaline region. On the other hand, they differ in their chemoselectivity, i.e. their tendency to produce amides as by-products. The production of fungal nitrilases is increased by up to three orders of magnitude on the addition of 2-cyanopyridine to the culture media. The whole-cell and subcellular biocatalysts were immobilized by various methods (LentiKats(R); adsorption on hydrophobic or ion exchange resins; cross-linked enzyme aggregates). Operational stability was examined using continuous stirred membrane bioreactors. Fungal nitrilases appear promising for biocatalytic applications and biodegradation of nitrile environmental contaminants.

Biotransformation of heterocyclic dinitriles by Rhodococcus erythropolis and fungal nitrilases

2,6-Pyridinedicarbonitrile (1a) and 2,4-pyridinedicarbonitrile (2a) were hydrated by Rhodococcus erythropolis A4 to 6-cyanopyridine-2-carboxamide (1b; 83% yield) and 2-cyanopyridine-4-carboxamide (2b; 97% yield), respectively, after 10 min. After 118 h, the intermediates 1b or 2b were transformed into 2,6-pyridinedicarboxamide (1c; 35% yield) and 2,6-pyridinedicarboxylic acid (1d; 60% yield) or 2-cyanopyridine-4-carboxylic acid (2c; 64% yield), respectively. The nitrilase from Fusarium solani afforded cyanocarboxylic acids 1e and 2c after 118 h (yields 95 and 62%, respectively). 3,4-Pyridinedicarbonitrile (3a) and 2,3-pyrazinedicarbonitrile (4a) were inferior substrates of nitrile hydratase and nitrilase.

The impact of acrylonitrile and bioaugmentation on the biodegradation activity and bacterial community structure of a topsoil

The analysis of the bacterial community within the soil using DGGE showed acrylonitrile (ACN) could lead to the selection of significantly similar communities. Moreover, Rhodococcus sp. AJ270 was successfully established in the soil community. High GC G+-bacteria also responded positively to ACN addition. Bioaugmentation or carbon addition had no impact on the rate or degree of ACN degradation. ACN could be readily degraded by the soil bacteria, however, the community structure was significantly affected by its addition as well as by the addition of carbon or Rhodococcus sp. AJ270. The bioaugmentation of the soil with this strain was successful, in that the organism became established within the community. ACN addition to a soil produces statistically significant changes in the bacterial community.