Isolation and characterisation of nitrilase producing Aspergillus species recovered from solid waste leachates at two dump sites in Lagos, Nigeria

@#Aims: Nitrile compounds are cyanogenic intermediates, products, byproducts and waste products of agriculture, chemical and pharmaceutical industries and fossil fuels degradation. The enzymatic hydrolysis of nitriles to non-toxic carboxylic acids or amides plays an increasingly important role in environment remediation. This study aimed at exploring the potential of Aspergilli in the detoxification nitrile compounds at two selected dump sites in Lagos, Nigeria. Methodology and results: Decomposing solid waste leachate samples (SWL) were randomly collected at two selected dump sites namely Olusosun (Ojota) and Isolo (Oke-Afa). Samples per site were pooled, processed by selective enrichment and screened for the presence of Aspergilli by culture technique and intergenic spacer sequencing (ITS). Biomass generation and pH changes in the culture fluids were monitored at 4-days interval by dry weight measurements. Nitrilase production was determined spectrophotometrically. Two nitrilase producing Aspergillus strains: Aspergillus fumigatus strain WO2 with accession number MF78882 and Aspergillus niger strain WO7 with accession number MH542673 were identified. Growth investigation revealed biomass generations of 17.8 g and 23.8 g dry weight per one liter media for A. fumigatus strain WO2 and A. niger strain WO7 respectively. Progressive pH monitoring showed decline from 7.2 to 4.5 and 7.2 to 6.2 was obtained for strains WO2 and WO7 respectively, during nitrilase production at different yields of 0.0150 and 0.0161 mg/mL/min respectively. Conclusion, significance and impact of study: This study supports the studied dump sites as important sources of nitrilase-producing A. fumigatus and A niger strains with potentials as cost-effective environmental bioremediation agents in Nigeria.

A high-throughput screening assay for distinguishing nitrile hydratases from nitrilases

A modified colorimetric high-throughput screen based on pH changes combined with an amidase inhibitor capable of distinguishing between nitrilases and nitrile hydratases. This enzymatic screening is based on a binary response and is suitable for the first step of hierarchical screening projects.

Response surface methodology of nitrilase production by recombinant Escherichia coli

Growth and nitrilase production by recombinant Escherichia coli cells harbouring pET 21 (b) plasmid, for the expression of Pseudomonas putida nitrilase were improved using response surface methodology. Central composite design was used for obtaining ideal concentration of critical medium components which include fructose, tryptone, yeast extract and lactose. The optimal values for the concentration of fructose, tryptone, yeast extract and lactose were found to be 1.13, 2.26, 3.25 and 0.9 percent (w/v), respectively. Here, fructose served as carbon source for the growth while lactose was preferably used as inducer for the expression of foreign protein. Yeast extract in the medium was used as a growth promoter while tryptone was added as a major nitrogen source. Using this optimized medium, an experimental growth of 6.67 (OD at 600 nm) and nitrilase activity of 27.13 U/ml was achieved. This approach for medium development led to an enhancement of the growth and enzyme activity by 1.4 and 2.2 times, respectively, as compared to the un-optimized medium.

The Nitrilase: Sources, Structure, Mechanism and Applications* / 微生物学通报

A Comprehensive review was present on the sources, enzyme stru cture, enzyme reaction mechanism and the application of the nitrilase.

RESEARCH PROGRESS ON ENZYMATIC HYDROLYSIS OF NITRILE / 微生物学通报

Enzymatic hydrolysis of nitrile was performed under mild conditions and afford high efficiency and selectivity,thus being highly potential for the synthesis of optically active carboxylic acids and their derivatives.The type of nitrile-hydrolyzing enzymes and hydrolysis reactions,reaction characteristics,factors influencing the hydrolysis and the prospect for its application to industrial production were reviewed in this paper.